guess who bought a power jack inverter

[oztules]

Good to see it work... make sure you give it a work out early on.
The problem as I saw it was where we were in the sine wave when we turn the AC off.
If we are at the peak of a wave, then all will be fine, as the inrush current to support the magnetising current will be normal.

If we get to turn it off at zero crossing, then surge current will be at max. This is where massive current can occur... not at sine max, but at zero crossing.... just where you thought it would be safest to turn on the inverter wave form.

Thats why testing it over a reasonable number of times to see if it blows early in it's life to get the warranty in the first week or so.

If  after say 20 on/off cycles, all is good, there is a good chance you have been near or at zero crossing,and everywhere in between, so will all be good.


Voltage switch is a simple comparator to a relay to initiate start, and use alternator voltage ( from motor alt, not the big alt) to indicate engine started or oil pressure if it has a pump to end start procedure.

But others with experience of generator turn ons may have other things more important... like AH meterage instead. I don't have nor will have auto generator support.... so I would not know, but state of charge is best done with AH out measurements, than battery voltage which is captive to so many variables as to be meaningless on it's own.


...............oztules

[rossw]

Voltage switch is a simple comparator to a relay to initiate start, and use alternator voltage ( from motor alt, not the big alt) to indicate engine started or oil pressure if it has a pump to end start procedure.

But others with experience of generator turn ons may have other things more important... like AH meterage instead. I don't have nor will have auto generator support.... so I would not know, but state of charge is best done with AH out measurements, than battery voltage which is captive to so many variables as to be meaningless on it's own.

"It's complicated" is an oversimplification!

If you know the current discharge rate, you can make an estimate on battery capacity from its voltage - but that has to be informed by monitoring it over time to see how it behaves.

Nett amphours (out-in) will give you a rough estimate, but it needs adjusted  for battery efficiency etc, and that changes over time and temperature, and what part of the charge cycle you're in.

A "moment in time" isn't great either, because a basic system can't anticipate what loads you're likely to apply, or when you'll get charging power, or how long it'll last before it get "urgent".

I use a combination of some smarts in the inverter and a decade of "accumulated gut feel". If we've had poor sun, and/or a lot of demand on power then I'll manually run the generator in the evening even though the batteries "probably don't need it (yet)" simply because I'd rather do it then, than have it start itself at 4am. If I know we're going to have a poor day, I will let the generator run, and then use "extra power" (like doing the washing or running the dishwasher, or the bore pump etc) while it's running just to keep the consumption down during the rest of the day.

The smarts to actually control the generator are pretty straightforward. Sequencing, monitoring temperatures, oil pressure etc, start and stop, all simple. But working out WHEN to run requires a bit more than just a comparator or an amp-hour counter!

[oztules]

...... and if Ross gets them 7kw of panels in the air ...... he won't have to cogitate either.

Put in inverter air con to use the hot days extra power..... just like AofJ.

My system is full every day.

The AH meter has the 750AH in it. It then reads the AH going out overnight. This reverses in the AM, and by 9-10am, it has counted back up to 750..... it counts no further, even though another 15-20% probably goes in after reaching 750. ( so really not "FULL" by 10am..probably 85% or more.... but full by normal usage standards..)

 By days end, it is still on 750... so  it actually just lets me now how many KWH have been consumed overnight. Really crappy days ( 4" rain)  it will eek out the 750 by nightfall, so it has technically recovered the AH used, but does not tell you about the 15-20% loss via chemical processes.... but very rare to have that 2 in a row.... and 80% charge is very  useful too.

If it did not reach full charge each day ( ie 4-5amps@58v is a fair indication) then the AH  would not be terribly useful...... also not useful to tell a motor when to start.... as it never needs it.

So system watching is the best criteria to work out start as Ross suggests.

