Minimum Battery Load, 21RBS

[charliem]

[font size="3"][font face="arial"]I measured the minimum battery loads with everything off including fridge and TV amplifier. The only things left on were the propane detector and possibly some minimal draw from the radio in off position and the SeeLevel tank monitor. The reading at the battery with a clamp on meter (another toy) was 120 mA. Adding the fridge on propane produced 1.0 Amps. Opening the fridge door to turn on the interior light brought the total to 1.9 Amps which was a surprise since I thought the fridge light was LED. The fridge also has a case heater that may add several Amps intermittently depending on the environment. The 1.0 Amp reading would be the minimum continuous draw when dry camping with no electric hook up.  
[/font][/font]

[tinkeringtechie]

I wonder if the fridge current on propane will fluctuate or if that 880ma is constant. It seems like a lot for essentially a thermostat. I'm hoping once it gets to temp that would drop. The interior light is definitely not LED, but it's an easily replaceable festoon bulb. I'm planning on swapping it out for one like this:

http://www.superbrightleds.com/moreinfo/festoon/de3175-led-bulb-4-led-festoon/231/

Unfortunately I didn't have any measuring devices on hand when I was out there, so I'm not sure if that's the correct size. I'll update here once I do measure though.

[charliem]

[font size="3"][font face="arial"]Now that I recall, I talked with the Dometic factory In January and here are some of my notes:

"Auto Frame Heater heats frame around door and sides to control condensation or frost. Runs all the time from 12 volts. 0.5 Amps continuous, no defeat switch, no sensor".

This tells me the extra 880 mA includes the frame heater which is on all the time and must also include a gas solenoid.  Previous models had a heater defeat switch, but no more. Amazing what manufacturers will do to save a few cents. Bad news is it's on all the time. Good news is there is no additional heater load. Someday one of us will find the easy way to add a defeat switch.

Re the light: again, for a few cents more........Fortunately the light is only on now and then and will last forever.
[/font][/font]

[tinkeringtechie]

Thanks for the info. I think that would be fine when I'm hooked to 120V, but if I'm boondocking I'd rather have more battery life than a condensation free frame. The gas solenoid should be held open by a thermopile (for safety reasons). One of these days I'll hunt it down the heater wire and put a relay in there so I can switch it off for extended trips. When I do, I'll post the details in case others want to make the same modification.

[mitch]

Hello all,

I have a 13QBB and at some point created this chart. My goal was to quantify the power use so that I could design a solar charging setup   
                              
                                 [span]    [/span][span]    [/span][span]    [/span][span]    [/span][span]    [/span][span]       [/span][span]    [/span][span]    [/span][span]    Hourly                   Hours[span]  [span]    [/span]  Daily [/span][span]    [/span][/span]
             [span]    [/span][span]    [/span][span]    [/span][span]    [/span][span]       Volts[span]    [/span][span]    [/span] Amps[/span][span]    [/span]  Watts    Use/Day[span]    [/span]Amp Use                  
Lights   [span]    [/span][span]    [/span][span]  [span]    [/span]  [/span]        12   [span]    [/span][span]    [/span]1.20[span]    [/span][span]    [/span]   14.4[span]    [/span][span]    [/span]      2[span]    [/span][span] [span]    [/span]   [/span]      2.4           Four, 3.6 Watt LED bulbs            
Furnace[span]  [/span][span]    [/span][span]   [span]    [/span] [/span]  12[span]    [/span][span]    [/span]   3.40[span]    [/span][span]    [/span]   40.0[span]    [/span][span]    [/span]      0[span]    [/span][span] [span]    [/span]   [/span]      0.0                  
Refrigerator[span]   [span]    [/span] [/span]  12   [span]    [/span][span]    [/span]0.50[span]    [/span][span]    [/span]   6.0   [span]    [/span][span]    [/span]24[span]    [/span][span] [span]    [/span]   [/span]     12.0        On propane mode w/electronic control panel            
CO Monitor   [span] [/span][span]  [span]    [/span]   [/span]12   [span]    [/span][span]    [/span]0.11[span]    [/span][span]    [/span]   1.3   [span]    [/span][span]    [/span]24[span]    [/span][span] [span]    [/span]   [/span]   2.6                  
Smoke Detector[span]    [/span]12   [span]    [/span][span]    [/span]0.00[span]    [/span][span]    [/span]   0.0   [span]    [/span][span]    [/span]24[span]    [/span][span] [span]    [/span]   [/span]   0.0                  
Water Pump[span]    [/span][span]     [/span]12   [span]    [/span][span]    [/span]4.00[span]    [/span][span]    [/span]   48.0[span]    [/span][span]    [/span]    0.5[span] [/span][span]   [span]    [/span] [/span]   2.0                  
Water Heater[span]   [/span][span]     [/span]12   [span]    [/span][span]    [/span]0.20[span]    [/span][span]    [/span]   2.4 [span]    [/span][span]    [/span]  0.75[span] [/span][span]       [/span]   0.2                  
                                                   [span]    [/span]Total AHr Draw/Day     19.1   
                                 
Given all this, a standard 85 amp hour battery will last about 2.25 days without draining it past the recommended 50% level.                                 

[charliem]

[font size="3"][font face="arial"]Mitch,

Great data and thanks for posting. Very closely matches my measurements, but I forgot the water heater. I'm guessing the WH 0.2 Amp draw is the gas solenoid when the burner is running.

