Duel battery installation question....

[Brijoe00]

I have been searching this forum for a while and am not finding exactly the answer Im looking for. Can someone spare a minute and give me a hand?

I want to install a duel battery system in my boat 1 for starting, and the other for running radio lights etc when I am beached or moored etc.

My question is. if my starting battery is on selection 1 on the switch and I leave it on 1 while under way will both batteries get charged from the alt? From what I have read you have to remember to switch it to both when under way for both to be charged. I want to be able to run on 1 then when I am stopped switch to 2 for radio etc. When I am ready to go switch to 1 to start and not have to worry about switching to both for both of them to be charged.

To accomplish this do I need a selector switch as well as a battery isolator? Any help would be much appreciated.

Thanks

 

[Silvertip]

Re: Duel battery installation question....

You need one device. That device is a dual battery switch, an ACR (automatic charge relay), or an isolator. The dual battery swtich provides the most versatility which I will get to. An ACR requires nothing for you to remember. An isolator is an inefficient solution due to voltage drop over the diodes. The dual battery swtich does require some operator intervention -- sometimes. All you need to remember is that whatever swtich position you have selected is the battery that powers everything on the boat and also is being charged from the engine. Remember also that with a dual battery switch, "everything" is connected to the COM terminal on the switch except perhaps an automatic bilge pump. As for operation, 90% of the time you can leave the switch on BOTH and be on your way. Both batteries are on-line and both are being charged. If you stop for even an hour, you will not run down either battery. If it bothers you, switch to BAT 2 so only the deep cycle powers everthing. When ready to go, switch to BOTH. Chances are the engine will start normally and you won't have to switch as you would if you started on BAT 1. You control how the system operates. An ACR is fully automatic in that it treats BAT 1 as first priority. That battery gets charged first and when topped off, it switches to BAT 2. With that system you loose the ability to start from the house battery unless that device has a "COMBINE" feature.

 

[mnmike3]

Re: Duel battery installation question....

I agree with silevrtip, however another option which is the way i'm going to set mine up is, 2 batteries #1 will be mainly for starting #2 will run my stereo and any interior lights/pumps etc that may get used while the motor is not running. I am going to use a 200 amp relay made by stinger to connect the 2 batteries together, my motor and many others have a wire that goes live once the motor is running/charging, I will use that wire to turn on the relay and charge both batteries. and finally I plan to install a master power switch between both batteries so should my starting battery die I can flip the switch and start with #2 and once the motor is running both will start to charge up.

I guess now that Ive typed this out its pretty much my own set up of the ACR silvertip talked about except using parts I have in stock at work

 

[RickJ6956]

Re: Duel battery installation question....

Unless you work at a marina, mnmike, it's not a good idea to use electrical parts that aren't rated for marine use.

 

[Silvertip]

Re: Duel battery installation question....

A 150 - 200 amp switch to power the starter from the house battery is not exactly a small piece either. Why not just use a $30 Guest/Perko switch and be done with it.

 

[mnmike3]

Re: Duel battery installation question....

Unless you work at a marina, mnmike, it's not a good idea to use electrical parts that aren't rated for marine use.

My boss has had the same setup in his boat for the past 3-4 years and hasn't had any problems with it yet. It will not be out in the open or in a compartment that will have anything wet stuffed into it. I am aware of the added moisture in a marine environment cause we deal with it alot when customers don't want to spend the extra money for marine equipment. We are extremely strict on our installers when working on boats to make sure everything will stand up to the moisture for a long time.

Silvertip- With my discount the 200 amp relay will only cost me $30 or so i believe we sell them for $75-$80 in the store. and I have a marine switch already in the boat from the previous owner that is just a simple on off switch, not sure why they put it in but they did. I tend to get forgetful so not having to remember to flip a switch is a huge plus for me. Your recommendations for this setup were great and I'm not trying to take away from your post just saying how I plan to do it cause I put the same setup in my bosses boat and he is very happy with how it works. Also my boat has an outboard motor I'm not sure how much the starter draws while cranking but am willing to bet its quite a bit less than 200 amps. I will test it to be sure but don't foresee any issues.