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Renewable Energy Questions/Discussion => Wiring and Code discussion => Topic started by: ksouers on April 28, 2012, 07:27:07 am

Title: Battery bus design
Post by: ksouers on April 28, 2012, 07:27:07 am
My little bank is growing and it's time to start thinking about hooking up to a bus. My criteria are fairly simple. As my bank is growing I need room for expansion. I will be switching from 12 volt to 24 volt in about 6 months or so. I also need to reduce the chances of shorting. I really don't want to drop a wrench and have it weld itself to the bus.

So, how has everyone laid out their bus? Did you put the bars end to end or parallel? How much separation between the bars?

I know brass would be the preferred material, but steel and aluminum are readily available. Brass would have to be ordered, not a problem, just extra cost and hassle. Are steel and aluminum acceptable materials with proper corrosion protection?

How did you protect the connections from inadvertent shorting? Did you mount them in a box? Put them in separate boxes for each pole?


Thanks,
Kevin
Title: Re: Battery bus design
Post by: bj on April 28, 2012, 08:29:29 am
  I will be interested in the replies as well Kevin, as I am at that point.
  At this point, I can only tell you that all incoming (solar/wind someday) will be in a box.
  I suspect my buss will be copper, as I have a large free piece.  Copper is pricey these days.
  As building a box is fairly easy for me, (and cheap) I am leaning towards putting the buss's in
one.
  If you use aluminum for a buss, put the anti-oxident grease on all connections, and it should be fine.
Title: Re: Battery bus design
Post by: ghurd on April 28, 2012, 08:38:12 am
I would not use steel.

Actually, I personally would not use AL either, but I think it would be better than steel.

Bus bars may be one of those items that is cheaper to buy than make, depending on the requirements.
G-
Title: Re: Battery bus design
Post by: tomw on April 28, 2012, 08:59:10 am
Kevin;

Avoid Aluminum like the plague. I think Stainless Steel is OK but higher resistance than other options. Among the common, affordable metals copper is where I would go for low resistance.

I do not use a bus as you think of it. I have 2 big boy traction batteries with 2 heavy cables each and factory interconnects on each for the cells within the individual "battery". One is copper cables with ends the other is tinned copper straps. The batteries tie together through a breaker and ginormous terminal blocks with 500 MCM connections.

I had access to a decent industrial salvage outlet and collected a few copper bars from electrical boxes 1 inch wide and a quarter inch thick and various lengths to build a "bus" but never needed to.

It seems that any decent metal dealer in a largish city should have copper bar stock available. I think copper is the best bang for the buck for conductors whether wire or bar stock. I use Aluminum triplex with 3 conductors the size of your pinky to feed from my turbines but that is an availability issue and weight consideration being overhead lines. I got 2 150 foot rolls of it for $90 each used. It never wears out and can move 200 amps all day without issues.

I guess I am saying Aluminum has its uses but NOT for a bus and certainly not near possible acid vapors.

Just from here.

Tom

EDIT:

I meant to add you could split PVC tube to cover your bus bars. My 810 AH GNB set uses a formed plastic strip to snap over the interconnect bars. PVC pipe split with zip ties be an easy way to duplicate that out of any hardware store.

Tom
Title: Re: Battery bus design
Post by: ChrisOlson on April 28, 2012, 10:18:52 am
I got a four bar 2,000 amp DC bus (for two inverters) from SquareD, rated 250 volts.  It has 6061 aluminum bars in it.  Seems to me that most all of the commercially made power panels use aluminum bus bars, including the DC Conduit Box for Xantrex inverters.

--
Chris
Title: Re: Battery bus design
Post by: tomw on April 28, 2012, 11:10:31 am
I got a four bar 2,000 amp DC bus (for two inverters) from SquareD, rated 250 volts.  It has 6061 aluminum bars in it.  Seems to me that most all of the commercially made power panels use aluminum bus bars, including the DC Conduit Box for Xantrex inverters.

--
Chris

I guess I need to preface comments with "In my Day"..

Anyway, I have personally had bad luck trying Al for battery interconnects. All the power boxes I salvaged had copper bars in them but being a dinosaur my experience is dated. Not all aluminum is created equal, either.

What counts is accuracy.

Tom

Title: Re: Battery bus design
Post by: ksouers on April 28, 2012, 01:03:01 pm
Thanks for the replies, everyone.

I'm not keen on the idea of using aluminum. I grew up with the stories of house fires started because of aluminum wiring. My personal experience is that it usually reacts badly when in contact with other metals. During trips to Home Despot and others it seems that all the commercial bus bars are aluminum. Copper or brass is not available anymore. They also seemed too small and only accepted #10 or #8 wire. I'd prefer #4. The price of copper has just gotten obscene the past couple years. A 100 foot coil of 10/2 wire is almost $200!

The scrap dealers here are a funny lot. There are only a couple and I think they are all related somehow. They really don't want to deal with walk-in traffic and small lots and will always try to rip you off. Even after haggling the price is not really any better than some of the online retailers. Since they are a long drive and out of my way to go there I'd just as soon save the aggravation and order it.

I have 6061 aluminum billet in the shop I can use, but that's a last resort. I'm not desperate, yet. I like the idea of using PVC for covers. I'll have to think about that one.

Thanks again,

Kevin
Title: Re: Battery bus design
Post by: ChrisOlson on April 28, 2012, 09:04:49 pm
During trips to Home Despot and others it seems that all the commercial bus bars are aluminum. Copper or brass is not available anymore. They also seemed too small and only accepted #10 or #8 wire.

