I currently have a motorguide 55# digital wireless trolling motor mounted on the bow of my boat.  It is a 12v model.  I have one deep cycle marine battery that runs it.  I have heard that you can add a second battery for this setup just by connecting the positve to positive and the negative to negative.  

1)  Would i see a huge gain in performance?

2)  Would it extend battery life enough so that it would be worth it?

3)  I currently have a 1 bank charger on my battery...would I have to go to a 2 bank charger to properly charge the second battery  separately if I did decide to go with a second battery?

Help a brother out!

Yes, that is the correct way to connect it to your other battery.

The only gains you will see is it will double you run time.  If the one battery lets you fish as long as you like, it wouldn't be worth it.

Your one bank charger will charge them but to propery charge two batteries in parallel with one charger (depending on size of batteries) it would need to be at least a 15 - 20 amp charge. A two bank would be better or you could keep the one bank and use it as a maintainer for the two and just connect a separate charger to charge them when you come in.

If you buy a two bank, I would go ahead and buy a three bank so you have your cranking battery on it also.

Way2Slow....I was hoping you would post a thread here.  After reading some previous threads about batteries, you obviously know your stuff.  

As of now, I am probably ok with one battery, but I am always looking to upgrade my equipment.  When I bought my boat, I didn't know a thing about electric trolling motors.  I should have insisted on at least a 24 volt; however, for the amount of time I am able to get out and actually fish....the run time on my current setup is usually adequate...as long as i'm not running it at full power.  

High wind days  do seem to suck my battery and after reading that it is best not to discharge the deep cycles beyond 40-50%....well....maybe it is worth it getting an extra battery?!?

Are the blue top  deep cycle batteries (optima) worth all the hype?  

Are they worth upgrading to if and when my current interstate battery dies?  

Can I mix and match an optima with my current interstate (not sure of the specs on this battery?)

In my personal opinion, you would be down grading if you got an Optima.

A good flooded cell group 27 is going to give you approx 200 Reserve minute capacity or 105 Amp hour, the last time I looked at the Optima group 27 is only has about 140 res min's or 66 Amp hours.

Even going to their largest group 31 you only get 155 res min's or 75 Amp hour. A good flooded cell group 31 is going to give 120 Amp hour or 225 res min's, and at a hellava lot less money.

Deka makes a hellava lot better AGM than the Optima and has way more power than the same size Optima.

The only thing I can say good about the Optima is they have great advertising.

I don't know of an onboard charger that's going to let you mix battery types. They need to be all AGMs, Gells, or Flooded cells. Working in parallel, you can get away with it as far as running them but it's always better to keep like batteries. Like batteries are a must if connected in series.

As for discharging your batteries, you can take them down to 30% without damaging them. The difference between 30% and a higher number is that the less you drain one, the higher the cycle count (a discharge and recharge). What his means if you drain it to 30% every time, it may last 200 charges, only drain it to 50% and it may last 500 charges. A lot this also depends on the quality charger you use. The better the charger, the longer the battery life.

Batteries can only produce the amount of power the plates will allow. This is measure in Amp Hour capacity, normally using a small load over a 20 hour period. Increase the load so it discharges the battery in a five hour period and it greatly reduces the Ah capacity. Another method used is the reserve minutes. This is how many minutes it will last with a 25 amp load (most common). So, it does not matter what kind of battery it is, AGM, Gel, Flooded cell etc, when it comes to run time none of them can last longer than their designed capacity.

The big difference is the cycle count, Gel's give the largest cycle count but have the least capacity for the same size battery. AGM's are next, they will give about twice the cycle count of the average flooded cell but up to 20% less capacity. The higher quality flooded cells will give way more cycle counts than the standard, cheaper floodel cells, like the those big yellow Walmart batteries, those are about a cheap as your gonna get and have a battery worth loading in your boat. The bottom of the food chain are those cheap imported batteries a lot of companies buy and stick what ever label that want on them, Stay away from those.

A good, high quality charger at the proper rating and keeping them charged and properly maintained is the main thing that's going to let you get full life from a battery.

Roger that Way2slow.  You were a huge help!!  Guess when its time to upgrade I will get another similar battery and upgrade to a triple bank charger so that I can charge my cranking battery too.  

Joe