very very roughly, yes. But it depends on a lot of details and factors.Somewhere around 2 hours, right
Battery: 90ah @ 12v = 1080wh Load: 42a * 12v = 504w. If steady 504w, then 504w * 1hour = 504wh.
At 80% DOD - that's .8 * 1080wh = 864wh of useable power in the battery.
864wh/504wh = 1.7hrs estimated run time.
very very roughly, yes. But it depends on a lot of details and factors.
Some of those factors are:
Depends on the manufacturer, but the 90Ah are likely when tested at much slower discharge rates.
If it's a lead acid battery, it's usually measured over 20hours. The usable capacity may drop by 1/2 if discharged at ~10x that rate.
Li-Ion cells are usually measured over ~5 hours. The drop in usable capacity won't be that great at ~2.5x that rate, but still noticeable at perhaps ~10%.
Actual voltage of the battery (higher voltage -> motor will run faster)
That's just on the battery side, and the load(motor) side will have a lot of factors, too.
Have you solved the issue with the motor cutting out prematurely due to the lower working voltage range of 3S LiIon batteries?
This is assuming 100% efficiency, which we know is not possible. Actual run time may be more like 80%, or 1.3-1.4hrs. And even 80% is a bit optimistic, to be honest.
Not really, unless you buy some really expensive equipment.Anything else I can do to improve efficiency ? Increase range ?
It probably would be easier, cheaper, and more efficient to go with higher string count, 4s instead of 3s, and use buck convertor to run everything. Going with 5 or more in series would be even better.You could wire in a toggle switch to reroute power through a boost converter when the battery voltage gets too low for the controller. That way you have no conversion efficiency loss when the battery is above 30% charge