Whoa - don't use those.  Those are for ground strips in AC service panels.  The bars in my SquareD bus are about 1/2" thick and 1 1/2" wide.  They got a big screw lug on the top that accepts 4/0 cable and the rest of the bar is drilled and tapped for 5/16" NF bolts.

Anything you find at Home Depot is going to be a toy for DC.
--
Chris
Title: Re: Battery bus design
Post by: ksouers on April 28, 2012, 10:12:53 pm
During trips to Home Despot and others it seems that all the commercial bus bars are aluminum. Copper or brass is not available anymore. They also seemed too small and only accepted #10 or #8 wire.

Whoa - don't use those.
--
Chris

Had no intention to. Way too small. I've looked several times and they have no other bus bars of any kind.

I checked current prices with one of the online vendors I use for metal stock. Copper is a bloody fortune, brass is a little more than 2/3rd that price.
A two foot piece is about the price of a tank of gas.  :o  Both are quite ridiculous.


Kevin
Title: Re: Battery bus design
Post by: ghurd on April 29, 2012, 12:35:07 am
It has 6061 aluminum bars in it.

Why do you believe it is 6061?
That's kind of a generic type of AL considering all the types made.  Seems like with all the different types, someone must make something special.

I'm not keen on the idea of using aluminum....
Home Despot and others...

Me too, about the AL.

600W and 1000W inverter, and a couple hundred watts of solar?
I was thinking more along the lines of parts for those obnoxious car stereos.  Retailers like best buy, or "stereo parts to PO your neighbors at 2:30AM with crappy music and rattling windows dot com".

I like ebay because of the photos, but.... here is a quick copy/paste with some pricing, they all have a cover, and these were all on the 1st page of my search.

STINGER SPD5210. SKU: SPD5210. Fused Distribution: ANL. Input Gauge (s): 0 Gauge. Inputs: 1. Output Gauge (s): 4 Gauge. Outputs: 2. ($30)

AudioPipe PB-1448. 1 in 4 out configuration. 4/6/8 gauge compatible (IN). 8/10/12 gauge compatible (OUT) . ($13)

AUDIOBAHN ADB48 CAR AUDIO STEREO WIRE DISTRIBUTION BLOCK (1) 4GA IN (4) 8GA OUT ($12)

Platinum Car Stereo Distribution Block. One 4 Gauge Input. Four 8 Gauge Outputs. Works with Power or Ground Wires. Platinum Finish with Gold Hardware. ($8)

All prices were "Buy Now" and included 'free S&H'.

Be hard pressed to find a metal retailer who would SHIP enough material to make a bus bar for $8 in S&H?
That's how I was thinking,
G-
Title: Re: Battery bus design
Post by: ChrisOlson on April 29, 2012, 08:35:47 am
It has 6061 aluminum bars in it.

Because that's what all the commercially made panels use for aluminum bus bars.
--
Chris
Title: Re: Battery bus design
Post by: ksouers on April 29, 2012, 08:47:57 am
Thanks G. Good suggestions. I hadn't thought about how much power those obnoxious rattle-traps need.

600W and 1000W inverter, and a couple hundred watts of solar?

G-

That's only TODAY. This is a growing system. I have more panels arriving in a couple days. I will be adding more panels and batteries throughout the year. Think more along the lines of a 2500-3500 watt inverter, that's the goal.
We budgeted 6000-9000 USD for a standby generator. I thought spending that money on solar made more sense. The genny is just a lump of iron until those days we need it. If the RE can be used to help mitigate the electric bill a little and feed my sense of independence, then even better. Made more sense to me. I'll never be off grid here, not in this house, but I'll put up as much solar as I can to keep the wife happy when the rest of the neighborhood goes dark.

We have really nasty storms here where the straight line winds can easily be 60-70 MPH, sometimes reaching 100. Then we also get those twisty ones that send little girls from Kansas to far off lands. Wintertime is subject to ice storms that also take down trees and powerlines. Time without electricity here is measured in days and weeks (yes, weeks!) not just hours after one of these storms. I'm on the edge of civilization*, it's a mix of family farms and subdivisions. It takes awhile before the power company comes out here to repair the damage.


Kevin

* "civilization" being as far away from the city and 'burbs as I can possibly get and still keep my day job.
Title: Re: Battery bus design
Post by: ghurd on April 29, 2012, 09:50:36 am

We budgeted 6000-9000 USD for a standby generator. I thought spending that money on solar made more sense.

Time without electricity here is measured in days and weeks (yes, weeks!)


Agreed.
Should be able to get by with a $500 genny?

My Bro-in-laws place had the power poles behind the houses, instead of on the road.  60 years of tree growth made it impossible to get to the lines quickly with trucks.
Ice storm took down lines all over everywhere.  Power was out for like 2 weeks?
He got by with a burrowed (from guess who?)1200W inverter, 2 times a day, connected to an idling Chevy Cavalier.
Inverter by the car, long extension cord to the fridge.  Once the fridge started running (would usually trip the inverter a couple times before it got running), he could charge the laptops and cell phones and hand held video games at the same time.
Seems like he only had to connect it to the furnace a time or 2, but the house was not very warm most of the time!
If he got by with a 1200W inverter, not sure how bad he would need a $9,000 back-up genny!  ;)

BTW- That was in the densely populated burbs of Pittsburgh, PA.
G-
Title: Re: Battery bus design
Post by: ksouers on April 29, 2012, 10:29:49 am
I already have a 5500 watt portable genny. But it's a finicky pull start and noisy and still needs to be fed. The last ice storm we had blocked all the roads out of here (3 escape routes) with lots of trees and powerlines down and we couldn't get out for a couple days. All the gas cans were empty by time I got out to fill them up again. We went through 20 gallons of gas in two days. That last night I was running a 300 watt inverter off the car to power a light (as much for heat as light) and a radio for news. The next morning they had one of the roads open and I was able to get gas, we were back in bidness.

