Anotherpower.com Forum
Renewable Energy Questions/Discussion => Automation, Controls, Inverters, MPPT, etc => Topic started by: ChrisOlson on February 02, 2012, 07:27:34 pm
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I service my batteries (24 Rolls-Surrette T12-250's) every three months. The service procedure involves fully charging the bank as the first step. Then, with the generator running and my RE system shut down, I flip my big Ronk 200 amp manual transfer switch. The transfer switch disconnects gen power to the inverters while simultaneously disconnecting the inverter output to the loads, and switches all the loads over to gen power. It totally removes the inverters and battery bank from the loads so the inverters go idle.
I takes about 4 hours to service the bank. Those batteries are heavy and hard to handle, but I pull them off the bank in pairs to check them out. I stick a 2" wide piece of painter's tape to the top of the battery and record the at-rest voltage of it on the tape with a marker. I check the electrolyte level in the cells, and check the SG of each cell with a hydrometer and record it on the tape. I then apply a 50 amp load to the battery with my Sun AVR for one minute and record the loaded voltage that it shows after one minute on the tape. If the battery checks out it goes back online.
When I serviced my bank in September 2011 I had the batteries hooked up this way:
[attachimg=1]
What I found was batteries all over the place on SOC. Some of the batteries varied from others by up to .28 volts at-rest and the ones with low at-rest voltage fell flat on their face during the load test.
After servicing all the batteries I sat on my upside down five gallon pail staring at the bank while drinking a beer and decided this is not good. I got 12 series connections in the bank and 24 cables going from the bank to the bus. No two batteries are ever identical. But the challenge is, when you connect them series, just how do you determine which ones are matched so they stay even during charging and discharge?
So I changed all the bank wiring around to this:
[attachimg=2]
I eliminated 12 cables from the bank to the bus. I eliminated 6 series connections in the bank. I figured, what the heck - with pairs in parallel like that, and connecting two pairs in series, maybe it will stay balanced better. It's worth a try.
I got a little behind on my bank servicing this last time with the holidays and stuff. I just got it done yesterday, for the first time since I had changed the wiring around. It worked! The furthest off any two batteries were in the entire bank was .04 volts this time. They all tested 1.270-1.275 SG, and all load tested so close to identical that it's not even worth mentioning or recording the difference between any two.
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Chris
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Are you sure about that second battery diagram ?
It looks like some of the batteries are shorted out . . .
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Are you sure about that second battery diagram ?
It looks like some of the batteries are shorted out . . .
They are not shorted, they are in parallel series. Equal to
l-- + 24v buss bars - ----- i
l l
l l
l --- + 12v group - - l l
l l l
l l l
l l l
l- +12v group - - l -- l l
l l
l l
l - l -- + 12 v group - --i l
l l l
l l l
l l l
l l l
l -- + 12 v group - -- l --l
that. IF it worked.
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Are you sure about that second battery diagram ?
It looks like some of the batteries are shorted out . . .
Yep. It works. You take two batteries and make one big one with parallel connections. Then hook the parallel groups in series.
My theory on why it works better is because batteries in parallel tend to support one another even if they're a little bit different. Series connections between batteries are always bad because if, for instance, the charging voltage is 30 volts and one battery is at 14 volts, the other will be at 16. The one that's "lazy" gets deficit charged and the other one gets the snot boiled out of it.
By grouping the batteries in pairs with the parallel connections it must've eliminated the problems with slight mismatch between batteries that tends to show up more with series connections.
I thought about doing groups of three in parallel. But then I would only have 8 cables from the bank to the bus instead of 12 cables. It's 9 feet from the bank to the bus and my inverters draw 720 amps @ 24 volt nominal at full load. With 12 cables I can get by with 1/0 from the bank to the bus, as each cable only carries 120 amps. If I used a triple parallel configuration, then each cable would have to carry 180 amps and I'd have to use 2/0, and I'd still get more voltage drop to the bus than I do with the 1/0 and 12 cables.
I got 4/0 cables from the bus to each inverter, but those are only 6 feet long.
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Chris
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My theory on why it works better is because batteries in parallel tend to support one another even if they're a little bit different. Series connections between batteries are always bad because if, for instance, the charging voltage is 30 volts and one battery is at 14 volts, the other will be at 16. The one that's "lazy" gets deficit charged and the other one gets the snot boiled out of it.
