12 to 18 volt

A car charger isn't a power supply, and depending on type might not work at all, might not be able to provide enough current, and could potentially damage the mower.

And even assuming it puts out a nice smooth 12V, that's far too low to make your mower useable.

OK. Thank you. Could you suggest a simple circuit that I could build from that would work satisfactorily?

Its complicated, just one example of a BLDC motors behavior :



Note not all electric mowers use BLDC, some brushed, some universal.

But lead acid car battery charges can be as simple as transformer/rectifier and not much else.

You could try adding a large cap to supply to get "cleaner" source. And measure your motor
current on battery versus charger. The other risk is transient V's affecting and mower control circuits.

Hippiccorn said:

OK. Thank you. Could you suggest a simple circuit that I could build from that would work satisfactorily?

Click to expand...

Not really, it's not a simple (or cheap) requirement - you need a high current DC power supply - startup and high load currents are MUCH higher than you might imagine (10A+?). If you want to run a grass cutter from the mains then buy a mains one, it would be far more powerful than an 18V one, and have the advantage of a much thinner lead and a large expensive mains power supply.

The existing battery is capable of really high current, which a mains supply needs to match.