Help me figure out this power meter

Discussion in 'Power - Site Power/Batteries/Generators/Solar' started by mpking, Sep 10, 2017.

  1. mpking

    mpking Well-Known Member

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    So my wife bought me this power meter:
    https://www.amazon.com/bayite-6-5-1...rd_wg=XNVYm&psc=1&refRID=JZABC87X091MEQ9AXJTC

    Before I cut a big hole to mount it, help me figure out if it's helping me. I have no idea how many Watt Hours my battery is rated at.

    It's a Group 24 battery.

    How do I equate Watt/hrs to something that make sense to me... (percent remaining?)
    here's a picture after the first morning of the trip (It started at zero, didn't photo it) (notice the .5W power draw from my LP detector)
    [​IMG]
    Here's the next morning after that (after running the furnace all night)
    [​IMG]

    and here is after I got home (Charging the battery from the 7pin connector)
    [​IMG]
     
  2. rabird

    rabird Howdy!

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    let's call a new fully charged group 24 a 75 ah battery. 12v is assumed, 12v * 70ah = 840 Wh.

    A Trojan deep cyccle marine g24 ~85ah, 1.13 kWh or 1130Wh. better than the average bear.
    http://www.trojanbattery.com/product/24tmx/

    if ya started @ 100% and ya ended @ 75% and used 116 wh , that suggests the battery only has 464 Wh!!!

    An atwood furnace is rated 40 watt. 2hrs of run time would be 80 Wh.

    cold battery will lower batt voltage / energy capacity
    http://jgdarden.com/batteryfaq/SoC.xls

    http://www.marxrv.com/12volt/voltchart2.gif

    in use with unknown load
    http://www.marxrv.com/12volt/voltchart1.gif

    Fully charge this battery and disconnect from loads!
     
  3. mpking

    mpking Well-Known Member

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    @ the Atwood Furnace. Seems to be pretty close on the nose. This measurement is from when the furnace was running (it's lit and blowing at this point)
    .4 watt for the LP
    2 watts for the LED bulb I had turned on
    37.8 watts for the furnace.

    So far it seems like it's pretty accurate.


    [​IMG]



    I can guarantee that I did not start with 100%. I had the 3way fridge (Dometic 2193) set to DC, and it ran for an undetermined amount of time. (No more than 2 hours, most likely 1 hour). I forgot about it, and the wife wanted to take a walk.

    Rated input power (DC) 115 W
    Rated input current (DC) 10 A

    So the meter seem's pretty decent?
     
  4. rabird

    rabird Howdy!

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    based on that, yes, use the volt meter, 12.2 as 50%. under furnace load you'll need to figure out. Did the furnace drop it that low (12.24v)? from 12.7

    Fully charge your battery, reset and disconnect so CO detector doesn't drain it.
     
  5. mpking

    mpking Well-Known Member

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    Yes. But that was the middle of the night while the furnace was actually running. I didn't think you were supposed to use the voltage till the battery had a chance to "sit" and settle. I.E, the picture with 12.39v was taken about 12 hours AFTER the one with the furnace showing 12.24v.
     
  6. rabird

    rabird Howdy!

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    that gives ya idea that the furnace when on drops ~.15v
     
  7. mpking

    mpking Well-Known Member

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    So my meter died (see first post). Beginning of the season, the display was real faint when I put the battery back into the camper, and over the course of an hour, the display disappeared. Seems like the LCD just up and quit.

    Anyhow, I now have a solar controller installed on my camper, which provides voltage (among other things).

    Do you think it's worth getting another dedicated meter like this? I'm at the point where I think I'll just pull the shunt off and clean up the wiring, since I never really used it after I got the solar controller. (Way to easy to just look at the phone app if I'm within 50 feet of the camper)
     

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