Suburban SW6 DE Water Heater Battery Draw

Last weekend dry camping our battery got sucked way down and basically was useless by the end of the weekend. We have converted to LED interior lighting and were unable to use the furnace because of the lack of power. Today I noticed the exterior electric element switch on the water heater. does the electric element work on the DC side as well as the AC side? If so does anyone know what the draw is? Trying to figure out the issue as the battery is fully charged now after a few days at home. I unplugged it and turned off the switch and the water heater ignited so I am a bit confused as to the electric element.

The water heater doesn't use 12 volts to heat the water. Some questions need to be answered first so we can help you out here. What is the year, make, and model of your RV and what do you have for a battery?

truline said:

Last weekend dry camping our battery got sucked way down and basically was useless by the end of the weekend. We have converted to LED interior lighting and were unable to use the furnace because of the lack of power. Today I noticed the exterior electric element switch on the water heater. does the electric element work on the DC side as well as the AC side? If so does anyone know what the draw is? Trying to figure out the issue as the battery is fully charged now after a few days at home. I unplugged it and turned off the switch and the water heater ignited so I am a bit confused as to the electric element.

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The element option is only 110 volt AC but you need 12 volt DC for the electronics for running off AC as well as running off the propane. 

The electric heater in the water tank is 120v only. The 12v power used by the water heater circuit board is insignificant and not worth trying to account for.

Most likely your battery amp-hour capacity has deteriorated substantially since new, especially if it has been drawn down repeatedly or the charging system is "dumb". Check the water in the cells (is it's not a sealed battery) and top up with distilled water if needed. That may help.  Assuming it is a typical small RV battery, they only have a useful life of 2-3 years and you may just need a new one. See my article on RV Battery Choices in the forum Library at http://www.rvforum.net/miscfiles/Choosing_right_battery.pdf

Thanks for the info. I am testing the rig right now. The rig is a 2002 25' Cougar. It is unplugged and all devices off except the exterior electric element switch on the water heater. The battery is a group 31 deep cycle from O Reilly Auto, purchased last year. We did have to replace the converter last summer after a trip to Yellowstone.  I don't have a battery meter installed and am only using the Kib Micro Monitor. This evening it reads charged. We'll see if it falls to good or fair by the morning.

Your test won't really prove anything about the water heater, since that switch only controls the electric heat element and that uses 120v shore power rather than battery.  And you cannot turn off the water heater 12v draw unless you remove the fuse that powers the circuit board. 

You have 12v loads in the RV that are not switchable, e.g. the LP detector, maybe a radio that is on stand-by, a clock, etc. Most gadgets do not actually power -off theses days because their circuit boards remain active to "listen" for the press of a switch.

It may also be that your battery simply doesn't hold a charge well. That happens after a year or two, especially if the battery has been totally discharged a time or two. The typical marine/RV battery in most trailers and small motorhomes doesn't have very long useful life.

Well it certainly did not like last night's test. It went from charged to low in 20 hours. That is probably way more than it should. Probably time to yard out the battery and see if it has a dead cell.

I would do two things before removing your 1 year old battery. First, I would check the levels in the battery. Then hook up an ampmeter to find out what your total phantom draw actually is. Second, what is the amp hour rating of the battery? Is it a true deep cycle or a marine type deep cycle/starting battery?
The answers to the above questions may point to a secondary problem assuming the current battery is in OK shape.

It is a Marine Deep Cycle Battery. It is supposed to be able to handle 105 amp hours. I had OReilly test it as it is under warranty (1yr, bought last July). They tested it three times and held it overnight and it passed according to them. When I put it in it read 12.7 volts. After hooking it all back up I unplugged the rig and the little KIB Micro Monitor was flashing at the low level when I pressed the battery button. I have never seen that before. I guess now I need to go and get a amp meter to see what is drawing on the battery.

Here are the battery stats:

Super Start Marine - Deep Cycle Battery
Line: SSB | Part # 31DCM
1 Year Limited Warranty
UPC: 83996011076
Battery Type: Deep Cycle
Group Size (BCI): 31
Cold Cranking Amps (CCA): 555 CCA
Marine Cranking Amps (MCA): 690 MCA
Voltage (V): 12 Volt
Length (In): 13 Inch
Width (In): 6-3/4 Inch
Height (In): 9-1/2 Inch
Group Size (BCI): 31
Cold Cranking Amps (CCA): 550 CCA
Cranking Amps (CA): 690 CA
Marine Cranking Amps (MCA): 690 MCA
Length (In): 13 Inch
Width (In): 6-3/4 Inch
Height (In): 9-1/2 Inch
Weight (Lbs): 59.5 Lbs.
Terminal Type: DIN
Voltage (V): 12 Volt

DETAILED DESCRIPTION
Designed to withstand the rigors of heavy-duty deep cycle use.
Exclusive dual-top stainless steel terminals for corrosion-free connections.
Includes handles for ease of installation and transportation.
Power for starting.
Special fiber

ADDITIONAL DETAILS
Terminal Style: Stud
Polarity: Left Positive
20 Amp Hour Rate (Ah): 105Ah
Battery Type: Deep Cycle
Reserve Capacity (min): 210 Minute
Reserve Capacity At 23 Amps (min): 225 Minute
Reserve Capacity At 25 Amps (min): 185 Minute
Electrolyte Composition: Acid 

More than enough info about the battery. Now it's time to find out just how much draw is on that battery while the RV is in the situation you described in your first post. The answer to that particular question should give the forum electrical gurus the info needed to help you further.

As already stated, the water heater element itself is not a part of the 12vdc system. The control boards of such appliances are.
Keep in mind that boondocking (dry camping) can be the situation that brings the light to some people on just how much power they actually use. Even when everything in the RV is turned off! I'm thinking the 105ah battery is marginal, at best. If another problem (draw) is added to the equation, the battery can't handle it. This is assuming that your monitor is working correctly, your battery is in good working order, and being charged correctly.

Do you have lights in your cabinets?  Closets?  Any of them left on?

In my opinion one battery is simply not adequate for any amount of boondocking.  Especially if you're running a heater.