Did i fry my battery?

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Pwnlord187

10 W
Joined
Jul 27, 2016
Messages
73
Hello ebike community,
I have a question, and if anyone could shed some light it would be appreciated.
So ive just finished pitting together my electric fat tire beach cruiser, (including a motorcycle headlight, taillight, turn signals,brake lights and high-beams. Rear view mirrors and everything its pretty sweet) i housed my 48v 30ah battery snug in the frame with a waterproofed tarp, rope and in a cage , ready to go..but it takes me about 10km then quits which is upsetting, ive spent so many hours on this thing. One thing, ive done (which is stupid i admit) is when linstalling and looking to build a cable from my battery to XT plug of my controller, while testing plugs i had laying around for a snug fit, one cable i tried was plugged directly into a live power bar so when i plugged it in i was welcomed with a large spark blast having the cable running 120v hot ac to my pack. The pack still measures full and at first seem to be fine, but now ive noticed severely less capacity from my expensive pack.

Could i just fried my bms needing to replace it considering it is the next component in line? Or is it likely this f*ck up is serving me more dire consequences?

Thanks
 
Ok i just tested my battery (that wont start up my bike) and it reads 49v, having died after going only 7km at max speed, starting at 54V (the one time previous, i went about 15k, shutting me down at 48.4v having started wih the battery reading 58v) is this a normal drain rate? (Aside from being cut off early) i thought i had remembered this pack taking me farther per volt..
 
Well something is amiss...
A ~1400wh battery should certainly take you more than 15kms (unless your a car!) even at20wh/km you should get 70kms before LVC.
I'm assuming it's a li-ion chem in a 14s config if you're charging to 58.8v. Lvc at49v is 3.5v which seems high...Is this voltage take under load? Or at rest afterwards?
You'll probly have to do some deconstruction and testing of cell groups to figure it out. Maybe you've got a dud in there.
If it's charging and LVC&HVC are working, your bms seems to have survived the insult but there could be something funky going on with it.

I'm just thinking that at 49v you prob do have a cell grp that is sagging down to Lvc with the rest propping up total voltage when you measure it.
Can you get at the cells easily?
 
After that KFF,, definitely time to start looking at the battery. Look for damage, you may just simply have some cells disconnected now.

As for normal drain rate,, rate for what? Some of us here have bikes that could drain a battery that fast. I'm assuming you don't.

35 wh per mile is typical for 25 mph. So it should have taken a lot longer to drain 1500 wh.

Started at 58v one charge, and 54 on another? That's sounding like one cell group at zero volts. Take it apart, at least enough to get at the bms wires and check voltages group by group.

This thread has some links to previous battery fix threads. some good info there. https://endless-sphere.com/forums/viewtopic.php?f=14&t=85951&p=1257829#p1257829
 
A faulty bms can play a trick for sure. I would start by looking for errors with the bms.
Especially if you connected wall power into the bms, can not imagine how that happened tho :shock:

Measure signal wire connections, to confirm the different cellgroups having proper voltages, and check main terminals in and out of the bms.

Do you have any idea about your current consumption when riding? Do you know how much energy those 10km took?
 
I typically put the frying pan on about half heat with a little butter on the pan so the battery doesn't stick. This makes a delicious meal that's not only fast to make but eco friendly as well!
 
Hey, thanks for the replies. When im riding id say i average at around 1500w (maybe more like 1750 actually) recently, ive been riding with the voltmeter open throttle pulls the meter down to 43-44V soon after riding (i know its normal to read a reduced voltage) just thinking maybewhen im gunning it , it hits 40..ill have torip open my pack within the next couple days (no its not gonna be easy! I binded it so tight to the frame that even i myself knew it be a b*tch to open or remove, little own a thief) anyways its a lifepo4, and, possibly 52V nominal (seems to be) although i was surprised i could charge it that high until after the f*ckup (although i could have just not noticed, i wasnt as focused on that kind of thing when i first got the battery) i got the battery used as well, so even more a reason to open up the pack. Didnt get rippedoff though, i could go at least 60 km on it easy on my last bike, before i stored it (empty for about 3-weeks, then full for about another 3-weeks..i know not the best) anyways, i guess ill have to take it apart, ill report back with my report.
Thanks again
 
