Issue about battery voltage & discharge port

Hello Everyone ,

On my chineese FatEbike, I have a battery 48V -20.3AH with panasonics cells 29PF connected to a 26A 1000W controller.
Battery is in a box like this one below with a key contactor and indicator charge level on top.

Bike was working fine until one day when I smell burn at full speed and bike and LCD screen control panel shutdown definitely :x
But battery level indicator on top of box is working fine and showing full charge of battery.





I though the controller was dead, and order a new one with new LCD, wiring looks ok but new LCD doesn't turn on.
After checking voltage on my wiring, I realized that discharge port of battery is showing 0 Volts with key on "ON" position, but if I check the charging port it is showing 51.4 Vots.

I opened the bottom of battery box to check if a wire is cut / burned or something else on discharge port, but red and black wires are OK, and going under heat shrink of battery, so I didn't wanted to cut the heat shrink before asking advice ....

I guess there is something wrong with this battery, maybe there is a BMS inside that is burned ? I don't really know ....
What else do you thing I should do to find issue ?

Thank you !
Regards

Quite likely there is a fuse in there which has popped.

A fuse in the battery box ? maybe... Does it smells burns a lot when it pops ? Because I had bad smell like plastic burned.
At the bottom of the box there is nothing, I will open the top to check if I see something...

Yes you were right !! There are two fuse in this battery box, one is 5A fuse and other one is 20A fuse.
The 20A was blown up, now it's working fine ! Thank you very much for the help
Regards

you maybe set the topic to solved. like

[solved] Issue about battery voltage & discharge port

this will help people having similar issues.

Well I was screaming victory too soon ... :|

When wheel is in the air it is working fine and showing 57 km/h speed, but problem is that this fuse blows evertime I seat on the bike and give full throttle.

I replace it to a 30 A fuse, but it burn as well and LCD shows error 10 which means Controller overheat.
I guess there is something wrong with battery now, maybe a short circuit somewhere, or a dead cell cause BMS to shutdown ?

I open battery box again yesterday, top and bottom but all looks fine, no overheat wire or anything else.
I couldn't access the cells to check voltage of each cells, there are hardly stuck in the box.

I figure out that problem is that new controller I'm using give more amps than older one and it's not designed for my battery.

The old one was a 26A controller 1000W and new one is a 47A 1500W.

After blowing many 30A fuse, for testing purpose, I bypass the fuse with aluminium sheet arround it.

So bike accelerate more faster with much more torque, and consume more watts according to LCD (up to 4000W at peak).
Battery fuse blow arround 2000W wich is probably the "safe" discharge limit of battery.

I try to limit AMPS in LCD control panel parameters but it doesn't seems to change anything.

So I would like to find a circuit board or something that would limit peak amperage to 30 OR 40A, any idea of the solution I can use ?

Hello,

I found specification details of my battery :



Rated Discharge Curent : 40.6A
Maximum Continuous Discharge Curent : 60.9A
Instantaneous Maximum Discharge Curent : 101.5A
Maximum Continuous BMS Limited Curent : 80A

So I believe this battery can handle much more than the 20A fuse inside, so why is there a 20A fuse instead of 60A ?
Is this fuse really necessary if there is already a BMS limiting Curent to 80A max ?

Is it risky to replace the 20A fuse to a 60 or 80A ?

Please let me know what you think, thank you.

What size is the battery wiring, and do you have the specifications of your motor?

Fixed the immediate problem, but your new controller will be slowly, or maybe even quickly killing that battery.

Cheap solution is going to be a new controller, but one that only draws 20 amps max.

TommyCat said:

What size is the battery wiring, and do you have the specifications of your motor?

Click to expand...

Well I have to check again, but it seems to be 14 AWG wire on the battery.

Motor is MXUS 1500W FATBIKE (probably the XF40 but nothing is written on it...)

I didn't find yet technical specification but according to commercial information, it's designed to handle 40A.

dogman dan said:

Fixed the immediate problem, but your new controller will be slowly, or maybe even quickly killing that battery.

Cheap solution is going to be a new controller, but one that only draws 20 amps max.

Click to expand...

Yes that would be an easy fix, but first, it's not that cheap ! I already bought new controller and LCD for 150$ ...
And second, 20A controller is very low for this 35 Kg FatBike, originally it was delivered with a "undersized" 26A controller which gives poor acceleration but acceptable top speed of 45 km/h.

If battery can safely handle 40A I would like to use this extra power, but taking a 47A controller was maybe to high ... :?

I believe they put a 20A fuse to preserve maximum durability, but I guess I can upgrade safely to 40A, no ?

pimoos said:

TommyCat said:

What size is the battery wiring, and do you have the specifications of your motor?

Click to expand...

Well I have to check again, but it seems to be 14 AWG wire on the battery.

Motor is MXUS 1500W FATBIKE (probably the XF40 but nothing is written on it...)

I didn't find yet technical specification but according to commercial information, it's designed to handle 40A.

Click to expand...

I believe it's this motor :

MXUS XF40-45H V1 type 48v 1500w electric hub motor
Motor:direct motor
Voltage:36V/48V
Power:1000-1500W
Speed:45-50km/h
Efficiency:≥81%
Weight:9KG
Drive freewheeltype:rear/6s-9s
Color:black\silver
Brake:v brake/disk
Stator: steel stator

Even cheap cells should be able to handle 2C discharge without overheating. A 40A fuse should be fine.

Run it hard for 15 minutes or more, then check the battery temps. If slightly warm, no problem.