Dual Batt problems

[swbpatrol]

i recently got a dual batt install with a standard solenoid doing all the work. What i found the other day i went to start the damn thing and i had a flat battery. Traced a power leakage on the main batt but shouldn't the second batt be smart enough to isolateitself so i can start? if not i might replace it with a 3 way switch style???? Is there isolation with a standard solenoid or are they working together all the time?

[Heathx4]

Yeah, it should be isolated if the 1st battery is not full and charging. But to start the car off the 2nd battery you'd have to run jumpers between the batteries.

[swbpatrol]

is it worth pulling the piece of crap solenoid out and replacing it with the 3 way marine switch? Is there a problem though if you have it on run on battery 1 and not 2 that battery 2 can get stuffed with no use over time? Is the best way to run that on battery 1 and for long trips switch on to 1-2 to get charge to battery 2. Is there any flaws to this system?

[Woop]

Your original system will work fine if its been installed properly, and the Solenoid being used is good quality and rated for continious use. When charging 2 batteries like this (parallel), they both need to be of the same type--ie Starting type not starting and deep cycle. This is due to the different types charging at different rates. Make sure that when the ignitions's off, that the solenoid de-energises thus isolating the 2 batteries.

The Alternator main output should be going to the main battery +ve as its probably doing now. A second suitably rated cable(ideally starting cable if you can) should then connect from the main batt+ve to the second Batt +VE VIA the solenoid. The 2nd battery should also be earthed to the chassis with the same sized cable. This is the set-up i use and its worked fine for me.


If your really set on using a switch instead, there are some heavy duty marine type rotary switches that will work fine. BUT you would have to lift the bonnet each time to switch in/out the second battery.

Nick

[Not For Highway Use]

The system you have is fine. What you need to add is a two position "Twin Pole" switch. The soleniod is powered from your acessories position on your ignition. However when the key position on your ignition hits the start position the accessories drop out. (see how the stereo drops out when cranking.) If you install a switch that in one position is powered from the accessories and in the other position is powered directly from the 2nd battery you can bypass the main battery completely and use either for starting. If you need any furthure details PM me and I'll fax you a diagram. If not a six inches of wire and two alligator clips will do the trick...