Batteries in my electric scooter.

I wouldn’t have a clue, but it’d be interesting to find out a bit more. Post away.

The battery in my scooter is labelled as 48V 10 Ah. Though the display when fully charged has it at about 52v. I gather that batteries can be charged above their stated voltage. It has a 500w motor and that battery ought to be able to deliver 480 watts for 1 hour. These batteries re made up of a number of smaller cells (18650 batteries - that's the name, not the quantity) each of which is about 3.7v so it's probably got 14 of them.

The scooter itself is, and virtually all of them are, a generic Chinese thing made with generic Chinese bits into a branded frame that suits whoever will sell it. In this case a Scoot.

If one would run the battery down then the motor will continue to do it's best to run at full steam given the impact of reducing voltage and then when it decides it's got not enough voltage left will simply switch off. That should be around 50km or so.

As one uses the scooter, especially quickly or otherwise under load one gets what is apparently a well known phenomenon, battery sag. Apparently one is using the power at such a rate that the battery, or one assumes the controller, loses track of where it is and the available voltage drops. As soon as the load reduces then everything catches up and the remaining power will rise up to it's correct position.

It's always been that way and on the  2 x 14km run I do never been a real problem though the first time I noticed it I got a scare.

Something has changed. The scooter seems to have the same power, achieve the same speed, but the battery sag occurs to such a degree that within 2 or 3 miles the thing decides it's got no power left and switches off. No amount of switching back on will coax it into life. When it is plugged into a charger it charges to full power so quickly that one can assume the batteries were not flat in the first place.

Could something have happened to 14 cells at one time? Seems unlikely. Could something have happened to one which would affect the other 13 in this way? They're in series so I am assuming that had a single connection broken in rough usage then it simply wouldn't work at all, and certainly visually I cannot see a problem but I'm a bit wary of wading into it when I don't really know what I am dealing with. Is the battery controller getting a headache and just getting stuff wrong?

For the small period it is running it seems to be running fine and as normal. This happened overnight - one day it worked, charged overnight as usual, next day it was like this. No collisions or accidents, thought the roads are mostly pretty rough and it does get shaken about.

Oh and in usage it charges overnight. Which means it's on charge for 12 hours or thereabouts, it probably takes 5 hours or so to actually charge, the charger senses when teh battery is charged and stops charging it. I guess it regularly gets taken down to 20% or thereabouts, rarely lower.

So, what's the problem? And before you say switch the battery just as a guess, they're £300 quid a go and more for a good quality one so I'd rather not guess. If I have to guess then I'll guess controller, mostly for no good reason other than the fact that it's only about £50.

No, it is a "trottinette" kind of thing, just a reasonably quick and large one - about 40 kph ish. disc brakes front and back, lights, indicators, etc. etc. It's rather good and, of course, cheap to use. My last one did about 4,000km before I passed it on to a friend when I got this one. Absolutely pays for itself over and over again compared to my otherwise use of public transport and taxis.

So my hopes are pinned on WDB's family member. Fingers crossed.

Thank you, but now my head hurts.

I guess I need to take the battery pack out and then apart and test the individual cells. I'll have a look at that, none of it is easy. I can get to the pack, but it's anchored somehow, I am not quite sure how.

Oh I can get the scooter apart ok, it's just that I think the pack is glued on to the plate. Taking it apart is apparently a matter of carefully cutting the shrink wrap. Just a little intimidating is all. Still, as long as I disconnect it from the PCB first there shouldn't be any danger.

I was thinking duff cell as I read down the thread and saw WDB had covered that. We had a similar issue with a Hybrid car that would not 'start' unless it was connected to the mains. That car was 6 weeks old and had to go back and have duff cell pack replaced.

What are the mobile phone shops like in your area ? These cell clusters are like packs of mobile phone batteries clustered together. It's possible if they have an electronics bod they may be able to diagnose the duff cell and remove replace it. I know, it's Chile, sometimes you find someone who has a real liking for taking this kind of thing apart.