It was a pretty bad disaster and a total CF by the county. The cops wouldn't let anybody cut up the trees blocking the roads until the utility company had untangled the power lines and cleared the snapped poles.

$9000 was the high estimate we got for a small genny with autostart, installation, natural gas service upgrade and transfer panel.


Kevin
Title: Re: Battery bus design
Post by: Rover on April 29, 2012, 11:21:01 am
As far as bus bars... I just order copper bar from Speedy Metals (speedymetals.com), price isn't that bad. I usually get 1" x 1/8" . Right now I have just wrapped with electrical tape (red and black) for a small piece of mind. The PVC is a good idea.

Cut and drill etc as needed. Obviously size your bars for the intended voltage and current.

I'm a little concerned you are planning on continuously growing your bank. It can be done, but you're typically better off starting with a larger bank, rather than having an arrangement of young and older batteries.

Rover
Title: Re: Battery bus design
Post by: ksouers on April 29, 2012, 12:46:04 pm
I'm a little concerned you are planning on continuously growing your bank. It can be done, but you're typically better off starting with a larger bank, rather than having an arrangement of young and older batteries.

Rover

Well, probably not grow continuously, but fairly quickly. When I get the bank up to where I want (about 650 AHr @ 24 volts by the end of July) they will all be less than 6 months of each other. That'll be about the limit I have for space to mount panels. The older group 27 batteries will be taken out of the bank before then and just used for camping and boating.

Now, if my wife decides she really does want that small farmstead she's been talking about then all bets are off. I will be heading off grid! But that's a very long shot and wouldn't place that bet. She's too much of a big city girl.

I looked at Speedy Metals a year or so ago, they seemed a little pricey compared to who I usually use, Online Metals, at least for the grades I wanted at the time. McMaster-Carr seems to have the best price for tool steels, kind of hit-and-miss on other metals.

Kevin
Title: Re: Battery bus design
Post by: Rover on April 29, 2012, 01:06:53 pm
I know this may sound hard, but consider the following. (I'm not assuming this is your plan)

You already have a plan and an end goal. Maybe finances preclude you from doing the one time everything at once.

I've been there, done that. Solar panels etc can be bought without worry at any time. But I'm very reluctant to see a battery bank built with batteries that some have already been in service, maybe even mixed with non matching types and ages. I've killed young and old batteries with that approach.

My opinion, buy the bank in one shot, or as close to age as possible. Try not to put part in service then add to it. Definitely do not mix battery types for an extended time.

I know you state that they will be within 6 months of each other. Stuff happens.. and that 6 months can end up being a year, for a whole host of reasons.. no money, other activities interfere, batteries not available... etc.

You probably already have thought all this out, I'm just posting for anyone else :)

Rover



Title: Re: Battery bus design
Post by: ChrisOlson on April 29, 2012, 03:18:15 pm
$9000 was the high estimate we got for a small genny with autostart, installation, natural gas service upgrade and transfer panel.

Are you sure you want a natural gas genset?  In a disaster, natural gas is one of the things that stops working because it takes utility power to pressurize the lines at the pumping stations.  A few of the interstate lines have natural gas pumping engines.  But most of the local infrastructure is pressured by electricity with motors.

We got a Generac EcoGen LP genset:
http://www.generac.com/Residential/EcoGen_Series/Product/6kW/

It can run for 400 hours (almost two years for us) on 450 gallons of LPG.  The only downside to the LP genset is that it refuses to start much below zero F.  So we also have a gasoline-fueled 3 kW Champion Power Equipment backup genset - also auto-start.  The Champion started last winter at -32F with no pre-heat.

The EcoGen is about $4,000.

If you have a decent inverter/charger with gen support, you do not need a genset capable of running your whole house.  If you have Outback or other cheaper inverters that do not have gen support, then you will need a larger genset.  Inverters with gen support are able to "blend" generator output with inverter output so your total capacity is the sum of both the genset and the inverter(s).

Spending $9 Grand on a standby gen is ridiculous.  If you are dead set on spending $9 Grand then buy a Xantrex XW (has gen support) and a smaller generator instead.
--
Chris
Title: Re: Battery bus design
Post by: ksouers on April 29, 2012, 06:00:35 pm
Chris, the decision was made to nix the standby genset and go with RE, but still keep the manual gasoline genny as backup at least for now. I may swap that out for an electric start some day, even better if it has autostart. I'm getting too old to yank on a cord anymore :)

The plan is to go with an Outback inverter when I switch over to a 24 volt bank. I won' t be off grid, just powering a few things around the house. But it has to be ready to be pressed into service as backup power for the house when the grid goes down. If I happen to knock $10 or $15 a month off the electric bill by using less, that's just gravy.

The bids we got were between 6 and 9,000 for complete installation. We decided to spend the $6,000 on solar especially in light of the debacle we had a couple years ago getting trapped with no way to refuel the genny. I figure with the RE we can stretch that 20 gallons of gas out for many days as long we get some sun. Running a fridge, a microwave, the furnace and coffee pot shouldn't be too taxing on the system I have in mind.


