PINNED - 230Ah (245Ah certified) A grade cells Amy, Docan

[Burgerman]

So… you say i am wrong? Look to page 2 on this thread on your photos with measure and your have 00.22mΩ and mine have 0.285mΩ so

0.2xxx AND 0.2xx are almost the same thing. Practically the same as a lump of cable. Thhe difference there os tiny! 0.065 of a mohm!

mine is with + 1-2 not 00 like yours

Dont understand what that means.
You are reading a microscopic 0.065mOhm difference. Which is so tiny is practically unmeasurable, same as a pit of wire/cable.

Where is this + 1-2 (whatever that means?)

[Burgerman]

Your IMAGE shows 2.85mOhms. TOO HIGH.
Your text says 0.285mOhms... Repeatedly. Which is OK.

Which is it? Because thats a 10X diference!!!
Its also hard to believe that its 10x higher impedance. It wouldnt seem credible. If its TRUE then send it back. Set meter to 10 or 100V.

Show me the probes on your meter. On the battery.

[elryko1992]

Your IMAGE shows 2.85mOhms.
Your text says 0.285mOhms... Repeatedly. Which is OK.

Which is it? Because thats a 10X diference!!!
Its also hard to believe that its 10x higher impedance. It wouldnt seem credible. If its TRUE then send it back. Set meter to 100V.

So you tell me i can sleep without problem? :-)) i know from PL8 if a cell is high than 1mΩ is weak no? And this have 1+mΩ

[Burgerman]

No.
READ nmy last post.

You gave 2 figures.

On your PHOTO it says 2.85mOhm
In your text it says 0.285mOhm many times.

WHICH IS CORRECT? Thats TEN TIMES difference.

Please read my last post.

[elryko1992]

Your IMAGE shows 2.85mOhms. TOO HIGH.
Your text says 0.285mOhms... Repeatedly. Which is OK.

Which is it? Because thats a 10X diference!!!
Its also hard to believe that its 10x higher impedance. It wouldnt seem credible. If its TRUE then send it back. Set meter to 10 or 100V.

Show me the probes on your meter. On the battery.

I write wrong, the IMAGE says better what i want to say.

[Burgerman]

OK then that is either a bad cell, or you measured it badly.
Let me SEE the ends of the measuring probes on the cells.

You cannot measure with bolts, terminal connections, etc MUST be the actual bare terminals. Or it will be reading your connection not the battery.

[elryko1992]

OK then that is either a bad cell, or you measured it badly.
Let me SEE the ends of the measuring probes on the cells.

You cannot measure with bolts, terminal connections, etc MUST be the actual bare terminals. Or it will be reading your connection not the battery.

I just dispatched the box and measure, is not first time when i measure a cell. I wait answer from Amy and will see what i do. The problem is not my money is for a friend. And is strange because all the cell have the same problem.

[elryko1992]

Look is measure another cell now

[Burgerman]

OK then that is either a bad cell, or you measured it badly.
Let me SEE the ends of the measuring probes on the cells.

You cannot measure with bolts, terminal connections, etc MUST be the actual bare terminals. Or it will be reading your connection not the battery.

??

[shirley_hkg]

1, select the most precise range

2, aim at the terminal face. I always take support at the weld joint, so I have a firm press against it to make good contact.

3, multiple tries and take the LOWEST value, not the highest or average one.

Relax and be patient. It's usual to measure it a few times, before you get the true IR.

[shirley_hkg]

OK

Let me SEE the ends of the measuring probes on the cells.

[elryko1992]

I reset factory the tester and works good now, LOL:-)). Everything is good

[Burgerman]

That one shown is fine! If they all measure between 0.2 and 0.3 thats great.

And as Shirly
ey says set to the closest range to that which you are measuring. A full pack inc all connectors, set to 100V. Single cell set to 10V. For impedance set to the next one above what you are expecting. Or Auto.

