[bnussbaum]

Hi guys,
I need some input on adding a second battery on to my 95 Shabah z202. Is there a recommended way of adding one on? Can I just daisy chain 2 batteries together, or would this cause an overload on the alternator?

[SEMIJim]

You wouldn't "daisy-chain" them together, in any event. That would supply 24V to your system, which would quickly fry everything you turned on. If anything: You'd wire them in parallel. But you don't want to do just that.

There are several ways to add a 2nd battery. The most common way is an off/1/both/2 switch, such as this Blue Sea switch:



You would normally start your engine in "both." Then, if you were going to run equipment for long w/o the engine running (stereo while you were out at a sand-bar or whatever, maybe anchor light and VHF while out fishing at night, etc.), you'd switch to either "1" or "2" so you had a battery reserve for starting.

The trick with such a system is remembering to switch from "both" to either "1" or "2", then remembering to switch back again. Also: If you run-down, say, "1" and you try to switch to "both" to start and then charge "1", you may quickly drain "2" (it'll try to charge "1" when they're combined) and be in trouble, anyway. Otherwise you have to start and run on "2" and wait to deal with the discharged "1" when you're back at home port or whatever.

It is generally considered unwise to switch battery switches while the engine is running. Even with modern make-before-break switches. You can easily fry your alternator in a heart-beat, doing that. Some 4-position battery switches have alternator field disconnect circuits that make switching while the engine is running safer, but won't work with all alternators.

The better system, IMO, would be a combination of this Blue Sea switch:



and this Xantrex Echo Charge unit:



The concept is you have a "house bank" and a starter battery. The starter battery is used solely for the starter motor. The "house bank" is used for everything else. The switch, when placed on "on," connects the starter battery to the starter (well, the starter relay) and the house bank to everything else. The switch does have a "combine" mode just in case. The Echo Charge distributes charging to the two (sets of) batteries, sending most to the house bank, which will usually need the most.

That's the way I'd do it.

Jim

[jasfiveo]

I have a Stinger SR200 battery isolator/relay. About 60 bucks on the internet. I added a second battery strictly for the stereo. Connect the postitive cable from the first and second battery to the posts on the isolator, run a ground cable from the isolator, and run a accessory wire from the isolator to your ignition switch and your done. I ran the accessory wire to an accessory switch on my dash and I turn it on when coved out and that isolates the stereo battery. I turn the switch off when I take off and that allows the circuit to open and recharge the battery. I probably made that sound confusing but it is simple. I think stereoman did a quick diagram. Just search forum for second battery.

[bnussbaum]

Thanks for the input. Would a transfer switch be hard to install on your own? I am not confident enough in doing major rewiring, but if it is something simple, I might be able to handle it. I tried searching for the diagrams, but I have not found any. If someone knows where I might find it please let me know. Also, whre did you install the switch, was it by the steering area, or underneath the hatch? Thanks again for the help.

[jdecoudres]

my boat has one battery and it also has one of those 1-both-2-off switches so if i wanted to add another battery manly for anchored out with the radio on or anchored out at night for the radio and lights whats my best best. I just bought this boat brand new couple years ago so really dont want to get into a big problem by re wiring the whole boat. Thanks u guys always have fast answers for my dumb questions. Im glad i found this site!