EBike charger not fully turning off?

[ralphius]

Hi,

I have an old Crystalyte 408 hub motor kit on my self-built ebike. After lots of commuting, the original battery (from 2014!) finally died in Jan 2020 and I bought a replacement "Hailong Battery 48V 13Ah 13S 5P Li-ion with charger" soon afterwards. The ebike got virtually no use through 2020 due to Covid and lockdowns, and ever since then I've been working from home so I only really use it to get myself up the hill to the pub! Not sure how many miles I do now but I find myself charging it once every 3 weeks so the new battery has had very few charge-discharge cycles.

I do carefully track the amount of energy it takes to recharge the battery with a power monitoring plug and I've noticed something odd recently. The charger doesn't seem to be switching off properly anymore?

This was the power and energy (595Wh taken) taken by the charger that came with the new battery when the battery was nearly new:

(It switched itself off with an audible click at 9:45PM)

And this is how the same charger behaves recently (580Wh taken):


I would have expected the charger to turn off at 20:00, but it didn't. Instead it continued to "trickle charge" until 21:35 when I manually switched it off. Is this normal or a problem?

Thanks in advance for any insights you may have,
Ralphius

 

[calab]

Depends on the charger, some if you leave them plugged in they continue to charge, might be called hiccup charging.

 

[john61ct]

Might be to accommodate the balancing process, most BMSs have a very slow balance current rate.

 

[ralphius]

I didn't think of balancing cells, yeah that could explain the 2nd smaller curve. Shame I don't have a way of monitoring the actual battery voltage & current like I can do with the 240V mains plug. Sounds like its not an issue then and I'll just ignore it. Thanks for the replies

 

[amberwolf]

I'd agree it is probably balancing the cells, if it is a balancing style BMS. Most of the cheap ones (meaning most of the common ones) only power themselves off one or a few cells, so those cells get drained further than all the others over time, especially with a pack that does not get charged very often or for very long when it does.


Wattmeters are cheap if you want to have a way to measure charging or discharging data.