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Thread: Battery recommendations for MinnKota?

  1. #1
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    Default Battery recommendations for MinnKota?

    I'm getting ready to set up some sort of electric propulsion with a 12v Minn Kota 48# thrust motor, and am looking for recommendations for an **inexpensive** battery to start with.

    The motor will not be set up permanently in the boat, nor will the battery. I'd prefer not to slop acid all over the place, but the AGM or Gell batteries are pretty pricey compared to the "maintenance-free" well cell batteries. I know that the regular open-top batteries allow better testing and water-replacement, and I have a plastic battery box, but still wonder about the sealed batteries as a better option.

    My boat is 14', weighs about 400lbs, and will have a fairly long cable run from the bow (where I need the battery weight) to the transom-mounted trolling motor. Weight is also a factor as I'll be hoisting the darn thing in and out of the boat.

    I won't be running the system for hours and hours, and realize that a 'proper' setup would consist of dual 6v golf-cart batteries, chargers / testers /meters / etc.

    But at this stage I'd like to pick up an inexpensive 12v deepcycle battery to test with, and might combine it with another deepcycle later on if the system works and I need the extended range.

    There is a lot of info on the web, mostly from battery manufacturers, but it sure looks like the AGM is replacing the gell battery and has a slightly reduced cost - but still 2-3x the cost of a wet-cell battery.

    http://www.windsun.com/Batteries/Battery_FAQ.htm

    http://www.batterystuff.com/tutorial_battery.html

    Any suggestions?
    Last edited by Thorne; 10-12-2006 at 11:18 AM.
    "The enemies of reason have a certain blind look."
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  2. #2
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    I used a wet cell deep cycle/starting battery to power my 20' sloop for about a year. I mostly sailed up and down the canal whenever there was a breeze, but the battery seemed fine. The sloop weighed 1 ton, the canal 4/10 of a mile long, it didn't leave me stuck. I don't remember how often I recharged it, but not every trip for sure.

  3. #3
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    A sealed gel battery will do the trick. No spillage and they are available in deep-cycle versions. An 85 amp-hour battery will weigh about 65 pounds. A little heavy; no matter what battery you use, be sure to secure it well.

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    Have a brand new one sitting downstairs......come and get it and it's yours....
    Wakan Tanka Kici Un
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  5. #5
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    My wife just flew out to NYC this morning, maybe I'll have her take a cab up your way and bring it home on the plane?

    ( NOT )

    ;0 )
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  6. #6

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    Just buy a cheap dual purpose battery and put it in a plastic box, and try it out. If you need something bigger, or more high tech, you can always use the battery you bought for the car. My sense is that you don't need something huge and expensive. A regular lead acid should be fine.

  7. #7
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    I'd look at Optima batteries -- their "Blue Top" is what they recommend for marine/deep cycle use.

    I believe you can get them at Sears. They're not too hideously more expensive than a good lead-acid battery (Froogle found them for about $180 online).

    The Optima batteries are actually lead-acid batteries, but the case is completely sealed and the plates are wound in spirals. They can be mounted in almost any position -- supposedly even upside down

    Optima also makes a case ("Troll Fury" ) that lets you bridge 2 of their batteries as one: you can configure it in series (24v, double the voltage) or in parallel (double the amperes).

    Here's how these batteries are put together:

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  8. #8
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    From what I can tell, the Optima batteries are AGM, not old-school wet acid. And AGM looks like a much better option than Gell, which it is replacing rapidly.

    But as I said, the cost per Amp Hour looks double for the AGM compared to wet acid. If I was building a serious electric launch, I'd certainly get the good stuff -- but I'm not, and not sure how much use the trolling motor will get. Hence my request regarding the cheaper wet acid style.

    http://www.windsun.com/Batteries/Battery_FAQ.htm

    "The major construction types are flooded (wet), gelled, and AGM (Absorbed Glass Mat). AGM batteries are also sometimes called "starved electrolyte" or "dry", because the fiberglass mat is only 95% saturated with Sulfuric acid and there is no excess liquid."
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  9. #9
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    Also note that AGM's must be charged at a lower voltage than standard wet cells. 13.8 v. rather than 14.2 v. While they are "sealed", they are also vented to relieve pressure if overcharged. The higher voltage will cause them to off gas, shortening their life. Be sure the charger you use has an AGM setting.