But do not measure the bolt as now you are measuring the resistance of the thread/terminal post interface or join which can be anything from nothing to much more than the cell itself. As shirley shows, and I show, measure terminal post or welded joint. Take lowest value you can measure so that you are only measuring the cell and not the mechanical "joint" between meter and vell.

But 0.28 is no problem! Less than 0.4mOhm still OK. Thats within the error bars when reading super low impedances.

[Scooterman]

They arrived!

I wasn't expecting them so soon, I even said to the delivery driver, "Are you sure you've got the right address?" as I wasn't expecting them until mid-sept earliest.

I was planning on temporarily hooking them up on the bench, charging them to see how well they balance. And if balance okay, whack 'em in the chair.

[Burgerman]

Do it!
I challenge you to run them down in a day.

[Scooterman]

Do it!
I challenge you to run them down in a day.

As someone in this forum once said, you'd need an iron arse to do that!

Just bench testing them at the moment to see if balance okay. IR of cell 1 sits around 4 milliohms which is still low but higher than rest, but I think I remember you saying cell 1 IR is usually higher than the rest?

Have you done a preset for the 230Ah cells? I'm current using one that I use for a lower capacity lifepo4 pack.

Reading the data sheet for the cells it says, "Standard charge cut off 0.05C @3.65v"

I have charge voltage 3.6V

But doing the maths 0.05 x pack capacity 230Ah = 11.5A which seem v.high to me?

Shouldn't it be about 10% of that value? But what do I know?

Confused.com

[Burgerman]

As someone in this forum once said, you'd need an iron arse to do that!

Just bench testing them at the moment to see if balance okay. IR of cell 1 sits around 4 milliohms which is still low but higher than rest, but I think I remember you saying cell 1 IR is usually higher than the rest?

You cant measure resistance of a cell that way. You are measuring cables, connections, etc.
You are measuring 4 mOhms. Its reading 16 times high! And its reading it incorrectly. Your cells are really around 0.25mOhm!

To get a measure of such super low resistance needs an impedance meter. That measures this at 1000mhz AC with 4 probes directly on the cell terminal - no connector. See above posts. What that may show is bad connections somewhere. Non soldered crimps for eg.

Have you done a preset for the 230Ah cells? I'm current using one that I use for a lower capacity lifepo4 pack.
Reading the data sheet for the cells it says, "Standard charge cut off 0.05C @3.65v"

Thats because they expect people to be using innefectual BMS that repeatedly bounce the highest cells and have a stupidly low balance current. These keep cutting off power and then waiting for the BMS to do something. To speed this up some they advise 3.65 as this offers some small level of self balancing as once 100% it cant get more full, and the rest can catch up quicker.

So we dont need go that high. 3.6 is fine.
So set 3.6V
Set say 30A
Set balance to start 3.5V
Set termination current to manual, and whatever it takes to achieve BALANCE COMPLETE + 15 mins. What is that level? It will be around .7 to 2 or more Amps.
I attached one to use on an initial charge. NOTE it has no CV time limit other than a global 16 hour one so you may need to restart the charge if balance takes longer.
Once it has completed an initial charge with this one (after everything is balanced, which may be fast or take a very long time depending on cell charge state) then discharge it with the same preset for 6 to 10 hours... Say overnight.


Now charge. And watch it...
Does it charge, balance at CV, and then after balance is achieved end within approx 10 to 20 mins?
If not, then increase termination current to make it end faster. Decrease termination current to make it end sooner.

Discharge overnight, rinse and repeat!

If its somewhere close, you are done. You can then set the CV TIMER 30 or 60 mins for safety.

I have charge voltage 3.6V
But doing the maths 0.05 x pack capacity 230Ah = 11.5A which seem v.high to me?

If charging a single cell, not waiting for balance, then at 11.5A it really is full. But if you are balancing at a lower voltage its safe to allow it to do so for longer. And if you do not do it for longer then the other 7 cells that dont reach 11.5A will all end at the same time!

