My 36V vpower battery does not charge.

[anders8899]

Hello,

I have an homemade e-bike and got a battery problem.

When I arrived to the bike one day, I noticed that it didnt get charged during the night at all.

I had ran out the battery during the previous day.

I have a 1000w 36W hubmotor connected to a Vpower 36V 10A [http://vpower.hk/product.php?id=18] and a 6A charger.

It follows with an BMS, a board for battery protection so I feel safe that I did not over-use the battery but rather that the BMS board [http://vpower.hk/product.php?id=114] can be broken.

I saw that one cable soldered from the charger was partially burned off, and I repared that cable to no avail.

The battery has ~33V of voltage and the charger outputs ~45V. When I plug the charger in the bike (with a normal ampere running), everything works but it does not charge the battery.

What could the problem be? I could try to troubleshoot it with my voltmeter if needs to be.

 

[Spacey]

Check the battery Positive terminal connection to the battery....they seem to think that you can solder Aluminium to Copper..... well they can't and you might find that it was only the pressure of the tape holding it on.

 

[dnmun]

why do you think the BMS is broken? is there burn marks on the pcb where transistor burned up or hi voltage wire from the battery touched it and shorted out?

you have to post up a picture of the repair you did and why you did it? did you find the cause of the burned up wire?

what happened to cause it to burn up?

did you check the charger connector to see if it is continuous or did you measure the charger voltage on the BMS?

when you analyzed the BMS to conclude it was dead, did you measure the gate voltages of the mosfets or the voltages of the cells on the pcb where the sense wires connect?

did someone else tell you that the BMS was bad? do they know anything about them?

i have a Vpower 12S BMS here so i can compare but you have to show what you did to that one. i assume you used it until the battery shut off for LVC the previous day and then you just put it on the charger and forgot about it until today. then you discovered a burned out wire and repaired it. is that the sequence?

 

[anders8899]

Check the battery Positive terminal connection to the battery....they seem to think that you can solder Aluminium to Copper..... well they can't and you might find that it was only the pressure of the tape holding it on.

I have a picture of the battery and the BMS at :
http://imgur.com/CRPZG7L
http://imgur.com/9ru5ktW
http://imgur.com/GPVsTOb

There seems to be no soldering at the cables, only on the BMS end, mabye thats what you meant? But that soldering seems rigid, not like the mosfet soldering which is of very dubious quality.

why do you think the BMS is broken? is there burn marks on the pcb where transistor burned up or hi voltage wire from the battery touched it and shorted out?
you have to post up a picture of the repair you did and why you did it? did you find the cause of the burned up wire?

what happened to cause it to burn up?

did you check the charger connector to see if it is continuous or did you measure the charger voltage on the BMS?

when you analyzed the BMS to conclude it was dead, did you measure the gate voltages of the mosfets or the voltages of the cells on the pcb where the sense wires connect?

did someone else tell you that the BMS was bad? do they know anything about them?

i have a Vpower 12S BMS here so i can compare but you have to show what you did to that one. i assume you used it until the battery shut off for LVC the previous day and then you just put it on the charger and forgot about it until today. then you discovered a burned out wire and repaired it. is that the sequence?

I think the BMS is broken because a EE-friend looked at the whole setup and concluded that since there was evidence of a partially melted wire in the plug to the charger and since there was no fuse to break, and the battery and charger showed voltages (I measured the battery and its 33.0V) then the fault must be the BMS. My EE-friend is not an expert of BMS'es but everything else seems to work.

There seems to be no burn marks, only corrosion since the previous owner made a terrible job waterproofing the container with the electronics.

I have not measured gate voltages or mosfets on the BMS, but the charger voltage is -33.0V and the other wire (battery) is 33.0V. I could measure these things if I only knew where

Yes the sequence is right, I used it until the end, charged for 8 hours, noticed its dead, took out the charger and then tried to fix it, charged it again, and noted that it doesnt work.

