Fishing accessory (marine battery

Question
Mark,

With all the fishing experience you've had, I'm certain you have much greater knowledge of this subject than I have.  So...

I've heard them all forever, but I'm not sure what they really mean to the consumer.  So, what do you think is the best measurement (CCA, Reserve Capacity, etc.) to use for comparing value (cost versus usefulness) of a Deep Cycle Marine battery for the exclusive use of powering a trolling motor?

I apologize if the question is poorly worded.  I'm just trying to figure out how all the numbers come together to actually mean something that will help me decide the best battery for the purpose.

Thanks,
Fred

Answer
Hello Fred,

Thank you for the great question. Forgive me for the delay...numerous days at work and no internet capability combined with the earliest fire season in many years has dominated my time. But, with no further a-do, I'm back...

First off, CCA's or cold cranking amps are only a fair measurement on starting systems...great in colder climates where you are often in temps below freezing...CA's or cranking amps are usually higher because the measurement is done in moderate temps above freezing... so if it is your main or starting bank of batteries, consider CCA's and CA's. Reserve capacity is really NOT reserve...you either have the juice or you don't...but it is a great marketing gimmick, (even if you can justify the claim due to a capacitor or some type of "reserve" circuitry.

Through trial and error, I have used marine deep cycle batteries from three manufacturers: The Sears Diehard Deep Cycle, Interstate Marine (SRM-29) and Kragen (O'Rileys)31DCM. I was initially purchasing the batteries based upon the price and the manufacturers?warranty but since warranties are so similar these days, I most often go by price匢抦 not proud!  So let's look at what a deep cycle battery is.

As you may know, the deep cycle battery is a battery that is designed to withstand repetitive discharges to a "20% depth of discharge or more and to continue providing its rated capacity" after hundreds of cycles. In my experience, the batteries last longest if completely discharged and then recharged rather than used for the day to say, 40% and then bringing it back to full charge...this greatly reduces the life of the battery and often creates "memory" with the battery capacity being reduced before the cells ever wear out. Remember the end of that sentence...."cells wear out"?  Maintenance is a pretty important thing to consider.

A) Keep the cells filled to the proper level with DISTILLED WATER and check the electrolytes
  annually.   
B) Keep the battery stable. Keep it tightened in a bracket. Impact and vibrations destroy the
  cells quickly.
C) Keep the battery as cool as reasonable...heat also breaks the cells down.

So in lead/acid batteries, I prefer to consider the price, the overall capacity and the warranty. The Interstate SRM29 is getting me about 6 hours run time on a Minn Kota Maxxum 55 at 70-100% power while holding over points in the wind or pounding the banks. 1 amp per pound of thrust per hour on high. This trolling motor has an impulse circuit that really gets you more time out of a charge by feeding juice to the motor itself much like an impact sprinkler waters a lawn...a broken stream if you will, that never lets the rpm of the motor drop but uses 30-50% less electricity. Keep in mind, I am fishing from a small, relatively light boat (+/- 1000lbs)and I do NOT keep my battery on a "maintainer"...I charge it the night before I hit the water and pretty much abuse the heck out of it.

The key is matching the amount of energy to your needs. You can get a LOT more longevity out of a couple of commercial 6 volt deep cycle batteries connected in series than one 12 volt unit. (That's why most golf carts are set up that way.)  But that is a heavy way to go unless you have a boat in which weight is not an issue. Another comparison is the actual size of the battery卼his usually means more amp hours or hours of energy at a certain number of amps drawn by the motor. An example would be the Interstate 29M versus the next size up?the 29M is 13攛6.75攛10?and provides 6.2 hours of juice at 15 amps draw. The next and largest size is the 4D is 21攛8.25攛10.125?and provides 11.5 hours at the same, 15 amps draw.

So far, I have yet to invest in the new sealed Absorbed Gas Mat batteries (AGM) like Optima, which are touted as lasting longer than all others, having less memory develop and take a lot more vibration than any other designs...but 200+ bucks each is painful...you will have to decide if you can justify that cost. So while they should be more durable, cost versus gain is debatable.

So in a nut shell, until lithium ion technology becomes common place and affordable, I will just let the price, warranty and the overall capacity dictate. With good care and maintenance, most major manufacturers will last a reasonably long time.

I hope all this mumbo jumbo helps...get out and catch'em!

Thanks again for the question.

-Mark