24v LiPo Electric Mower Conversion

[paracidium]

Thought I'd post some info regarding my LiPo conversion on a faulty 24v 4Ah Li-ion (BLDC motor) mower bought from eBay for £30.

I added 6s2p LiPo at 12Ah. The only problem that I encountered was the fact that the old battery had 3 terminals: B+ B- and a thermistor connection.

Without the thermistor connected the motor will only start for 2 seconds and then cut out.

The thermistor is supplied with 5v via a pair of wires from the controller. The controller will be looking for a volt drop across these wires caused by the 10k resistance of the Thermistor at room temperature. It is a NTC thermistor so the resistance drops as the thermistor heats up and the motor will cut out (originally intended to monitor battery temperature).

In order to bypass the thermistor connection I simply connected a 10k resistor across the two wires and viola... Mower works perfectly and has more than enough capacity to mow my lawns

I understand that this is not the safest option and ideally I could have just purchased a 10k thermistor but I was being impatient!

I posted this info because I searched for quite some time online in order to find a solution and it would have been a godsend to find such a post on ES.

Such an easy conversion only took about an hours actual work!

Sent from my HTC One_M8 using Tapatalk

 

[Cowardlyduck]

Thanks for sharing this paracidium. Only just found it via your facebook post, but this is still very useful info.

I'm curious how you managed to determine the need for the thermistor...or was it just a guess based on the way it was cutting out?

I've come across a number of gadgets over the years with 3 pins like this and never been able to figure out how make them work with LiPo so ended up throwing them out as a result...such a waste!

Cheers