Trolling motor battery size?

[7lazy77]

Just recently picked up a used MinnKota 70# 24v trolling motor. Was looking for suggestions on what batteries to use (brand / deep cycle / 24 or 27 group)??? Thanks

 

[JB]

Re: Trolling motor battery size?

Generally, the biggest batteries you can find room for.

I had good service and great value from Wal Mart Everstart Marine Maxx batteries.

 

[Silvertip]

Re: Trolling motor battery size?

You need deep cycle batteries and you also need an amp or bigger dual bank on-board smart charger, or a 10 amp portable charger to charge the batteries immediately AFTER each use. Never leave them in a deeply dishcharged or even partially discharged state. Batteries are like buckets of electricity. The bigger the bucket the longer the motor will run on the avialable power. Generally two group size 27's would be fine unless you happen to be tournament fisherperson and are on the water from sun up to sundown (or after). Group 31's may then be in order. There are a couple of schools of thought regarding high-tech batteries vs the discount store type. I happen to have very good luck with deep cycle batteries from my local farm store. $75 right now gets you a store brand deep cycle with 180 minute reserve capacity at 23 amp draw. You can spend two to three times as much money for a high-tech battery that may or may not last any longer and may have little to no greater capacity than the cheap battery.

 

[lmuss53]

Re: Trolling motor battery size?

One thing to ad, if you are getting group 29 or larger, make sure you can take the boat to the charger. You do not want to have to pull group 29 or 31 batteries out of a boat (like from a storage place or camp with no power) to carry to the charger, they are HEAVY.

 

[7lazy77]

Re: Trolling motor battery size?

I apolagize, but I was unsuccessful with the search function on the site & couldn't find how to calculate running time of a trolling motor. I found the calculation when "Reserve Capacity" is known, but I am not sure what it is on these batteries since it did not list it. I am comparing a 27-group (115AH@1V) with a 29-group (125AH@1V), both deep cycle.

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?? If somebody reply with how to calculate, then I can do it.

 

[fishrdan]

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.

 

[7lazy77]

Re: Trolling motor battery size?

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.

I have the PowerDrive V2. According to the MK website, it appears the TM is digital!
Looked in my owners manual at the exploded parts diagram & it did not mention the current draw (amps@24V). The book only says the "motor draws .75 amps/hr for each pound of thrust (70# Minn-Kota) produced when the motor is running on high". So this is where I am getting confused on coming up with a decent calculation.

 

[Silvertip]

Re: Trolling motor battery size?

The motor operates on 24 volts so the numbers you have are based on that. .75A x 70# = 52 amps. The .75 number you were given is incorrect because the MinnKota specifications for that motor indicate the motor draws 42 amps maximum at 24 votls. Are the batteries you are looking at "deep cycles", "dual puirpose" or "starting batteries". You need to be comparing "deep cycle" batteries.

 

[fishrdan]

Re: Trolling motor battery size?

MinnKota specifications for that motor indicate the motor draws 42 amps maximum at 24 votls.

Yep, here's the 70# V2 exploded diagram

 

[sschefer]

Re: Trolling motor battery size?

I've had the Terrova in a 70 24v and the older PD in 65 24v. I ran two group 27 Interstate batteries and got 5 hours of good solid run time before I hit the magic 60% charge mark. That's the baseline for the manufacturers RCA number. On a onboard Pro-Mariner 20 amp tripple battery charger it took a minimum of 10 hours to bring them safely back to full charge.

This time around I went with the PowerDrive V2 55# with Ipilot and in the 12v version. I used Minn Kotas rule of thumb where they figure 2lbs of thrust for every 100lbs of load. They were dead on the money. Mine holds its own well in the wind and current but there's not much to spare. So far it's not been a problem. The V2 runs only as fast as it needs and if you have the iPilot it will do that based on the speed over ground via the GPS. This makes it a miser and really super efficient with a tail wind. It sort of reminds of gleefully watching the mpg number hit 99 on my F350 SD Diesel when I'm comming down the mountan.

I'm running two Optima Blue Top D31M's in parrallel and it takes all of about 2 hours to bring them back from the 60% mark. The charge indicator on the motor is darn close to where 60% is on the batteries when it say's low.

I now have a Yamaha 2000 Watt generator that I use to charge them and they're usually done by the time I get the boat back to the dock, moored and cleaned up. If they're not done, i go clean fish or something.