In a normal RE situation, 1.275sg  (100% full)  is not easy to achieve..... unless you have lots of solar, or an unusually good windmill.... a generator will be running for a long long time, putting in very little current to get there in the last 4-5 hrs



............oztules

ps Ross, it's 9.30am here, misty rain all morning, and yet still running the house, and putting in 14amps.... lots of panel = power in any condition. It's currently showing 714ah.. or 95% recovered. Still got to get to 750, plus chemical losses, but if the rain/mist stops at any point, it will be a shoe in, and even with rain , we will be 750 by 12-1 o-clock.... the rest of the day will finally get the SG up to full I expect.... shocking conditions at the moment, and don't look like changing any time soon.

[OTG]

This thread just keeps giving, love it! 

I've lost the page now, but oztules, I'm curious about your earlier comment about the variable specifications of each unit, depending (it seems) on how much you pay for it (e.g. buy-it-now vs a sneaky pete dying seconds cheaper than dirt bid). I think you basically said that you sniped a cheap bid on a second 8kw LF unit, but the trannies were two 3kw units with the number nikko'd out? And thats not whats's on the inside of your other 8kw unit...

Is that the crux of your experience oz? If anybody else has similar points to share on price vs spec, please do!

And did I also read that they have fixed the standby power issue now? If anybody can confirm this that'd be great.

Reason I ask is;

1) for starters their pricing is all over the shop, and they appear to be running two ebay stores now for some reason... maybe one is to flog off the lesser spec'd units, or perhaps older units that still have the standby issue?
http://stores.ebay.com.au/solarempireinverters
http://stores.ebay.com.au/Power-Jack-Shop

& 2) I want to get a 24v 8kw unit and I'm tossing up on whether to just go buy-it-now or risk lesser spec'd trannies by sniping my own cheap bid to save a few bucks? (Yes I'm a tight arse!  )

PS: I've been using a 24v 5kw LF unit for 6 months now, pretty much issue free. Only issue is it sometimes gives the overvoltage alarm/shutsdown (particularily on sunny days) when the batteries are at full charge round the 28v mark. If I'm quick enough though, I just chuck a few more DC loads on (e.g. 24v lights, radio, etc) to drop the voltage, and the thing soon shuts up and keeps chugging along!  I also found the battery terminals were getting a bit too hot on heavy loads, so I doubled all my cabling (2 x 4AWG 100a) and they never feel hotter then ambient now. So despite the various shortcomings covered in this thread, at the end of the day these little beggars certainly still get the job done!  So my plan is to use a new 8kw unit as my perm/frontline unit for the house/shed and I'm going to repurpose the 5kw unit for a small remote solar setup to power a 240v bore pump I need to get going.

Thanks all!

[off the wall]

I've lost the page now, but oztules, I'm curious about your earlier comment about the variable specifications of each unit, depending (it seems) on how much you pay for it (e.g. buy-it-now vs a sneaky pete dying seconds cheaper than dirt bid). I think you basically said that you sniped a cheap bid on a second 8kw LF unit, but the trannies were two 3kw units with the number nikko'd out? And thats not whats's on the inside of your other 8kw unit...

Is that the crux of your experience oz? If anybody else has similar points to share on price vs spec, please do!
. . . . .
& 2) I want to get a 24v 8kw unit and I'm tossing up on whether to just go buy-it-now or risk lesser spec'd trannies by sniping my own cheap bid to save a few bucks? (Yes I'm a tight arse!  )

In order to help others along the solar and off grid path in England I have been buying and selling PJ inverters on UK ebay for a little while - and because the lady at PJ who deals with me values the business that comes through me, people who buy through me get support that I've found does not come through other sources. I don't do it as a business but to try to help and encourage others. The lady who I buy through has given me a price list on a "trade basis" and the prices are very often higher to me than I see inverters being sold on ebay for . . . .... (go figure . . . ) so this is why it's not a business for me as people buy through the Chinese sellers on ebay because they are cheaper . . . . (go figure . . . .)  The profit I have made on the units I sell has only just about covered the expense of writing off those bad buys from the sellers in China.

