Understanding Deep Cycle Batteries and Electric Trolling Motors...

[Jelly]

Questions:

So basically, what you should look for is a deep-cycle battery with the highest amp hours. (?)

Also, you should pick a trolling motor with the lowest amp draw for whatever thrust you want. (?)

Cables running from motor to battery should be as short as possible and of heavy gauge using clamp or screw-on connectors, not clip-ons. (?)

Is there a way to determine the amp draw of a trolling motor at any given speed setting? Specs usually only show max amp draw (full thrust)...not what is used at other various speeds.

Does the power output of a deep cycle battery vary with charge level...regardless whether it's 5% or 95% charged, would performance vary?

What else should one consider?

 

[1 FMF]

http://www.uuhome.de/william.darden/

http://auto.howstuffworks.com/frame.../www.4unique.com/battery/battery_tutorial.htm

these'll explain battery info far better than i can, or care type, and should answer all your questions.

Yes, basically look for the highest amp-hour rating or reserve capacity. The limiting factors will be weight of the battery, size, and cost. Group 27 may be more than you need, big & heavy costing $100 or more, Group 24 is the norm and typically has 100 minutes Reserve, which is a constant 25A draw for 1.5 hours before the battery has less than 11 volts (ie dead) and needs recharge.

The power output will not vary with charge level. It will vary however with temperature, but probably not enough to notice with a healthy battery.

For determining the amp draw, my first idea would be to divide the max amp draw at full thrust by throttle position. To know exactly, hook up an ammeter; typical inexpensive multimeters will measure up to 20A.

For connections, I like the batteries with wingnut terminals best, they alway maintain a solid connection when using ring terminals on the wire and are easy to setup. Clip on or alligator clips would work fine too. Biggest thing of course is whatever the connection that its clean.

Wire gauge should match the amp draw and wire length you need. 10 guage typically fits the need for everything up to 20A and 20 ft, and is easy to work with. Home depot sells spools of it for a good price, don't buy the wire at a marine store. They charge 500% more than it's worth.

The other big thing is to have a good battery charger. I think we argued not too long ago here about battery chargers and battery maintainers. I still stand behind my claim of a charger/maintainer that maintains at 1-amp or less constantly, not the 2-amp trickle chargers you see everywhere.
I also recommend staying with the traditional wet-cell battery. They're easier to maintain in terms of charging. The newer AGM and gell-cells exxagerate their performance and durability claims, cost too much more, and if you don't have the proper charger for them with the right voltages you will ruin them. The extra money you would spend on an AGM or gell-cell will buy you a nice charger/maintainer.

[ January 12, 2005, 11:54 AM: Message edited by: 1 FMF ]

 

[Jimbo]

Autozone has the best prices I have seen on deep cycle batteries. A group 24 for my camper was under $50 and the 27 is under $70. Just buy the most amp-hours for the least money. I dont trust Optima. If they are really so long lasting, why is the warranty so short?

 

[Bio-T]

What is the size of the boat and what are you going to use the trolling motor for? Bass fishing, lakes, rivers, saltwater???? I have three boats with 3-Group 27 Delco Voyager Deep Cycle batteries each and built in chargers. One has a 24/36V trolling motor and the other two are 24V only. Plus a Grp. 27 battery on my power washer and a Grp. 24 battery on my travel trailer. All Delco Voyager Deep Cycle batteries that I use a portable charger on.

 

[Jelly]

quote:

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Originally posted by 59 Vetteman:
What is the size of the boat and what are you going to use the trolling motor for?

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Would be used as primary propulsion on a small jon boat or canoe (most likely, a canoe, since I enjoy paddlin' as well).

Here's something from MinnKota I have a hard time understanding:

Maximizer™

Conventional trolling motor design (speed coil technology) delivers a constant, steady flow of power to the motor, regardless of the speed setting. This constant flow results in wasted power and excessive heat—both of which reduce your time on the water and the life of your motor. And with speed coil technology, you are limited to a pre-determined number of speed settings.

Minn Kota variable speed motors utilize our exclusive Maximizer technology to deliver the precise amount of power needed at any speed, along with infinitely variable speed settings. You get the ability to “dial up” the precise speed setting you desire and your motor runs cooler with no wasted power. By properly regulating the amount of power that is delivered to your motor, you get up to five times longer run time on a single charge."

