Lithium battery upgrade for mobility scooter

[Robint]

OK so basically you were just able to drop the Ping 24v 30Ah battery straight into replace the Lab - and fix the cable to suit. and it worked. you didnt do anything else
Sounds like you had the classic worn brushes problem on the motor, you need to get a new set of brushes only a few bucks/probable on ebay, measure them with a caliper and get some longer size

So you still have that issue with not giving it too much wellie when starting off else the bms cuts out? So if you go up a steep ramp will it also cut out?

As for a SoC meter, i suggest you get one of those cheap LED volt meters off Ebay 30v range so you can read the voltage as say 28.1v down to 24.5v (low volt cut off). https://www.ebay.co.uk/itm/Mini-0-36in-DC-2-4V-30V-2-Wire-LED-Digital-Display-Panel-Battery-Voltmeter-K/224137826134?hash=item342fa7cf56:g:YEsAAOSwABlfSHu7
You need to find the Full and cut off points by trial and error then make yourself a little chart in 10% steps vs volt readings. That will give you quite a good estimate of SoC (far better than a Lab). The reading should be taken at standstill no load for 5 mins. Good practice for long life is to keep charge between 20% and 80%. personally I wouldnt go below 40%
You can also use a smart phone app GPS speedometer distance meter free which will tell you mileage covered
Trial and error will show you whats safe to do.

Cheers

 

[Diamondback]

Apart from the soldering of the battery and charge wires it was a straight drop in. With a small change to the battery mount and hold down.

Once the brushes were sorted, it never had any more issues starting. Or hill climbing. In fact it climbs hills now better than it did with the SLA batteries.

For soc, I used a cheap meter off eBay. It’s not ideal. But it works as it does show voltage.

 

[Robint]

Hi DB ive been doing some more digging and it turns out that the Lifepo4 batteries have a very flat curve and a sharp doorstep cut off ie 3.2-3.0v. This make the SoC rather difficult and potentially unreliable. The fit young bodies on pumped up ebikes dont worry about this too much as they can always push their bikes home. Mobility users may not be so lucky and get stranded on the pavement - this is the ultimate nightmare.

So we users need to err very much on the side of caution - eg never go below 50%DoD then assuming you can measure this accurately given ambient temp summer winter, age, cycles, current draw.

The current wisdom seem to be to use a charge meter (ca £30) which measure battery charge/discharge Ah and uses a hefty current shunt 50A in the battery lead. For the inexperienced fitting one of these in a weatherproof box is not trivial but I think its essential for mobility use plus use the smart phone app gps tracker to give you distance. Experience will give you safe limits

I have been seriously stranded once due to major mechanical breakdown in winter- it was a terrifying experience