P.s If you have any blueprints of the BMS, it would help so I can investigate more d.s
p.s2 thanks! d.s2

 

[dnmun]

one last try.

please post up a picture of the wire you repaired after it burned up.

again, you did not say if the wire burned up before you used the battery all the way to LVC or if it happened afterwards.

your friend who is the EE would have measured the gate voltage on the mosfets and checked to see if the mosfets were still functional if he determined it was dead. so ask him what he measured. or have him post up on your thread.

 

[anders8899]

one last try.

please post up a picture of the wire you repaired after it burned up.

again, you did not say if the wire burned up before you used the battery all the way to LVC or if it happened afterwards.

your friend who is the EE would have measured the gate voltage on the mosfets and checked to see if the mosfets were still functional if he determined it was dead. so ask him what he measured. or have him post up on your thread.

Hi and thanks for helping.

This is the wire that looked burned:
http://imgur.com/wLyQBCK
It is connected to the charger on the outside of the bike.

I do not know when it happend and have no evidence of why. I found it when investigating the bike after using the battery to LVC and seeing that its not charged. I think it happend because of bad soldering by the previous owner which made the resistance in the cable too high, and which then made a part of it melt.

I have now fastened the cable really good with a device like this: http://www.conrad.de/medias/global/ce/3000_3999/3700/3700/3706/370670_BB_00_FB.EPS_1000.jpg

Well we didnt measure the mosfets, but I asked the manufacturer for a blueprint that I can send him so he can show me where to measure.

 

[OlderThanDirt]

In instances when I have accidentally run my battery down to LVC, my charger refuses to charge also. It seems to have an internal protective circuit to guard against output short-circuits. The fix is to momentarily connect the charger to the battery output terminals (not the charging terminals). This resets the BMS and charging then proceeds normally.

You might try that trick just in case that might be your problem.

 

[dogman dan]

It could be something like that, but it shouldn't be that way if it is. That should only happen if the battery is way below bms cutoff.

The most likely thing, is that some where else along the line, the charger is not getting connected to the battery.

Does the red light on the charger go on? If it doesn't, it's not getting a connection. That broken connection could be in the wire to the bms, or the wire from the bms to the battery, or even in the bms itself.

If you bypass the bms completely, and it won't charge, then it must be the charger or it's wire and plug.

 

[Tommy L]

Some chargers will not charge at all if it detects a battery voltage too low.

My Bionx chargers will not charge if the pack is too low.

I have this charger. It is very smart and detects a low pack voltage and very slowly ramps up the
voltage/current to get the pack slowly charged.

Tommy L sends....

 

[anders8899]

It could be something like that, but it shouldn't be that way if it is. That should only happen if the battery is way below bms cutoff.

The most likely thing, is that some where else along the line, the charger is not getting connected to the battery.

Does the red light on the charger go on? If it doesn't, it's not getting a connection. That broken connection could be in the wire to the bms, or the wire from the bms to the battery, or even in the bms itself.

If you bypass the bms completely, and it won't charge, then it must be the charger or it's wire and plug.

The charger has a green and a red light on when the bike is not plugged in and when the battery is full. When its charging its only a red light and the charger is humming. Right now the lights are green and red and theres no humming when I plug the bike in.

In instances when I have accidentally run my battery down to LVC, my charger refuses to charge also. It seems to have an internal protective circuit to guard against output short-circuits. The fix is to momentarily connect the charger to the battery output terminals (not the charging terminals). This resets the BMS and charging then proceeds normally.
You might try that trick just in case that might be your problem.

I will try this trick, I just want to confirm that I intend to plug the charger in in the right way, and how long should I try to charge the battery directly, bypassing the BMS?

http://imgur.com/q5tbTEI - I will try to plug the charger in the red thicker cable shown on this picture
http://imgur.com/yPW5GpP - I deduced which wire should go to which with the voltmeter, and since it shows +xxx Volt and not -xxx Volt, then I can guess where the + is.

 

[dogman dan]

The green light indicates either charged, or disconnected. You are still disconnected somewhere.

I thought that 35v was a bit high for it, if the charger was just refusing to charge a low battery. Possible, but not so likely at 35v for a 36v battery. Now, if he'd said his pack was resting at 26v, then I would find the low voltage a more likely culprit.

