96 replies to this topic

[Terrapin]

Attention electrical sleuths
My 2013 Hawk has a very challenging electrical mystery that has so far, shown to be insolvable by several RV service departments including the FWC Woodland factory in California as well as reputable RV Centers in states Washingron, Montana and Oregon.

So far the only solutions from the "plug and play," pro community has been: (1) buy new batteries, (2) buy a new refrigerator, (3) buy bigger solar panels, (4) buy a generator. So I'm throwing this mystery out to DIY community attracted by 4WC in hopes that there are still some of our species that like to solve problems the old fashion way.

Our Hawk was purchased with the promise of stealth camping for more than a weekend (2-3 weeks at a whack actually). It was outfitted with factory installed Dometic 2-way model 110 fridge, 90 watt solar panel, 2- Exide Deep Cycle 12v AGM batteries, Morningstar SS- Controller, Iota 30 amp charger and LED lighting. We've since added Iota"s IQ-4 smart charge module and Bogart Engineering's Trimetic-2030 Battery Monitor.
Our routine for each outing starts 2 days before departure with A/C Shore power to insure the fridge and contents are brought to temperature and the battery array is completely charged. The Trimetric verifies A1 battery condition at the get-go.
Off-grid night 1, no problems, night 2, off-grid, even though battery stats indicate 12V and 98% full, a negative power surge begins. The fridge compressor runs on and off with 90 second rest intervals and the power fault light blinks red.

During a surge:
~V drop to 11.9V
~A jumps to 4.5A then quickly peak @ 7.5A
Then, just as quickly, the condenser stops and all readings fall back to a nominal 90 second rest state. (.2A > 4.5A >7.5A >0.2A and 90 seconds of peace)

Simultaneously, should there be any additional electrical devices in use, such as the water pump or LED lighting, they too are immediately affected with loss of power and ratchet down in performance to the point where the lights go out and the pump grinds to a halt. At this low point, as the surge cycle immediately resets itself, the fridge compressor goes to idle, lights come back to full brightness and the pump resumes normal operation usage drops to minimal amp and power reading. In precisely 90 seconds the surge cycle repeats itself until the fridge is taken off line.

Clues in the mystery:

-During daylight hours when solar is active, there is no detectable problem.
-The battery minder shows the batteries have at least 12V during a surge
-Storage Amps are generally 85-98% full
-All devices run fine if the refrigerator is off.
-The Atwood propane/carbon monoxide meter's Power Fault light blinks red until batteries are receiving a solar "trickle" the next day (I believe indicating insufficient
power to function properly)
- Trimetic data confirms that the 90watt panel is insufficient to keep the batteries full even after 6-7 hours of direct sun supplemented by the truck's alternators. Power loss is roughly 2% per day.
-If shore power is introduced at any point during the surge, all faults stop and the systems run perfectly.
-A block of ice in the fridge helps keep the cycling/fault from occurring.

Is it the battery? .....The fridge?...... The solar panel?..... All of the above, non of the above?
Please don't suggest we buy a generator.

[DrJ]

I love these. Nothing funnier than a crazy electric problem.

 

My 2 cents...

 

It is likely a battery problem. One of the batteries probably has a bad cell and under a load cannot maintain the necessary voltage to keep up.

 

Why?

 

a- the solar runs the system during the day because it provides enough amps to negate the bad cell but when you are off solar and on battery for too long, your problems start

b- most of your other electrical appliance problems are due to low voltage - your fridge runs fine on solar supplied voltage and 110 voltage appears to be no problem.

c- other devices run fine when the fridge is off - also bad battery - if the battery doesn't have to supply a lot of amps it can still do so with a bad cell.

d - shore power overcomes your problems for the same reason solar does - outside power 

 

I recommend replacing your batteries and see if that fixes the problem.

No need for a generator.

[nikonron]

Sounds like batteries to me also, that's where I would start, change them out.  Ron

[wuck]

Yeah, what they said.

 

But, I would start with testing the batteries at your local auto parts store rather than dropping a few hundred bucks. Charge them with the Iota, bring them down to get a load test. A bad cell or high internal resistance will show up immediately.

 

While you're in the battery box, make sure all connections are tight and CLEAN. Check around any connections for signs of corrosion, or even heat discoloration. A high resistance connection can behave like a bad battery - but at the load levels for our campers, it would have to be a really, really bad connection.

 

[DrJ]

Wuck - great call on the connections and battery testing.

 

Both easy to do and a great place to start.

[Happyjax]

Separate the batteries, let the fridge run off each one a bit and check voltages. If one is bad the other will make up for it as much as it can so by separating you can often isolate the problem. Not sure fire but pretty good chance if it's a bad batt you will see it. If you have a bad cell you will lose about 1.2 volts.

[Stan@FourWheel]

A few things I can think of ...

Your compressor refrigerator, does it have both top & bottom exterior vents?

The 90w solar panel wont be enough power to keep up with that refrigerator.

Have you checked the voltage coming out of the Surepower battery separator?

Depending on your answer to the first question, you might have a bad refrigerator, or its simply drawing more power that your putting back in the system. FWC is now using a minimum 160w panel for this specific reason. That compressor refrigerators need more power to be off the grid for days and days at a time.

[Terrapin]

Wow!
What a terrific and gratifying series of responses, thank you all!
Several places have claimed a "load test." I've only seen them use a hand held devise which makes me suspect.
Happyjax's uggestion is one I'm going to try this morning. It makes sense and uses an actual load.

STAN, the Dometic 2-way was installed at Woodland. There is a narrow vent spacing along the bottom and top of the fridge door providing a convection path. There are no external vents to the back of the fridge area. There does not seem to be excessive heat emanating from the upper interior vent.
Historical data gathered from the Tri-metric does suggest that the solar does not provide the depth of charge needed even with the truck turning for several hours. Once the surge problem is solved, I plan on a 200w Zamp replacement. Unless, that is, if persueded otherwise.
During our last outing we were off grid for 9 consecutive days using ice block and shutting the fridge off at night to get by.
I have an upcoming three week Montana flyfishing trip scheduled in June with nearly no opportunity to plug in for days at a time.

[Wandering Sagebrush]

I would look into a couple of things as potential solutions. As Stan said... External venting would be the first thing, and a 12 vdc computer fan to move air across the heat sinks so the refrigerator doesn't have to work as hard.

[welsch]

All the suggestions that pop'd to mind have been covered.

 

If the batteries are ok, all I can add is:

Check the 12v near and "outlet" during the surges to see if it's dropping from 12v, your indicators can be giving you 98% at the battery but if something down line is defective (battery separator as Stan pointed out) your 12v lines inside the camper may be way below that. (edit: actually the fact the light are dimming already tell us it'd dropping voltage)

 

If that ok, then run the fridge directly on the battery without the monitoring, charging and other controllers you have. This is not to check the batteries but to be sure the electronics is not guilty. In my 30 years in engineering I've seen some strange interactions. (edit: the exact 90 second cycle has me leaning towards an electronics issue rather than a analog (battery) or heat issue)

Edited by welsch, 15 May 2016 - 05:39 AM.