Kevin
Title: Re: Battery bus design
Post by: ChrisOlson on April 29, 2012, 06:29:33 pm
We decided to spend the $6,000 on solar

I'm breathing a sigh of relief.  Your money is MUCH better spent on them solar panels than a freaking generator.  Like Glen said, you can probably just get by with a $500 generator.  When people start talking about spending $9 Grand on a residential standby generator, I'm like, WTF you got?  A 50 room mansion?    :o

Businesses, factories, etc. - $9 Grand is a little generator.  In fact, a tiny generator.  But for a home, and the needs that most people have in the event of a power outage, $3 -4,000 is a good price for a capable 14 kW standby generator.
--
Chris
Title: Re: Battery bus design
Post by: rossw on April 29, 2012, 06:35:31 pm
I figure with the RE we can stretch that 20 gallons of gas out for many days as long we get some sun. Running a fridge, a microwave, the furnace and coffee pot shouldn't be too taxing on the system I have in mind.

Long time since I used an electric coffee pot, but don't they draw quite a lot?

Years ago I got (as an emergency backup) a little camping grill type thing. A single gas burner, runs on a can of butane. One can lasts a surprisingly long time - and cans were about 50c each, store easily and should last in storage forever and a day. Sure, it's not renewable - but it'd sure stretch your RE electric resources. The whole thing - burner, carry case and a couple of cans of gas cost me $5 or $6 brand new from one of the cheapy "reject" style stores. Might be worth having on hand too.
Title: Re: Battery bus design
Post by: ksouers on April 29, 2012, 06:45:53 pm
I figure with the RE we can stretch that 20 gallons of gas out for many days as long we get some sun. Running a fridge, a microwave, the furnace and coffee pot shouldn't be too taxing on the system I have in mind.

Long time since I used an electric coffee pot, but don't they draw quite a lot?

Years ago I got (as an emergency backup) a little camping grill type thing. A single gas burner, runs on a can of butane. One can lasts a surprisingly long time - and cans were about 50c each, store easily and should last in storage forever and a day. Sure, it's not renewable - but it'd sure stretch your RE electric resources. The whole thing - burner, carry case and a couple of cans of gas cost me $5 or $6 brand new from one of the cheapy "reject" style stores. Might be worth having on hand too.

Hi Ross,
Yes, they do draw quite a bit, about 600 watts. But it's only for a few minutes while the pot is brewing, when done I grab a cup and the rest goes into a thermos and the the machine is turned off. Sterno is also cheap if one were to go that route. The microwave also draws a lot but for a short time so It's not too bad as long as long as you don't over do it. Can of soup is done in a minute, cold cut sandwich, yum.

As long as the furnace pumps out heat and the beer stays cold I can live on that for weeks.


Kevin
Title: Re: Battery bus design
Post by: ChrisOlson on April 29, 2012, 07:42:20 pm
Long time since I used an electric coffee pot, but don't they draw quite a lot?

We brew fresh coffee for breakfast every morning.  Our coffee maker draws about 1,200 watts while it's brewing.  Then it drops to about 250-300 watts intermittent while the heating plate cycles on and off to keep the pot hot.  So they're not really that bad.
--
Chris
Title: Re: Battery bus design
Post by: ghurd on April 29, 2012, 08:49:19 pm
Years ago...  runs on a can of butane.... cans were about 50c each...

That must have been MANY years ago!
6~8 years ago it was retailing for like $6~8 a can?
A ma&pa dollar store up the road had it for $2 a can, and I'd get all they had to take to a store 45 miles away to sell it for $3 a can, and they'd sell it FAST for $5 a can.

Might be different Down Under, but the US has ALL kinds of rules about shipping that kind of thing, and it got worse after 9-11.  The price went through the roof after 9-11.


I agree with Chris about coffee pots, mostly.
Not sure about the one I use now (has more damn buttons than a laptop).
The one 2 or 3 ago was like 600W or <1W.  It only had 1 heating element.
When brewing it was a high duty cycle.  Then the duty cycle was a lot less to maintain a hot pot.
The Average Power may have been only 50W, but a 100W inverter was not going to make it work. LOL


How I was thinking about a genny is like I usually think in this kind of situation.
The battery bank is USUALLY big enough to supply adequate power in an emergency, right?
And the bank, with RE input, is often enough to deal with an emergency, right?

I am thinking a lawn mower motor and DC genny is going to use a lot less gas for the same results (warm house and cold beer).
I know a guy who put a PMA on an old 3 or 4 HP rototiller engine, and had a hard time keeping it below 300W(?) at idle.

"We went through 20 gallons of gas in two days" ?
That is EXACTLLY what I am talking about.
Try to burn that much gas with a decent 3.5HP B&S lawn mower engine.
No reason to burn that much fuel except to keep the motor at 3600RPM and the output frequency at 60HZ, but the inverter keeps the frequency at 60HZ even if the motor is NOT running!

G-
Title: Re: Battery bus design
Post by: ChrisOlson on April 29, 2012, 10:32:52 pm
I am thinking a lawn mower motor and DC genny is going to use a lot less gas for the same results (warm house and cold beer).
I know a guy who put a PMA on an old 3 or 4 HP rototiller engine, and had a hard time keeping it below 300W(?) at idle.

That's what I'd do too.  Back when we used to run short on power all the time I put a little Delco 10SI on a Tecumseh 6hp snowblower engine:
[attachimg=1]

In the evenings I'd start the thing and let it run just above idle, about 2,000 rpm, and it would keep the bank up with our heavier evening time loads on before we went to bed.  It would put out 20 amps @ 14 volts on about 1 pint of gas per hour.  Later on when we went to 24 volt system I swapped out the rotor in it with a 24 volt rotor.  I used the stock stator in it, and full-fielded the rotor by grounding the regulator tab.  Never changed the regulator either.  But the rotor had to be changed because the 12 volt rotor would burn out full-fielded on 24 volt.  On 24 volt it would put out the same 20 amps @ 2,000 rpm.  But it made the engine work a lot harder so it burned more gas - almost twice as much.

