PINNED - Lithium battery conversion/info

[Burgerman]

At 3.65 which is too high, they maybe never drop. At 3.600V they should if geniunely new half decent cells drop to a fraction of an amp in a short time.

[steves1977uk]

I dropped the voltage to 3.600v and they dropped to 0.11A which I assume is full for 105Ah cells.

Steve

[Burgerman]

On those ones by the sounds of it, 3.65 is an overcharge that they dont like.
This is exactly why you need a charger that allows you to set a proper voltages and termination current to suit your specific cells.

[terry2]

I just setup a 10GB network for a friend.

He has paid me, and he wants to know if I want of of these as he is buying one.

https://m.aliexpress.com/item/1005002643757309.html

I don't think it's ok for single cells but not a 8S pack.

Here is the manual. https://www.manualslib.com/manual/16882 ... -A40l.html

Thoughts as it's free

[Burgerman]

I doubt you will use it but its free so why not. As long as YOU have the tech knowledge it can test single lithium cells.

[shirley_hkg]

Have to assembly this notorious EVE-LF105 200Ah pack again .

Woke up in the morning but found cells were divided literally into 2 groups , due to huge difference in SOC. (turn out to be Δc up to 40Ah.)
Would take forever to balance. Thought of topping up cells individually , but … … IS THREE A EASIER WAY. Took the 2 alligator clips off the battery mains , and tap on a cell . Since the BMS was still in action, I was able to tune the charge volt and amp up, without worrying of overcharged the cell. It worked and all 4 were topped up in 3 hours.

Re_connected the charger @24V, pack was balance in 30 mins.

On second thought , this BMS would be able to top up new cells in the initial charge too. I don't have to do initial charge for each cell anymore . Cool.

[shirley_hkg]

[terry2]

I doubt you will use it but its free so why not. As long as YOU have the tech knowledge it can test single lithium cells.

I spent a day reading and watching videos of it.

I was hoping it could do my 8S pack.
No point in having it if it can't.

Thanks

[steves1977uk]

I'm charging another of saker98's cells, this particular one read 2.64v and when I hooked it up to my Digimess PSU it initially took 7.2A at 3.6v. I was expecting it to take 10A since it's a low cell and I'm using the front bananas for ease.

I started the charge about 90 minutes ago and it's down to 2.6A. Once I've done them all, I'll charge them with the PL8.

Steve

[Burgerman]

It sound like a high resistance cell. It should take about 100A if its a 100Ah cell when that low. At least to pull it up high to 3.6V.

And should take 10 hours at 10A. Since its about 100% discharged. So that sounds like these cells are all going to be junk.

When charged, do a full discharge test. You might be horrified.

The cell you are doing now, do a 10A discharge test on that one alone. And you may find its only good for a fraction of what it should be. And may have very high resistance and high self discharge too.

[expresso]

why not just do a full charge - then a full discharge and see what the really are

i always done it that way - when cells arrived - i charge each cell full using 20A charge rate or you be there for weeks - and 20A is not alot to charge with -

then do a full discharge down to what ever you like - 2.5V or 2.9V - then do a full charge again -

each cell - build and charge with PL8 to balance -

unless the way i been doing it for past 6 years is wrong ?

[Burgerman]

Its not wrong.

[steves1977uk]

It sound like a high resistance cell. It should take about 100A if its a 100Ah cell when that low. At least to pull it up high to 3.6V.

And should take 10 hours at 10A. Since its about 100% discharged. So that sounds like these cells are all going to be junk.

When charged, do a full discharge test. You might be horrified.

The cell you are doing now, do a 10A discharge test on that one alone. And you may find its only good for a fraction of what it should be. And may have very high resistance and high self discharge too.

This is what I was afraid of BM, James (saker98) paid over £1,000 for 18 of these cells. This low cell has been sat at 2.3A for the past hour, should I keep on charging it?

Steve

[steves1977uk]

why not just do a full charge - then a full discharge and see what the really are

i always done it that way - when cells arrived - i charge each cell full using 20A charge rate or you be there for weeks - and 20A is not alot to charge with -

then do a full discharge down to what ever you like - 2.5V or 2.9V - then do a full charge again -

each cell - build and charge with PL8 to balance -

unless the way i been doing it for past 6 years is wrong ?

Doesn't matter which way you charge them, an adjustable switch mode PSU can do the same as the PL8 provided you do the cells in parallel. The Amps should drop fairly quickly if they are healthy.

Steve

[steves1977uk]

Here's two photos of the weak cell...

Melissa also helped me check another cell and that had more or less the same mOhm reading. Don't think these cells are healthy.

Steve

[Burgerman]

Not sure what you are doing.