  10. #10
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    My co-owner buddies and I just spent a lot of time researching batteries since the old set of 4 golf-cart 6V batteries died. We concluded the advantages of the sealed gel-cells and other more expensive types aren't worth the extra cost.
    I think, and my own experience bears it out, that careful maintenance of a basic lead-acid deep-cycle battery will get you years of use. In short, pick one up at K-mart - you may even get a good end-of-the-season price now. The main thing is to recharge it fully right after use, monitor the levels and keep it charged over the winter. Batteries that die young have usually been abused.

  11. #11
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    Thanks again, everyone! Battery is on the tricklecharger as we type...

    I hit Kragen's Auto parts on the way home and picked up an Exide Nautilus Gold marine deep cycle battery for $64. 80 Amp Hrs, 140 reserve minutes. Priced out by Amp Hours, the old wet batteries are still a better deal, even if they aren't the 'real thing' for serious electric motor use.


    I got the NG24 - http://www.exideworld.com/products/m...old_specs.html
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

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    Don't go yacht, go commercial. A friend of mine owns a golf course and says the Trojans hold up better than others.
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  13. #13
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    I was going to recommend either a Trojan or Rolls Series 27 for about $95...and you would have very good quality batteries. The Rolls (Surette) is probably better than the Trojan but costs about the same.

    RB

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    Quote Originally Posted by Peter Malcolm Jardine
    Just buy a cheap dual purpose battery and put it in a plastic box, and try it out. If you need something bigger, or more high tech, you can always use the battery you bought for the car. My sense is that you don't need something huge and expensive. A regular lead acid should be fine.
    Whatever you do for the battery, dont scrimp on the cable. If it is undersize, half the battery power will just be going up in heat in the cable.

    Pete
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  15. #15
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    AGM batteries supply the equivalent power of wet acid for about the same cost, but half the energy. This means they cost twice as much per hour of running time. Advantages are low self-discharge, no liquid to spill, and high resistance to deterioration due to deep discharge. The latter offsets the basic capacity limitation somewhat.

  16. #16
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    For cheap steady power, nothing beats a 6v golf cart battery.
    If you can afford it the rolls or mastervolts are the trick item.
    Use a variable pulse charger on the boat. don't scrimp there.
    Chargers kill batterys if they are cheap.
    Too many times I have seen good expensive batterys on $2 buck chargers, and when they fail the battery gets blamed.

  17. #17
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    So, you have a series 24 there. If it's technology you like and it doesn't produce enough steam you can fit a series 27 in the same box. From there you're up to a series 29 and that's going to need a couple more inches of length but no more width - still way smaller and lighter than an 8D or a couple of 6V golf cart batteries, and available from the same maker as the one you have. From the direction you've gone those are your options if that one doesn't work - but I think it will. You made a good call in terms of cash economy in my opinion.
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  18. #18
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    Rather than confuse everyone, I'll start a new thread on charger recommendations.

    -----------------------------------
    Last edited by Thorne; 10-13-2006 at 12:17 PM.
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  19. #19
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    You need at least a dual purpose battery. I found one for my trolling motor at the local battery manufacturer in town. Reconditioned for $30 for a size 24. The more amp hours, the more they weigh. The size 24 only weighs about 35 lb.

  20. #20
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    Question about Epoxyboy's post and general wiring --

    Does it do me any good to buy and string huge thick wires if the Minn Kota leads are relatively small in diameter?

    Seems like the little electrons would jam up and get frustrated at having the pipeline get so much smaller before they could reach the motor?? Or is the gain in lowered resistance for 80% of the length of wire run worth the cost in extra copper?

    ;0 )
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  21. #21

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    Should be able to find a chart on the net that shows voltage loss over length... Use a good quality #6 wire... marine grade, and good connectors. Should be fine. The connectors are crimped, and maybe a small covered pair of terminal blocks to connect the minn kota to... that way you can permanently install the wires in a tidy fashion.

  22. #22
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    There is a chart in the waste marine catalog that shows recomended wire gage for length of run and current draw for both 2% and 10% voltage drop.

  23. #23
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    It does make sense to use battery cables to hook to the dinky wires on the motor. The energy wasted as heat in the wire is a function of amps (not volts), wire gage and length.

    Scroll down on this page http://www.powerstream.com/Wire_Size.htm to find a voltage drop calculator. You would want less than 2% drop in your wire. For instance 50 amps and 14' results in a drop of 3% with 4 gage wire, 1.9% with 2 gage. You can put in your actual max amps and cable length.
    Denny Wolfe
    www.wolfEboats.com

  24. #24
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    And remember, the wire length is the total length of the circut, from the battery to the load and back to the battery.

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