Bike electrics cutting out

J

jic

New Member
Region
United Kingdom
Hi,

I have built a 52v/12.5Ah (14s5p) battery with old ebike cells that came from a previous battery where the bms failed.
It works fine on my bike until it depletes to about 48-49V (about 10 miles) then all the electrics on the bike just shuts off.
It's currently connected to a 48v/26A controller with a rear hub 1000w motor.
I have ordered a kt 1000-1500W sine wave controller as im not sure if the old controller is working well (according to the previous owner).
Does anyone have any idea what i can check or any ideas why the electrics maybe failing?

Thank you in advance.
 
jic said:
Hi,

I have built a 52v/12.5Ah (14s5p) battery with old ebike cells that came from a previous battery where the bms failed.
It works fine on my bike until it depletes to about 48-49V (about 10 miles) then all the electrics on the bike just shuts off.
It's currently connected to a 48v/26A controller with a rear hub 1000w motor.
I have ordered a kt 1000-1500W sine wave controller as im not sure if the old controller is working well (according to the previous owner).
Does anyone have any idea what i can check or any ideas why the electrics maybe failing?

Thank you in advance.
Click to expand...
Check your low voltage setting on your controller and adjust if necessary.
 
jic said:
Thanks. I didn't even realise you could adjust something like that.
Click to expand...
I very much doubt that it is the Controller LV cutoff as by default they are usually a lot closer to 40v
You need to check with a voltage meter on whether or not the battery is shutting down or the controller is shutting down.
What are the LV cutoff parameters of the BMS that you used to build the new battery?
How did you determine the voltage of 48-49v? Display? With a meter?
 
Gionnirocket said:
I very much doubt that it is the Controller LV cutoff as by default they are usually a lot closer to 40v
You need to check with a voltage meter on whether or not the battery is shutting down or the controller is shutting down.
What are the LV cutoff parameters of the BMS that you used to build the new battery?
How did you determine the voltage of 48-49v? Display? With a meter?
Click to expand...
This is a 2nd hand controller. You have no idea what the low voltage is set at .
 
Sounds like voltage sag to me. Battery too small or too old for motor,

He's using a 48V box, so the bike's LVC is 40-42V. Meanwhile, it's a14S pack (52V). That means full charge at 58,8V, 50% charge at 52v, and pretty weak at 45V. Actually 48V is 35% charge for 14S, so it's not gutless, but there's not much left if you're running high current.. If these are older or weaker cells, it may be that when he gets that low, there is voltage sag, not unexpected with a 26A controller. Probably enough to shut off LVC on the bike controller.

Can you still read the individual cell voltages on the rebuilt pack? Are they're all even and there's no misbalance. Did it get to a full charge at 58.8V? Does the bike restart after a 49V poweroff? Can you limp along on minimal throttle?

For future work, get a $13 RC wattmeter, . It will record the minimum DC volatge and highest current, and tell you what voltage sag you're getting. Will also give you instantaneous power/current/voltage, but it's not easy to rig them so you can see them when riding. For now, you cab put a voltmeter on your bike and watch it when you're running to monitor sag.
 
harryS said:
Sounds like voltage sag to me. Battery too small or too old for motor,

He's using a 48V box, so the bike's LVC is 40-42V. Meanwhile, it's a14S pack (52V). That means full charge at 58,8V, 50% charge at 52v, and pretty weak at 45V. Actually 48V is 35% charge for 14S, so it's not gutless, but there's not much left if you're running high current.. If these are older or weaker cells, it may be that when he gets that low, there is voltage sag, not unexpected with a 26A controller. Probably enough to shut off LVC on the bike controller.

Can you still read the individual cell voltages on the rebuilt pack? Are they're all even and there's no misbalance. Did it get to a full charge at 58.8V? Does the bike restart after a 49V poweroff? Can you limp along on minimal throttle?

For future work, get a $13 RC wattmeter, . It will record the minimum DC volatge and highest current, and tell you what voltage sag you're getting. Will also give you instantaneous power/current/voltage, but it's not easy to rig them so you can see them when riding. For now, you cab put a voltmeter on your bike and watch it when you're running to monitor sag.
Click to expand...
I concur on the voltage sag... That's why I asked about how the reading was taken.
Taking a 5p bank with only 12.5Ah tells me that they weren't very robust cells to begin with... then add that it's a rebuilt pack out of used cells and the potential for sag is probable.. I'd think a 6-9v sag is pretty deep with a proper healthy battery
 
harryS said:
Sounds like voltage sag to me. Battery too small or too old for motor,

He's using a 48V box, so the bike's LVC is 40-42V. Meanwhile, it's a14S pack (52V). That means full charge at 58,8V, 50% charge at 52v, and pretty weak at 45V. Actually 48V is 35% charge for 14S, so it's not gutless, but there's not much left if you're running high current.. If these are older or weaker cells, it may be that when he gets that low, there is voltage sag, not unexpected with a 26A controller. Probably enough to shut off LVC on the bike controller.

