Weird voltage reading from wires connected to batteries

[benzy]

We had an old-school Rutland charge controller on our boat that never worked since we bought the boat. So we ordered a new HRSi controller and fitted it the other day.

Before fitting it I was testing the voltage across the wires coming from the boat batteries. I measured 11.8 volts, which was a bit lower than expected since the digital battery monitor was showing 12.5 volts, but voltage was still obviously present.

I fitted the new HRSi controller as per instructions, which state that after connecting the batteries to controller, it will sense whether the system is 12 or 24 volts, then the led will light up to show the state of the battery (red: low charge, orange: almost full, green: full).

However, no led came on. Again with the multimeter I measured voltage across the wires (still connected to the controller) and saw only 2 volts - very strange. Then, oddly, voltage started to slowly climb. Over the course of the next maybe 3 minutes, the voltage climes linearly to over 11 volts and the led on the controller came on!

Does anyone know why this would happen?

Thanks

[StuM]

Sounds like a very cautious sensor which starts out with very high resistance and slowly ramps up to avoid an overload if connected to a high voltage.

[smac999]

you have a bad connection or wire. when the contoller turned on it drew power and voltage drop increased a lot. as it turned on less current was drawn and voltage went up.

the controller can not control the voltage of the battery cables coming from a battery.

[benzy]

Thanks for the replies

I figured it might be a bad connection. Will investigate!