Often people make terrible comments on YouTube or other places about the inverters because the Chinese seller they have bought through on ebay has left them in the lurch - and sometimes if they contact me I put them in touch with the lady I buy through and she has been able to sort something out.

Thinking that I was being ripped off buying at prices higher than the ebay sales, I bought a couple of the cheap inverters. One was a 6kW unit in a 6kW case but with only one transformer instead of two, and that was a 5kW transformer with the rating obscured. I bought a 5kW unit which was a 3kW unit with the rating similarly obscured. I think it was certainly a night-shift unit, or a backdoor production line.

So the answer is that if anyone buys a cheap one on ebay they may well be getting a night-shift unit. It's not worth trying to save a few bucks because the sellers that sell the back-door cheap units couldn't care less about customer service.

With regard to the unit cutting out at above 28V this was the old version control boards and the new version is adjusted for the realistically higher voltage. There are two resistors that one can change on the board to adjust the voltage but otherwise one can buy a new control board.

The 8000W unit that I use for part of my house offgrid continues to give good service.

A friend who has an 8000W unit writes to me:

I switch the main switch to the centre position “off” and the start my generator, I then push the switch up to charge the batteries and have 220V power to the boat, but for the past couple of weeks its been reluctant to cut in when I switch up ( or even down) I have to switch on and off maybe 6 or 7 times to get it to click and start charging ? any ideas

Any ideas?

Best wishes

OTW

[oztules]

Hmmmm, I think the only real difference between the cheapies and the normal priced units is the transformers.

If they skimp on the trannies, they will probably have an extra fan in there.. thus technically increasing the power rating of the smaller or lower numbered transformers.

They are what they are.... but better than anything else in the price range by miles... purely because of the transformers.

So yes I did get one unit with 2x 5kw transformers, and one with 2 x3kw transformers with the writing blacked out on those two. the second one had an auxiliary fan to compensate for the smaller transformers...

The boards has been proven to be very very good, and mine have many megawatts under their belts now.... for sheer grunt and no messing around and a near 100% duty cycle, the W7 cannot be beaten as an off the shelfer.... but the 5kwh/day overhead is a problem if your skimpy on panels.... if like me you have far too much power every day, then the W7 would be the best bet, otherwise the PJ , whose ratings are fairly optimistic without a few changes, is superior.

If you do the big transformer add on I do, then you have a very serious unit... eg running the hot water at the same time as a 230 amp mig welder... and the water pump, and the fridge, and big freezer.... they just work....

A friend who has an 8000W unit writes to me:
"
I switch the main switch to the centre position “off” and the start my generator, I then push the switch up to charge the batteries and have 220V power to the boat, but for the past couple of weeks its been reluctant to cut in when I switch up ( or even down) I have to switch on and off maybe 6 or 7 times to get it to click and start charging ? any ideas "

Only thing that will effect this part is the frequency and voltage of your generator if your voltage is too high /low at the right frequency, or the frequency is too low or high at the right voltage range... then it will be hard to get it to stick.

I had a W7 do this once, and it was a spider across the voltage rails... which caused failure soon after....same boards basically.... interchangeable but for the pretty lights on the W7.

Good to see you can help a few folks there OTW.... they are a good deal regardless of what has been said... here or anywhere else.. even the cheapies are fine if you know what your doing, or you bought a unit way over rated for your uses.... QC is always an issue with the cheapies though.

OTW.. do you have any information at all on the overvoltage shut off actually working properly without the zener or resistance changes by the user..and see if you can scare them into using that very nice lcd display for something useful other than the silly price of power....

I see they are also spruking a generator to integrate ... good idea too.




...............oztules

[off the wall]

One the difference between the cheapies and the normal priced units, it's the transformers they skimp upon but on the units I have seen there are no extra fans.

The chap with difficulties with the battery charger reports that it was not the frequency of his generator that was the problem but a capacitor had failed in the genny causing it to drop voltage from 240 volts to below 200. Sorting that problem out solved the battery charging.

