Is my battery dead?

[tofuuu]

So after maybe 2 months of not using my ebike I come back to it and realize I still had the controller plugged in Realising that I frocked up I connect the charger and it doesn't charge, lights come on and the charger acts like the pack is already full. I check the pack and its limping at around 37v and its a 16S 5P a123 lifepo4 pack so that's not good.

So... did I kill it ? Im already ordering another charger just in case cos the current one has always been a bit iffy, sometimes it shorts out the house when I connect it. sometimes I need to flick it on a few times but this time I think its not even trying to charge it this time.

Help please !

 

[dnmun]

nothing wrong with the charger. put the current charger on the battery and measure each cell's voltage at the BMS where the sense wire plugs in. post up the voltages here, measure while charging, using the 20V scale, to 1/100V.

then we can tell you how dead is dead.

 

[dogman dan]

37v is not promising, but far from garanteed to be dead. I did the same thing to a ping, and it was clearly dead. Like 3v and puffed to twice normal size. So if no obvious damage happened you have some hope. There could be some good cells, and some bad ones now though.

One possibility is that part of your problem is that the plug broke, or just the wire to the plug disconnected on the DC output side of your charger. That would result in a green, full battery light when you plug it in despite the lack of charge. It's a common charger problem, and green light means either charged, or disconnected.

So check on that, then if the plug is fine, follow the procedures dnmun is advising. If all your cells are above 2v, they should be savable. They might have some wear on them more than normal, but if none are 0v, you have a good chance.

 

[Tommy L]

Some chargers won't turn on unless the charger senses enough voltage. 37v might be too low for the charger to respond.

I've used and I sell these chargers that are smart.

I drained my LifePO4 pack down to near nothing and my chargers are smart to recognize this and slowly apply voltage and slowly revive
the cells. Out of a 40S pack, I lost 4 cells. Lucky

I'm not sure what your BMS does during charge. You might have to by-pass your BMS and go direct to the main pack + and -

Tommy L sends.... \\m//

 

[dnmun]

do not charge your pack without the BMS. do what i said, measure the cell voltages and let us know. to charge up the pack now without the BMS will ruin the cells that did not die already. measure the voltages and report them here.

 

[Tommy L]

do not charge your pack without the BMS. do what i said, measure the cell voltages and let us know. to charge up the pack now without the BMS will ruin the cells that did not die already. measure the voltages and report them here.

dnmun is correct.... first check all cell voltages.... I was assuming that this was already performed and all cells have dropped equally.


Tommy L sends.... \\m//

 

[dnmun]

equally is the problem. he will have some cell that are already fully charged, and some still discharged. the high cells have turned off the charging mosfet. if he can find the high cells and drain the charge off with a big power resistor then the charger will come back on. but he has gone, and i bet he thinks that just using a new charger will solve the problem. but he just wasted a buncha money on another charger for no reason.

 

[tofuuu]

I haven't gone yet :| Ive had a pick at it and im pretty sure where the sense wire meets the bms has been glued so im staying back a bit till I figure out the best way to take it apart as it seems theres quite a lot of glue everywhere and I don't want to go tearing anything off yet. Thanks a lot for explaining this to me though it has been extremely helpful.

 

[arkmundi]

equally is the problem. he will have some cell that are already fully charged, and some still discharged...

Syncronicity. Thanks for the attention to this. I'm just now experiencing this. My accident/insurance claim allowed me to take my ebike to the local bike shop to fix the bent wheels. I left it with the battery still connected to the Watts Up meter & controller. Because of bodily injury, didn't pick my bike up for 10 days. I'm attempting to revive my pack with a combination of my batteryspace smart 6amp charger and Voltsphreaks 2amp single cell charger. No BMS. I bought some extra AMP20 cells, so as to have them on hand. I may end up swapping out any low margin cells. I'll let you know how it turns out.

 

[dnmun]

I haven't gone yet :| Ive had a pick at it and im pretty sure where the sense wire meets the bms has been glued so im staying back a bit till I figure out the best way to take it apart as it seems theres quite a lot of glue everywhere and I don't want to go tearing anything off yet. Thanks a lot for explaining this to me though it has been extremely helpful.

you don't have to tear it apart. just measure the voltages on the sense wire plug end of the BMS. you will see which cell is high and can drain it from there.

is this a ping pack? the LVC on the BMS will shut off the discharge when one cell reaches 2.1V so that pack will be saved, but it will be unbalanced, which is preventing it from charging up quickly.

once the high cell has been drained the charger will come back on and charge up the others to catch up.

this is where the BMS helps, to prevent it from accidentally overdischarging when your forget to remove the load. it will also allow you to get the pack balanced again.

 

[tofuuu]

That's the thing though. Im pretty sure that where the sense wires meet the plug has been glued!
Ive peeled a bit of the side off now and see that the rest of the wiring hasn't been glued down anywhere.
The pack is an a123 pack from cell_man/emissions-free

 

[dnmun]

ok, gotcha. really glued.

that is the new headway BMS and those screws are impossible to get off even when the BMS is free to work on. no space to really get the voltmeter probes in the crack either. keep charging, the shunt resistors are only 84 ohms so it takes a long time to balance even when the charger is able to trickle the current in during balancing. but your BMS is shutting off for high voltage on one of the cells, all you can do is leave it charging 24/7 365+ days a year until it get back up to the 58.4V. but when it gets there it will be balanced. i really think those are the best BMS around.

if you can measure the voltages, from the side, do that and we can figure out how to drain the high ones.