So you must then set in the PL8 in the TERMINATION Tab, that ALL CELLS BALANCE = YES. Plus 15 mins to be sure the last cell is full. At this point, depending on how fast it balances the termination current will have dropped below 11.5A. And will be anywhere between .7 and that 11.5! Thats for you to determine.

Shouldn't it be about 10% of that value? But what do I know?

Confused.com

On a single cell, no need. 11.5A is ok. On a pack with common charge across all cells plus a drag on the highest cells as it balances, it will end up about 10x less. Give or take a lot! As I said, charge and see!

[Burgerman]

Starting point!

It has no CV time set, terminates 1000mA at the moment after balance is complete. Change that, aim for 15 mins CV post balance.

Password 123

[Scooterman]

Thanks for the comprehensive answer BM I'm pretty sure I understand

I notice with your "starting point" preset that fuel parameter is ON. And cell tab while charging shows fuel percentage. On my existing older presets I've got fuel set to off.

With docan cells I noticed when first charging that fuel was around 30%. Is fuel an indication of SoC?

30% SoC seems about right for manufacturer storage prior to dispatch.

[Burgerman]

Its on but pretty meaninless...

[Scooterman]

[Scooterman]

I charge my powered mobility devices in garage and use the smart meter display unit to give me a rough idea when charge current starts dropping. It's obviously not as good as the android bluetooth app that some of you guys have. But with just me and the cat living here it gives me some indication.

[Scooterman]

Last night I read something but it was about 2 years old.

The guy reckoned that the reason Lifepo4 prismatic cells have dropped a lot in price in recent years is that people who once bought them for solar storage are no longer buying them. They're buy pre-made lifepo4 plug and play solar banks/storage units instead?

I was wondering that if in the future lifepo4 manufacturers reduce the number of prismatic cells they produce then the price of said cells will go back up? Supply, and demand, and economies of scale, and all that?

Hmmm

[Scooterman]

Cells certainly have BIG CAPACITY, I think I put about 165Ah into them.

They eventually balanced after about 1.5hrs.

This might be an SFQ aka stupid f***ing question, but if charge terminates after about 15mins and around 1000mA CC, how do we know if charge has terminated on (15min) CV timeout or (1000mA) Termination Current.

I suppose the answer is it doesn't matter?

[Burgerman]

They eventually balanced after about 1.5hrs.

Next time will be less.
Time after that will be shorter again...

This might be an SFQ aka stupid f***ing question, but if charge terminates after about 15mins and around 1000mA CC, how do we know if charge has terminated on (15min) CV timeout or (1000mA) Termination Current.

You watch the graph on your PC and the current. If its balanced, all lines are at the top ad flat...
At this point, watch it. Anywhere from 5 mins, to 25 mins, or so it should end.
If its still going after half an hour, increase termination current.
If it ends as soon as the cells seemed balance (they only appear to be but are not yet) then reduce termination current.

Then take at least 10% capacity out (20+Ah) and try again. Its better to do this in use really.

*****
This is all to do try and do the following...

1. To MAKE SURE it is properly balanced to 99.5% (that means it must not only appear balanced (all lines on the graph at the top equal voltage) but should not need any significant current sucking out of the other cells by the balancer inthe charger to do this. And so that also means a low charge current by the charger to stay that way once balance is turned off/low. If we end the moment it looks balanced then the last cell to reach 3.600V or whatever you chose, isnt really full yet. The rest are, they were full some time ago - soaking at 3.600V! So IF we disconnect charger straight away that final cell will now drop faster than the rest as you watch on a cell log/monitor. So we have to decide how long post balance, is long enough. 15 mins approx after balance usually is.

2 Why noy set it so it stays "fully balanced" for longer? To ensure a full balance? Like 45 mins, 2 hours, etc? You could. But the cells hate being full. Hate being at any voltage above the natural free standing level. It causes degradation over time.
IF you want to do that, then set 3.550V as the charge voltage as then it doesent do much harm even after an hour or so post balance.

