Hi there, could do with some help !

[Dave Bunker]

hello to you guys
I am looking for some advice on my ebike project. I have a 48v hard case battery from egg bikes. All has been find but now when the power bar on the KTLCD3 reads half full and the voltage reads 47v the bike just shuts down. Its been fine with the power indicator working all the way down to blinking and the battery reads 53.8 volts after charging, any ideas on what going on ?
cheers in advance
Dave

 

[Deleted member 4366]

Possibly a bad cell. 53.8 is a bit on on the low side. The only way to know for sure is to run the battery until it cuts out, then open it and measure the cell voltages on the multi-pin connector. You could try running it'til cut-off, then measure the voltage on the terminals to confirm that it's the battery shutting down. You need to be quick though because the cell voltage can bounce back and switch back on again.

When it shuts down, does the display go off?

 

[JuicyBike]

Perhaps the recent November drop in ambient temperatures with the onset of winter could be having an effect.

I'm not sure if lower temperatures help expose a weak cell, or exacerbate voltage sag. Maybe someone else knows...

Have you dabbled with any settings at the display recently? Battery BMS, bike controller and programmable displays all control when the bike shuts down due to low voltage.

You may not fancy opening up the battery to check the voltages that the BMS (as Dave describes) uses to determine whether to shut off battery supply, and you would need to be very quick to get useful information.

But taking voltage readings from the battery output may be just as useful in showing if a cell might be faulty.
Take readings immediately after the bike shuts down, then for the next ten minutes. Sudden jumps in this reading rather than a smooth rise in voltage values can indicate problems with an individual cell.

But it's dead hard to properly test in this manner without someone like Dave holding the prongs.

You can get your battery tested at many specialist ebike shops. If you're near our workshop we'd be glad to help.

 

[Dave Bunker]

hi and thanks for the replys
yes the display shuts down but the voltage readings hovers around 47v then tumbles and shut down then happens.
I charged the battery and took a reading this evening and its 54.4 volts. Took the bike out and turned the display to show volts and under the full 1500w the battery is showing 44 volts at times but the system does not shut down,
completely confussed now.
Was a tad cold to run the battery past half way so will try to get the battery to drop out and see what the actual voltage is then.