Battery Tender ?

[Waldo]

I have a battery tender that I have used on a boat with a single battery. However, my new boat has dual batteries. Anyone use a tender on their dual setup? If so, anything I need to do differently? Thanks.

[Hallett19]

make sure the battery switch is set to "Both" and that will juice up both. Those tenders are great investments.
[ February 26, 2003, 11:01 PM: Message edited by: Hallett19 ]

[h2oski2fast]

You'll have to have the battery switch set to both the batteries, all the time. The "tender" maintains charge according to the resistance of the battery. If the 2 batteries get out of sync with each other then the "Tender will only charge the batteries till the highest(charge) is full, then cut back to a trickle/maintain charge. Tenders are great, but as anything else they have their limitation.

[LUVNLIFE]

Even Though I set my switch to both someone told me that because I hooked up to one battery only to charge to the other one it overcharged the battery I hooked up to. Any thoughts. That battery did go bad.

[JetBoatRich]

I do one battery at a time, the batteries need to be very close in voltage in order to charge them together. You can damage the better battery if they are not equal. At least that is what i have seen and heard wink

[Mandelon]

Buy two chargers....Its only money. and Waldo, where are the pics of the Carrera????????????

[Waldo]

Mandelon, they are posted in the "hot boats" section under "Carrera vs. Cobra"...I don't have time to post them here. Time to go to work.

[Froggystyle]

If you want to ensure an even charge, with one tender, you need to put the negative lead on one battery, and the positive lead on the other battery. Turn your switch to "both". This will force the negative signal to start at the one battery and make it's way to the negative on the other battery. The positive will do the same thing. By doing this, you equalize charging potential by making each lead take the path to the other to charge properly.
Check out the Stereo Battery discussion on the other thread for greater detail.

[LUVNLIFE]

RICH that's probably why I toasted my battery then and FROGGY now that I am thinking about it that would be the solution to I guess making a complete circuit. Thanks

[h2oski2fast]

Froggy, that would only work if the batteries were wired in series (which can not be done in your typical boat, because it would yield 24 volt which would damage all the electronics). Since the batteries are wired in parallel it doesn't matter where you put the charge leads. If you put the leads where you suggested, the voltage would still find its way though the battery cables. The only proper ways to charge, and get the charge, would be to do each battery individualy or to put the batteries on a isolator (which is common use in motorhome and rv applications). An isolator keeps the batteries from "seeing each other" through the use of diodes. Diodes are like a oneway check valve for dc current. When batteries are connected to each other they try and balance out. A lower voltage battery that is connected to a higher voltage battery, will rise in voltage, so that both batteries havbe the same voltage. A battery with a bad cell connected to a good battery will eventually kill the other battery. Batteries that are not connected with each other all the time will have different internal resistance, which is what a charger sees to know when the battery is charged. Thus, one battery will get fully charged, then over charged, because the charger still sees a high resistance that is coming from the battery that isn't fully charged. I hope this helps. I have 4 batteries in my boat, they are split into pairs, each pair is hooked together. They have always been hooked together, and when I change 1 I change both. I do however, every so often, unhook them and cherge each battery to a full charge.
[ March 02, 2003, 01:52 AM: Message edited by: h2oski2fast ]

[JetBoatRich]

Yea what I said, only better.

[Havasu Hangin']

LUVNLIFE:
...it that would be the solution to I guess making a complete circuit. Thanks Unless you have 6 volt batteries, your batteries are wired in parallel. Turning the Perko switch to both will charge (and equalize) both batteries- it doesn't matter which battery you put the tender on, because it already is a complete circuit.
I agree with these guys...unless your boat is sitting in a slip for months on end, I would just rotate the tender on each individual battery a couple times during the winter.

[LUVNLIFE]

Better safe than sorry and do one battery at a time.