I have the feeling we have been over this before, but everything I have ever read by solar installers and people who have been working with batteries for over 20 years, recommends the opposite. I have heard that it is parallel strings tend to stray in their SOG and that this tendency is reduced if one has a single string of big old honkin 2V cells.
Isn't a 12V battery just a series string of six 2V cells? Why are 6 2V 100ah batteries in series bad but a single 12V 10 ah battery in parallel with nine others good? Do all ten of those parallel strings really support each other?
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I have the feeling we have been over this before, but everything I have ever read by solar installers and people who have been working with batteries for over 20 years, recommends the opposite
That's because they like to sell batteries :)
I don't care what they say. I'm going to go with what works and keeps my bank balanced.
Why are 6 2V 100ah batteries in series bad but a single 12V 10 ah battery in parallel with nine others good?
Probably because you don't have to deal with voltage drops and resistance across cables when all the cells are in one unit. And being that all the cells in a multiple cell battery are the identical same age, and they were manufactured under the same "batch" or "lot number", they are closer matched to one another.
You only have to look in the automotive world to see that series connections are not good. The Toyota Land Cruiser with its 24 volt system - nothing but constant problems with trashed batteries in those. Google it on the internet and you can read about it on all the forums where guys are always coming up with new schemes to prevent smoked batteries in their Land Cruisers.
On the other hand, look at Class 8 semi rigs that have 4-6 12 volt batteries in parallel - you rarely see battery problems in heavy trucks. And when one does go south, you only have to replace the bad one, where with a 24 volt system you have to replace them both if one goes bad or it will very shortly smoke the new one because it runs at higher voltage than the old one.
So like I say, I go with what I see works. I don't like series strings of any sort of batteries because all it takes is one failed battery in the string, and you are in for a constant headache and battle keeping that string balanced from that point forward unless you replace the entire string. With parallel configurations you can put a 50 ah battery in parallel with a 225 ah, and it works fine with not a single problem.
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Chris
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I have the feeling we have been over this before, but everything I have ever read by solar installers and people who have been working with batteries for over 20 years, recommends the opposite
That's because they like to sell batteries :)
I don't care what they say. I'm going to go with what works and keeps my bank balanced.
Why are 6 2V 100ah batteries in series bad but a single 12V 10 ah battery in parallel with nine others good?
Probably because you don't have to deal with voltage drops and resistance across cables when all the cells are in one unit. And being that all the cells in a multiple cell battery are the identical same age, and they were manufactured under the same "batch" or "lot number", they are closer matched to one another.
You only have to look in the automotive world to see that series connections are not good. The Toyota Land Cruiser with its 24 volt system - nothing but constant problems with trashed batteries in those. Google it on the internet and you can read about it on all the forums where guys are always coming up with new schemes to prevent smoked batteries in their Land Cruisers.
On the other hand, look at Class 8 semi rigs that have 4-6 12 volt batteries in parallel - you rarely see battery problems in heavy trucks. And when one does go south, you only have to replace the bad one, where with a 24 volt system you have to replace them both if one goes bad or it will very shortly smoke the new one because it runs at higher voltage than the old one.
So like I say, I go with what I see works. I don't like series strings of any sort of batteries because all it takes is one failed battery in the string, and you are in for a constant headache and battle keeping that string balanced from that power forward unless you replace the entire string. With parallel configurations you can put a 50 ah battery in parallel with a 225 ah, and it works fine with not a single problem.
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Chris
Have a question for you Chris regarding the 50ah battery paralleled with the 225ah battery.
If, in equalize mode, that smaller battery is being cooked because the voltage and time required to equalize the larger battery.
Got any thoughts?
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Maybe you're on to something, Chris? :)
If you take LiIon batteries, you won't find Series/Parallel strings; only Parallel/Series (Parallel cells to get the amp up, then Series to get the voltage). (Ok; LiIon are different beast, but...)
Maybe 'A Truth' are about to be rewritten? ;)
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I guess this is Parallel/Series as well and I've had better luck with this arrangement. But, I didn't document why I changed from the previous drawn arrangement.
( + ) 24v buss bar ( - )
l l
l l
l l -- (+) 12v group - ---- + 12v group - --l l
l l l l
l _l l_ l
l l
l l
l -- (+) 12v group - ---- + 12v group - --l
I keep the cable lengths the same for the y connections and the interconnects.
