hailong battery on/off switch

[goatman]

I put my dmm on the battery connectors, its 13s5p, voltage said 52v. turn off battery voltage dropped to 44 volts. why isn't it 0-volts? is that normal? its not connected to the controller.
im thinking its something to do with the bms

 

[madin88]

I have exactly the same problem and yes it is the BMS which doesn't turn off completely.

Can you open the case and post a picture of it?

Mine also shows around 44V (13s battery), however if i short the wires it goes down to 0V without any sparking so at least if you have it switched off and attach it to the bike, the contacts will not suffer damage from controller inrush current. But kinda annoying if you planned to use the BMS to power on your controller with display as it will stay somwhere between on an off state.

 

[fechter]

There is a high resistance resistor across the FET switch in most BMS units that allows it to detect load. Your voltmeter has a very high input impedance, so you will see a reading. If you put some resistance across the meter, like 1k, the reading will be much closer to zero.

 

[goatman]

I have exactly the same problem and yes it is the BMS which doesn't turn off completely.

Can you open the case and post a picture of it?

Mine also shows around 44V (13s battery), however if i short the wires it goes down to 0V without any sparking so at least if you have it switched off and attach it to the bike, the contacts will not suffer damage from controller inrush current. But kinda annoying if you planned to use the BMS to power on your controller with display as it will stay somwhere between on an off state.

I had the case open and the battery is siliconed to the housing, tried to get it out but im going to break something.
I was thinking the same thing, use this battery to turn on/off the controller. atleast its not the LVC of the BMS

 

[madin88]

There is a high resistance resistor across the FET switch in most BMS units that allows it to detect load. Your voltmeter has a very high input impedance, so you will see a reading. If you put some resistance across the meter, like 1k, the reading will be much closer to zero.

That would make sense, but the LED voltmeter display (on throttle grip) also reads around 44V, so the resistance can't be that high and there is still a little spark if i short the output. But i will try with some resistance and see what happens. thanks for the hint

I bought this BMS from aliexpress, and other buyers had same issue as they have mentioned it in the review.
I have found a different BMS with on/off function which turns off the output to 0V instantly and will use this one for future battery builds.

 

[goatman]

There is a high resistance resistor across the FET switch in most BMS units that allows it to detect load. Your voltmeter has a very high input impedance, so you will see a reading. If you put some resistance across the meter, like 1k, the reading will be much closer to zero.

That would make sense, but the LED voltmeter display (on throttle grip) also reads around 44V, so the resistance can't be that high and there is still a little spark if i short the output. But i will try with some resistance and see what happens. thanks for the hint

I bought this BMS from aliexpress, and other buyers had same issue as they have mentioned it in the review.
I have found a different BMS with on/off function which turns off the output to 0V instantly and will use this one for future battery builds.

I just hooked it up to a phaserunner and even though the bms is 44v it turns the phaserunner off and on. maybe the phaserunner eats up that resistance.

I just turned off battery and it turned phaserunner off so I slid battery out and dmm the prongs. 45.2 volts weird. the other time I checked at the Anderson clips 2 feet away.
its turning on and off the controller and I don't think the bms is consuming energy, this pack has been sitting atleast 3 months and its voltage was 50 volts.

 

[docw009]

I installed a 48V BMS that did that. The vendor said it was fine. I would have been happy if an attached controller would pull it down to zero, but but the battery could sink about 50 ma when "OFF". I took it out.

Doesn't have to happen, in my opinion. Got a half dozen packs that turn when asked to turn off.

 

[goatman]

I installed a 48V BMS that did that. The vendor said it was fine. I would have been happy if an attached controller would pull it down to zero, but but the battery could sink about 50 ma when "OFF". I took it out.

Doesn't have to happen, in my opinion. Got a half dozen packs that turn when asked to turn off.

im still playing with this battery, its new to me. the charger was set to 52.6v/4.05 per cell. I took it out full throttle at 30 amps? I haven't looked at the bms yet. 7 volt sag. I reset the charger to 54.6v to see if the pack is out of balance. first charge to cut off it dropped to 54.3v so I plugged it back in to charge. im going to leave it plugged in to see if that fixes the sag/out of balance.

 

[amberwolf]

I installed a 48V BMS that did that. The vendor said it was fine. I would have been happy if an attached controller would pull it down to zero, but but the battery could sink about 50 ma when "OFF".

that sounds like there's a problem in the gate drive circuit for the fets in the bms, leaving the fets partially turned on, allowing leakage current thru them.

that may mean the gate drive doesn't turn the fet all the way on, either, which means the fets will heat up durign discharge, potentially quite a lot.

same thing for charging, if it's done thru a different set of fets thru a different port than discharge is done thru. means that if they're not turned off fully, the charger can still force current thru cells when the bms has tried to turn that off to protect tehm from overcharging, if that current is higher than the balancing shunts (if it's taht type of bms) can shunt around the cells that are already full.

so if you ahve a bms with the first problem, i recommend checking for all the other potential related problems.

 

[docw009]

so if you ahve a bms with the first problem, i recommend checking for all the other potential related problems.

Not problem. I replaced it with one from Annpower.

For the first leaky BMS, I got a replacement and that one blew up when I tried to run power thru it. The vendor blithely went on and on about how he was gonna take care of me, until the Paypal dispute deadline expired. Then silence. That was my intro to how Paypal sets a deadline.

 

[madin88]

Not problem. I replaced it with one from Annpower.

Would you mind to share a link to the shop?
was it this one maybe:



those with the large yellow part i have tried and they work well too (they are even available with USB board on alibaba):



This is the one i have which does not turn off complete:

View attachment 2

 

[docw009]

I had the Annpower 13S 25A with on/off switch. The one that failed/blew up looked like yours last picture.

 

[amberwolf]

the yellow thing looks like a ptc autoresetting fuse. guessing it's in series with teh charging input to prevent sparks on chargeer connection? if so then it wastes power in charging as heat, if charging fails ot happen then bypassing it with a wire would fix charging.