Dual Batteries with Low Voltage Protection

[Count Fred]

So, I want a slightly different dual battery system. For most trips the typical system which completely isolates one battery makes sense. Especially if I am out in the middle of nowhere and likely not stationary for more the 24 hours.

However, this summer the Land Cruiser has started to see a new use which involves going to horse shows and sitting for up to 4 or even 5 days without moving. Right now on my deep cycle I can get about 3 days out of the fridge before the battery doesn't have enough juice to start the vehicle.

Eventually I may consider a solar charger to keep things topped off, but in the mean time I just want to throw another battery at it. The following image shows what I'm thinking:

What I'd like to have happen is be able to run the accessories off both batteries until the main battery is about half full (or whatever it needs to start the car and maintain the alarm and stock parasitics for several days). Then the isolator will active and the accessories will keep running off only the aux battery, meanwhile the main battery is only powering the stock systems and has enough charge to start the vehicle.

Ideally my low-voltage isolator control line could be manual activated if I wanted to isolate the main battery immediately while it was fully charged (when in remote locations). Probably the default setting.

I would also like to have a timer to allow the alternator to have 10 min. or so alone with the main battery to recharge it some after a low-voltage situation before switching to charging both batteries. I am concerned that even if the alternator adds some charge to the main battery that when it switches to charging both it will rush to equalize the battery levels and were I to shut the Cruiser down at that point I would be unable to restart.

I'm guessing most low voltage isolators will not be able to handle 350A of continuous winching current and hence the other switch which can be used to combine the batteries for winching or jumping. Ideally this switch would be remotely controlled, but if that's the difference between a $60 and $360 switch, I may settle for a manual switch.

Any recommendations or suggestions on parts or my plan?

Cheers,
JFS III

 

[eugene]

Since you have the 1-2-both selector switch why bother with the isolator, just use the switch. The soloniod isolator is basically just a way to automatically parallel the batteries. Since your going to have a manual switch your going to want to manually check it each time to make sure you didn't leave it set wrong so you might as well just manually set it to both after starting the engine.

But I wouldn't run a switch like that anyway, what happens when you think your just going to use a little bit of the starting battery so you set to both then a day later find out you estimated wrong and there isn't enough to start the engine? Why not a larger or third battery?

 

[dzzz]

A switch isn't going to be reliable enough to automatically isolate the battery just in time to allow starting. The ones I'm familiar with latch on charge and "unparallel" on discharge when in automatic mode.

A solenoid with a cockpit switch:
Blue Sea 7622
500 amp, cockpit switch for: combined - auto- disconnected
waterproof, manual control on solenoid
$160

This doesn't have a 10 minute timer, but you would be able to do what you want manually while driving.

Note that 7622 does come with a remote switch. This is confusing on most web site.