I'm adding a leisure battery to my van so I can run some stuff with out fear of draining the starter battery.
My leisure battery is wired to my starter battery so it can charge from the alternator when driving but is separated by a relay to avoid draw while stationary. I have split a wire from my dashboard which becomes live with the ignition and reads 14.5 volts with the engine running to use to activate the relay, and grounded the other side.
My Problem
When I connect this wire to the relays trigger circuit (pin 86 I believe), it's voltage drops to 0.6 which doesn't seem to be enough to close the circuit.
Any one know what I'm doing wrong?
edit
I'm using this relay
I have wired it up like this;
the switch
- pin 30 positive on starter battery
- pin 87 positive out of relay
control/coil
- pin 86 live from dash
- pin 85 ground.
Van is mk6 ford transit, wire is white and green one from display behind the steering wheel which I thought might be alternator warning light…
hope that helps.
Best Answer
You should be looking at installing a battery splitter instead of this relay. The splitter is a pair of high current diodes mounted on a heatsink and equipped with nice stud terminals for connecting up the wires and a case cover. The alternator output goes to the common anode terminal of the splitter. The two cathode terminals connect off to each battery.
No special control wiring is required!! Also no mechanical part to wear out.
simulate this circuit – Schematic created using CircuitLab
The diodes block the leisure load from discharging the running battery. Such splitters can be found at common RV supply outlets.