Group 24 cells

[Burgerman]

Well I have it!
I dont use it though.

I either drop all the files in a folder on the desktop, and just run setup from inside windows.
OR
I put the same files on a bootable MACRIUM bootable disk, and run setup.
OR
I use the strellec bootable USB.
OR
I just clone a current working windows drive to a USB SSD drive and boot from that into windows and install it to the C drive from that.

Theres a lot of ways. The ISO way isnt really needed unless you are doing some odd virtual thing. Why would you do that? LTSC is better anyway!

[jefferso]

I just started the first charge.

[Burgerman]

Set graph to display all cells. Then you can see how out of balance it is when it gets near the full point. Thats where the lack of balance will show. At 3.3x volts they can be well out of balance and all look exactly the same. In fact trying to balance below 3.4V actually puts them out of balance. It wont do that if you are using one of my profiles though. So all good. Other than the choice of computer

Is there a reason to only charge at 10A?
I would choose 30 at least. Or you may be there a long time. Its quite safe, as long as your power supply is up to it. I usually charge at 35 or 40A. 30 is a good safe figure, wires dont get hot or anything.

[jefferso]

Set graph to display all cells.

You mean like below?

Is there a reason to only charge at 10A?

I was just being cautious since it's my first charge. In case anything heated up or sparked I thought it might give more of a chance to react.
I also set it to charge to 3.5v.

[Burgerman]

Yes. When it gets to around 3.4v each cell will suddenly shoot up and would then exceed the 3.6V or whatever you set. But then the charger will throttle back power and the balance circuit will pull the high cell or cells down while the rest catch up.

On the next charge, which you can do by choosing discharge for 3 or 4 hours, they should all shoot up almost together and at this point you are good to go.

[jefferso]

The virtual Windows machine went to sleep and disconnected from the PL8. I restarted at 35 amps.

[jefferso]

Other than the choice of computer

I have software I need that runs on the Mac. I'm thinking of buying a used/refurbished Windows laptop from ebay or somewhere just to run for charging. I guess it wouldn't need to have much ram or cpu, and with an SSD wouldn't use much electricity. Maybe I can find something for £50 or so if I'm lucky.

[Burgerman]

Or flog the mac and buy a real computer. And I can give you a proper operating system as used on air traffic control, banks etc that just works. And any other software you want.

[Burgerman]

Still awaiting more screen shots! But its taking a bit of time... When charging a big lithium pack you are putting more in than the old lead battery.

[jefferso]

I had to leave it and some time while I was away the usb stopped working. The graph is generated while it's connected I guess, so I missed the record of what happened with the charge. It looks like the cells are not very well balanced at this point. I wonder if it's because I lowered the target voltage to 3.5 for the first charge.

[jefferso]

I got this error PowerLab 8v2 message.

Access to the path 'C:\Program Files (x86)\Charge Control Software\CHGM8S\TempGraph.xml' is denied.

when I stopped the charge and it asked if I wanted to save. I had to go to that file and give the user write permission. After that it saved.

Screenshot 2024-07-07 at 10.11.50.png (10.9 KiB) Viewed 1782 times

[Burgerman]

All this is likely because you are using it in an emulation on a daft apple achine.

But the out of balance thing was inevitable.
It should be balancing now as I type.

No it has nothing to do with the 3.5V thing, but you should really be doing this at 3.550V as I think its likely set to begin balance at 3.500V.

I would have fully charged each cell before assembly, then balance would happen fast. If its say 10Ah out of balance that it may be balancing for 10 hours. And if its less then the time will be less. If its more...

If this was a BMS doing this with a typical 50mA balance current then you would be weeks.

BUT on your graph above I see no balancing? Bypass. And no curent - charge. So be sure that you dont have it set to 3.5V charge. Set that to 3.550V.

And be sure balance is set to begin at 3.500V. Charge to 3.550V and Use that daily.

OR set balance to start at 3.40V and charge to 3.500V. But thats OK just for the first charge where it sits a long time balancing.