After we bought our big battery bank I've never used it anymore because it can't put out enough power to amount to peeing in the ocean to charge our bank anymore.  But I put a LOT of hours on that thing over the years without dumping much gas in it when we didn't have the battery capacity we needed.

No reason to burn that much fuel except to keep the motor at 3600RPM and the output frequency at 60HZ, but the inverter keeps the frequency at 60HZ even if the motor is NOT running!

Glen makes a good point about 60Hz AC generators here.  When you buy one to power your house for power outages the usual recommendation is to size the generator so it runs at 50% load carrying your normal loads so it has reserve for surge loads.

For off-grid it's different.  You size your battery bank, inverter chargers and generator so that when the gen comes online it runs at full load.  Example: our battery bank is 2,400 amp-hours @ 24 volt nominal.  The bank likes 10% of the amp hour rating for bulk charging, which is 240 amps.  Our inverters put out 120 amps each and our 6 kW generator can deliver enough power to run the inverter chargers at the full 240 amps during initial bulk charging when it comes online.  There is no "reserve" for surge loads, but we don't need it with a battery/inverter system because if a heavy surge load comes on during charging the inverters take over and cut the amount of amps the chargers are taking from the generator to prevent gen overload.

People who just have grid power with a standby generator don't have that luxury so the generator has to be sized different (much larger).

60Hz generators are most efficient (kWh/unit fuel) at full load.  They are least efficient at zero load.
--
Chris
Title: Re: Battery bus design
Post by: rossw on April 29, 2012, 10:38:23 pm
Years ago...  runs on a can of butane.... cans were about 50c each...

That must have been MANY years ago!
6~8 years ago it was retailing for like $6~8 a can?
A ma&pa dollar store up the road had it for $2 a can, and I'd get all they had to take to a store 45 miles away to sell it for $3 a can, and they'd sell it FAST for $5 a can.

Might be different Down Under, but the US has ALL kinds of rules about shipping that kind of thing, and it got worse after 9-11.  The price went through the roof after 9-11.

It was while we were building our new place - so in the last 6 years or so.
One of the guys working here had one, and on those bitterly cold days, a hot lunch was a great idea.

I just went looking, and yes, they've gone up.
8oz cannisters are now $15.20 for a 12-pack from amazon.com. http://tinyurl.com/cmyprtz
 Thats $1.25/can. And yes, there are restrictions on posting them. I'm sure I saw them selling locally at the reject shop here for under $1/can recently. Ahh, "progress". *sigh*.

And Amazon have the little cooker still listed, more than I paid - for $11.78 for the "deluxe" version.
http://tinyurl.com/8xljgsa


Title: Re: Battery bus design
Post by: ghurd on April 30, 2012, 11:01:46 am
Those are much smaller cans, but a lot cheaper per ounce!
$15.20 + $16.75 shipping.  LOL
G-
Title: Re: Battery bus design
Post by: ksouers on April 30, 2012, 05:42:18 pm
"We went through 20 gallons of gas in two days" ?
That is EXACTLLY what I am talking about.
Try to burn that much gas with a decent 3.5HP B&S lawn mower engine.
No reason to burn that much fuel except to keep the motor at 3600RPM and the output frequency at 60HZ, but the inverter keeps the frequency at 60HZ even if the motor is NOT running!

G-

G-
I should mention that was the first time we used the genny under emergency conditions. It was purchased shortly after a summer storm had taken out half the power in St Louis county and about a third of neighboring St Charles county. I admit I could have done a much better job of fuel and power management and probably stretched that much gas out for at least 3 and possibly 4 or more days. I had no method to hook into the house wiring, hadn't even thought of it. Extension cords were stretched out all over the house. We were running 2 1500 watt space heaters, fridge, lights etc and I was trying to keep an aquarium full of saltwater fish alive. I had the genny running full time. Of course, I had no RE system at the house at the time, either. Not even a spare battery anywhere and my only solar panel was on the boat 40 miles away.

Since that time we have only lost power twice, and only for a couple hours each. We are overdue.

Kevin
Title: Re: Battery bus design
Post by: RichHagen on May 02, 2012, 09:11:14 pm
In my 48V setup, I just took a couple of approximately 24 inch 1 inch by 1/4 inch 6061 aluminum bars and drilled and tapped 10/32 holes every inch or so, staggering them 1/4 inch from the edge from the top with the next 1/4 inch from the bottom as they are mounted horizontal.  The ends and middle have 1/4 inch holes which also serve as mounting points, with the inverter attached at one end.  Smaller stuff is attached to the 10/32 brass binding screws I put in all of the tapped holes.  I have a small cnc, so it was easy to make.  I had originally planned for copper, but did not have it in hand when the need arose, so I programmed the drill template and made one out of aluminum in the interim.  I ordered up the copper, probably from online metals or speedy up in Wisconsin, but it is sitting for now, as the aluminum one, with the Noalox antioxidant grease on every connection has performed flawlessly thus far, and of course cost only a tiny fraction of what the copper would for the same resistance level.  For a permanent installation I would still prefer the copper bus bar as it has lower overall resistance per unit of cross section and fewer oxidation issues if using similar copper conductors or leads, but aluminum is far cheaper and in my case (as well as many breaker boxes and other commercial products) is working out fine thus far.  I think I would have more concern if it was in an area with more humidity or condensation, or a marine environment, but I have not seen any corrosion whatsoever on my aluminum bus bars thus far and have had zero problems with them.  Rich
Title: Re: Battery bus design
Post by: rossw on May 02, 2012, 09:28:11 pm
but I have not seen any corrosion whatsoever on my aluminum bus bars thus far and have had zero problems with them.

