Battery pack shut down problem

[RTLSHIP]

I have a 48/20 Lifepo4 pack that suddenly shuts down when throttling. It has always worked well on my bike. Recently, I did attach new 10AWG wiring
from pack to controller which replaced a busted 12 or 14 awg wire. I suspect the BMS is fine. Could it be the excessive and thicker wiring?
This bike runs with other packs. Any helpful feedback would be appreciated.

 

[dogman dan]

Bad connection? Too thick wire couldn't be a problem, but a bad connection could be. Did you solder directly to the bms? Maybe cooked something on it?

It's clear, for some reason you have voltage sag, Or the battery is not fully charged.

 

[999zip999]

Like to know who's pack is it, What type of lifepo4 ?

 

[neptronix]

cell level monitoring is a good way to find out for sure.
My suspicion is that you have bad cell or two in that pack.
Watch the voltages in real time as you hit that throttle; my bet is that a few cells are dropping out and you are hitting the LVC point.

 

[dogman dan]

That would be the most likely reason for all the sag, that's tripping the bms.

 

[RTLSHIP]

I did not solder directly to BMS. Rather, I soldered (and taped) to leads. It worked initially. These are 18650 cells and it is or was good for 16.5 ah. I will consider Dogmans soldering advice. Pack was sold from a Volgood (ebay) to icecube57. I bought it used in June '09. has maybe 100 cycles
thanks to all

 

[BLUESTREAK]

Talk to AMBERWOLF he was able to do some repair on a pack like yours.,same problem.

 

[dogman dan]

Hmm, a bargain 18650 pack. That gets more likely it's a worse problem. Popped spot welds in the pack is common, along with just weak cells that die off with that type of inexpensive cells.

 

[RTLSHIP]

ok I soldered wiring directly to BMS. The multi meter reads 46.5v. I charge for 2 minutes and it's up to 59.
Some contact has come loose or the BMS is faulty.
I did get the tire to spin at top speed but it's hard to trust the pack at this point. Any buyers or suggestions?

 

[dnmun]

measure cell voltages while charging, list them, then we can start guessing.

 

[Bill H]

You mentioned in the original post that this problem started after you upgraded from 12 or 14 awg to 10 awg wires. I suspect you did not have the problem in the past because the smaller wires were causing voltage sag at the controller enough to limit the current from the pack. Bigger wires allowed the controller to see more voltage and it was able to pull more amps until the BMS hit one of its various limits. I had a BMS in my setup and it would cut out when I hit my horns (dual car horns in series on a 8S lithium setup).

I have a bunch of 18650 cells from laptop battery packs so I have small packs hooked up to my lights that work great instead of AA and AAA batteries. My main pack is made from them also but I currently have a dead controller stopping me dead in my tracks.

Bill

 

[RTLSHIP]

I can only charge it for 3 or 4 minutes. It then gradually drops from 59v to 46v. I don't want to take the duct tape apart yet.
I'll contact amberwolf

 

[dogman dan]

May as well just give it to AW. Then look at something better. At least a ping, allcell, or better, an A123 pack.

 

[999zip999]

Check cell levels and or after 2yrs. it's almost time to cut it open.

 

[dnmun]

you don't have to cut your pack apart to measure the voltages or inspect it. you can measure the voltages on each cell on the sense wire plug on the BMS. just don't short out the probes while doing it.

then charge it and find which cell charges up fastest by measuring the voltages at the sense wire plug while it is charging, and list the voltages, and in 5 minutes you will have most of the info you need to figure out what is wrong. then we can guess.

 

[RTLSHIP]

I have 5 other battery packs, so I don't need to buy another pack yet. Cost per mile to ride. maybe 1500 miles/250.
16 cents per mile assuming, among other things, pack is not repaired or resold.
Update: I'm shipping it out to "Amberwolf." He's going to operate on it and set up a thread w/ pictures.
Could be a "loose string" or two in the pack.