Then again, this could just be marketing hype, but it makes me think that a "conventional" trolling motor draws max amperage at all times, regardless of speed setting...that doesn't make any sense to me!

 

[Jelly]

quote:

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Originally posted by 1 FMF:
The other big thing is to have a good battery charger. I think we argued not too long ago here about battery chargers and battery maintainers. I still stand behind my claim of a charger/maintainer that maintains at 1-amp or less constantly, not the 2-amp trickle chargers you see everywhere.
I also recommend staying with the traditional wet-cell battery. They're easier to maintain in terms of charging. The newer AGM and gell-cells exxagerate their performance and durability claims, cost too much more, and if you don't have the proper charger for them with the right voltages you will ruin them. The extra money you would spend on an AGM or gell-cell will buy you a nice charger/maintainer.

---

Yes, I will be staying with the traditional wet-cell batteries.

What about this charger?
http://www.minnkotamotors.com/products/chargers/MK_110.asp#

 

[Bio-T]

Three stage charges are great. Looks like a good one. The MinnKota is refering to the pick off click type trolling motor selectors. Really only two major players now in the market. MinnKota and MotorGuide. Both have similar features and both are really efficient. For your purpose a trolling motor in the 35lb thrust area with a Grp.24 battery will serve you well. Hand operated, not foot control.

I have 2 Motor Guides and one MinnKota. Both work well, I just ignore the marketing hype and look for the pounds thrust, mount, operation mode and voltage that I need. I always get a bigger one than required for the boat, and operate at a lesser speed so I am not at wide open to do what I need, less wear and tear on the motor IMO.

 

[Jelly]

quote:

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Originally posted by 59 Vetteman:
For your purpose a trolling motor in the 35lb thrust area with a Grp.24 battery will serve you well. Hand operated, not foot control.

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Funny you mention that. I'm looking at the Minn Kota Endura 36. It has a 34 max amp draw and operates on 12 volts.

http://www.minnkotamotors.com/products/motors/fw_transommount/endura.asp

Isn't a group 24 battery a little low in amp hours (80-85, I think?) when used with a trolling motor that serves as primary propulsion? Then again, I don't know what this trolling motor uses at other speeds than full thrust, which I'm sure use less than the "max amp draw" spec.

 

[Bio-T]

I was recommending the Grp. 24 because of weight in a canoe. If you can use a Grp. 27, by all means use that. A trolling motor used on med speed intermittently should last you all day and then some. Always recharge the battery as soon as you can after use.

 

[Jelly]

Thanks Vetteman and everyone else for helping me out here.

As a kid, I lived on the water and had a small jon boat and trolling motor. After several hours out on the water, I had very little power left. Then again, I wasn't doing the charging, and don't remember what battery size we used (it was a deep cycle though).

So a group 27 should last all day (if not at full thrust)? I travel good distances on the water from the launch location.

If this motor pulls 34 amps at max draw, and a group 27 has 105ah, then that would give me approximately three hours at full thrust (assuming that I can completely disharge a deep cycle?) Wonder how much it pulls at "medium" throttle. Gotta figure travel time plus usage when actually fishing...

[ January 12, 2005, 05:49 PM: Message edited by: Jelly ]

 

[brianl703]

quote:

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Originally posted by Jelly:
If this motor pulls 34 amps at max draw, and a group 27 has 105ah, then that would give me approximately three hours at full thrust (assuming that I can completely disharge a deep cycle?)

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Keep in mind that amp-hour ratings are determined by using a 1/10th discharge rate AND the efficiency of the battery goes down as the current draw increases.

That is, a 105 amp/hour rating is telling you that the battery can supply 10.5 amps for 10 hours.

With a 105 amp draw, that same battery may only last 45 minutes.

 

[brianl703]

quote:

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Originally posted by 1 FMF:
For determining the amp draw, my first idea would be to divide the max amp draw at full thrust by throttle position. To know exactly, hook up an ammeter; typical inexpensive multimeters will measure up to 20A.

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You can also get a current shunt to measure larger amperages (up to 100 amps or more) with any multimeter.