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If, in equalize mode, that smaller battery is being cooked because the voltage and time required to equalize the larger battery.
It doesn't appear to. Last fall when I put the boat away I took both batteries out of it and put them in series on my bank and hooked them up to the bus. I figured it was better to use them and maintain them that way than leaving them in the boat.
They're just little Group 27 deep cycles - 95 ah.
I have monitored those quite regular because they're not in a battery case, and they seem to be doing fine alongside those big suckers. I've equalized the bank with them hooked up and they boil good, but they have never taken any water yet after being on there for close to three months.
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Chris
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Thanks Chris, I've been a bit too afraid to give that a real go cuz I'd read where it may be disastrous.
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I also place my boat deep cycles inline with my battery bank on the inverters charger. I have never had a problem even with a controlled equalization
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I know. I've read the same thing. But in parallel it seems that the internal resistance of the battery determines how many amps it's going to draw during charging at a set voltage. The smaller battery must increase its internal resistance as SOC comes up so the larger one draws a bigger proportion of the amps going to them. At least that's what it appears to do.
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Chris
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I also place my boat deep cycles inline with my battery bank on the inverters charger. I have never had a problem even with a controlled equalization
I should've mentioned that the batteries in my boat are 2005, so they're 7 years old this coming spring. I've put them on the bank every single year instead of leaving them in the boat. They're still like new. I got an older Minnkota (I think it's a 565) trolling motor on the boat and I can troll at the lowest setting for an afternoon and evening of walleye fishing for 8 hours steady and the trolling battery never drops below 12 volts. That would be about 50 amp-hours out of the battery, and I consider that pretty good for (what was last summer) six year old batteries.
Early last June my wife and I were fishing on Cedar Lake and found a school of walleyes off the edge of a sunken island and we had so much fun we didn't quit until about 1:00 AM. So I fired up the old Merc 40 four cylinder and headed into the landing. It was like a five mile run up the lake to get to the landing. Got 'er up on plane and we were enjoying the night run up the lake when the motor quit about 2 miles from the landing. The frickin' reed valve block that goes around the crankshaft between cylinders #2 & 3 busted. So I raised the outboard out of the water, dropped the trolling motor in, threw 'er in high and started out for the landing on electric power.
By golly, that six year old battery got us there, but it was not fast.
What was really funny was that my wife figured since we're "trolling" might as well throw a bait in the water and drag it. About 200 yards from the landing she caught a rock bass and that little sucker fought so hard she figured she had the Monster Walleye on the end of the line ;D
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Chris
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Have a question for you Chris regarding the 50ah battery paralleled with the 225ah battery.
If, in equalize mode, that smaller battery is being cooked because the voltage and time required to equalize the larger battery.
I'm not Chris, but we do it all the time.
85, 120, a few pairs of golf cart 6V 220, maybe an 8D sometimes. No problems.
I should've mentioned that the batteries in my boat are 2005, so they're 7 years old this coming spring. I've put them on the bank every single year instead of leaving them in the boat. They're still like new.
I am kind of confused about that.
Are these in the 24V system the new batteries with the gawd awful high voltage and long duration equalization routine?
dropped the trolling motor in, threw 'er in high and started out for the landing on electric power.
By golly, that six year old battery got us there, but it was not fast.
Yikes.
Slower is more efficient in that situation.
With six year old batteries at 1AM, I'd have been running at about half the peak MPH.
Still slower, but a better chance of getting back with dry oars.
I HATE rowing.
Had to row up wind with a broken oar and a net.
Actually had to do it twice in the same week.
(different boat, different broken oar, different Chinees Merc, different lake, same net)
The only thing that would have been worse was doing it at 1AM.
Yup, I HATE rowing.
G-
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I am kind of confused about that.
Are these in the 24V system the new batteries with the gawd awful high voltage and long duration equalization routine?
Yessir. They do not seem to mind it at all. They don't get excessively warm when I equalize, and I have not had to add a single drop of water to them. I've checked the voltage on each individually during equalization and they stay within about .05 volt of one another running at 16.0 volts (Edit: just to clarify this is at 32.0 volts with the batteries in series).
After they cool down they go back to work with the rest of them and I have just not noticed a single thing going wrong with them. With their age, those 16 volt equalizations might be doing them some good and maybe get another season out of them yet :)
Yikes.
Slower is more efficient in that situation.
