44 replies to this topic

[carld]

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. 

Edited by carld, 07 February 2016 - 09:36 PM.

[DrJ]

Carl,

I think the FWC folks (myself included) have a different battery isolator.

I believe it's this one:
http://www.wanderthe...attach_id=21561

I'd have to go look at my Grandby again to be 100% sure.

This may be part of the confusion too - Different systems.

[DrJ]

Field test of the system

Camped out near St. George Utah for several days. February does not have long daylight hours but mostly clear days. Made for a nice trip.

Ran the compressor fridge, heater at night (lows of 40), watched TV (12 volt TV) each night, lights and anything else we wanted to do. No real attempt at conservation.

Overnight my system would reach about 80-85% of battery life (using 30-40 amps after sun was down - almost 13 hours total each day). It was easily charged by the 250 watt solar system usually by noon or 1 pm. Did not need to deploy the portable panel this trip. Day time hours the solar easily kept up with the fridge, fans or anything else we ran and still charged the system.

I am very happy with my setup and it works great for us. It worked great for a winter trip and I'm pleased with how it came together.

Edited by DrJ, 13 February 2016 - 04:26 AM.

[Ronanmd1]

Hey guys - another useful post on charging issues related to the alternator and camper batteries (running through the isolator).  I struggled with this same issue.  In short, the wiring from the truck alternator in my 2013 Hawk was too small to carry sufficient current to the batteries when they are heavily discharged.  The consequence was a significant voltage drop (read by the isolator) which shut down the connection.  Problem solved by rewiring with larger gauge wire.

 

http://www.wanderthe...harging-issues/

 

 

Jason

[DrJ]

We had a successful testing of our solar system last month.

 

68Siesta and I spent a week at a boy scout camp.

 

I was able to successfully run TWO compressor fridges off my system for a total of 6 days.

 

Here's the specs:

Input:

250 Watts of rigid panel on roof

135 watts of flexible panel (deployed on my windshield of the truck - works great there by the way)

2 6 volt batteries with about 200 amp hours of power

Fridge fan system on temperature sensor

 

Output

Dometic 110 litter compressor fridge (runs at 4.5-5 amps an hour) - used as the fridge at 34 deg

ARB 63 quart compressor fridge (runs at about 3 amps an hour) - used as the freezer at 0 deg

 

We had cold food, popsicles, and ice cream all week for the scouts.

 

I am happy to report the system has ample power to keep 2 power hungry compressor fridges going.

Edited by DrJ, 13 August 2016 - 02:03 AM.