adding 2nd battery for stereo

[captiva190]

I want to add another battery to dedicate the stereo to it, In the past I had a drain problen, so I put in a battery shutoff on the main battery, ad I have to run the stereo batt+ wire directly to battery so it wont loose memory, my friend said put in 2nd battery, run the neg to eng block and run a wire from alt to pos so it will charge, so if it is charging the stereo battery will the regulator recognise that the main battery is full charged if the stereo battery is low causing an over charge or not fully charging the second battery?, what is the best way of going about this, or should I just run the 2 batterys together, I dont want to mess up my alternator, or have dead battery the next morning, Thanks

 

[drewpster]

Re: adding 2nd battery for stereo

The wire from your alternator connects directly to your main battery. If you connect your second battery to the alt you are connecting both batteries together causing them to drain at the same time no matter what you do.
You want to be able to save a fresh battery right?
So here goes.
What you need is a way to select which battery you want to use at a given time. This leaves the un-selected battery unused and fully charged. One way to do it is to use a 1-2-both battery switch like this one:

The way it works is before you start the engine set the switch to the "Both" position and start the engine. Leave the dock and go have fun, ski, ride, pickup women, whatever. Then when you stop and shut down the engine switch to number "2" position. (this disconnects the number 1 battery from everything and supplies power from only battery number 2) While you are stopped be sure to play the stereo way too loud, charge your cell, and generally consume all the power you want.
Before starting the engine again be sure to switch to the "Both" position on your battery switch. Start the engine and go have fun. (this will effectively turn both batteries into one big battery charging them both until their combined voltage reaches a fully charged level)

This setup works ok if you do not run your accessory (house) battery down too much AND you have a good alternator on your boat.

There are many options to fix the dead battery problem. This is only one of them. It is a subject of great debate in here and there are many posts on the subject. Try the search features of the board to do some more research if you like...... or just stay tuned. Some other folks in here may chime in, I hope.
BTW- Remember to switch the switch! If you leave it on "Both", you drain both!

 

[captiva190]

Re: adding 2nd battery for stereo

thanks, I wasnt sure about the alternator wire thing, that is perfect, I have set something up like that for this vacation weekend, I hooked both batterys up but put an isolator between the pos that leads to the second battery which runs the stereo, your method will be much easier I can replace the 2 position switch I currently have with the one you showed, and yes I have forgot to shut that one off and you know what happend then, Thanks a ton

 

[jklnhyde]

Re: adding 2nd battery for stereo

I have a similar question; unfortunately I don't have room for two full-sized batteries, so I was hoping I could use a powersport (ski/motorcycle/etc) battery to power my accesssories instead.
Will the charging amperage/rate of the alternator be too much for such a small battery?
I think a powersport battery should last several hours of radio play/fishfinder duties before it is ready for a charge, right?
I know they are not designed for deep cycling, but what other alternative do I have when there is no room?

My dual-mode (starting/deep cycle) battery has never let me down, but I'm too chicken to try my luck...

 

[mthieme]

Re: adding 2nd battery for stereo

The memory for the radio shouldn't drain your battery at all.
Tell us more, do go months in between using the boat?
How old is the battery?
Have you checked your charging system out?

 

[achris]

Re: adding 2nd battery for stereo

If you hook a second battery directly to the alternator and the primary battery is slightly low, you will burn out the wiring between the second battery and the primary battery when you go to start the engine. The second battery will supply the shortfall in current, but via smaller wires. Lots of smoke... Sorry, no mirrors this time.

The current drain from the memory on the stereo is about 2mA, I know because I measured it. That would give the average battery (60 or more AmpHrs) a life of about 3 years.... If you are running the stereo and it's draining the battery while you are fishing...turn it down... I don't want to hear half way round the world....

Chris..........