[jefferso]

Now I think it's balancing. I reloaded the preset 'LiFe Charge 8S 230AH Pack.PS8' which has it set to 3.550V

[Burgerman]

Yep, ITS PROGRAMING logic if configured correctly (and on other chargers if the code is written correctly and it frequently isnt) is this:

1 CC at max Amps.
2 When first cell hits the 3.550 or 3.600V the charge current MUST decrease until that cell doesent pass the set CV coltage.
3.The balance circuit pulls out 1A or 1000mA. To stop the cell increasing its state of charge and holding it as low as it can.
4.This happens across all 8 cells.
5. When all cells are balanced, and balance current is low, then the CV timer cuts in to end charge (can be set to off/no timer on initial charge or safe figure of 4 hours on a healthy balanced pack.
6.The termination current should be manually configured so that the CV stage ends charge 15 mins to 45 mins (30 ideal) after CV stage starts, on a normal charge after use. This will take a week or so of use to get correct. Its normally around 1/320th of the pack capacity in mA. But not always.

So after this completes. REMOVE say 10% by Ah, and then do another charge and it should balance faster. And give an idea if the termination current is set somewhere close! And now its safe to set CV safety limit to 4 hours. It should never hit than now.

[jefferso]

Thanks. I think it was because the first time I set the charge voltage lower to 3.500V, and the Balance Start V. was still 3.50V so it never really tried to balance.

This time charge voltage is back to 3.550V so it's actually balancing.

[shirley_hkg]

begin balance at 3.40V and charge to 3.500V. But thats OK just for the first charge where it sits a long time balancing.

That's wise for the initial charge.

I choose 3.485V .

[jefferso]

It finished.

How do I do the discharge? Do START then REGEN. DSCH. ONLY?

[shirley_hkg]

No.

REGEN DISCHARGE needs another battery to receive the energy.

[jefferso]

How is a normal discharge done with the PL8?
What happens with the energy if there is no other battery?

I had set it to 3.30V discharge voltage and clicked the button before I saw your message after reading some old posts.

All cells are now at 3.325V and it showed Cap OUT of 10848 mAh. The charger fan was blowing but it didn't feel too warm.

[Burgerman]

Now charge.

[jefferso]

Now charging.

[jefferso]

Now it finished charging.
Took 45 minutes Capacity IN = 11766 mAh

[Burgerman]

Took 10 mins to balance. Not bad. Now dischrge and do the same again.

Should get better. Maybe.

Then install it. And ride off into the sunset. Be amazed how far you can go. Do at least 1 charge while new to 3.650V now its balanced up. Because the manufacturers recommend this on commisioning. Dont know why. But I always do it. Then from then on stick to 3.550V for longevity.


You can see now why trying to balance at say 99% charged wont work. You only see the significant voltage rise (above noise and measurement accuracy) above 3.45V. So all these BMS that have "active" balance that runs all the time spend HOURS unbalancing your pack all day long!

[jefferso]

The grey cable is your breaker. Add this into the loop. At the positive end.

Thanks. So I'll connect the black cable to the negative of cell 1, the short grey cable to the red cable directly (not attached to any post, maybe with a nut and bolt, then perhaps covered in insulating tape), then the long grey cable to the positive of cell 8.

I'll use one of these M6 10mm bolts to bolt the short grey and red cable together.

[Burgerman]

If your balance traces look odd after you connect that dont be surprised. They have a resistance across the internal contacts and bimetalic strip.

[jefferso]

Charged again.

[Burgerman]

Looks pretty good. Get it fitted!

How is a normal discharge done with the PL8?
What happens with the energy if there is no other battery?

100w max. So slow. It wastes energy as heat and blows it out the rear.
With another (discharged) battery and correct settings, you can discharge at 40A...

[shirley_hkg]

If your balance traces look odd after you connect that dont be surprised. They have a resistance across the internal contacts and bimetalic strip.

Probably not , if balance lead is bolted to cell terminal directly.

[jefferso]

What's a good way to insulate the top with all the posts sticking up?
I think I have a few rubber caps, but not sure they'll cover the post and the nut.

[Burgerman]

But a balance lead is connected BETWEEN cells. So to read voltage each cell is needing 2 wires. So if that breaker is connected between cell 4 and 5 as per the normal way on lead batteries, then one cell is connected across that resistance. And that means voltage drop or gain if it is being charged. Remember we can see a single mV on the screen!