Bigbadjohn

When I put it on charge the red light does not come on, dead battery
I took it apart and measured batteries with multimeter all say 3.5 V is this because they are all connected
what first steps should I do to repair this pack

gregf83 

Is the total pack voltage 35V? It looks like there are 3 cells in parallel with 10 in series. You should be able to measure 10 separate cell voltages. 3.5V isn't low so the protection circuit shouldn't be disabling anything at that voltage.

Doc_Wui

Measure it like this, Starting at one end, keep the black probe on the last plate. Move the red probe up on successive plates, looking at both sides. Write down the values. You should see the voltage increase from 3,5 volts on the first number, to 7.0 volts on the next, and so on til you reach the end, The battery is 30 cells, right? Arranged as 10 groups, with three cells in parallel per group. As you walk the probe up, you get to see the voltage on each group.

By the way, in the picture , you started on the most positive end of the battery ... which is why it shows -3.5 volts. You should start on the other end if you want positive numbers.


Do it this way, and you'll know what the general health of each cell group looks like,

What's the open load voltage from the charger. Is it 42 volts?

And be careful. Lot of energy in that battery, It's not "dead".

The more interesting picture would show the side with the circuit board. Does it extend the length of the battery?

Bigbadjohn

Thank you so much for taking the trouble to make the diagram it greatly helped.

2 more pics from either side

I went up on the right side of diagram readings 7, 14, 21, 28

left side 3.5, 7.5, 10.5, 17.5, 24.5, 31.5

open load is 35V

this is a 36 v can you tell the AH would be 10

I guess these batteries would not be the best to reuse as they are completely covered with zinc and hard to remove
I can't understand why they don't make them with terminal then you would not need a spot welder.
Soldering or spot welding can't be good for the batteries


I watched a Youtube and it suggested bypassing the BMS for a short time to charge batteries then BMS might kick in

Doc_Wui

I'm not able to follow the data. If each cell is nominally at 3.5V (about 40% charged), the voltages should increase to 35V in increments as follows.






You have a 3,5, 7.5, 10.5, 17.5, 24,5, 17.5 sequence that doesn't fit.

I took an educated guess and figured the negative end of the pack is on the right side. If, not, then the reading will just get more negative, but otherwise the readings will be useful.

What you want to see is that none of the ten series groups are below 3 volts. And you can see there's still over 31V on the pack, so take care, with all the wires exposed like that.

Bigbadjohn

I re-did it and got exactly the same as your diagram above, so the batteries overall look good I think. now have to figure out why it is not taking any charge I will try to charge again.
possibly the BMS is at fault, better that than the batteries.

Thanks again John

Doc_Wui

The charger puts out voltage? It should be around 42.0 volts with nothing attached. The wires from the charge plug to the battery are intact?

You never showed the side picture of the BMS circuit, but my guess is that it runs the length of the battery, and the metal plates on the cells are attached to it. That would make it harder to replace.

Bigbadjohn

Yes, runs the length of the battery, and the metal plates on the cells are attached to it, posted another pic.
I am charging it from main terminals and its taking charge with red light, doing it the normal way did not take charge giving it a couple of hours and will measure voltage I know this is not the best way but the only way, all batteries seem good .
More concerned about damaging charger as its the only one.
I have another electric bike I ride every day using same charger 36 V.
These Ebikes are amazing did 30 miles yesterday with little peddling still had over a third left AH 14 Panasonic



should be OK.

Doc_Wui

Cautionary warning. Charging thru the main wires is not safe. It bypasses the overvoltage circuits. You can overcharge your cells if they get unbalanced, and that will happen because you're also bypassing any balance circuits. You can also overcharge if the charger puts out too much voltage. Overcharging is probably one of the main reasons batteries catch on fire while charging, I wouldn't do it.

That BMS now looks like it's easily replaced if you know how to solder. They only cost about 20-30 dollars. Much better than having your battery start a fire,

Bigbadjohn

Thanks, I knew it was not good to charge that way I let it go to 40.5 V then disconnected
I think I know the problem everything works except the XLR I think its called microphone charging plug all wires are live
it looks like a fuse covered with shrink insulation that would explain why that the only think not live.
not a good place to put a fuse and not easy to replace I will send a picture to the bike manufacturer and ask them what to ddo




Other side

Doc_Wui

Good detective work on the fuse. Take care.