He's just got something disconnected. But it could be that frying something caused it. That melted wire would have me hunting for the short.

 

[anders8899]

The green light indicates either charged, or disconnected. You are still disconnected somewhere.

I thought that 35v was a bit high for it, if the charger was just refusing to charge a low battery. Possible, but not so likely at 35v for a 36v battery. Now, if he'd said his pack was resting at 26v, then I would find the low voltage a more likely culprit.

He's just got something disconnected. But it could be that frying something caused it. That melted wire would have me hunting for the short.

Well hunting for the short, we could only point out the BMS as the culpit, but it doesnt seem to have any fuse...

 

[dogman dan]

Trying to charge it completely bypassing the bms will confirm that the problem is, or is not, in the bms. The short could be in the charger too. It might light up normal, but not send current to the plug.

It could be that a poor connection just heated up that wire, but that's usually seen on the discharge side, not the low amps charging side.

 

[anders8899]

Hello after some days of tinkering, then I discovered that the battery might be the dead one.

I did connect the charger directly to the battery outputs as per this thread:

In instances when I have accidentally run my battery down to LVC, my charger refuses to charge also. It seems to have an internal protective circuit to guard against output short-circuits. The fix is to momentarily connect the charger to the battery output terminals (not the charging terminals). This resets the BMS and charging then proceeds normally.

You might try that trick just in case that might be your problem.

But after that try nothing seems to have happend (no sound, no lamp change) when I charge the battery in a normal way.

The only thing that happend is that the battery current went up from 33V to 36V.

When I try to bypass the BMS and connect the battery directly to the bike battery input, nothing happends, whilst when I do that with the charger everything on the bike runs fine.

I guess the battery does show voltage but does not output any current, so I guess it could be dead?

I will try to repair, and if it fails buy a new battery even though I only used my eBike for a month, since I really love ebiking and I would not want to buy a moped. I did expect some troubles with maintenance, but thats a part of it, and while its broken then I pedal

 

[dogman dan]

You have confirmed that the charger is still outputting 45v?

 

[anders8899]

You have confirmed that the charger is still outputting 45v?

yes I did

 

[anders8899]

would there be any point in cutting the battery open and peek around inside?

 

[dnmun]

it would help if you posted a picture as requested. not a link.

 

[anders8899]

it would help if you posted a picture as requested. not a link.

 

[DAND214]

didn't I see those PICS before?

Dan

 

[dnmun]

somebody has hacked the shunt already.
can you measure the voltage on the gate of those mosfets between the source leg or B- and the gate?

the mosfet legs are gate drain source from left to right. measure the voltage on the left leg.

 

[dnmun]

too much to measure?

 

[dogman dan]

Ok, I finally have it clear in my mind, that it's not a charger problem.

Time to open up the pack, and see what the shunt mod allowed to melt inside. You got nearly no amp limiting I bet.

Best guess at this point, you have killed it with something drawing a few amps. It might not be visible, but just some really dead cells. You can check that at the bms plug, one cell at a time. Bet some are below 1v.

 

[anders8899]

somebody has hacked the shunt already.
can you measure the voltage on the gate of those mosfets between the source leg or B- and the gate?

the mosfet legs are gate drain source from left to right. measure the voltage on the left leg.

Hello! I just got back from a long vacation (honeymoon), and will start working on the bike.
Can you provide some tips or write on the image where the source leg/B- and the gates are located?

Ok, I finally have it clear in my mind, that it's not a charger problem.

Time to open up the pack, and see what the shunt mod allowed to melt inside. You got nearly no amp limiting I bet.

Best guess at this point, you have killed it with something drawing a few amps. It might not be visible, but just some really dead cells. You can check that at the bms plug, one cell at a time. Bet some are below 1v.

I will try to follow the examples from this video tonight: https://www.youtube.com/watch?v=TI2NfqE_Yas and lets see if a cell is dead!

 

[Jason27]

Can you still return the battery or get your money back??