Rob G wrote:


Any chance of getting you lot back On Topic and answering the original
question.

Bosch claim that this 36v driven machine will mow 300m^2 on one battery
- that's at least 30 minutes continuous running I reckon, or 1.8kwh at
50A, based on the poster mentioning model aircraft motors.


36v at 50A for half an hour? thats a tough call: You would need a 25Ah
battery.

Not impossible, but does it have one?

You could get all that in a couple of pounds weight of motor probably,
if done well. 5lb done cheaply.

Motors I use range from about 60% to 90% efficiency. Thats not such a
huge variation in running time. It is a huge variation in waste heat
though, which is why the less efficient motors need to be bigger to be
able to dump the heat.

As I said, mutatis mutandis, there is no real theoretical efficiency
difference between mains and battery DC powered motors.

Both CAN do better than 90%, most generally do 60-70%, as that is fairly
easy to achieve. The devil is in a lot of tiny details..iron quality and
shape, pole geometry, magnet quality - if PM - quality low friction
bearings..commutator friction and brush design (if brushed) or switching
losses in electronic commutators (if not)...etc etc..