With six year old batteries at 1AM, I'd have been running at about half the peak MPH.
Still slower, but a better chance of getting back with dry oars.
Well, I still had the starting battery I could revert to if the main one went dead :)
I restored this Backtroller 14 a few years back:
[attachimg=1]
[attachimg=2]
[attachimg=3]
[attachimg=4]
It's my favorite boat of all time. When I tore the engine down to put the reed block in it I worked a little magic on the ports to improve cylinder scavenging and increase the port timing a bit. Let's just say it's a pretty "strong" 40. It goes about 44 mph with a 12" pitch prop on it.
It's the best walleye boat you could even imagine and we've taken it to Canada behind our fifth wheel camper countless times.
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Chris
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I seem to recall your battery guy telling you no other battery would survive that kind of eq charging?
And you agreeing with him?
My favorite boat only happens when it's the only boat on the lake.
Then again, my LEAST favorite boat on the lake is a boat with a Chinkineese Merc, even if it is the ONLY boat on the lake.
(can't find the pics)
Not a 5th wheel within 100 miles of here, and thats maybe 5% of the lakes areas...
Notice there are no wakes, because I was not there yet...
(http://cathiehilston.com/Images/hilston_firstlook.jpg)
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Seems maybe my question was too vague or general. I assumed maybe that the suggestion of putting one battery of 45ah ( 12v ) in parallel with one group of 1000ah batteries ( 12v ) might cause problems. What I didn't consider was balancing, or not, the other now unbalanced 12v battery group since I assumed they were in parallel series to make the 24v system. I had guessed the now smaller group would be in absorption longer than required because the time taken for the now larger group to complete each cycle/phase of charge. By amp hour capacity, it seemed to me the then larger paralleled group would require more amperage at the same voltage to get through those cycles. And due to the now resistance difference of the groups.... Anyway, thank you for your answers.
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I seem to recall your battery guy telling you no other battery would survive that kind of eq charging?
And you agreeing with him?
Well, like I said those batteries are old in marine deep cycle years. I suspect if they were newer they wouldn't like it too well. They're not getting worked as hard on my battery bank as they would if they were in the boat and I think they've gone thru two equalization cycles since I put them on there last fall.
So I dunno. If they fail I'm not out much. They have served well. But they sure seem to be thriving for right now.
Seems maybe my question was too vague or general. I assumed maybe that the suggestion of putting one battery of 45ah ( 12v ) in parallel with one group of 1000ah batteries ( 12v ) might cause problems.
Again, Watt - I just have not seen it make any difference. Based on what I've seen I'm going to say it's perfect "safe" to put batteries with different ah capacity in parallel groups. I'm sure some battery manufacturer might have a fit over it and say it's the worst thing ever to do that. But I have to go by what I see that works. :)
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Chris
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I bet you are right Chris. Seems some of us get too wrapped up in what we read. Sometimes a feller has gotta just get'r done. Thanks again.
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Just for giggles I went and took a photo of those two boat batteries and checked their voltages. I have them in a plastic tub in case one would explode or something.
[attachimg=1]
[attachimg=2]
The inverters were pulling 82 amps at the time I took the photos and the wind turbines were putting out 27 amps. So the net load on the bank was 55 amps. Theoretically each battery in the bank (26 batteries including these two) should be delivering 4.2 amps. I don't know if this pair is or not. I suspect not because I got them hooked up with a piece of 10 gauge extension cord with a 30 amp fuse on it. Being these are way smaller their voltage will drop quicker than the big ones under load, so they don't put out as much amps as the big ones, I don't think.
But even so, this is where they always seem to run - about .04 volts difference from one another.
The first six years of their life they get worked pretty hard in the boat all summer. The boat has a built-in Minnkota dual channel battery charger so they always get recharged right away when the fishing is done. The Minnkota unit absorbs them at 14.4 volts but it has no temperature compensation on it. For summer time temps, that's probably a good voltage for them.
When I put them on my bank in years past, we had a 12 volt system back then. I used to absorb at 14.5 and equalize at 15.0 so they endured 5 years of that during the winter, many times being worked harder than in the boat.
If I end up getting 8-10 years out of these cheap $65 batteries then I'm going to conclude that the early demise of most deep cycle batteries is caused by inactivity and/or being undercharged. The last thing that's happening to these poor old things is being underchanged harnessed up with my Surrettes, at the voltages I run those at. I absorb the Surrettes at 30.0 and equalize them at 32.0 (temperature compensated).