So that balanced on screen + 15 mins time length, depends on how well your set of cells balance, temperature, the balance current of the charger, etc.
In our case on the 230Ah cells that are very low impedance 15 mins seems OK. Not quite long enough... But after 5 or 6 charges they end up very very close. Just not on a single charge. Thats does the least harm, with the best balance and a complete charge.

***************
By doing this you have ENSURED a full balance,
while holding the battery at the elevated 3.600V
for the shortest time that you had to do. And thats the point!
You are aiming to avoid holding it at high voltage longer than needed, while getting a full balanced charge.

You can get a 100% charge at 3.650V, 3.600V, 3.550 equally. Every time you lower this, you still get a full charge as long as its 3.500V or above. But the balance and CV stage take ever longer to fully achieve.
The slower the battery balances (hello weedy BMS with 50mA Balance! like the common ones) the longer the battery has to stay at an elevated voltage. The shorter its lifespan.

***************
Charging a single cell as per spec sheet, at 3.650V and stopping as soon as it drops from that 0.5C (115A) charge to 11.5A is a different matter!
The REASON you stop at 11.5A (0.05C) is because the high charge voltage, means it IS fully charged, no need to torture it and wait longer, and the fact that you are not balancing anything.

[Scooterman]

Thanks BM I understand. The goal is to achieve consistant balance over repeated cycles by a compromise between charge voltage and balance time. Ideally both want to be least to achieve balance over reapeated cycles. But bearing in mind cells balance quicker at higher voltge, and the last cell to reach CV needs time to soak. Basically we're trying to achieve consistant balance over cycles by not keeping cells at elevated voltage any longer than we have to. They're happiest sat around 3.2v and aound half full, but we need to elevate charge voltage to around 3.6v and hold for a time, to soak cells and balance pack.

And the bigger the pack Ah the less amount of times you need to recharge pack, so your not stressing cells as often by raising their voltage to circa 3.6v to charge and keep at 3.6v to soak cells and balance pack.

NB: I may have over-explained in above, but I'm pretty sure I get the gist of what you mean. Thanks

[Scooterman]

Comparing my old life presets with the "starting point" 230Ah preset. I notice on my old presets I have the balance mode set to proportional whereas the 230Ah preset balance mode is set to digital ON/OFF.

Powerlab brief explanation is that digital ON/OFF is something to do with experimental mode?

[Burgerman]

The bigger the pack the slower it balances and so we want 1A on/off to speed things up a littel.

The PL8 is intended for hobby stuff, I charge 250mAh batts, upwards. So the balance current can be 4 x higher than the charge current! And pack. So on paces that are under an Ah, or up to manybe 10Ah propertional gives a more stable smoother balance voltage as we charge. Beyond that on/off makes more sense.

Why?
If a battery is only a few mV out of balance. then proportional will give maybe 10% of its 1A balance current or 100mA. Unoticible on a 230Ah battery!
On/Off will give a 1000mA "drain" on a high cell, in the few mV difference situation. So faster. On a small battery, hobby sized, a 1A drain is overkill, so propertional works better and smoother/faster.

[Scooterman]

Ah! Okay thanks BM your help is very much appreciated
And like you say the PL8 user manual is mainly for hobbyist who use much lower capacity cells, and probably mainly lipo cells at that.

I'll copy your 230Ah "starting point" preset and rename copies for my 180Ah and 150Ah packs. And fine tune termination current for each to achieve 15-20min balance.

The below graph is 2nd charge of 230Ah Docan cells. I had the termination current set to 900mA but charge terminated after only a few minute at balance.

So I'll reduce termination current to 800mA for next charge and see if that gets me nearer15-20min balance phase.

There's no reason why I can't install pack now, and fine tune charging with pack installed in chair.

[Burgerman]

Check connections as 5 and 7 seem odd...