Batteries and Trolling Motors

[Star Man]

I started an earlier thread on battery charging but maybe I should have started with batteries. First, is there a listing of marine batteries that are recommended by users? I'll be using two trolling motor one in front and aft. I want to be sure that there is sufficient power to run these as well as the batteries lasting as long as possible both on the water and before needing replacement.

As I have found out, the charger will help determine the life of the battery by the quality of the charger but the next question is what are the best value in marine batteries? I know they will need replacing but there must be a point of value where the battery last long enough to equal or exceed it's cost. Any suggestions on how to figure this out? I saw a FAQs on batteries talking about life cycles but it appears that many batteries don't have this information available and again I would imagine that the charger will play a large roll in that as well.

Another issue I didn't see addressed was when to charge. Do these marine batteries have a memory like Ni-Cad batteries and need to be fully discharged before they are recharged?

Sorry to ask so many questions but better to find out from those that know than the hard way and $$ down the road.

Thanks,

[Way2slow]

Not going to get into what's the best battery because you can ask 10 people and get 10 different answers, each swearing their's is the best.

As for cycle count, a discharge and recharge equals one cycle.  Yes, some batteries have a lot higher cycle count than others.  Wally World batteries are at the bottom of the chain, Trojan's and Deka's are at the top of the chain.  There are a few others that give good life also but it won't be a cheap battery. 

AGM's give a high cycle count but not worth the extra dollars or the loss of run time.  The same size AGM will have as much as 25% less run time as a good  flooded cell battery.

Lead acid batteries do not develop a memory. 

The less the battery is discharged, the higher the cycle count you will get from it.  For max practical life from any lead acid battery, use a large enough battery that you only disharge it to 50%.  Discharge to 75% will give even higher cycle count, but it's not very pratical to think you are only going to fish long enough to come back in with 75% left in your battery.  NEVER discharge one below 30%, that will cause the plates to start flaking and coming appart.

[Star Man]

Are there reliable gauges to show you how much the batteries are drained? From what you are saying, it sounds like experience is going to be a major factor on how much battery is required.

[Wayne P.]

From a battery information site:

Battery Testing can be done in more than one way. The most accurate method is measurement of specific gravity and battery voltage. To measure specific gravity buy a temperature compensating hydrometer, to measure voltage use a digital D.C. Voltmeter. A quality load tester may be a good purchase if you need to test sealed batteries.

For any of these methods, you must first fully charge the battery and then remove the surface charge. If the battery has been sitting at least several hours (I prefer at least 12 hours) you may begin testing. To remove surface charge the battery must be discharged for several minutes. Using a headlight (high beam) will do the trick. After turning off the light you are ready to test the battery.

Voltage

State of Charge Specific Gravity 12V 6V

100% 1.265 12.7 6.3

*75% 1.225 12.4 6.2

50% 1.190 12.2 6.1

25% 1.155 12.0 6.0

Discharged 1.120 11.9 6.0

[Jig Man]

You can get a good deep cycle battery with 180-200 reserve amps.  When you use it, take it home and charge it as soon as possible.  Check the water level regularly and add distilled water when needed. 

An inexpensive hydrometer from any auto parts store will let you check the specific gravity of each cell to tell whether or not it is fully charged.

Use a 10-15 amp charger, keep the water level up, charge when you get home, keep the battery clean and you should get 4-5 years of good service out of most batteries.  I have used lots of brands and gotten good results from all of them.

[Star Man]

Thanks Guys. Looks like I'll need a good battery charger and then just keep an eye on the battery condition and make sure it stays charged. I have a Sears trickle charger, should that be used when the boat is stored over the winter?

[Jig Man]

When your boat is stored if away from home, take the batteries out and take them home.  Charge them every 3-4 weeks and check them on the hydrometer.