So lets consider it The Experiment. LOL! As of right now, these old batteries have endured unbelievable pounding in the boat making fast runs on rough water, get pulled down to 50% or below on average 3 times a week during fishing season for six years, have been worked on my battery bank every winter since new, and they still appear to me to be pretty dang healthy.
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Chris
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I assumed maybe that the suggestion of putting one battery of 45ah ( 12v ) in parallel with one group of 1000ah batteries ( 12v ) might cause problems. What I didn't consider was balancing, or not, the other now unbalanced 12v battery group since I assumed they were in parallel series to make the 24v system. I had guessed the now smaller group would be in absorption longer than required because the time taken for the now larger group to complete each cycle/phase of charge. By amp hour capacity, it seemed to me the then larger paralleled group would require more amperage at the same voltage to get through those cycles.
The bold part is correct.
The spin implied is often published on the internet, but it is incorrect.
Theoretically each battery in the bank (26 batteries including these two) should be delivering 4.2 amps. I don't know if this pair is or not. I suspect not because I got them hooked up with a piece of 10 gauge extension cord with a 30 amp fuse on it. Being these are way smaller their voltage will drop quicker than the big ones under load, so they don't put out as much amps as the big ones, I don't think.
But even so, this is where they always seem to run - about .04 volts difference from one another.
Theoretically, it is all completely incorrect, except that the #10 may cause a voltage difference due to current flowing (in either direction). At rest, they will be the same voltage.
This was known, and published, 20 years before Lincoln was shot.
Or about when the percussion cap was introduced to replace flintlock firearms.
get'r done?
Lets connect a 1000AH 12V battery in parallel with a 0.6AH 12V battery.
Lets run a 500W 12V load.
So the 0.6AH battery will be down to 11.9V before the 1000AH battery is down to 12.6V?
Think about it.
G-
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Theoretically, it is all completely incorrect, except that the #10 may cause a voltage difference due to current flowing (in either direction). At rest, they will be the same voltage.
This was known, and published, 20 years before Lincoln was shot.
I don't know what Lincoln has to do with it, but my bank is NEVER at rest. It is under load, or being charged, 24 hours a day, 365 days a year, unless it is disconnected for service.
Those boat batteries will (obviously) always stay at bus voltage, plus the voltage drop in the 10 gauge wire. What I was talking about was the amps they have to deliver to meet the 55 amp net load when harnessed up with the big ones. With 26 batteries, and all are the same size, every battery is delivering 4.23 amps to the load. I don't know what the actual load is on this pair when I took the photos, but I know it's less than the big ones because they're smaller.
And that's why you can put batteries of unequal capacity in parallel and it don't make one bit of difference. And taking it one step further, you can put series pairs like this in parallel with bigger series pairs and it still don't make any difference. If you go to some "battery expert" and suggest that he'll probably start babbling about how you can't do it or you'll wreck them all. Well .... I'm doing it and it don't wreck anything. What WILL wreck them in short order is having unmatched batteries in series.
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Chris
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I was telling people it would not hurt anything, and I was doing it many years before you had a 24V battery.
Theoreticallyeach battery in the bank (26 batteries including these two) should be delivering 4.2 amps. I don't know if this pair is or not. I suspect not because I got them hooked up with a piece of 10 gauge extension cord with a 30 amp fuse on it. Being these are way smaller their voltage will drop quicker than the big ones under load, so they don't put out as much amps as the big ones, I don't think.
THINK about it.
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So the 0.6AH battery will be down to 11.9V before the 1000AH battery is down to 12.6V?
Think about it.
G-
How could a little battery be at 11.9 volts when it is connected to a 1000ah bank running at 12.6 volts ?
Isn't the whole system running at the same voltage ?
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So the 0.6AH battery will be down to 11.9V before the 1000AH battery is down to 12.6V?
Think about it.
G-
How could a little battery be at 11.9 volts when it is connected to a 1000ah bank running at 12.6 volts ?
Isn't the whole system running at the same voltage ?
That's what I said!
Apparently almost 2 centuries of physics no longer applies.
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Or put simply.....
All things in parallel will have the same terminal voltage. (where they meet the parallel connection points)
All things in series will carry the same current.
..............oztules
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So the 0.6AH battery will be down to 11.9V before the 1000AH battery is down to 12.6V?