The fridge load pops out as the biggest user and most of that is the full time frame heater. When I called the factory they said they used to provide a defeat switch for that heater, but have eliminated it for new models. If I read the brochure correctly you have a 5cu.ft. fridge. Do you have a switch to disable the frame heater? That would save a bunch of battery.

Let us know what you do with solar and how it works.
[/font][/font]

[mitch]

Hi Charlie,

You are correct, I do have the 5 cf fridge, I don't have a switch for the frame heater though. Truth be told I didn't know about the frame heater but I don't think I'd be so bold as to change the set-up anyway.  The fridge would be expensive to mess up.  As for the solar I built my own set-up.  I'd like to think it was cheaper (and it was a bit) but mostly I did it that way because I'm a tinkerer (polite word for nerd).  I got a 70 watt panel, built a folding frame so that I could move the panel around based on the sun and then built a control enclosure for the charge controller.  I added a few gauges to the enclosure box so that I could monitor the voltage and amperage from the panel to the battery.  Sounds much more difficult than it is.  Here's a pdf of the schematic in case you're really bored. [attachment id="61"]

Mitch




 

[stewartnp]

[quote source="/post/658/thread" timestamp="1398168770" author="@mitch"]Hello all,

I have a 13QBB and at some point created this chart. My goal was to quantify the power use so that I could design a solar charging setup   
                              
                                 [span]    [/span][span]    [/span][span]    [/span][span]    [/span][span]    [/span][span]       [/span][span]    [/span][span]    [/span][span]    Hourly                   Hours[span]  [span]    [/span]  Daily [/span][span]    [/span][/span]
             [span]    [/span][span]    [/span][span]    [/span][span]    [/span][span]       Volts[span]    [/span][span]    [/span] Amps[/span][span]    [/span]  Watts    Use/Day[span]    [/span]Amp Use                  
Lights   [span]    [/span][span]    [/span][span]  [span]    [/span]  [/span]        12   [span]    [/span][span]    [/span]1.20[span]    [/span][span]    [/span]   14.4[span]    [/span][span]    [/span]      2[span]    [/span][span] [span]    [/span]   [/span]      2.4           Four, 3.6 Watt LED bulbs            
Furnace[span]  [/span][span]    [/span][span]   [span]    [/span] [/span]  12[span]    [/span][span]    [/span]   3.40[span]    [/span][span]    [/span]   40.0[span]    [/span][span]    [/span]      0[span]    [/span][span] [span]    [/span]   [/span]      0.0                  
Refrigerator[span]   [span]    [/span] [/span]  12   [span]    [/span][span]    [/span]0.50[span]    [/span][span]    [/span]   6.0   [span]    [/span][span]    [/span]24[span]    [/span][span] [span]    [/span]   [/span]     12.0        On propane mode w/electronic control panel            
CO Monitor   [span] [/span][span]  [span]    [/span]   [/span]12   [span]    [/span][span]    [/span]0.11[span]    [/span][span]    [/span]   1.3   [span]    [/span][span]    [/span]24[span]    [/span][span] [span]    [/span]   [/span]   2.6                  
Smoke Detector[span]    [/span]12   [span]    [/span][span]    [/span]0.00[span]    [/span][span]    [/span]   0.0   [span]    [/span][span]    [/span]24[span]    [/span][span] [span]    [/span]   [/span]   0.0                  
Water Pump[span]    [/span][span]     [/span]12   [span]    [/span][span]    [/span]4.00[span]    [/span][span]    [/span]   48.0[span]    [/span][span]    [/span]    0.5[span] [/span][span]   [span]    [/span] [/span]   2.0                  
Water Heater[span]   [/span][span]     [/span]12   [span]    [/span][span]    [/span]0.20[span]    [/span][span]    [/span]   2.4 [span]    [/span][span]    [/span]  0.75[span] [/span][span]       [/span]   0.2                  
                                                   [span]    [/span]Total AHr Draw/Day     19.1   
                                 
Given all this, a standard 85 amp hour battery will last about 2.25 days without draining it past the recommended 50% level.                                 
[/quote]Do you have a link to the bulbs you got? I am interested in upgrading the ones in my 13QBB.

[charliem]

[font size="3"][font face="arial"]Thanks, Mitch,

I was pretty sure you didn't have the switch, but I thought maybe they had left it in on some models. That heater is a real watt sucker and probably isn't needed except in hot humid environments. I guess the they're saving a few cents or cutting down on customer service calls when people forget to turn it back on. The solar seems pretty basic, but should work fine. Why the on/off switches on the three meters? Are they analog or digital?
[/font][/font]

[mitch]

Hey Stewart, the bulbs were Putco White 230921W-360-P 921 type, I got them on Amazon but right now they show as unavailable.  I'm sure you can get them on other sites also. They are a fair amount bluer in color then the incandescents that they replace but that doesn't bother me much.  

Charlie, the panel seems to do the job for me. If I had to do it over I'd probably go with a 100W panel instead of 70W. The sizes are close enough and I'd get another 1.3 amps per hour which, over the course of a day is a fair chunk.  As it is now if I get 5 hours of good sun I can replace my entire days usage. I was boondocking at a music festival in West Virginia for 10 days last year and never got anywhere close to low on juice. I put the switches on the box so that I could eliminate even the tiny draw of the voltage meters, probably overkill but as I said, I'm pretty nerdy. The switch on the amp meter can also completely shut off power flow to the battery.  The 2 voltage meters are digital but the amp meter is analog. I used that one because it has the shunt built in and the digital amp meters didn't.  It was a fun project to do, kind of an introduction to solar power.

Mitch