Battery Cutting out

pavelmac

New Member
Region
New Zealand
Hi,

I'm a noivce at ebikes and this is my first post, so please bear with me.

I replaced a front hub 250W motor with a BBS02 500W, but now the battery trips out when throttle is used.

The battery:
36V 10S4P with Samsung 26F batteries 2600msh & 5.2A max draw, all this with a 15A BMS.

So with my limited understanding, I believe that the motor would draw 14A max (500W/36V), which means that the battery should be just within spec?

I've read that the motor may peak to higher load, especially under throttle, and this is probably what's causing the battery pack to shut down.

How can I move forward?

Should I up the BMS to 20A?
or
replace batteries for higher draw items and a bigger BMS 20A or 25A?
or
is there something else I should be looking at?

Cheers
Pav
 

JES2020

Active Member
The 5.2 max draw battery looks suspicious, your BMS should be fine at 15 amps and 500v motor.
Take that with a grain of salt because I am not up to speed on max battery draw. But to me that looks like an issue, because the BMS will draw more from the battery than it can provide.
I'm sure someone else will chime in that knows more about battery amps.
Good luck
 

pavelmac

New Member
Region
New Zealand
The batteries are samsung 26fm's, which were probably sufficient for the original motor.
 

Gionnirocket

Well-Known Member
Region
USA
City
Y. O.
Depending on how much you need the throttle... You're best bet would probably be your second option with a larger battery and rated bms.
One thing that you can do is install a watt meter on your current set up and monitor as you normally ride. With a little mindfulness you may be able to utilize the current battery as is or with a 20a BMS if the cells actually are as advertised
Another option to the watt meter is to upgrade to a display that shows current/watt such as the 750, 850 or 860
 

kmccune

Active Member
Make sure the battery is making contact with the power terminals, had this problem on a "Eahora" bike I owned, got a little hot under the collar till figured out what was wrong.
 

K PierreR

Well-Known Member
Region
USA
Why not reprogram the BBS02 to max out just below 15 amps. It would solve the problem for now. I think you can reprogram the throttle for its range as well and keep the current max current draw.
 

harryS

Well-Known Member
The Panasonic 26FM indeed is rated for 5.2A, so your 4P battery will max out at 20A. EVen though your BMS is rated for 15A, I am sure it will push 20A. I have two 48V packs with a 15A BMS and both will push 25A into my 750W BBS02, although one of them will do exactly what your pack does ...shut off under throttle.

In my opinion, your problem is not enough battery headroom. You want 25A capablity to run a 500W BBS02. One or more cell groups is sagging too low under throttle and the BMS shuts off. Get a bigger battery.

DId you build this battery yourself? Most novices wouldn't even think about replacing the BMS or upgrading cells? Most don't even know what's inside. If you did build it, is it a Vruzend type kit?
 

pavelmac

New Member
Region
New Zealand
That's for your responses.

Gionnirocket: I'm waiting on a watt meter to see the actual draw, but will try switching display to show watts - once battery is back together.

K PierreR: I've checked my display unit and that doesn't allow me to limit current draw. I believe though you might be referring to reprogramming BBS02 directly. I remember reading something on that and don't i need to get a special cable?

harryS: I'm inclined to believe cells are not up to the task. There is a good source of reclaimed NCR18650BD 10A cells on the local market, 10A rated with near full capacity at a good price. Does anyone have any concerns using these cells?

I haven't built a battery pack myself, but watched a number of youtubers and read some articles. I would basically just copy the existing 10S4P factory battery pack with the higher draw cells. But before I commit to building my first battery pack, I might just try repacking one of my power tools that i know had some bad cells.

Thanks for the advice guys.
 

harryS

Well-Known Member
Unless one is using a Vruzend type build, or owns a battery spot welder, repacking cells into a purchased ebike battery requires a lot of skill. I have cut out two bad battery group on a softsided 10S-2P and replaced it, but I had to solder in the new cells, and it was difficult, although it works fine now. There was no financial incentive to do it, as the battery was only worth about 60 bucks new.
 

Gionnirocket

Well-Known Member
Region
USA
City
Y. O.
That's for your responses.

Gionnirocket: I'm waiting on a watt meter to see the actual draw, but will try switching display to show watts - once battery is back together.

K PierreR: I've checked my display unit and that doesn't allow me to limit current draw. I believe though you might be referring to reprogramming BBS02 directly. I remember reading something on that and don't i need to get a special cable?

harryS: I'm inclined to believe cells are not up to the task. There is a good source of reclaimed NCR18650BD 10A cells on the local market, 10A rated with near full capacity at a good price. Does anyone have any concerns using these cells?

I haven't built a battery pack myself, but watched a number of youtubers and read some articles. I would basically just copy the existing 10S4P factory battery pack with the higher draw cells. But before I commit to building my first battery pack, I might just try repacking one of my power tools that i know had some bad cells.

Thanks for the advice guys.
Yes you need a cable to reprogram the controller... I'd get one as tweaking the BBS* has many advantages on top of your current need.
And practicing to build a power tool battery is a good exercise... It's not as easy as one may think and being on a smaller scale you don't have to invest as much for the lesson. Spot welding being the biggest hurdle