Think about it.
G-
How could a little battery be at 11.9 volts when it is connected to a 1000ah bank running at 12.6 volts ?
Isn't the whole system running at the same voltage ?
That's what I said!
Apparently almost 2 centuries of physics no longer applies.
ghurd... So, for the simple guy, what are you saying?
If the " think about it " statement was to be answered by me, I'd say the batteries would be equal in voltage depending on the size of wire to it and current.
My question was about the voltage and time at that voltage. Will the time it takes to bring the larger batteries from bulk to absorb and from absorb to float and from say float to equalize matter if that little battery is in series with a 1000ah group. I know I wouldn't want to keep a .6 at 16v for 2 hours. But, maybe I should.
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My question was about the voltage and time at that voltage. Will the time it takes to bring the larger batteries from bulk to absorb and from absorb to float and from say float to equalize matter if that little battery is in series with a 1000ah group.
Watt, what I have seen is that it doesn't make any difference. Equalization is a process where you overcharge the battery until the SG of the individual cells stops rising in relation to one another. If the smaller batteries actually need equalization, then it will take the same time as the bigger ones. If they don't need it, then disconnect them.
But the same applies to your big ones. That's what they make battery hydrometers for, and why it's not usually recommended to run automatic, unmonitored equalization charges. You should be checking and recording SG during equalization, and quit when the SG stops rising in the low cells.
As far as absorbing those batteries at 30.0 volts (15.0 each), I have seen zero problems with that. I haven't had to add a single drop of water to them, nor do they get excessively warm. If they were actually being overcharged by absorbing at 30.0 volts, they would take some water by now.
My Surrettes take a little water from service to service, but not much. A few cc's per cell is all I've ever added at every service. But they don't have those "maintenance free" caps on them like the boat batteries do that are designed to minimize water loss.
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Chris
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Hey Chris
I feel you have answered my questions and I don't want to make it sound like I was arguing or didn't believe you. I do, believe me, believe you and appreciate your experience. I do have my reservations regarding a big battery in parallel with a little battery but I will overcome that once I just do it and see what my results are.
Thanks again for all your detailed help Chris.
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I feel you have answered my questions and I don't want to make it sound like I was arguing or didn't believe you. I do, believe me, believe you and appreciate your experience. I do have my reservations regarding a big battery in parallel with a little battery but I will overcome that once I just do it and see what my results are.
Oh, not at all. I had reservations about putting the boat batteries in series and parallel connecting them to the bank. I know I read someplace, but don't remember where I seen it, that you just "can't do that". But when it says, "WARNING - do not push any buttons - especially the last one" I will typically push them anyway, and start out with the last one, to see what happens ;D
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Chris
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" But when it says, "WARNING - do not push any buttons - especially the last one" I will typically push them anyway, and start out with the last one, to see what happens ;D "
I do believe this fits you well.... :P
Thanks again Chris.
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To see what happens with a small battery and a larger battery in parallel; why not connect them together with an amp meter between each, and load/charge/equalize them? An easy enough test, and it will put many of our minds to rest... ;)
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To see what happens with a small battery and a larger battery in parallel; why not connect them together with an amp meter between each, and load/charge/equalize them? An easy enough test, and it will put many of our minds to rest... ;)
I think I was more concerned with heating the little battery too long. But, I guess my IR heat gun would answer my question easier than anything.
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I was also interested in the amp draw. I always put my boat batteries in parallel with my bank also. I have never seen a problem yet,and they are going on thier 9th year .. I'm rather amazed at how long they have lasted given the abuse I put them through. But these are golf cart batteries also ..
I have never monitored them myself, never even thought about it. I figured it HAS to be better than letting them go dead, or worse.. freeze.
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They should never freeze if they're charged until it gets down to -70. Of course, if you're anywhere close to International Falls that could happen :)
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Chris
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The lowest temp last night here in Norway was -44deg C... :(
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@ Chris. exactly my point. If I don't keep them on something to keep them charged they lose charge on their own, and will freeze in Minnesota temps.
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I put a little 19 watt Coleman solar panel on the roof of our 5th wheel RV a couple years ago and that works pretty good to keep the battery up in that. I got the picnic table sitting by the camper so I can reach the roof and sweep the snow off that little solar panel.