IF that power supply is really 3.6V and connected to that battery then the battery MUST be 3.6V too. You show he meter reading 3.3V? So if both the meter and the power supply are connected then both should read the same unless your power supply is in need of serious calibration.

Set the power supply so that it is 3.600V with the meter. Then connect it to the cell. And ignore its volt reading on the power supply. Use the multimeter. It appears that you are trying to charge at 3.3x volts... And use say 20A and heavier cable.

And you cant read resistance/Impedance that way. The only way to measure ohms of a cell is to measure voltage drop under a known load and use ohms law.

[shirley_hkg]

Measure psu at its output poles .

[steves1977uk]

The Digimess was set to 03.6v which should be the correct voltage for charging? Both sets of clips are directly connected on the cell's bolts.

Steve

[steves1977uk]

I'm waiting for some M8 terminal rings to solder on some 3.3mm2 cable which is rated for 40A. Then I can use the rear connections on the Digimess and up the current.

Steve

[LROBBINS]

One of the nice features of the ZXD power supply is that it estimates voltage drop in the connecting leads and load and increases the supply voltage as necessary so that the voltage at the battery is what you set on the supply. At high currents (relative to whatever gauge leads you're using) the voltage drop is I*R so the higher the lead resistance the higher the drop for a given current. The voltage drop may indeed be as much as the 0.3V difference you seem to have between what the Diginess is set at and what you have at the battery.

It appears that the Diginess doesn't boost its output voltage to compensate for voltage drop (and that's not surprising for a normal bench supply) so you may have to do that manually - increase the voltage at the Diginess to get 3.6 at the battery, but then keep an eye on that and reduce the Diginess voltage as the current drops so that you don't exceed 3.6 at the battery. Make SURE that it never rises near or above 3.65. It will also help to increase the wire size as that will reduce the voltage drop.

[steves1977uk]

I realise that Lenny. At the moment it's charging at 5.7v at 13.9A on the Digimess and it shows 3.3595v on my Fluke. Would it be better to use the ZXD until I get the ring terminals as I can't up the Amps any higher at the moment until I get the other cable made.

Steve

[Burgerman]

Do tis:
Disconnect the battery.

Connect the fluke to the power supply no battery. Set it to 3.60V and tell me what the fluke says.

LEAVE that the same, still connected, and now connect the battery.
What does the meter say. Mine is pretty accurate and very close to the power suply display.

I suspect your power supply is not reading voltage correctly. Only trust the fluke. It cannot be that you are losing so many volts under charge load unless your charge cables are smoking! You either have a very bad connection, and or a faulty power supply display calibration.

[steves1977uk]

I will do that BM, when my Brother or Melissa can help me. The banana charge leads were hot to touch at 14A, so daren't push them any higher! They are about 1.5m long.

Once the cell reached 3.6000v on the Fluke, I immediately dropped the volts to 03.6v on the Digimess and the cell volts dropped quite quickly to 3.45xx volts before slowing down.

Steve

[Burgerman]

Then the power supply is lying or your leads are rediculously high resistance. Thats why you have a meter! Measure and test.

[shirley_hkg]

Both sets of clips are directly connected on the cell's bolts.

Steve

That's VERY wrong .


The strut is not copper I suppose , and you've put Loctite around it . High resistance all together. Didn't you find it hot there @14A ?

Use lug, so everything is from the terminal surface .

[steves1977uk]

I know it isn't the ideal setup Shirley, but I'm limited to what I can do myself. When my Brother makes my new cables, I'll recharge it again and measure voltage at the lug.

Steve

[shirley_hkg]

No. I meant fasten an empty lug to battery terminal , and clip on its barrel.

[Burgerman]

I think you are charging the cell at 3.3 something volts. And you power supply is miscalibrated. Or you have a seriously bad connection.

Its not possible for the cell end of the charge wire to be at such a different voltage that the power supply end. Unless many Amps, and a very very hot wire! It makes no sense.

[steves1977uk]

Went to check the volts on my Digimess PSU, turned it on, it made a crackling sound and it went off instantly. Now it refuses to power back up. Both fuses (mains plug and internal one) tests fine. My Brother opened it up and nothing looks blown.

Bugger!

Steve

[Burgerman]

I suspect that that was the problem. Your power supply wasnt doing what it said.
Because what you showed on that photo wasnt actually possible. The cells when connected to an ACTUAL 3.600V will likely charge at high amps quickly as they should.
Do you have a shirley one?

Incidentally I sent mine (digimess) back once after connecting a 24V wheelchair in reverse (smoke and noise!) and they charged a fixed amount to repair and return it. Dont remember where though. It was 17 years ago...

Also https://www.eevblog.com/forum/repair/am ... on-smps_s/