carld
Senior Member
Looking at the data sheet for the AOPEC dual sensitive isolator it appears to be a relay type isolator not solid state. It has two voltages: a cut-in, 13.3 V, and cut-out, 12.8V. When the relay is closed both batteries have the same voltage. The relay only opens when the connected batteries drop below the cut-out voltage,12.8V. This is the voltage for a normal 100% full charge battery. So if the truck is off the relay will open after short time isolating the camper load insuring that you don't drain the truck battery. The relay will only close again if the truck alternator is running and the truck voltage is more than cut-in voltage of 13.3V.
There is no reason I can see that if the camper battery is low (below 12.8V) and the truck is running with the alternator producing 13.8 V to 14.2 V that the isolator won't switch on and charge the camper battery or least switch on and off repeatedly. There are only these two reported sense voltages and I know that my camper battery normally runs below 12.8V.
One thing I have discovered with all of this is that batteries have a very low resistance. If there is too much resistance between the truck battery and the isolator, once the relay cuts-in the camper battery/load can draw enough current to drop the voltage at the isolator causing it to switch off. Maybe this is why I can hear it clicking on and off when I'm at idle with the 12V 3-way fridge on. Something to check on. Oh one more thing I see in the Isolator spec is that it has a 5 second delay so that it should switch on and off about every 5 sec.
I just went out to check the camper voltages. My 50 W panel had the battery in the float state and the camper voltage was at 13.5 V. The panel was producing about 10 W at 18V and the battery current was 400 mA and the load was 200 mA. When I plug in my voltmeter in the truck and turned on the key, the truck voltage was around 12.6 and I could hear the isolator switch off. Went back in the camper and the battery was in bulk mode and the voltage was below 12.8. The system when off is definitely sensitive to small changes in loading.
There is no reason I can see that if the camper battery is low (below 12.8V) and the truck is running with the alternator producing 13.8 V to 14.2 V that the isolator won't switch on and charge the camper battery or least switch on and off repeatedly. There are only these two reported sense voltages and I know that my camper battery normally runs below 12.8V.
One thing I have discovered with all of this is that batteries have a very low resistance. If there is too much resistance between the truck battery and the isolator, once the relay cuts-in the camper battery/load can draw enough current to drop the voltage at the isolator causing it to switch off. Maybe this is why I can hear it clicking on and off when I'm at idle with the 12V 3-way fridge on. Something to check on. Oh one more thing I see in the Isolator spec is that it has a 5 second delay so that it should switch on and off about every 5 sec.
I just went out to check the camper voltages. My 50 W panel had the battery in the float state and the camper voltage was at 13.5 V. The panel was producing about 10 W at 18V and the battery current was 400 mA and the load was 200 mA. When I plug in my voltmeter in the truck and turned on the key, the truck voltage was around 12.6 and I could hear the isolator switch off. Went back in the camper and the battery was in bulk mode and the voltage was below 12.8. The system when off is definitely sensitive to small changes in loading.
