Batery does not reach full voltage

[3wheeler]

I purchased a 52V 24Ah triangle pack from Luna (14S7P Panasonic GA 18650 cells) in June.

I have not been able to get this pack to charge beyond 57.46V. I have 2 different chargers (Luna 300W advanced charger and 52V 2A charger) Both chargers show 58.8V output.

I have more than 20 charge cycles. Several times I have run the pack to 44V or a little less. It charges back to 57.46 each time.

I realize this works out to about 4.1V per cell (14 x 4.1 = 57.4)

The Panasonic GA 18650 cells are supposed to achieve 4.2V per cell. As a new battery, I expected they would reach this State of Charge.

What has been your experience with batteries that do not reach the full charge?

[Rodney64]

Running the pack to 44 volts is under 10%. My advise is do not discharge below 46 volts.

[ykick]

I would guess the pack might need some balancing? Leave it connected to the charger for long periods of time (days if possible) and see if the battery pack voltage will get closer to 58.8V.

[paxtana]

Although 58.8 is the ideal, you would be hard pressed to find any pack that doesn't sag a little after the charge cycle completes, especially if the pack has repeated deep discharges and that sort of thing. We cover this on the documentation.

https://electricbike.com/forum/forum...ries-basic-faq

It doesn't necessarily take much to lose some of that initial capacity. Once I had a couple new mini batteries that were identical, I used to run them in parallel, same charge percentage and charge cycles, they had just a few cycles and you would see 58.6...my bro used just one of them on a bike with a 50a peak controller for just a few miles, didn't ride it so hard that it shut down but the battery got fairly hot since they are minis. Ever since that single ride, that pack sags 0.4v more than the other.

[3wheeler]

ykick - I have left the battery on charge for extended periods, assuming the same. The best I can get is 57.46V.

[ykick]

Is 57.5V immediately after charge termination? Or, is it after a day or so of sitting? In other words, try measuring it within a few minutes after the charge completes?

It may simply be what brother Pax described above? Or, perhaps BMS component variations?

[3wheeler]

paxtana I wouldn't be concerned about a little sag. This pack have never produced more than 57.46V I opened a trouble ticket to report this issue after a couple charge cycles to document the problem. I was told it take a few more cycles to get a battery to full voltage. I continued to charge after various discharge levels.

I tried charging at 1A, 3A, 5A with he 300W advanced charger. Voltage comes out to 57.11 - 57.46, averaging about 57.28. With the 52V 2A "Shark" charger, I get a consistent 57.46V.

I don't run the battery to shut down or even drain it hard. I run at PAS 2 most of the time. (sometimes PAS 3-4 on a hill)

[paxtana]

Ok..are you saying the charger shuts off before it reaches ~58.8 then sags to 57.4?
Or are you saying it goes to 58.8, does regular balancing (fan spinning up momentarily, lights changing etc depending on the charger) then you see voltage drop after charge cycle to 57.4

[Kocho]

57.5V is too low, thats more than a full volt below full charge. Rather than do a relatively big discharge then charge and keep the battery plugged in for many hours in an attempt to balance, do more but shallow discharges with gentle use (don't overstress the pack during discharging), then charge fully and keep it plugged-infor only anhour or two max after it seems it is no lo ger charging. Repeat that a few times.

The logic for doing shallow and gentle discharges instead of deeper ones is that a shallow (small) discharge, say from max to maybe 90% SOC or even higher will not (or should not) disbalance the pack like a dep and hard discharge might be more likely do. And it is safer for any potentially disbalanced cells. So you will shorten the time to recharge and reach the point where equalization begins to happen. Let it equalize for an hour or two. Do it 2-3 times and see if the voltage is climbing higher each time. Because of the shallow discharge taking little time, you can do several such cyles in a day - charge, ride 5-10 miles, charge fully again, let equalize for an hour, repeat.

If after a few such quick cycles (which are gentler onthe pack than full cycles), if you see no improvement then something is wrong. I've had several electric motorcycles and two ebikes and none was disbalanced enough to be 1.3V below full charge. The 17.5Ah GA cells pack I got and the anothr 8.8Ah pack of unknown chemistry both charge to within several milivolts of their target max voltages of 58.8 and 42V respectively. And that has been the case from the very first charge cycle.

[3wheeler]

Thanks for the input Kocho. Last weekend i read a post that described the process you detailed. Over the last week, I have been doing this process. I run the battery down a few volts by riding around my neighborhood. Finishing at 54-55 V. Then charging again. The results were exactly the same. I tried my small charger 2 days and the large charger 3 days. Still stops charging at 57.2-57.4.

I am anticipating there may be something up with the BMS...

[3wheeler]

I have measured right after pulling the charger off the pack, a few hours later and the next day. The measurements are within a few hundredths of 57.46.

the chargers shows 57.4 and is satisfied. It has green lights lit and the fan has stopped. Also 0.0 amp output. If I unplug the charger for a little while and plug it in again later, without discharging at all, the charger starts up and then goes to idle after a short bit, as if satisfied.

Both of my chargers show 58.8V output when measured off the battery.

[3wheeler]

paxtana the chargers both seem to be satisfied when the battery reaches 57.46. 58.8 is not reached.

The advanced charger shows 57.2-57.4V and 0.0 amps with all indications that it has completed its cycle. (Green light, dann is off. )

Neither charger ever reaches 58+ V.

[paxtana]

Ok please email support again and asked to be transferred to Seb, and link to this thread, I would like to have his input.
There is a way you can adjust the charger so it ends at a different voltage but if you are seeing this on both chargers it may be something else.

[3wheeler]

Thanks, paxtana. I will do that.

If I was only getting this result on one charger, I would suspect the charger. With 2 chargers giving similar results, it not the chargers.

I just checked the pack and the voltage was 57.44. I plugged in the advanced charger and it would not start a charge cycle. It was satisfied. I did the Shark charger and got the same. I took the bike around the house a few times to burn some power. Got the pack to 57.1. Plugged in the Shark charger and it started up and ran about 10 minutes. The pack was back to 57.46.