 

[arkmundi]

A123 AMP20 12S pack, no BMS.

I successfully revived my pack from a apparently dead state. By that I mean my Watts Up meter would not register (turn on) and my batteryspace smart charger would not start charging. After disconnecting the pack and leaving it overnight and attempting again, the charger now started charging OK. After completion of the charge, here are the individual cell voltages:
Cell Voltage 9/29/12
1 3.50
2 3.96
3 3.90
4 3.35
5 3.86
6 3.34
7 3.20
8 3.61
9 3.82
10 3.45
11 3.84
12 3.34
Sum 43.17
Watts Up 43.01
Voltmeter 42.60

Question: Are the above an indication the cells are balanced or unbalanced? I don't have sufficient experience to judge. I'm going take a trek and after returning, will again check individual cell voltage. Thanks.

 

[dnmun]

can you put a BMS on it to balance it or can you buy a balancing charger? getting them all to the right voltage is gonna be hard. especially if you are inexperienced.

those five cells above 3.8V up to 4V are at risk of overcharging if you charge it more. as in a minute or two. you gotta stop the bulk charging. hope you haven't been charging after this was recorded.

 

[999zip999]

Arkmundi that is the problem of the smart charger or bulk charging after a sit with the power on and drained you need to balance charge. You need to run some balance wires to tap into a cell for balance charge. You are the bms not the smartcharger bulk charger dumb chager ect... So an A123 20ah pouch is charged at 3.6v. NO need to go above. It wiil fall to 3.5v something and as soon as you put a load on it will level around 3.4v where the power is till 3.2v maybe 3.1v done.At this time put it back on charger. Going above 3.6v without bms is no good. Drain the high cells. Buy buy a 6s balance charger and put two 6s plugs on it. I always unplug the battery with out a bms it's just one wire.
I look at the pic of those short tab cells and the one tab look like swiss cheese is these how your's came ? Still thinking above buying some.
Good luck

 

[dnmun]

i am afraid some of those cells are already dead. those voltages were recorded long after he took it off the charger so all those high cells were .4V-.6V higher when charging, so maybe they sat at 4.4-4.5V for a long time.

this is what makes me mad about the dumbasses that tell newbies they can build a battery without a BMS and use it without a problem. now this guy has lost very valuable A123 cells because he believed the misinformation he was fed by the self styled experts.

if he had put a $75 ping signalab on there, it would never have drained to zero and never overcharged, and he still has to buy one now to get the pack to balance and it will be even harder with these bad cells in there with the screwed over internal resistance preventing them from balancing together with the others.

you guys who talked him into this should recognize what you did and send him some money to recover from your misinformation. you know who you are!

 

[tofuuu]

Thanks a lot for the help guys! That was gonna be my next question "should I leave it on the charger" cos the pack is up at 38.9v today over the 37v yesterday ! :lol:

 

[Tommy L]

i am afraid some of those cells are already dead. those voltages were recorded long after he took it off the charger so all those high cells were .4V-.6V higher when charging, so maybe they sat at 4.4-4.5V for a long time.

this is what makes me mad about the dumbasses that tell newbies they can build a battery without a BMS and use it without a problem. now this guy has lost very valuable A123 cells because he believed the misinformation he was fed by the self styled experts.

if he had put a $75 ping signalab on there, it would never have drained to zero and never overcharged, and he still has to buy one now to get the pack to balance and it will be even harder with these bad cells in there with the screwed over internal resistance preventing them from balancing together with the others.

you guys who talked him into this should recognize what you did and send him some money to recover from your misinformation. you know who you are!

This is interesting yet your telling the "Tofuuu" to keep charging a 16s from 37v with out knowing if there are dead cells or a possible failure of his
BMS. Is it possible for the bms to be bringing up 10s or 11s of the 16S to 3.7v per cell/parallel string and showing him a 37v pack voltage?

I have learned to charge without a BMS. It is a skill. A good BMS would make charging easier (agreed). I prefer to go BMS less because I know
when I charge my pack, each "S" parallel bank is fully charged. Going BMS less is not for people who lack the knowledge. There will be people
who can learn to accomplish this task, and others who may fail. One would expect that a person who builds their own pack would learn about
charging procedures/discharging procedures as these batteries are not inexpensive.

At this point, I'm interested in a BMS and building one, as I now understand what a BMS duties and responsibilities are.......I can watch the BMS
to ensure it is functioning properly

Also, I would hope that you would not be referring to me with the words "misinformation". Any information that I've give is from:
Experimenting - Observation and Taking notes
If one reads many threads here, I'm sure they'd understand the risks involved during the learning process.
After all......didn't all of us start this way? Combination of learning, takings risks, experimenting, observing and taking note of outcomes.
Sounds like a regular day in a life

Tommy L sends....\\m//

I'm neither for or against BMS. I like to learn how everything works 8)

 

[tofuuu]

Its alive!!!!!! After hanging around 40v for a day and a half the charger kicked in and topped it up! Now its sitting happily at 58v thanks guys !

 

[arkmundi]

Its alive!!!!!!

Syncronicity once again. Just today, I brought my pack back, very much alive & healthy. Replaced one cell on this A123 AMP 12S pack, then balanced each of the 12 with a Voltsphreak single cell charger, then bulk charged with the smart charger. Back up to my normal 42V on full charge and 39V on 25% discharge.