Motor Controller cut out during riding

[newb123]

When I take my battery pack w/BMS off the charger, charged at 42 volts, when I go to throttle from a dead stop the controller cuts out. I disconnect my pack w/BMS from the controller, re connect, and it will operate normally as long as I get up to speed from a dead start with pedal assist. I dont think its the BMS doing this. I dont have a wattmeter display module yet to see the amp draw from a dead start.
Is there anyway to stop this annoying cut out?

 

[newb123]

I think I posted this in the wrong thread so I will re post it here

I have a 36 volt 10 amp brushless ebike motor (Chinese kit brand) and controller

42 volt (20 batteries in series parallel config) li ion pack. all cells balance charged to 4.2 V each

when I throttle from a dead stop with the pack fresh off the charger, the controller ( I think ) cuts off

When I dis connect re connect the power cable from the pack, to the controller, the controller, throttle works

Is there anyway I can correct this annoying situation?

 

[fechter]

You probably need a bigger battery. Try measuring the pack voltage while running the motor.

 

[newb123]

why would I need a bigger battery, if its charged full at 42V, and my motor is rated for 36 V?

Your saying its sagging under load?

I guess one of those watt meters with amp volt features also, would help real time in this situation

once I ride, and the voltage goes down, seems the cut out goes away, but I have experienced every time I start with a fresh charge

a bigger batttery means, more cells in parallel?

 

[fechter]

once I ride, and the voltage goes down, seems the cut out goes away, but I have experienced every time I start with a fresh charge

OK, that's maybe not from excessive voltage sag. If it was too saggy, it would get worse as you ride more.

Another possibility is the BMS is cutting out. If this was the case, voltage at the controller would be zero after it cuts out and you would have to cycle power or disconnect the battery to reset. If this is the case, you need a higher rated BMS or modify the one you have for a higher current.

 

[newb123]

would have to cycle power or disconnect the battery to reset

this is exactly what I have to do. The BMS is rated at 48 V, so would the cut out cause be the current?

 

[kdog]

Not the voltage you are concerned about here, but the amps . What are the amp ratings on both the controller and bms?

 

[newb123]

well here are the general specs for the BMS



10 string 36V 37V 42V lithium battery power protection board

Overcharge, over discharge, over current and short circuit protection

Split-mouth 35A discharge current, with balance circuit

for the controller, not sure as its old

 

[fechter]

That seems like it should work, but possibly it's defective. If the BMS trips, the controller will lose power and turn off.

 

[newb123]

oh so your saying if it was the controller, then once I restored power, it would still be off?

anything inside the BMS to hack, to bypass or limit the current limit?

like a current resistor value for the total voltage and current?

 

[spinningmagnets]

I think voltage sag is causing the the BMS to believe the battery is low. I think there is a chance the battery pack is worn and you need a new one. If this is the case, I suggest you store the pack at 4.1V per cell or lower.

I know this is inconvenient. Most people want to plug the battery in immediately after a ride, and then the next time they want to ride, the pack is always full. However, doing that will kill the battery pack sooner...

Of course, I could be wrong...

 

[newb123]

yeah that makes sense so your saying, dont charge up after every ride? when I measure the volts when I get the cut out situation, its at 41 or so, so it doesnt seem to be a low voltage issue, but I cant see what it is when I throttle, at that moment, until my wattmeter display arrives

 

[AngryBob]

In order to help YOU solve YOUR problem, it might be just slightly useful if YOU would describe YOUR equipment and situation, motor type, total vehicle weight with rider, age of battery, YOU know, some sort of actual INFORMATION about WTF you are dealing with.

Also, when you state about measuring the voltage "When" it cuts out, NO you are NOT, you are measuring the voltage after the cutout has come and gone. Battery has a resting voltage, load is applied, voltage sags below LVC, BMS or controller triggers a cutout, voltage rebounds, then you measure. Not really useful.

IF the battery is old, or IF you have a bad connection somewhere, or IF your motor is very high draw, or IF you weigh over 300 pounds, or IF you live on a big hill, or IF you are hauling a heavy trailer, or IF several other possibilities which I have to guess at because YOU have provided NOTHING WHATSOEVER in terms of useful diagnostic information.......

Lastly, while you do not want your battery to sit for extended periods of time fully charged, neither do you want to let it sit for long in a largely depleted state. Both can be very bad.

 

[newb123]

if I was riding on a hill...think I would of known to post that...becuz..uh..thats a no brainer that it would trip on a hill..or if I was 300 pds..or if I was pulling a trailer (why would I be pulling a trailer???) or other useless variables you posted

not sure of your education level, but if you would of read, more carefully, you would of seen that I posted the voltage (36 volts) brushless DC motor China kit 10 amps. By the caliber of your reply, I see that your more of a novice than professional, therefore I do not wish to receive your advice :lol:

I would, by using common sense, eliminated those problems myself. Im trying to determine if its the BMS or the controller.

stay in your lane dude, Ill ask a more senior member, thanks, and when you get more experience/knowledge, then you can post answers, otherwise learn like the rest of us.

 

[AngryBob]

This thread has been merged or changed. The information at the top was not present when I made my reply.

Next, ALL of the things I have asked about have been left out of previous problem reports by other posters. I know this, because I have read every problem report posted on this site for the last five years.

And, finally, G F Y. Do NOT, EVER, tell ME to Read More Carefully.

You made an empty worthless post and are now trying to Cover Your Ass.

Good Luck to you. Fix it yourself.

 

[kdog]

Geeze so angry.... Not really warranted.
Hard to telling it's bms or controller. Easy way to tell is to bypass bms (take pos and neg directly from the battery) and try. If problem goes away, it's bms, if not, controller. one other thing is to check all connections for corrosion etc esp phase wires...might be tripping controller through perceived fault.

 

[newb123]

And, finally, G F Y. Do NOT, EVER, tell ME to Read More Carefully.

Read More Carefully, but only while on your meds. I have no other suggestion for your condition, well, that I can post here anyway.

for the poster who said by pass the BMS, I will try that, thanks, that makes sense. another poster was having a similar problem, it was suggested he check all connections, I will do the same.