14S5P pack won't charge past 90%

[Recumbent Bicycle Source]

I have tested the Voltage at the Charger and get:

Setting 1. 53.4 V

Setting 2. 57.5 V

Setting 3. 58.9 V

I have never been able to charge past 57.2 Volts (Which is what my Cycle Analyst shows - also matched on my volt meter).

I have complete Trouble Shooting instructions, but no way to seal the pack back up if I tear it apart.

My question is this:

Is there any benefit to trying to recharge for a minute or two through the discharge cable? I read this may do something to reset the BMS.

True?

The pack works fine at 90% and I don't want to damage it... but once in a while I'd like to get the last bit of extra capacity out of it.

I believe the Cells are Samsung 22P. The pack is 4 years old.


Thanks.

 

[e-beach]

I have never been able to charge past 57.2 Volts (Which is what my Cycle Analyst shows - also matched on my volt meter).

When you say never do you mean in 4 years even with the charger set to 58.8v?

I have complete Trouble Shooting instructions, but no way to seal the pack back up if I tear it apart.

Is there any benefit to trying to recharge for a minute or two through the discharge cable? I read this may do something to reset the BMS.

might charge up, or you might just unbalance a 4 year old pack. Is your bms configured to balance at 57.2v?

The pack works fine at 90% and I don't want to damage it... but once in a while I'd like to get the last bit of extra capacity out of it.

That last bit of capacity won't get you far. But by not fully charging your cells they will last much longer.

Can you tell us the maker of the battery and show us some pictures? Can you at least get to the BMS without fully opening the battery?




Thanks.[/quote]

 

[amberwolf]

THere are packs by some vendors that have a BMS that cutoff (HVC) and balance at less than what teh cells inside the pack are actually capable of.

See here:
https://endless-sphere.com/forums/viewtopic.php?f=14&t=81108&hilit=+luna+pack#p1194739
for one example of a pack that uses 4.2v-capable cells, but a BMS that has a 4.15v/cell balancing and pack HVC based on that.

The bad news is the packs made this way don't have as much capacity as they could, in theory.

The good news is they will probably last longer than they would otherwise.

 

[Recumbent Bicycle Source]

It's an EM3EV pack and it's supposed to charge to 58.8 or thereabouts.

And yes I didn't really notice it wasn't going to full capacity because I was told it's best not to do that. So I always just charged to 90%... then one day not that far back I planned on going on a 60 mile ride and I realized it wasn't charging past 57.2 (Once connected to the bike).

EM3EV packs have a nice thick shrink Wrap I can't duplicate and I probably shouldn't be playing with the BMS either. Best to leave it alone because it still works pretty good.

But I was curious if I could charge through the discharge port to somehow reset the BMS.... I read that somewhere.

I realize the extra capacity is not that big a deal... but I also wonder if there is a benfit to a full top off that I don't know about.

In the RV World I use CTEK Chargers and just leave them alone to do everything. This Chinese No Name Stuff I have little confidence in... but it does seem to work. So I shouldn't complain. It seems to work.

I have no idea how Lithium Chemistry ages over time... but 4 years seems pretty good (Although I'd like to get as much as I can). I haven't even hit 300 Charge Cycles and I usually don't even drain the pack down to half the capacity. It'll probably die from old age not charge cycles.

 

[Recumbent Bicycle Source]

BTW: I've read 90% and 80% being the best... but I don't know which is going to increase cycle life the most. I thought it was pretty safe to discharge 90% and that what I do.

Battery Tech keeps moving forward I'm already looking at a Samsung 25R pack in case mine dies. But by then there will just be something better.

 

[e-beach]

If it is EM3EV contact them. They will let you know about charging issues.

http://www.datasheetspdf.com/datasheet/ICR18650-22P.html

Those cells are spec-ed at 4.2 full charge and 3.62 nominal. So if you did charge them to 58.8v you would get a bit more range out of them...1/2 to 1 mile in my guess-ta-mation. However it is top-end charge and heat that really kill your cells. Age also is a factor but less so then over charging.