I guess everyones experience is different.

In my original setup, I used Aluminium for the interconnects between 48, 2V cells.
(http://house.albury.net.au/30dec2004/MVC-092X.JPG)

There were a few of them:
(http://house.albury.net.au/30dec2004/MVC-091X.JPG)

I was quite pleased with my handywork.... but they required almost constant attention.
They would come lose for no apparent reason, they got warm, they oxidised....

After the tradespeople destroyed that bank (a whole other story), and I had to make a temporary string out of other cells, I initially used Aluminium bar and it was a total disaster. They needed tightening every few days, they ran quite warm to the touch.... and I couldn't replace them quickly enough with copper.
(http://house.albury.net.au/30nov2005/MVC-632X.JPG)

After that - I never had to touch them again.

And when I got more of the AGM cells, I went straight to copper interconnects and they've given me zero problems.
Title: Re: Battery bus design
Post by: ChrisOlson on May 02, 2012, 11:13:56 pm
I believe most battery posts are lead.  So you set up a galvanic couple using aluminum on lead posts.  The most common metals used for sacrificial anode are zinc, magnesium and aluminum.  It's not surprising that aluminum did work well for battery interconnects, ran warm and kept coming loose.

ASTM B 236-07 outlines the requirements for aluminum bus bars made of 1350-H19, or 6101/6061 alloys.  Aluminum is used in the electrical industry quite regularly for bus bars, and should not be a problem.  Chances are the main electrical panel in your house, if bought commercially, has aluminum bus bars in it.  SquareD, Allen-Bradley, you name it from all the big names in electrical panels, use aluminum bus bars.

Is copper better than aluminum?  Yes, because it has lower resistivity.  But aluminum is perfectly fine if sized properly for an off-grid DC main power bus.
--
Chris
Title: Re: Battery bus design
Post by: rossw on May 02, 2012, 11:22:33 pm
Chances are the main electrical panel in your house, if bought commercially, has aluminum bus bars in it.  SquareD, Allen-Bradley, you name it from all the big names in electrical panels, use aluminum bus bars.

Might be where you are, Chris, but not here.

Here are some of my 4 "switchboards". They are all commercial over-the-counter boards, installed by a professional sparkie and myself.
(http://house.albury.net.au/05apr2005/MVC-559X.JPG)

(http://house.albury.net.au/05apr2005/MVC-554X.JPG)

(http://house.albury.net.au/05apr2005/MVC-553X.JPG)
Title: Re: Battery bus design
Post by: birdhouse on May 03, 2012, 12:02:26 am
i don't know chris, siemens panels at home depot here have copper busses, or atleast copper cladded busses.  they're in line with pricing with square-d ect. 

they're my personal favorite, as even if the buss isn't pure copper, at least it has copper where the breakers connect!

adam
Title: Re: Battery bus design
Post by: Wolvenar on May 03, 2012, 01:34:37 am
I believe Siemens use full copper.
My local electrician friend speaks highly of them, and says many of the commercial jobs he works on are starting to use them exclusively on any new construction.

The main Square D fuse/disconnect box I have on my setup has a tinned copper bus in it (yup I checked it really is not aluminum).
Though my smaller one for the solar panels are aluminum.

All I can say for sure about the debate is everything I see in the manuals I have with the inverter, controller, and solar panels say all wire and connections must be copper.

I might use aluminum on my future longish run to where the solar trackers will be, because the cost vs loss when at higher voltages.
I would never used aluminum on the batteries, that's just asking for trouble.


--Edit, I just went out to watch natures little light show we have here tonight (storm)
So I decided to check on the little panel, it is actually standard copper (not tinned) instead of the aluminum I wrongly thought it was.
It must be the newer box I have future plans for.
Title: Re: Battery bus design
Post by: rossw on May 03, 2012, 01:44:48 am
I believe they are full copper.

Oddly, pure copper connectors here are quite rare.
Probably because of coppers tendency to oxidise quickly.
The *vast* majority here are Brass. (I think Brass is also harder than Copper - so the screws are less likely to strip)
Title: Re: Battery bus design
Post by: Wolvenar on May 03, 2012, 02:35:54 am
smaller box
(http://www.anotherpower.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=20515&g2_serialNumber=2)
Title: Re: Battery bus design
Post by: Wolvenar on May 03, 2012, 02:49:17 am
I little research just to be sure on the Siemens products

Quote
Bussing — Busbars and breaker branch
bus is tin-finished aluminum per UL 67
unless otherwise stated. See panel
submittals for optional call outs. Copper
bus is available as an option.

From the manual describing their panels.
Title: Re: Battery bus design
Post by: ChrisOlson on May 03, 2012, 09:55:03 am
I think SquareD has copper as an option for some panels too.  But the aluminum ones are a lot more common these days.  Knife-type contacts in disconnects and so on are usually some sort of copper alloy.  Like Ross said, pure copper would be very rare as it turns green quite fast when exposed to air and moisture.

But back to the debate - I really see no problem with aluminum bus bars.  The SquareD box I bought for my bus was used and is probably 20 years old.  It was a bus box at one time for a huge industrial DC motor setup of some sort.  The bus bars in it are just soft 6061 aluminum and not the T6 tempered stuff that's more common.  T6 tempered aluminum will break when you bend it and the bus bars in my box are made of the same stuff that lots of aluminum wire is made of.  It's a just a soft 6061 alloy.

