Trolling Motor Batteries

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wadestep
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Re: Trolling Motor Batteries

Post by wadestep » Sun Dec 18, 2011 8:02 pm

i just did a lot of research on this subject for my Dad, who was replacing (4) 6-volts, (3)8D, and (3) group 27 on his boat. - Over $2,400 in batteries. Here's what I found:
1) 6 V batteries (lead-acid) for a big house bank on a large boat are the cheapest and very long-lived. (not for a small boat, 24V.)
2) If recharge rate is important to you, AGMs are the way to go. They can recharge 2x as fast as lead-acid. (up to 50% of battery bank capacity per hour - ie a 2-hour recharge rate during bulk phase). Lead-acids can only recharge at 25% of bank capacity per hour. This is not important if you plan on recharging overnight. AGMs last almost as long as true deep-cyle lead-acids, but are quite a bit more expensive. AGMs also don't really off-gass, and don't need their water levels checked.
3) for a trolling motor, True deep-cycle, lead-acid batteries are going to be the most long-lived and most cost effective.

Be sure not to get ones that are starting or 'dual purpose'. Find some that are true deep-cycle. Big, thick lead plates and good liquid chemistry are what you want. The AGMs are mugh higher profit-margin for most resellers, so they will be pushing them. Lots of BS flies around, and the people saying it generally don't know what they are talking about at all.

This is my recent experience with buying boat batteries.

Also - if you have a battery monitor and don't draw them under 50% of their capacity, they will last MUCH longer. Even deep-cycles will die quickly if drawn much below 50%. So figure out your average draw per hour (amps), multiply by a long day of fishing (how many hours do you use the trolling motor in a long normal day), and multiply by 2 (so you only use half your capacity). That should be your battery bank capacity in amp-hours. That will help you figure out what size (group 24 vs 27) you should buy.
Beyond that, remember that the stated battery capacity on a battery sticker is at 12 volts. If you're pushing 24 volts, you will be drawing 2x as many amps (at 24V) as the battery is rated for (at 12V).
ie, two batteries rated at 80 amp hours, 12 volts will deliver 160 amp-hours at 12 volts, but only 80 amp-hours at 24V- 40 each. Then figure you only want to draw them down 50%, so you only have 40 amp-hours at 24 volts TOTAL you want to use.

One good reference is a book by Charlie Wing called Boatowner's Illustrated Electrical Handbook.
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Re: Trolling Motor Batteries

Post by Uncle D » Mon Dec 19, 2011 10:30 am

I gotta say the gel cell,they will last longer...especially mounted up front. Mine typically lasted only about a year before they would short out from the bouncing and shaking. After replacing with gel cells, I got 4 years. Might have got more but sold the boat. Can't commit on the AGM's. They are 120.00 from Cabela's What the heck does AGM stand for anyway. :doh:

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Re: Trolling Motor Batteries

Post by wadestep » Mon Dec 19, 2011 10:59 am

I believe its for absorbed glass matt. Instead of each cell having a large lead plate sitting in a liquid, everything is held in these matts of fiberglass-like substance.

PS - the extreme vibration of being in the bow of a small boat - ie XF20 running through a chop- may well weigh the balance away from lead-acid traditional batteries. When the battery is discharged, the lead plates form this loose, flaky substance on them (I think it's some kind of sulphate) and then slamm through the waves, may very well shorten their life span. When the lead sloughs off and collects in the bottom of the battery, and when that pile is large enough to touch the bottom of the lead plate it came from, the battery is shorted out = dead. That's my understanding of batteries, anyway.
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Re: Trolling Motor Batteries

Post by ks8 » Mon Dec 19, 2011 11:30 am

AGMs will last longer than gel-cell, but gel-cells will do well if you charge them very carefully with a smart charger designed for gel-cell cycles. AGMs are more forgiving regarding the charge cycle. Gel-cells *will* gas out* if over charged, and once they do, you can't put it back in... :? . My gel-cells are still going at about 5 years (used for nav lights and electronics), but the smart charger fails them now (for the last two years). I use a dumb lead acid charger to charge them now (at only 2 amps - no explosions please), and can still get them to 13.2V, but they are on the way out (shhhh... don't let them know). That constant charge from the dumb charger needs supervision. These veteran gel-cells (group U1 -- about 24 pounds each) have never bulged at the 2 amps. I still get a week's worth of night boating out of a charge (I've switched to mostly LED lighting now... quelle différence!), but I don't think I'd trust these batteries for a trolling motor or critical bilge pump anymore. Got a fresh Group 24 for that. :)

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Re: Trolling Motor Batteries

Post by rjezuit » Mon Dec 19, 2011 12:22 pm

I like either Trojan or Surrette true deep cycle. A little costly, but can take some abuse and have a good reputation.

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Re: Trolling Motor Batteries

Post by wadestep » Mon Dec 19, 2011 1:04 pm

Yeah, those Rolls/Surrette are the real deal. But probably an overkill for a non-commercial trolling motor use.
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Re: Trolling Motor Batteries

Post by majorgator » Mon Dec 19, 2011 5:35 pm

Its taken me way too long to read all the comments and respond :wink: Thanks for all the input so far.
I like Interstate batteries. If you have any friends in the auto business they can get you jobber pricing from them too.
We can get the Interstate blems locally, but I've really heard some mixed reviews on how well they perform.
Buy a couple of good deep cycle batteries " you said you could use the extra weight " and use the
money you save to get a good batt charger, one that will maintain them when not in use .
That's kind of the direction I'm currently leaning in. I already have a good battery charger, so no worries there. My only problem with batteries that size is that I need the weight in the bow and nowhere else. Putting Group 24 batteries in the bow would mean I'd have to put them in the same compartment as the fuel tank, which is not preferable by any stretch. I do have some thick plastic welding shield that I could "fence" off the fuel tank with...now there's a thought :doh: That compartment is well vented, so I'm not overly concerned about fume buildup.
I'm a big fan of...Walmart batteries.
Now here's a man that I can agree with :wink: My two main batteries are Wal-Mart brand. Sorry for the edit :wink: :wink:

To those who commented about the 4 golf-cart batteries, while I agree in principle that it would more than likely work just fine, I would be doubling my battery bank, thus doubling my amount of electrical connections. Since we often spend a fair amount of time dealing with saltwater corrosion in electrical circuits, I'd prefer to maintain a simpler approach. BTW - I used to own a golf cart, and I believe that the 6-volt batteries were just as large and heavy as the standard Group 24? I need the extra weight, but not that much :wink:

Wade, thanks for the well thought-out comments. I understand most of what you're trying to say :wink: That's some good information to have on this forum.

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Re: Trolling Motor Batteries

Post by Southern Gent » Thu Dec 22, 2011 10:27 am

Seth, I have used Interstate both 24 & 27 class. I really like the Interstate 27 class best. Don't forget battery boxes and venting. I'm locating my batteries under my Xf20 console to reduce pounding them in the open bay waters. Merry Christmas. Bill

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Re: Trolling Motor Batteries

Post by tobolamr » Thu Dec 22, 2011 2:55 pm

I have been using trolling motors for some time - not as long as others here, but a solid 18 years now - and all of the above is very good input. I strongly agree with a good charging system, too. As for the batteries themselves - I know what *I* am choosing, and why. But most of our local bass club guys and the like get, as CL said, Wal Mart batteries. They also store them inside during the freezing cold months, and replace them when it warms up.

I, personally, have gone AGM. And I do meet a few people who are die-hard Optima Spiral Cell battery lovers. Not sure if it really matters, in the long run, what you use for a battery. :doh:

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