Do I need to exchange my battery?

[Juniah87]

Ordered the Shumacher just to be on the safe side, thanks Amx!

[Larry3215]

Cranking amps is a useless spec for an electric trolling motor, what you need to pay attention to is reserve capacity stated as RC. As stated above, the amp hour rating on your Wal-Mart battery is very misleading. G-Man gave the amp hour rating that is more meaningful, but even then, you need to know your amp draw to compute usable capacity. For your application reserve capacity is most meaningful.

Reserve capacity (RC) is how long a battery will continually discharge 25amps @ 80° before voltage drops to 10.5v. That's a meaningful number if you know what your continuous discharge rate is. A 30lb thrust Minn Kota Endura will draw 30amps at full thrust.

RC is 140mins per battery, combined that's 280mins and I can run my 75lb thrust bow mount all weekend without recharging.

One minor correction - maybe. You said you were using a 75# trolling motor, so Im guessing thats a 24 volt trolling motor? If so, that would mean your batteries are wired in series?

If you are running those batteries in parallel, for a 12 volt trolling motor, then the RC/Amp Hours will combine so you get double the run time.

If you have two batteries in series, for 24 volts, then the RC/Amp Hours do not double. You still only have the same run time as a single battery.

[hewesfisher]

Went back through the thread, so it looks like the Minn Kota draws 30 amps, and the RC rating of the battery is 65, so I should expect it to last just a hair over 2 hours at full thrust? If so, that may actually be OK for me...

Please re-read my previous reply - RC is how long it takes a 25amp load @ 80° to deplete battery to 10.5v. So, no, you will not get 2hrs of run time (120mins) with a 30amp load from a battery that provides 65minutes with a 25amp load.

As I said before, CCA and MCA are useless specs in a pure load application like your trolling motor, so ignore them and focus on RC or at least a realistic AH rating at 20amps.

If you want 3hrs of run time at full power (180mins), you need a battery with a RC of at least 200 or one with a 100 AH rating @ 20amps. You'll only get that kind of performance from a much larger and heavier battery. If you can live with a 61lb battery, go to NAPA and buy this one - https://www.napaonline.com/en/p/NBE7235. 3yr warranty, 195mins RC, and $165.

Don't fall prey to the "gp27 is better than gp24" thinking either. I've compared dozens of gp27 vs gp24 batteries, and for most, there is only a very marginal increase in performance which, IMO, is negated by additional cost. Group size (gp) is the BCI standard for physical case dimensions and terminal configuration and has nothing to do with battery capacity.

Notice what I recommended in my earlier reply:

Decide what max weight you can comfortably add to your pontoon, choose a battery that provides the highest RC at that weight, then choose the battery with longest warranty for the price you can afford.

Buy based on what you can comfortably carry in your pontoon, with highest RC for that weight, and best warranty for the price your willing to pay. Not a word about cranking amps, amp hours, group size, or brand. Focus on the specs that matter for your application, reserve capacity or AH @ 20amps.

You're right Larry, but you also have to factor in a 24v trolling motor has a lower amp draw per pound of thrust when compared to comparable 12v trolling motor.

[Bodofish]

Not to harp on the basics but maintenance of whatever battery you choose is the most important part of big batteries. Arguing about types of batteries is like Ford V. Chevy, don't care.
1. Always make sure the electrolyte is up to acceptable levels on all cells (Don't care what anyone says about maint free. Unless it's an AGM, it has wet electrolyte, pry off the caps and make sure.).
2. Try to never take the battery below 50% capacity or 6 volts.
3. Always charge the battery immediately after use. Lead acid batteries like to be charged to full when at rest.
4. New / smart battery chargers lie whenever they can. Only use them when life is good. Get yourself a cheap, non smart charger that just puts out 6 amps or better all day any day. Lead acid batteries are all about shoving ions from one plate to the other. if your smart charger says it's dead, see first sentence in number 4. Make sure the cells are filled up and put the dumb charger on it and it will slowly but surely shove all those little ions back where they belong. It may take a week but as long as you haven't run it dry and shorted the battery, it can be charged. It just takes time.
5. If you can afford the $10, get a float charger for your battery and leave it on all the time. Check the cells again to make sure the electrolyte it up to the line.
6. Keep your battery happy, store it in a cool dry place.
7. Cement floor, don't care, batteries are made of plastic now. The 1950's want their rules back.