Outer Limits 4x4 Board

Ive recently installed a dual battery system in my Bundera and have had problems charging the second battery once it has been used. I have one of those automatic isolators that opens the circuit once the main battery reachs 13.7v to charge the second battery. However once it reaches this it does open for about 5 seconds then it closes again as it would seem the main battery cant hold the 13.7v.

Is this a battery problem or and alternator problem. And what are your suggestions.

Thanks

Hi BundyMonkey, if anything it sounds like the dual battery controller is the problem. What make is it and does it say how it is suppose to work.
A number of things can cause the isolator to work incorrectly, the most common is the use of inadequate size cable or a badly sourced earth.
Cheers

It could also be a case of the reference voltage for the controller being taken from the wrong place.

Its one of those VSR sealed units which were being sold in the for sale section a while back. Will check out the earth on the weekend and see if I can get a better one.

I have one of these on my car, good little units.

It should not cut back out until the voltage drops down to somewhere abouts 11.7 volts. so you might just have the two leads around the wrong way and its reading your second battery for switching on and off.
If not then its a faulty unit. does it have a LED to show its on?
mine has a little red LED to show when its running, and doesn't turn off for a while after turning the engine off as the main battery has to get down low enough for it to turn off.

I had a similar problem with my Jaycar unit cycling (faster than yours.) Turned out to be bad contact on the fuse in the line from the main battery. As soon as the second battery started charging the resistance caused a voltage drop, and the controller decided the main battery was too flat. Once it switched off the input voltage came back up, the controller turned back on and the cycle repeated itself.

Apart from blowing the transistors in the early days, every problem I've had with my unit was from high resistance joints in the battery wires.

Good luck,

Scott

That sounds exactly what mine is doing. I have put the leads to the correct batteries I checked it bout three time to make sure.

Problem fixed one of the connections had become loose now it works a treat