Can you still read the individual cell voltages on the rebuilt pack? Are they're all even and there's no misbalance. Did it get to a full charge at 58.8V? Does the bike restart after a 49V poweroff? Can you limp along on minimal throttle?

For future work, get a $13 RC wattmeter, . It will record the minimum DC volatge and highest current, and tell you what voltage sag you're getting. Will also give you instantaneous power/current/voltage, but it's not easy to rig them so you can see them when riding. For now, you cab put a voltmeter on your bike and watch it when you're running to monitor sag.
Click to expand...
"Sounds like voltage sag to me. Battery too small or too old for motor"

Is it possible for multiple issues?
IE weak battery and or high LV setting?

I always start with the simplest items first, it takes a whole 2 min. to check the LV.
Digging right into the battery cells is not what I would start with?
In any event, even with a weak battery, he can more range by lowering the LV setting.
As a computer programmer, I was taught to KISS.
 
Gionnirocket said:
I very much doubt that it is the Controller LV cutoff as by default they are usually a lot closer to 40v
You need to check with a voltage meter on whether or not the battery is shutting down or the controller is shutting down.
What are the LV cutoff parameters of the BMS that you used to build the new battery?
How did you determine the voltage of 48-49v? Display? With a meter?
Click to expand...
There is very little information on the label, which is partly why i bought a new one, because everything was documented better. So i don't know what the cutoff with the controller is. The one i have just got has a 40V cutoff.
I measured the 49V with a multimeter.
 
harryS said:
Sounds like voltage sag to me. Battery too small or too old for motor,

He's using a 48V box, so the bike's LVC is 40-42V. Meanwhile, it's a14S pack (52V). That means full charge at 58,8V, 50% charge at 52v, and pretty weak at 45V. Actually 48V is 35% charge for 14S, so it's not gutless, but there's not much left if you're running high current.. If these are older or weaker cells, it may be that when he gets that low, there is voltage sag, not unexpected with a 26A controller. Probably enough to shut off LVC on the bike controller.

Can you still read the individual cell voltages on the rebuilt pack? Are they're all even and there's no misbalance. Did it get to a full charge at 58.8V? Does the bike restart after a 49V poweroff? Can you limp along on minimal throttle?

For future work, get a $13 RC wattmeter, . It will record the minimum DC volatge and highest current, and tell you what voltage sag you're getting. Will also give you instantaneous power/current/voltage, but it's not easy to rig them so you can see them when riding. For now, you cab put a voltmeter on your bike and watch it when you're running to monitor sag.
Click to expand...
Yeah i get a full charge at 58.8V. The bike will restart and the power comes back on but i don't get very far before it shuts off again.
Thanks for the info. I've just got the new controller so will see how it goes. If that shuts off then I can be sure it's battery.
 
tomjasz said:
I missed this, my bad! This should be obvious. It's a battery issue, not a controller.
Click to expand...
The old cells are actually hardly used. They've done 100 odd miles. I had to buy extra samsung 25r cells to make up the 14s5p setup. I charged and discharged each and every cell and almost all of the cell came out at very good values (mah). I ordered them all so that there was roughly the same 12.5mah in each 5p. Bad cells weren't used in my battery.
 
jic said:
There is very little information on the label, which is partly why i bought a new one, because everything was documented better. So i don't know what the cutoff with the controller is. The one i have just got has a 40V cutoff.
I measured the 49V with a multimeter.
Click to expand...
Very good.
Connecting a volt meter during a ride or hobby watt meter as Harry suggested can help with diagnosis. My Fluke meter has a Min/Max function that allows me to view and record voltage drops and with an audible tone to alert me of a new low reading. The hobby watt meter is a lot more affordable if you have neither. To really know what's going on you need to know what the voltage is just prior to time of shutdown and how deep any battery sag is. Does your display provide a voltage reading?
Since you have the new controller and don't seem happy with the current one anyway you might as well change it as you say.
 
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