Phantom draw on House Batteries

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Well-known member
Apr 9, 2005
Benson , AZ.
We have not boondocked in a bit, so our first night here in Quartzsite we found our batteries drained.  These were 2 12v Deep cycle that were in the coach when we bought it.  Unknown age.  That gave me the 'opportunity' to replace with 2 6volt batteries.  The first night we left furnace off and monitored, and we had some drop in voltage, but enough to start gen and run lights etc.  The second night ran the furnace at a low setting, but in the morning they were quite low..  Could still start gen but with battery boost used.

We had running a freezer that runs on 12v or 110, an inverter on with nothing running off it.  fridge on gas, and really not much else.  The freezer seems as though it might be the culprit, but we have had this freezer tin two coaches for a number of years and over the years many nights on battery with no issues. (it might have developed an issue over the years, need to check), but maybe some other draw. 

Need to get my meter out and start some monitoring.

Any other ideas?  The inverter is a new device to us, but I don't see how it could draw that much, it only feeds TV and sat receiver, but neither were on.

Obviously an issue we need to track down. 
Chakara said:
What is the make model of the Freezer - like you that would be my first suspect.....

Agree. I also have a freezer, an Engel. By far the most expensive but I chose it due to limited power draw, under 2 amps on about a 50% duty cycle - about half of most freezers I found. The more typical 4 amp draw and 50% duty cycle is 48 AH/day, about half of your available AH from a pair of 6V. This leaves just about 50 AH for the furnace, fridge and everything else, and that assumes batteries were brought back to 100% (float charge) which would have likely taken the genset upwards of 5 hours if the batteries were low.
  One draw that is often overlooked is electronic devices ie. I have three televisions (visio) and two jensen radios that all draw power even when turned off. One example was a radio in our pontoon boat that would draw the battery down in about three days, then it would turn itself on and run the battery completely out. strange to go outside and hear you radio playing, knowing you havent been around to turn it on. Same thing with the radio in our Jeep.
Although a small draw, the CO and LP detectors are usually powered from the battery.
The inverter without load will still use amps as well.
Tonight we are at full hookup, but before bed will kick breaker off.  The freezer is plugged into a separate outlet.  It is a Dometic, and is supposed to have low draw, we have had it 10 years and it never has been an issue, but, it is 10 years old now, so possibly is the issue.  Not quite positive the inverter was on or off last night, I am old, I forget, but it is not on now.  Tonight the draw should only be furnace and refrigerator igniter.  We shall see.  Tomorrow, I'll leave freezer on DC.  Being on FHU, no big deal in the morning if house battery low.

Guessing I may have replaced 2 good batteries, but long run, I have 2 new 6's I know the history of.

Going to order a monitor panel.

Using my monitor panel with everything I can turn off, and inverter off, my parasitic load is about 40w.  Culprits I suspect are the CO and LP monitor and thermostats.
Hi Bill, nice to meet you at Q. We will likely stay until the first.

Generally speaking the larger the inverter, the larger the current draw even when not powering a load. Before I went to my large batteries and whole coach inverter I had a 75 watt inverter powering the bedroom TV and Dish Wireless Joey. It?s power consumption was minimal and I left it on most of the time. The 250 watt inverter powering the front TV and satellite system was turned off when not in use. Running the furnace at night I often found the 2 GC2?s down to  50 some percent.

Getting back to 100% required lots of genny time. And the last 10 percent accounted for 50% of the genny run time. (Which I seldom did.)

A good battery monitor (Tri-Metric or Victron) is essential to really know what's happening and manage your batteries.

A Power Meter is a good way the learn the daily usage of your freezer.

My trailer, with everything "off" pulls 0.5A or about 6W.  I just checked my new Victron BMV-712 sitting here on the couch in the Sticks and Bricks :).  Of course things like the Fridge aren't pulling their light load.  I plan on doing a full audit to understand what uses the most/least and make better decisions like which lights to use.

We mostly boondock - and this is my first Battery monitor....I have a feeling I'm gonna like it :)


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