Battery isolator?

[mrxlh]

I am looking at adding a second battery to my Ranger and want to eliminate the no start from a dead battery from running accessories. I am dealing with a 575 watt@3K rpm charging system. I am thinking preliminarily on just running a marine 1,2,both switch, as well as adding an onboard 5volt battery tender waterproof to finish charging and or maintain both batteries overnight or while not in use.

 

[DNFXDLI]

Switch would be a good way....avoid a diode isolator at all cost.

 

[DNFXDLI]

Another way is to use a continuous duty solenoid that activates when the engine is running to charge the 2nd battery....this avoids potential "forgetting to turn the switch" issues.
You can then run the tender connection to both batteries.

 

[mrxlh]

I thought about the second way, but what about 2 different size batteries and states of charge? Would the weak battery pull down the charged one in that scenario?

 

[DNFXDLI]

I thought about the second way, but what about 2 different size batteries and states of charge? Would the weak battery pull down the charged one in that scenario?

It can but normally it doesn't become an issue....if you know that you are going to pull the aux. one down lots all the time and then not run the engine much before stopping again then that's when you can run into a problem.
As far as two different sized batteries and states of charge, not an issue...the charge will go where it is needed.