In corrosive environments like marine or salt air, or directly on the batteries, I think you'd want to use a different material - and copper alloys would probably be better there.

My bus is central to my DC system.  The batteries feed the bus with six positive and six negative leads, with a 200 amp ANL fuse on each positive lead from the bank.  The inverters are fed from the bus with 4/0 cables going to each inverter.  All incoming power from turbines and solar goes into the bus.  I got a 200 amp DC service plug wired into the bus for a DC generator in the event I ever decided to buy one.

The inverters are fed off the end of the bus bars because there's big screw lugs there that accept 4/0 cable.  Three feed wires from the bank go to each bus bar (four bars), and I got jumpers between the two positive bars and the two negative bars in the bus (dual inverters require a common bank).  At 700 amps to the inverters I only get .3 volts drop between the bank and the inverter studs - and that's in the wiring not the bus.

I'll see if I can take a photo of it at noon when I go in for lunch.  It's padlocked shut because a 1,200 amp DC bus is one dangerous SOB to be fiddling around in when it's live**.

** I would like to put out a caution for folks aspiring to build or install a high amperage DC bus.  They are dangerous.  Very dangerous.

Back when we had our 12 volt system I had a homemade bus in the basement (that also had aluminum bars).  I was working in there one day and had laid a steel handled Craftsman claw hammer on top of the (hot) bus box.  I bumped the hammer and do not know how it did it.  But I think the claw on the hammer caught the top of the bus box and it flipped and went inside the box and came in contact with two of the bars in there.  The explosion was about like a M80 going off in front of your face.  Part of the head on that hammer INSTANTLY vaporized and sprayed me in the face and arms with molten metal.

And that was just a 12 volt bus.  Since then I have great respect for what a big bank of batteries with big wires feeding a bus can deliver.  I had 24 Group 29 marine deep cycle batteries @ 125 ah each.  Each one of those batteries can deliver 700 cranking amps.  With 12 4/0 cables feeding that bus, and no fuses at the bank, I'm sure the surge that vaporized that hammer was over well over 3,000 amps.

That was back when I was young, dumb and full of vinegar.  I learned that you ALWAYS fuse your bank and you NEVER work on a hot DC bus.
--
Chris
Title: Re: Battery bus design
Post by: RichHagen on May 04, 2012, 01:06:30 am
To clarify, my bus bar of aluminum is not battery interconnects, it is a DC distribution bus kind of like what Chris described for his system, only smaller.  For batteries I would want the least active metal I could find for the interconnects, or lead itself.   Aluminum, because of its rapid corrosion in acids and its much larger potential difference with lead, would not be among my first choices, in fact it would be one of my last.  I think lead tinned copper interconnects would be my first choice for battery interconnects for batteries with lead terminals.  I've seen brass marine terminals partly eaten away by corrosion, and I would expect aluminum to fare much worse in that application.   I do use Aluminum interconnects on my ultra capacitor banks, but, the terminals of those capacitors are of aluminum alloy.  Again, with greased connections, I have had no problems with those as well.  Unless there is a reason to do otherwise, I would use the metals with the closest electrical oxidation potential for junctions to avoid galvanic corrosion.  I heard somewhere that a general rule of thumb is not to join metals together in exposed joints if the oxidation potential between them was greater than .5 volts, and it seems like a basically reasonable guide.  Junctions of metal where the oxidation potentials exceed that would have to have protection from the environment in order to avoid galvanic corrosion because any of the more noble metal oxidized would likely be reduced in favor of oxidation of the more active metal at the junction if a galvanic cell were to form, such as condensation, rain, or such.  This is the idea behind sacrificial anodes, often made of magnesium or aluminum, which are used on pipelines and in some hot water tanks.  Most Junctions with Aluminum would require protection from the environment.  In my case I used anti-oxidation grease made for such a purpose.

Here are the different potentials of some common metals relative to the oxidation of hydrogen from my chemical dictionary:

Magnesium   -2.38 Volts
Aluminum     -1.66 Volts
Zinc     -.763 Volts
Iron (2+)  -.409 Volts
Nickel -.250 Volts
Lead  -.126 Volts
Copper +.34 Volts
Iron (+3) .771 Volts
Silver +.799 Volts
Platinum +1.2 Volts
Gold  +1.489 Volts

I'm not certain, but I would guess that the Iron would break down at the lower voltage listed for the plus 2 (Ferrous) oxidation state first, so that is what I would use to gauge, as I know that if you join iron plumbing to copper without a dielectric, in general your iron pipe will corrode away.  I seem to recall a historical article where the Brits built a copper sheathed boat in the age of wooden warships, but ran into a problem where all of the iron nails used to hold it together corroded away within weeks in sea water.   
Title: Re: Battery bus design
Post by: tomw on May 04, 2012, 08:46:25 am
One reason I like copper so much is the hundreds of cathedrals, etc in Europe with original copper roofs that are centuries old. I know it is not electrical in nature but sheets of material that last that long on a roof has to be tough and resistant to decay.

Plus, every plumber I know tells me to use copper if I want it to last.

Just sayin...

Tom
Title: Re: Battery bus design
Post by: bj on May 04, 2012, 09:30:41 am
  Kind of where my thinking goes as well Tom.  Now if I could just figure out what I did with that nice piece of
tinned bussbar I've been saving.  :(
Title: Re: Battery bus design
Post by: bj on May 08, 2012, 07:31:38 am
    I like copper, but I sure wish somebody else was paying for it.   Couldn't find my prized piece, so, had to go to the big city to
pick up my ammeters and bought another chunk.  My, My, copper has gone up. :o  Only money ;D
    Makes me glad I hoarded all that copper wire.
Title: Re: Battery bus design
Post by: ghurd on May 14, 2012, 10:17:08 am
I stumbled on this today.
Midnite Solar bus bar, "Four 1/0 & eleven #6 useable wire slots. Comes with two sizes of 10-32 screws. 4.63" UL and CSA recognized, Made in USA.... Remove the plastic insulators for ground bus applications."
Comes (insulators) in Red, Black, or White.
~$15.

