yesa battery, 2009 doc test subject

[friedwires]

so i took a chance and bought this battery condition unknown. http://endless-sphere.com/forums/viewtopic.php?f=9&t=34397
The battery was shipped right away and it showed up sooner than expected. the first thing i noticed when comparing the battery to the one on the test thread was that this is the same exact battery that DocBass had tested back in 2009. I also noticed that the enclosure is in pretty rough shape, its got a few shipping miles on it.
i went ahead and measured voltage on the charge and discharge plugs,and read barely over 9v on each, i also measured at cell level, the highest being 2.2v, and the lowest being 0.00 with several being under 1.0v. i changed out the charge port to a 3-pin xlr and hooked up a 2.5a 60v sla charger and it would'nt take the charge. i did some more measuring and found that the pack voltage was 19.5 actually twice the voltage that was reading on the charge and discharge plugs. other than soldering terminals and doing instalations,i have no experience with lithium batteries. so far its just been plug and play for me. There is definately something up with the bms so i bypassed it and got the charger to turn on. i let it run for a couple hours till i got a voltage of 52.5v. i let it settle a bit then i connected 2 300w light bulbs directly to the pack and discharged to 47v or so and repeated the process three times. i tried to discharge through the discharge plug,but once the load was put on it the voltage on the plug went to zero. here are the cell readings from last night about 15 minutes after charge

3.32 3.32 3.32 3.31
3.30 3.30 3.30 2.95 52.5v
3.32 3.32 3.32 3.32
3.30 3.30 3.30 3.22

and here are the readings after resting overnight

3.29 3.29 3.29 3.28
3.28 3.29 3.29 0.88 50.0v
3.29 3.29 3.29 3.29
3.29 3.29 3.29 3.07

one thing i did notice while discharging was the low cell would actually reverse polarity only a couple minutes into discharging, i imagine that one is junk. i'm also still measuring only half of the pack voltage at the charge and discharge ports, i'd like to just pitch that stupid bms and run the battery without it. will these cells self ballance? and when should i stop the charge? is 3.32 enough?

 

[dnmun]

nope, your BMS seems to be functioning normally. you just have one cell that is so low that the BMS is shutting off to protect the pack. if you discharged without the BMS with that cell so low then it is now most likely dead from being overdischarged.

you should measure the voltage while charging. but it does look like that one cell is dead now.

 

[999zip999]

Friedwires you may have luck out. Dennis of comcycleusa ( Dirtdad ) sold bmc kits. Had 3 or 4 bikes on the side of his house none running at the time. He had trouble keeping a battery alive for them. He sold me a bmc600 kit for 1200usd turned out to be the old bmc600hs blow the center out of the clutch, he told me to call the # on the hub that's it.I had the hardest time getting the thing to work ( wasn't plug and play ). And lots of his customers had same story and he no longer sells them as of 2 yrs ago. Took them off his website. Went by comcycleusa San clemente 2yrs. ago and his wife said he no longer works there, was told to contact him at comcycleusa website. No answer ever. That one of his or a customers battery that failed. Looks like maybe one bad cell. So good luck as he couldn't figure it out. Maybe a winner.( All sells final ). Good luck.

 

[sangesf]

I asked that he test the cells on the larger format packs and got different numbers from what he stated on his for sale threads..
(e.g. He stated 14v (not via the BMS) on a 48v battery and when he emailed me the cells voltages, they added up to alot more than 14v. (Like 22v or so), so I'm a bit cautious...)

I'll buy that one (via paypal), but if the cells are not at the voltages stated, I'll be sure to do a refund procedure through paypal.. (even IF he says, "all sales final.." going through paypal, nothing is final.)

 

[friedwires]

Sorry to hear about your bad deal there 999zip999 but so far im pretty happy with this deal. even if i could only salvage four cells out of the pack it would still be worth my while just in the lessons learned in reviving them.

nope, your BMS seems to be functioning normally. you just have one cell that is so low that the BMS is shutting off to protect the pack. if you discharged without the BMS with that cell so low then it is now most likely dead from being overdischarged.

you should measure the voltage while charging. but it does look like that one cell is dead now.

you're right about keeping an eye on the voltage while charging and discharging, i've been watching the pack voltage pretty closely and only occasionally measuring at cell level. its amazing how fast that one cell fell on its ass though. one minute it was a bit low and a few minutes later it reversed. I guess that bms is there for a reason, lesson learned!
about eight hours ago i started charging that single bad cell with a 5v 150ma wall wart and its up to 2.90v and slowly creeping so hopefully i can get it to come around.

I asked that he test the cells on the larger format packs and got different numbers from what he stated on his for sale threads..
(e.g. He stated 14v (not via the BMS) on a 48v battery and when he emailed me the cells voltages, they added up to alot more than 14v. (Like 22v or so), so I'm a bit cautious...)

I'll buy that one (via paypal), but if the cells are not at the voltages stated, I'll be sure to do a refund procedure through paypal.. (even IF he says, "all sales final.." going through paypal, nothing is final.)

go for it and good luck sangesf, let us know how it goes

 

[friedwires]

i let the bad cell rest overnight and all day while i was at work, the voltage ran down to 1.66v in about 17 hours, now its back on the charger for the evening.

 

[liveforphysics]

You need to charge them ALL to 3.6v (or 3.65 or 3.7v etc) before doing any discharging.

With LiFePO4, you simply can't judge any state of charge or balance while you're between 3.2v and 3.4v. You could have one cell at 95% charged and one cell at 5% charged, and both are reading 3.3v.

