One of Two Batteries Discharging Yearly

[smartbuffboy]

I have a 1996 Speedster (Twin 85hp) and for some reason almost every year it seems that one of my batteries dies or does not hold full charge, the other battery is fine. These batteries are connected together with the neg. cable... does this actually provide power to both engines using both batteries, or is that just to connect the ground together or something? I'm wondering if there is something wrong with one of the engines that is discharging one of the batteries (it's always the same one each year I think).

Any thoughts on what could be causing this and if both batteries are used for both engines?

Thanks.
Richard.

 

[timmyboy76]

Have each battery there own ground, won't hurt, also, you disconnect (+) leads from battery when done using???

 

[kustomkarl]

You could also just install a battery switch to turn off the power after use.

Karl

 

[Gunsrunner]

Having each battery there own ground is a bad idea, unless you mean that they will still be linked by a common ground. You should link all your ground points together to make a circut.
It sounds as if you have a drain on the one battery, this will be through the positive if all negatives are connected as they should be.
Karl is dead right fit an isolation switch and use it, it should cut all power drain and fix your problem.:cheers:

 

[smartbuffboy]

Power Switches

Thanks for the comments! I do have them connected through a common ground (linked together).

As far as the switch, would I need to have a switch for each battery? Where would you attach them to, the fiberglass hull somehwere?

Any that you particularily recommend? Will this work:
http://www.westmarine.com/webapp/wcs/stores/servlet/producte/10001/-1/10001/268741/377%20710/0/battery%20switch/Primary%20Search/mode%20matchallpartial/20/0?N=377%20710&Ne=0&Ntt=battery%20switch&Ntk=Primary%20Search&Ntx=mode%20matchallpartial&Nao=20&Ns=0&keyword=battery%20switch&isLTokenURL=true&storeNum=5002&subdeptNum=9&classNum=297

What about these devices that attach to the positive cable and are supposed to maintain the charge and catch any possible drainage of the battery... are those any good?

Thanks again.
Richard.

 

[timmyboy76]

That would work, or battery switch from HARBOR FREIGHT for $4.00, I mounted mine under the latch above the shelf, (guess you would call that), on the side, above the battery...
Statement about hav'n each own ground...could've been a little more clearer