G-
Title: Re: Battery bus design
Post by: ksouers on May 14, 2012, 05:24:03 pm
Thanks G.
That sounds like these, I think.  http://www.solar-electric.com/mntb.html

I've got couple of these in my combiner box. Still seem a little small to me for a battery bus. They are only about a 1/2 inch by 3/8 inch (uncalibrated eyeball method).
The web where they drilled the holes is a little on the thin side. Fine for the combiner but I don't think it'll take a high-amp hit from an inverter if a couple motors start up at the same time.

No matter how distasteful I find it I may end up using aluminum for the bus. Copper is going to cost almost $100 just for a .375 x 1.25 x 2 foot piece. Brass isn't going to be too much cheaper, maybe $20.

Thinking I should have put my money into copper instead of Apple stock...


Kevin
Title: Re: Battery bus design
Post by: Dave on May 14, 2012, 07:08:30 pm

Hey Kevin,

Are you being over charged?

3/8"x1-1/4"x 24" C110 (standard buss grade) $47.80 + $10.57 shipping for me.

http://www.onlinemetals.com/merchant.cfm?id=87&step=2&top_cat=87

Could save a bit more going with 1/4" thickness... Made several buys through these folks with good service. :D

Cheers Dave
Title: Re: Battery bus design
Post by: ksouers on May 14, 2012, 07:57:46 pm
Dave,
Thanks for double checking me. Now that I think about it, it may have been a little thicker and wider. 1/2 x 1.5 maybe? I looked at so many I don't remember the details anymore. I've got CRS real bad. Anyway, I do remember it would have worked out to over 80$.
It was Online metals I was looking at. I've used them many times over the years and their prices have always been reasonable.
$50 is a little more doable (still outrageous!). It's been a couple years since I've ordered any brass from them but I don't recall copper/copper-bearing metals being so stinkin' high!


Kevin
Title: Re: Battery bus design
Post by: ghurd on May 15, 2012, 09:30:14 am
I would not be so concerned with the resistance of AL : CU.
If it is big enough (for me) to work with, and get screws in it to hold the big wire(s) securely, seems like the resistance would still be less than the wire.

Something about the AL discussion I think is very important:
Quote
bus is tin-finished aluminum per UL 67

I am not so big on 'owl s#!+'.
I would rather not have any issue, than smear goop on it to hopefully stop a known issue.

Quote
Fine for the combiner but I don't think it'll take a high-amp hit from an inverter if a couple motors start up at the same time.

Don't most of those big inverters have 2 or more input wires per +/-?
I had a big 24V Trace with 3 + and 3 - inputs... I think.

Why not run them straight to the battery terminals?
There would be 10 reasons that is a good idea.  There could be 10 reasons its a bad idea.

G-
Title: Re: Battery bus design
Post by: ChrisOlson on October 11, 2012, 03:44:29 pm
Our SW+4024's just have one set of input studs.

I built a new bus box with two bars in it.  They are made of 6061-T6 1/2" thick bars.

[attach=1]

We're in the process of upgrading our system (again).  I kept on building turbines until I replaced all my direct hooked ones with MPPT ones.  In the process I acquired four Classic 150's.  I kept screwing them to the wall where ever there was an empty spot, and now I got wires running all over hell.

We're going to eliminate our leg balancing system by removing one SW+4024 and replacing it with a Magnum MS4024PAE 240 volt split phase inverter for the 240 volt loads.  And keep a single SW+4024 for the 120 volt loads.  This will eliminate the leg balancing transformer (Xantrex T240).

I'm putting in two bus panels - one for the 24 volt system - and the other for the high voltage DC source power from solar and turbines.  The Classics are all going to be lined up in a row, connected by 1" conduit with a raceway below, with the high voltage bus on the left side of the Classics and the low voltage bus on the right side where the 24 volt power comes out.

Need to get all that wiring in conduit and clean things up a bit before winter.  Hoping to have it done by November.  I'll have one SW+4024 and a T240 transformer for sale when I get it done.
--
Chris
Title: Re: Battery bus design
Post by: ChrisOlson on October 14, 2012, 11:07:50 am
Why not run them straight to the battery terminals?
There would be 10 reasons that is a good idea.  There could be 10 reasons its a bad idea.

I think a bus is better than using the battery bank for a bus just because there's a lot of wires.  When you have multiple inverters, multiple controllers, fused circuits for things like running the MNBCM battery bank monitor, 24 volt furnace controls in the house, power to the clipper relay panel for the turbines, and other things - that would be a LOT of wires going to the battery bank.

I snapped a photo midway thru wiring up our new bus yesterday:

[attachimg=1]

[attachimg=2]

We were on generator power for 14 hours yesterday during the upgrade.  I got enough done last night to get one inverter online for overnight.  Hopefully get the Magnum inverter online this afternoon (barring unforeseen problems).

One of the unforeseen problems yesterday was with the Classics.  The holes on the Classic are for 1" conduit.  You can only get four 4 AWG THHN wires in a 1" conduit.  So I have to move my generator transfer switch and mount the other two Classics down below the first two with their own 1" conduit going to the bus.  But I need the other inverter done first, and that's top priority after lunch   :)
--
Chris