Basically, more or less was hoping to hear that my bms just took the hit, to relieve myself of having to think about financing another battery, until i open it ..but i guess theres inly one way to find out
 
Ok. Thanks. (The fact that it LVC@48V is strange..must be screwed ip) another thing, should i take battery cooling into deeper consideration? Ive waterproofed the hell out of my pack..wrapped a tarp around it, then roped it a zillion times, then put a cage around it. With waterproofing it in focus, not so much with keeping it cool. Is it harmful to ride it while waiting for a bms to arrive? Will take months unless i can find something local..
Cheers
 
I had a pack doing the similar story, dropping voltage quickly and getting short distance. That case the battery was sitting for a bit. I ended up leaving it on charger for 3 days letting the BMS do a good balance to the cells. I got another year from the pack before I sold the bike. Now reading your story I would go with a new BMS still as that is likely the issue. Also The high reading on the low voltage shut off was same as mine as one cell pack was dropping to low giving the BMS reason to shut down the pack.
 
Since it still runs,, I tend to think not the bms. I think I know nothing till you open it up and see if anything obvious happened, like a wire melted when you flashed it.

BMS may be letting it run, because its fried stuck that way is one possibility. Open the bms first, and look for an obviously cooked fet.
 
Only thing i know is its a blue bag lifepo4 and 48v30ah (although appears as it may be 52v labelled 48v)
Im in vancouver canada
Cheers
 
how many watts are you pulling? A lot of ebay lipo BMS are rated for only 1000watts unless you specify more watts for better BMS. Also does your display (if you have one) go blank and shut down when bike shuts down? If your display stays lit and bike shuts down could be another issue. Give us as many details as you can even if you think they are not important.
 
Thanks. Im pulling about 1750w maybe higher when it shuts down, and when it does, everything is down instantly. Plugging the charger back in (even for a minute) seems to allow me to fire it back up, and also check the voltage (by pressing pwr on the lcd3 twice) and last time this happened it read 52v
 
Ok go for a slow drive as long as you can. You are likely pulling to many amps for your bms. Without more specs on your battery that is my best guess. Have you tried to fully balance charge it? Long charge to let the bus do a full balance. That is alot of watts if it's a 1000 Watt pack.
 
Ok, i will do that. Thanks.
Wouldnt my pack be 1500W?
And my motor is also labelled as that as well.

Another thing, how much voltage drop is normal to see on the meter under full load? Someone told me if its a lot, it means my pack has lost its max capacity. And does the bms cut me off when the voltage hits that amount even when it dips down under full throttle?
Was just riding started at 52 and with the throttle open it dips down as low as 40.1. I set the controller to allow 5% less voltage before cutoff compared to the default 40, maybe this is why i didnt get shutdown on my last ride. But the time it takes riding from full, to get the voltage to read near 40V isnt very long. So im suspecting -12v reading at max throttle might be abnormal?might
 
Ok, lets back up a bit. What is the history of this battery? Did it sit for months waiting for your bike? Get a cheap voltmeter, or hook up your DVM, and see how much its sagging under load.

Sounds to me like it may be sagging a lot. which means the cells can't handle the amps you are giving them. It may improve if you just get it more balanced, it may be just one half charged cell group sagging so much.
 
48v lifepo4 has 16 cell groups and all it takes one low group to hit lvc to shut off the bms. Like 2.8v or 2.9v. Si balance first. Then if no help it's time to get to the bms and sense wires. Check voltage of each cell and write down on paper 1- 16.
 
Pack voltage fully charged, then each cell group starting at neg. End.
58v
1. 3.65v
2. 3.50v
3. 3.45v



16. Xxx volts.
Must be on paper and shared.
 
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