The cells you got have a LVC at 2.75v per cell, or in your case 38.5v for your pack. If you take it lower then that, you will degrade the cells as well.

90% charge is going to help your cells live a long time while giving you good range. However, a full charge of 58.8 once in a while isn't going to kill them.

I still think you should contact Paul at EM3EV and find out about the BMS.

Although thinking about it, what is your charger wiring setup? Show us a picture of it. Be sure it is in focus.

 

[999zip999]

Just use daily or more. Don't be sacred to charge it.

 

[kdog]

This is a possibility if you have never/hardly ever given it a full charge, but have used the 90%setting all the time.
The bms will start to balance at a particular voltage say 4.2v. If you have only ever charged to 4.15v (90%) then it may not have ever balanced the cells. So they drift slowly apart. Not noticed by bms cause it's under the threshold.
Now you try to do a 100% charge it cuts off early when one hits HVC- appearing not to charge fully.
Try a 100% charge and leave it on for a few days (even when it's full) to allow bms to balance.
Search to find out what em3ev bms specs are and see if it is a possibility.
Charging to 90% will roughly double cycle life but usually you need to give them a full charge once in a while to allow bms to balance.
K
Oh and have you checked with a good DMM? My CA is about .8v out.

 

[dogman dan]

I don't think he said he uses the 90% setting. Do use it if you don't plan to ride immediately. then top off with 100% setting when just about to ride.

I would start the process by charging full. check voltage. ride around the block, charge full again. See if voltage goes up any at all. If it does, repeat.

If that does not force a balance, then start looking at all your cells individual voltage after a full charge. If a cell is way high, and the bms does not pull it down after awhile, you have a bms that is not balancing properly.

It sounds like it acts like my allcell pack. It never really wanted to fully balance from day one. It gets close, but not all the way. I can force it though, by overcharging it. Mine is 54.6v,, but balances much better if I overcharge to 57.5 or so. Since you don't want to overcharge that type cell often, I don't worry about it, and ride off with 54v or a little less. Not much capacity lost anyway.

Now that your pack is 4 years old, it's time to expect it to never hold 4.2v per cell anymore. It may not balance at 58v with or without the bms connected. it may charge full, then self discharge to 90% every cycle now.

 

[EM3ev Assistance]

We changed the parameters on our BMS back about 2-3 years ago, to increase the HVC cut slightly, as we found that the BMS configuration we had been using (4.17V Balance, 4.2V HVC) was consistently preventing packs from getting to a 100% full charge of 4.2V per cell (it would typically stop play at ~4.15V/cell, even on new packs) and it was getting rather tiring to have to explain this (non) issue to concerned customers (that even though the Charger was outputting 58.8V, the packs would only charge to mid 57s). The BMS used in Li-Ion BMS have a balance and HVC voltage that is very close and this tends to result in these sort of issues (BMS not allowing the cells to reach a 100% charge), even though the BMS is supposed to cut at 4.2V/cell.

The long and the short of it, is this. You are not experiencing any sort of issue as such, you just are not able to get the very last bit of capacity from the cells (due to the BMS not allowing this to happen). The upside is that this is kinder to the cells and despite this slight under charging, the packs would always deliver more than we rated them (typically the 22P cells deliver ~2.15Ah cell in a finished pack and at that time we specced them at 2.05Ah/cell, later adjusted to 2.1Ah/cell).

We suggest you measure the capacity with some sort of Wattmeter (full charge to BMS trip) as the delivered capacity is the most important point, not the precise charge voltage. We suspect you might be pleasantly surprised by what this 4 year pack is still delivering if you measure the delivered capacity

Checking the cell level voltages from the BMS balance plug, does not require the pack to be disassembled. A check of the cell level voltages after a full charge and full discharge is the best way to determine if the pack is reasonably well balanced and if you have any weak (low capacity) cell groups. We can provide some testing steps you can follow, if you drop us an email.