I was in the camper the other day to grab a stainless frying pan out of it that my wife wanted. So I pressed the "test" button on the "Command Center" in the camper and it showed the battery at 12.62 volts. The last time we used it was in September when we took it to Canada. That little solar panel only puts out about a 1/4 amp most days in the winter, but it's enough to keep the battery up.
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Chris
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Back when I was starting this journey through the wastelands of RE, I studied up on batteries and read anything I could find on them. Most helpful (then) was RV and boating crowds. Solar and wind were kind of fringe stuff then. Mostly folks "selling" and not much historical data on the RE installations and long term battery health.
I got a lot of my battery "attitude" from the Blue water sailors. Their stuff has to work. Period. Can't pull over at the roadside battery mart any time you want on the high seas for a replacement.
A lot of what they did was not according to manufacturer specifications. Things like a bit higher voltage for float charging and numerous other little bits that I follow yet today but will not get into lest I set off a battery abuse intervention by some user(s).
I have routinely mixed sizes in parallel but would NOT do so in series. I figure they are both a source and a load and simple DC electric theory 101 tells me they will see exactly the same voltages (discounting cabling losses) and will draw or deliver the amperage it is capable of into or from it as if it were in the same situation alone if the load is X volts and Y ohms you get Z amps. The confusing bit is the big boy bank holds the voltage up and this seems to just put the baby battery into a form of stasis where it does not have to provide any current because the big boy is pushing the amps into the load until a point where the voltage is low enough that the little one can shove some amps and so on and so forth. They just act like any source or load in parallel because, ultimately that is what they are. Curiously enough at the same time sometimes.
Hope that was as clear as the mud spattered rear window on the Dakota!
Some of the seemingly complex puzzles are just as simple as this.
No quantum physics.
Loads and sources.
Thevenin would be proud of me ;=>
Or say **Cough**BULLSHIP**Cough**
That is my take on morphodite battery combinations.
There you have it so have a blast showing me I am full of it.
Same voltage batteries, obviously.
Tom
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I'm not even convinced that the same solution works the same in different environments.
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I am mostly with Tom on this.
However Ross brings an interesting aspect to the mix. Environment, in my area could be interpreted as temperature of the bank.
Here if say its that batteries are in a colder area, or if or all are in a cold area, it may be that smaller batteries would be colder not having the mass and not have a normal internal resistance if under light use. Under heavy use they may be the warmer of the bunch This would make a big difference on its draw and capacity, but would it make a difference on its overall voltages?? It is not anything I would worry about, but it becomes an interesting exercise trying to calculate the variables.
I have no idea..
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I am mostly with Tom on this.
However Ross brings an interesting aspect to the mix. Environment, in my area could be interpreted as temperature of the bank.
I meant "environment" in the fullest extent of the word.
How hot or cold it is. How far down it gets drawn, and how quickly. How long it remains discharged. How quickly and how hard it gets recharged. If it's a pulse charge or a heavily smoothed and filtered charge. How much rest they get along the way.
For example: I know my batteries behave differently when being charged from the hyper-smooth DC from the PV compared to the "ripply" charge from my turbine. I know they behave differently over winter to summer - even though their temperature remains only a few degrees different (being burried 15' underground sees to that). But in summer they spent far more time in float, get discharged less overnight, get recharged earlier the next day. However in winter they get a much faster charge (from the genset) - put puts the same amphours back in, but they don't seem to "hold" the charge as well as if they get it more slowly and can "digest" it better.
Nothing I've measured and/or tried to quantify, just what I've observed.
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However in winter they get a much faster charge (from the genset) - put puts the same amphours back in, but they don't seem to "hold" the charge as well as if they get it more slowly and can "digest" it better.
I've noticed the same thing. A genset charge don't last near as good as a long "soak" with the turbines and solar panels. I don't know how yours works, but mine bulk charges and absorbs, then the inverter shuts the generator off. I have the absorb "done point" set at 2% of ah capacity of the bank, which is what the manual recommended. But I don't think the batteries are "quite there" yet at that setting and they require several hours at float to really get fully charged up.
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Chris
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I've noticed the same thing. A genset charge don't last near as good as a long "soak" with the turbines and solar panels. I don't know how yours works, but mine bulk charges and absorbs, then the inverter shuts the generator off. I have the absorb "done point" set at 2% of ah capacity of the bank, which is what the manual recommended. But I don't think the batteries are "quite there" yet at that setting and they require several hours at float to really get fully charged up.
