Is my battery toast?

[wildblueyonder]

Ok, my first e-bike project (yeah!), I've got a 48v rear hub motor and I ordered, and received, a 48v 30ah vpower battery from China. Upon receiving the battery the voltage read 55.3, good to go right?

So I order some Anderson powerpoles and solder the ends so I've got a nifty, efficient connection, rig the whole thing up for a test run and BAM! off and running like a shot! Sooo exciting, that sucker flies, awesome, right?

So the thing is really just jury rigged on there just to see if its gonna go, so I take it apart to charge the battery and fashion a more sturdy and permanent arrangement... And now the thing won't work. Not even a jerk. Lights to the throttle, yes, but zero movement.

Looks like its the battery, after plenty of charge time it only registers 45.9v. I assume this is just not enough to move a 48v motor, correct?

So any thoughts. The battery is a duct taped job, my feeling is that I'll have to go ahead and take it apart and diagnose and replace the offending cells. Could this be a BMS issue? If so, where to start a diagnoses. Any help would be great, thanks!

Man, though I only rode it a few times around the block it was sweeeet!!

[Tench]

Check the polarity on your charger output first, do you have another charger you could connect to see if the pack voltage rises with a different charger? Was the chargers input voltage correct for your mains supply?

Where you trying to charge it through the output leads?

[dnmun]

do you have a voltmeter? can you measure the voltages of the cells while the battery is charging? at the sense wire plug if the pack is still wrapped up in tape.

[liveforphysics]

The BMS has tripped off for some reason.

You should try to get some charge in the pack ASAP, after checking balance on the cells to confirm you don't have one at 0v or something.

[dogman]

How is the charger acting? Does the red charging led ever turn on? Don't peel it just yet, just get acess to the wiring from the pack to the bms.

You could have a few different things happening, bad bms, or bad charger. Kind of unlikely that the battery died that fast, but still possible.

Get a voltmeter, and check stuff, charger works, to start with. Polarities are correct. If the charger works, attach it to the + and - leads of the battery before the bms, and try to get some voltage into it if the battery is that low.

Most likely, is your bms just smoked, and you can fairly easily replace it.

[Jason27]

Dude, seriously people need to stop buying crap batteries from china. More and more people are having bms issues which is probably the problem your having. have you tried to contact vpower??

Just because you think you're getting a great price does not mean you're getting a great product. Lessons learned.

[999zip999]

Voltage on main output.
voltage before bms
voltage from charger
voltage on 16 cells, can you get to sense wires to check. Should be between 2.5 to 3.6v and not over 3.9v per cell, but all should be in same range like 3.2-3.3v. ect

[wildblueyonder]

Well, its occam's razor - used a new charger and while not back to my base voltage I'm at 53.5 - that should be sufficient, no? Thanks to you all for your suggestions. Going forward, is there any way to 'test' a battery charger? Any advice at all when it comes to chargers, or charging batteries?

So still not back up and running, I think I've got a controller issue now. The lights on my throttle light up but I just get a 'click' noise inside my controller when I try and engage the throttle, I will start another thread once I open it up and see what's up. Boy they sure don't make it simple to do that, looks like about 20 screws just to open a little 8x4 box.....