Nice site. Thanks for posting it.
I didn't find a specific discussion of two batteries on a 12-volt connected in parallel.. 55 lb thrust versus two batteries running a 24-volt series connected ..80 lb. thrust system. I did find this quote..
"In order to approximate how long a certain motor will run on the water, you simply take the battery's amp hour rating and divide it by the amperage draw. For example, for a motor that pulls 20 amps at medium speed using a 100 amp hour battery, the run time would be: 100 amp hour rated battery / 20 amp draw = 5 hour run time"
I would have thought that they'd be equal......
However, THIS discussion says different, due to the efficiency of a 24 volt trolling motor's windings.
https://www.bassfishin.com/bassfishingforums/showthread.php?s=75cacc58154a8a68a14ad503dbe93b03&t=22238&page=2
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"Okay, ...let me stop trying to talk in laymen's terms. If I start talking about coulombs, people's eyes are going to glaze over.
current x time = charge
I admit, I was incorrect in my choice of the word "energy"...it was too hastily typed.
current x time x voltage = energy
I never said this was Ohm's Law.
Ohm's Law is the defining principal in determining resistance losses.
If you run a 12V motor, you will have half the voltage, but twice the current of a 24V setup. Once again, this is for different voltage motors of the same thrust rating. The two-battery connection (series vs. parallel) does not matter.
What does matter is the resistance of the wires to the trolling motor, and the resistance of the windings in the motor itself. This is where Ohm's Law, V = IR (for DC only) comes into play. Resistance losses are based upon the square of the current:
power = voltage x current = I*R*I = I^2*R
When you double the voltage, you halve the current, but the resistance losses in the wire change by a factor of 4; i.e, only 25% of the resistance losses in a 24V system vs. a 12V system. This is what provides extra running time to a 24V system vs. a parallel battery 12V system.
I don't really need to Google it.
I taught circuits at the college level, and I'm an Electrical Engineer.
This topic is closed as far as I'm concerned."
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