Years since I set mine, so I'm working from a combination of memory of the original setup, plus the odd tweek since.
The inverter will call for the generator to run in a multitude of events. The only relevant at the moment are:
(a) if the voltage falls below (x)
or (b) if the amphours discharge is more than (x)
or (c) it's within (y) hours of the generator going into "night lock" and the batteries are discharged more than (z) AH
or (d) the generator is in "night lock" but the volts dropped below (z)
or (e) the generator is in "night lock" but the amphours are more than (y)
Once it's started, it will run for a minimum of 1 hour. If there's no other reason for it to turn off, and assuming there isn't more renewable comming in than some set limit, and assuming the total load is less than some other set limit (sounding like a nightmare to document already!), then it will continue to run until the voltage reaches the "absorb" setpoint, at which stage it goes into the absorb charge stage, which it will do until it gets to the "float" threshold. Then it goes into the "float" charge mode and will hold there for a set time before it turns the generator off.
It's very inefficient to run the generator just to hold the cells in float for 2 or 3 hours, so it usually drops the generator fairly quickly - I think I have it at 30 mins of float.
Even so, I think that 100 amphours of generator charge "holds" the batteries for less time than 100 amphours of solar charge does, assuming neither of them actually gets the batteries to float.
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It's very inefficient to run the generator just to hold the cells in float for 2 or 3 hours, so it usually drops the generator fairly quickly - I think I have it at 30 mins of float.
Yes, when the generator starts because of an automatic start setting, I have float disabled to save on fuel, so it shuts it off as soon as absorb is done. If I would enable that and let the generator float the bank for an hour or so before it shuts off, it would probably be better (for the batteries). But I set a goal for this year to cut our gen hours in half for 2012 over what we ran in 2011. So floating the batteries with the generator is not going to help me meet my goal :)
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Chris
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Back when I was starting this journey through the wastelands of RE, I studied up on batteries and read anything I could find on them. Most helpful (then) was RV and boating crowds. Solar and wind were kind of fringe stuff then. Mostly folks "selling" and not much historical data on the RE installations and long term battery health.
I got a lot of my battery "attitude" from the Blue water sailors. Their stuff has to work. Period. Can't pull over at the roadside battery mart any time you want on the high seas for a replacement.
A lot of what they did was not according to manufacturer specifications. Things like a bit higher voltage for float charging and numerous other little bits that I follow yet today but will not get into lest I set off a battery abuse intervention by some user(s).
I have routinely mixed sizes in parallel but would NOT do so in series. I figure they are both a source and a load and simple DC electric theory 101 tells me they will see exactly the same voltages (discounting cabling losses) and will draw or deliver the amperage it is capable of into or from it as if it were in the same situation alone if the load is X volts and Y ohms you get Z amps. The confusing bit is the big boy bank holds the voltage up and this seems to just put the baby battery into a form of stasis where it does not have to provide any current because the big boy is pushing the amps into the load until a point where the voltage is low enough that the little one can shove some amps and so on and so forth. They just act like any source or load in parallel because, ultimately that is what they are. Curiously enough at the same time sometimes.
Hope that was as clear as the mud spattered rear window on the Dakota!
Some of the seemingly complex puzzles are just as simple as this.
No quantum physics.
Loads and sources.
Thevenin would be proud of me ;=>
Or say **Cough**BULLSHIP**Cough**
That is my take on morphodite battery combinations.
There you have it so have a blast showing me I am full of it.
Same voltage batteries, obviously.
Tom
Thanks, I guess ???
How about you share some of that " controversial " battery information you know. ;D
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Even so, I think that 100 amphours of generator charge "holds" the batteries for less time than 100 amphours of solar charge does, assuming neither of them actually gets the batteries to float.
I agree totally.
#1. Git'r done. I see it in real life.
#2. Science. The Peukert Effect works both ways.
How about you share some of that " controversial " battery information you know. ;D
It is not controversial in most circles.
Kirchhof and Peukert stuff is over a 100 year old news. Thevenin stuff is too.
simple DC electric theory 101 tells me...
Me too.
It is as basic as a higher voltage system is better for a higher power system, better batteries than 12V marine from wally-word are better for a higher power system, and fancy eBay Chinese inverters without a known brand name are junk.
But tomw, you knew that more than a decade ago.
Me too.