 

[999zip999]

These threads are great for pieces of information LFP on the state of ( meaning of of ) There are great hero's hear THANKS for the help you guys give to many how we just ride and ride because of you. Thanks Zip

 

[sangesf]

i let the bad cell rest overnight and all day while i was at work, the voltage ran down to 1.66v in about 17 hours, now its back on the charger for the evening.

That's a bad cell, no matter what...
Even IF you can get it to hold a charge (3.2v for at least a day), then it's cycle life and AH is gonna be way... LOW!

 

[999zip999]

Fried your batt. is a 48v and sangfs yours is a what ?

 

[sangesf]

Fried your batt. is a 48v and sangfs yours is a what ?

48v 10Ah (16 cells in series).
I only want to use the "good" cells to match with some other 10Ah (actually tested to 8Ah) Yesa cells I have, to hopefully make a 36v 8ah battery to give to a friend. If I have to, I make it a 12v (??Ah) battery for him to use as an accessories battery.

If I can get 8 of those 16 to work (probable), I'd be happy...
If I can get 12 to work (doubtful), I'd be estactic!

 

[friedwires]

i let the bad cell rest overnight and all day while i was at work, the voltage ran down to 1.66v in about 17 hours, now its back on the charger for the evening.

That's a bad cell, no matter what...
Even IF you can get it to hold a charge (3.2v for at least a day), then it's cycle life and AH is gonna be way... LOW!

that one cell may be doomed but i still want to give it a shot, even if its just to see the pack cycle through the bms. a waste of time? maybe, but i'm having fun so what the hell

is it possible to trick the bms into running 15 cells? i dont mind the battery being 3 volts lower.

You need to charge them ALL to 3.6v (or 3.65 or 3.7v etc) before doing any discharging.

With LiFePO4, you simply can't judge any state of charge or balance while you're between 3.2v and 3.4v. You could have one cell at 95% charged and one cell at 5% charged, and both are reading 3.3v.

thanks LFP 3.65v it is then.

 

[sangesf]

It's never a waste of time testing. (or learning)

Well, if you can get that cell to stay at ~2.7v, I'm sure the BMS will charge the whole thing...
I don't see why it wouldn't?
If after it does charge the whole thing... Prolly won't discharge through the BMS if that cell drops below 2.7 very quickly..
Hence why I said, it would need to hold a 3.2v for at least a day..

 

[friedwires]

all cells are now resting at 3.4v and i'm still measuring only half of the pack voltage from the charge and discharge ports. and it still wont charge through the bms. i'm clueless

 

[999zip999]

Loose wires going into the bms

 

[dnmun]

all cells are now resting at 3.4v and i'm still measuring only half of the pack voltage from the charge and discharge ports. and it still wont charge through the bms. i'm clueless

gotta start with the fundamentals like i said in the first reply. measure the voltage of each cell while charging. list them.

measure the voltage on the gate of the charging FET if the charger will not push current into the pack.

measure the gate voltage of the output FETs to see if the controller has turned on the output FETs.

 

[friedwires]

Ok, the fet on the left i imagine is the charge fet and i have no idea which pin is the gate but from top to bottom it measures 21.0v 26.6v 26.2v , the five fets on the right all measure the same from top to bottom 53.0v 26.6v 52.8v

 

[friedwires]

i just read this interesting thread and i'm seriously thinking of going bareback http://64.64.13.141/forums/viewtopic.php?f=14&t=15757&start=7

 

[999zip999]

Yes I did run my 48v20ah ping without a bms for 3 weeks monitoring the pack and it stayed balance very well the charger shit off at 61.3v and didn't go to low. A lot of work checking cells, but all played along well. Ping didn't like it and got my new 60amp bms and plugged it in and was much happier. Yes you can if you what to be the bms.

 

[sangesf]

It's also MUCH easier when you use large format prismatic cells.
(I currently use 60Ah TSs.. Easy to be your own BMS with those.)

 

[friedwires]

at the price i paid for this pack i really have nothing to loose. i think i'll buy 16 single cell chargers from voltphreaks and rig up 16 panel meters.

 

[dnmun]

3rd try.

measure the cell voltages at the pins on the BMS from 1-16 while they are charging and list them.

go google wikipedia mosfet, and learn to use a voltmeter so you can figure out how to measure the voltages on the BMS.

 

[friedwires]

measure the cell voltages at the pins on the BMS from 1-16 while they are charging and list them.

go google wikipedia mosfet, and learn to use a voltmeter so you can figure out how to measure the voltages on the BMS.[/quote]


i do appreciate the help, although i'm new to bms it doesnt mean i'm new to a voltmeter or batteries. i measured voltage on the fets like you suggested, can anything be determined from those readings? i'll go ahead and take cell readings from the board while charging.

 

[dnmun]

nope the readings had no meaning because it appeared you had the positive lead of the voltmeter on the top of the battery trying to measure a voltage in the BMS which is in the ground of the battery.

once we see what the cell voltages are while charging we can try to figure what cell is the problem that causes the BMS to shut down to protect the pack. this is the first thing to do all the time when the pack doesn't work. 1st thing, #1, measure first. measure at the point on the BMS where the wires connect, put the tip of the probes in the solder at the base of the pin, black probe on the low side, red probe on the high side, write them down so you can compare later. post the list here so we can guess what to do next.

there is nothing wrong with the BMS. i saw the picture of it. if it had blown up it would be obvious. it is easy enuff to read about mosfets so you know what you are measuring. wikipedia is most probably the best place for you.

it doesn't matter how cheap the pack is or that you got it rather than someone else. if you don't destroy it by running it to over discharge or over charge it, then it will provide a lot of power for a long time.

 

[dnmun]

if you can list the individual cell voltages while it is charging, we may be able to help you find the problem with your pack.