Someone has come to me wanting an inverter to maintain freezers during 2- 6 hour power cuts which are happening on a daily occurrence in South Africa at the moment - and so really needing the UPS function. Has anyone had experience of the UPS functioin with mains regular cutting off and being reapplied on a daily basis? And is there any issue with the battery charging in those circumstances?

 Best wishes

OTW

[oztules]

I'll be interested in the replies for this, as my experience is patchy with this setup.

If most folks have a seamless experience, then it must be my massive transformers exacerbating the inrush current problem that would occur normally, but in managable proportions perhaps.... small change to the code here would be wonderful....

As he is running for relatively short periods and on grid when not......... if he can afford the 200w overheads, maybe  the W7 versions would be the better option..... they have leaky ( normal)  transformers compared to torroids.....( massive too.... 40kg or so), and so this lowers the inrush currents .

I have not seen them fail in this condition (ups). Very honest work horses they are.... their 6kw units are 6kw units, their 18000w surge is massive too.... in fact are my choice of inverter if you don't care about magnetizing losses of 5kwh/day.... cant have everything for nothing i guess......... although, if you can use the 5kwh/day of heat generated to advantage ( help warm the room?), then it may not be the disadvantage it seems.


...............oztules

[davidwillis]

I just bought a PowerJack 10,000, and also just found this thread.  This is very interesting, however most of it goes over my head.

I also have a 5kw grid tie system.  I would love to be able to use this inverter with batteries as the grid when or if the grid goes down.  But I have a few question...

1- Do I need to mod anything in order for the inverter to feed back extra power generated to charge the batteries?

2- I just checked how much Power is used with no load, and it is only .4 amps (at 24v).  This does not seem too bad... I wonder if the 10,000 watt powerjack has incorporated your mod?

3-  Are there any relays or switches I could use to turn of my solar panels to my grid tie inverter when my batteries get full?  (sorry if this is somewhere in this thread, I read through most of it, but since most was over my head, I skimmed a little)

Thanks.

[oztules]

.... hmm where to start...
1. No if the grid tie is put on the outputs of the inverter it will run backwards through the transformer and synchronously switch the ac to dc and charge the battery... but with no control. Your point #2 tells us that there is filtering on the transformers, so the grid tie will work.

3.... yes and no........ as a general observation, as the batteries come out of bulk charge, their needs become dramatically less, ie where they may have been charging at 60amps, they will drop down to 10 and much less when they are 90% charged.
The effect of this is that the AC being generated by the grid tie inverter will force the AC voltage higher, and there is an excellent chance the grid tie will drop off of it's own accord because of high AC... thats what happens with mine anyway. I built a battery voltage switch to do this, but found it does it on it's own anyway, so I have two systems to shut down the over charging  that would have occurred if this did not happen one way or the other.,... neat.

If your battery bank is at least500ah@48v, you will be able to charge at 100 amps max... or 5kw or there abouts, but it will soon drive the AC or the battery voltage up too high, and shut down either the inverter (PJ) from high battery voltage ( 61 or 62 ) which is annoying, or high AC which will drop off the grid tie inverter... which will try again in another three minutes etc etc etc.

So a battery over volt switch is really a very good thing to install.

However, once you bring your real grid into this mess, your better not to do any of that!!... they will take a dim view of this.

Your best to run a battery charger and float the batteries until the outage, and carefully use the inverter then.... you should not switch or change the grid tie arrangements from what you were contracted to do originally, or they may kick you off the feedback tariff, or shut your grid tie down if you piss them off enough.

You should have interlocking  isolating switches before you even consider this, as it must be the case that NO power from you can get to the grid from your PJ or any other AC source when the grid is down, or someones death may occur.... very slim, as the impedance of the dead grid will be very very low... but it can happen in the right circumstances..... take note..... this is serious.

However if you have a secondary household circuit not connected to the grid in any way, then you can power that..... or use extension cords and lots of power blocks etc etc...... but don't mess with the grid unless you know what your doing. Normally it is just you who is at risk, but with backfeeding by mistake, it is not just you.

