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Jason, Marine Mechanic
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Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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Minn Kota 65 - 28 Lbs Thrust... want to know what battery

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Have a Minn Kota 65 - 28 Lbs Thrust... want to know what battery I should get. Boat is a 12 foot day sailer. Weight maybe 200lbs.  To be used on inland lake... less than 100 acres so no real waves. Max 3 people aboard, but may use later with larger boat. Intend to charge using a solar trickle charger it that matters. Wanted to know what size / type of battery to buy.
Submitted: 3 years ago.
Category: Boat
Expert:  Jason replied 3 years ago.

Hello, and welcome to Justanswer. My name is XXXXX XXXXX I will be helping you today. If you need clarification on something please post back here.

 

You do need a deep cycle battery. They come in different group sizes, 24, 27, 29 ect. The bigger the battery the higher the number group size. The bigger the battery, the longer it will run before it needs to be recharged. Also, the bigger the battery the more expensive it is going to be. The best answer is to buy the biggest battery you can afford.

 

a 28lb thrust motor is going to draw roughly 20 to 25 amps on its fast setting. Here is a deep cycle from sears that I will use as an example.

 

http://www.sears.com/shc/s/p_10153_12605_02827582000P?prdNo=5&blockNo=5&blockType=G5

 

That battery has a 200 minutes reserve load time. At a 20 amp draw you should get the full 200 minutes run time out of the battery, at a 25 amp draw, the run time will be less.

 

The next part of it is you really don't want to use a solar charger to charge the battery. The battery simply will not last. What you want to do is run this battery as dead as you can possibly kill it, and then when you get back in throw it on a quality charger and charge it back up. And you want to throw it on the charger when you get back in fishing for the day. Not the next day, and not the next week, but that night. If you don't charge them like that, you will be likely if the battery makes it a season. If you charge them the right way, then you will get a few years out of a battery. So when you set your budget, budget in a decent battery charger.

 

Post back if you still have questions on this.

Good luck!

Jason

 


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Customer: replied 3 years ago.

So cranking amps don't matter? just the group #?

 

Local fishing store had 4 batteries. $99 to $195. But the cheapest one said 1000 amps then the next was 690, then 750 and then 870. Didn't seem to make any sense at all. The last three all had more cold crank amps for more dollars but why would the Interstate 24MxHD be cheaper with more amps?

 

Engine says at 28 lbs a 105a battery should last 3 hours. Clearly that 105a isn't amps ??? I'm confused.

Customer: replied 3 years ago.

Jason,

 

Have to run... wife booked diner. Will definately be very happy to pay for your time. Last Q was just if you have a personal brand recommendation or is it all just about the price? IE: Die Hard, Interstate...even WalMart's brand. Is there one that you personally feel is best? Don't do any research on that... I know it wasn't really in the original Q so just off the top of your head... Thanks again.

 

Rob

Expert:  Jason replied 3 years ago.

Cranking amps don't really matter in your case because we are not cranking over an engine, just spinning a little trolling motor.

 

The bigger a battery is, the more lead and the more acid is going to be inside of it. The more lead and acid, the more power, both in cranking and reserve.

What you need to look at is not the cranking amps, but the reserve capacity. And that will vary size by size. The group size is not the capacity of the battery, or its power, but just its physical size in height, width and depth.

 

When you go to the stores to look at the batteries, don't even look at cranking amps, because it just does not apply to you. (we are not cranking over an engine) Look at reserve capacity. Reservice capacity is how long a battery can supply current (amps) before the voltage drops. Most batteries are rated at 25 amps. So the battery I gave you above had a 200 minute reserve capacity. At a full 25 amp draw, the battery should last 200 minutes before it needs to be recharged. Compare batteries by size and reserve capacity.

 

All batteries, both starting type and deep cycle types will list both cranking amps, and reserve capacity. A starting type makes good cranking amps, but has little reserve. A deep cycle will not deliver as much cranking amps, but it will have a lot in reserve. They are opposites.

 

I am copying and pasting this from a battery FAQ that I keep. But here are more or less textbook definitions between the battery types.

 

  • Starting (sometimes called SLI, for starting, lighting, ignition) batteries are commonly used to start and run engines. Engine starters need a very large starting current for a very short time. Starting batteries have a large number of thin plates for maximum surface area. The plates are composed of a Lead "sponge", similar in appearance to a very fine foam sponge. This gives a very large surface area, but if deep cycled, this sponge will quickly be consumed and fall to the bottom of the cells. Automotive batteries will generally fail after 30-150 deep cycles if deep cycled, while they may last for thousands of cycles in normal starting use (2-5% discharge).
  • Deep cycle batteries are designed to be discharged down as much as 80% time after time, and have much thicker plates. The major difference between a true deep cycle battery and others is that the plates are SOLID Lead plates - not sponge. This gives less surface area, thus less "instant" power like starting batteries need. Although these an be cycled down to 20% charge, the best lifespan vs cost method is to keep the average cycle at about 50% discharge.
  • Unfortunately, it is often impossible to tell what you are really buying in some of the discount stores or places that specialize in automotive batteries. The golf car battery is quite popular for small systems and RV's. The problem is that "golf car" refers to a size of battery (commonly called GC-2, or T-105), not the type or construction - so the quality and construction of a golf car battery can vary considerably - ranging from the cheap off brand with thin plates up the true deep cycle brands, such as Crown, Deka, Trojan, etc. In general, you get what you pay for.
  • Marine batteries are usually a "hybrid", and fall between the starting and deep-cycle batteries, though a few (Rolls-Surrette and Concorde, for example) are true deep cycle. In the hybrid, the plates may be composed of Lead sponge, but it is coarser and heavier than that used in starting batteries. It is often hard to tell what you are getting in a "marine" battery, but most are a hybrid. Starting batteries are usually rated at "CCA", or cold cranking amps, or "MCA", Marine cranking amps - the same as "CA". Any battery with the capacity shown in CA or MCA may or may not be a true deep-cycle battery. It is sometimes hard to tell, as the term deep cycle is often overused. CA and MCA ratings are at 32 degrees F, while CCA is at zero degree F. Unfortunately, the only positive way to tell with some batteries is to buy one and cut it open - not much of an option.

Let me know if you still have questions about this.

Best,

Jason

 

If this answers your question please do not forget to hit accept. Hitting accept is the only way justanswer compensates me for my efforts.
You can still come back here at any time in the future at no extra charge to ask follow up questions to this even after hitting accept.
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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 9483
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
Jason and 3 other Boat Specialists are ready to help you
Expert:  Jason replied 3 years ago.
I gave the answer above as you were typing at the same time. Personally I like Interstate and Exide batteries. But that is because I have had good luck with them over the years. Most quality batteries will last if you take care of them. You do have to maintain them.

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