2 batteries...switch or isolator?

[airdvr1227]

I'm considering a dual battery setup for my rig. I'm concerned about mooring my boat at a dock with no electric and having enough juice for the bilge pump to run for an extended time if needed.

I've looked at both and I like the isolator idea but I can't find info on what happens, if anything while the charge is being drawn down. DOes it use both batteries simultaneously? Draw down one then the other?

 

[H20Rat]

Re: 2 batteries...switch or isolator?

an isolator will do exactly the opposite of what you want, it ISOLATES the batteries except for charging purposes. This is fine, if you hook up a bilge pump to each battery and let them run by themselves. Otherwise, if you are just looking to increase raw capacity, get a bigger battery or find two identical batteries that you can run in parallel.

 

[airdvr1227]

Re: 2 batteries...switch or isolator?

Thanks. The alternative is the switch or wiring them in series? How important is the ratings for each battery? I read somewhere that without the isolator the "both" switch will just mimmick the least charged battery. So I'm thinking the batteries must be nearly the same rating or it just won't work that well. Any other ideas?

 

[q5ka]

Re: 2 batteries...switch or isolator?

Either I am misreading this or you got your teminology mixed up. If you wire your batteries in series, you will have 24 volt instead of 12 volt. To add capacity, you wire your batteries in parallel. Then you will have twice the running life (if both batteries are identical). The isolator may not be a bad option though. So you wire your bilge pump to the secondary battery, use an isolator so both will charge as the motor is running, and switch if you have an emergency. This way if the bilge pump runs the battery low, you can still start the boat but you also have the bilge pump able to work. If your bilge pump is running enough to drain a bettery in a day or two, you may want to think about fixing your leaking boat instead of just adding more batteries because what would you do if the bilge pump fails with that much leaking

 

[airdvr1227]

Re: 2 batteries...switch or isolator?

LOL...electric is not my thing. Series, parallel...whatever. So I wire them in parallel and the net effect is having 2 batteries and something close to twice the reserves. Just looking for piece of mind. Slip is an hour away and we might not be able to get there every weekend. Thanks.