Re: Trolling motor battery size?
My motor draws .75 amps/hr for each pound of thrust (70# Minn-Kota) produced when the motor is running on high. Assuming I was running it on high, how long will each of the batteries last me??
What model of 70# MinnKota do you have? I'm looking to see if it's a digital or speed coil TM? While this won't matter with calculating the max power draw, the digital motors use a LOT less power as slower speeds.
My MinnKota 70# Vector's max current draw is 42 amps at 24V, this spec comes from MinnKota's exploded parts diagram. So with 2- 125AH group 29 batteries (24v at 125AH) you are looking at 3 hours at max speed before the batteries are depleted. The calculation would be 125AH/42 amps. (Forget the battery voltage since you have a 24V TM and will be adding the batteries voltage to get 24V) When I use that 70# TM on my 18' boat constantly trolling under a heavy load at speeds 5-6, it will go around 5-6 hours before the batteries start tapering off. I should say the batteries are not 100% depleted, but they are low and not providing the power I want, so I charge them back up. When I use that 70# TM on my light 14' jon boat constantly trolling at speeds 3-4,,, I don't know how long it will go as I have never run down the batteries to where they need to be recharged and I've been out on trips where I was constantly trolling for 16 hours, before dawn to well after dusk.
From my example you can see there are a lot of factors that come into play when figuring out how long a battery(s) will last; type of TM, battery capacity, load they need to push, speed, wind, current.
For what size battery to get, It really depends on the things above. But personally, I would get at least group 29 batteries,,, bigger bucket of electricity to tap into.