So...
1. don't use your grid tie to inverter to charge the batteries in this case, this is for off grid use... and very useful it is too... but not to be mixed with the real grid.
2. your idle figures are superb...
3. use a charger to float the batteries from the grid. They will be isolated by the transformer ( HF or LF), and will not interfere with your contract with the power supplier, and your grid tie will be driving the grid anyway.... all wins no losses if you use a timer to not charge or not float charge during the night... say only turn charger on between 10am and 4pm etc etc.
4. work out how you are going to use your PJ when the power does go off.


................oztules

[off the wall]

Yes - very comprehensive answer. The only way of coping with circumstances where you might be off-grid on account of a power cut is to take the branch feeding the grid tie system through a rotary double pole double throw switch to connect the grid tie spur either to a grid circuit or to the circuit fed offgrid by the PJ inverter.

Thinking about this, when power is applied to the PJ inverter then that power is fed straight through to the sockets for the output of the inverter. When power goes off, the connexion to the mains is disconnected and the inverter trips in. So if the grid tie circuit is connected to the output of the inverter, and mains is connected to the input, then when there is mains the grid tie will feed into the mains and when there is no mains, it will feed back into the batteries through the PJ

Am I thinking unclearly here and have missed something glaringly obvious why this might pose a problem?

Best wishes

OTW

[davidwillis]

Thanks that is very helpful.

Just a few more questions...

1-  I am not sure what interlocking  isolating switches are, however I do have a large 300A disconnect switch that will disconnect my entire house from the grid.  I figure this should be safe, however I will not know when the grid comes back up, so I may add a light or something on the other side of the switch...

2- How do you work the battery voltage switch?  I was thinking about putting a relay switch (normally closed) on the output of the grid tie inverter, then have some sort of controller that will open that relay when the voltage on the batteries get past the bulk stage (I would probably have to play around with it a little to get a good set point).  I really have no idea what to use for this right now though.  But I would like to leave my pj on when the batteries are charged. 

3- is 100 amps the max?   My PJ is a 24v, and I was thinking of adding about 1200 ah at 24V.

4- I tried using my charging by plugging in the pj to 110 power (this would be used for when the grid is up, without the output of the pj connected to anything, just using the pj as a charger).  But it did not do anything, and the instructions were not clear on this.... is it better to use a separate charger to keep the batteries full while the grid is up?

p.s.  This is really exciting!!!

[davidwillis]

I have been thinking about this more.  I wonder if there is a way to make a controller that will add resistance to the incoming solar panels to the grid tie inverter (make it think there is less sun out) when the batteries begin to fill up.  This way we could get a "float charge" to maintain the voltage until a point where the grid tie inverter shuts off when the batteries are full (the inverter would think the sun went down).

If that is not possible, we could setup some normally closed relay switches on each string of solar panels, and turn one off at a time until they are all shut off... My 5kw grid tie inverter only has two strings, so it would not be as good as gradually turning it down, but better than nothing...

[off the wall]

It's an interesting thought. But the problem is that switching high voltage DC is not something one wants to switch with a relay - the arc is spectacular. Whilst wiring up a new set of panels it's great fun (potentially lethal of course) to connect them up with bare wires and to short them together and take them apart, the arc becoming a flame often 1/2 inch long and melting the wire insulation further along. Of course I only do this having taken the panels to the switch and then before connecting switch into the grid tie inverter but very seriously 250-300V of DC can kill, and it's really for that reason why the string is taken straight into the GT inverter without meddling in any way with it.

Playing with 24V of course is perfectly safe other than handling the high currents involved on a larger power load.

Best wishes

OTW

[davidwillis]

Yes, I understand the issue with dc.  That is why I originally thought to just switch off the AC power to the inverter.  But It looks like there is a way to do it...

http://www.power-io.com/california/

However it would be even better if we could get some type of potentiometer that could turn down the solar panels gradually until the inverter just shut off.  I would guess this would need to dissipate some serious heat thought, and I don't know of any product that can do it.