Watts up meter for monitoring?

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nc_tom
nc_tom Registered Users Posts: 2
in Solar Beginners Corner #1
Hi all,

I've built a tiny system as a homeschool project with my 7th grader. 20w panel / 22ah battery / sunforce 7amp charge controller. Here's a more complete description: http://bit.ly/HXdW6f

I'd like to add a monitor so I can see panel output and battery charge capacity. I bought a watts up meter, looks like it might be what I need. http://www.rc-electronics-usa.com/ammeters/dc-amp-meter.html

Do you guys any any input for me? Specifically, I am interested to know where to connect it. Should it go in the circuit before the charge controller or after?
Do you think it will tell me what I need to know about my system performance? I also have an analog volt meter which is cool but I doubt will be as effective at data collection.

Thanks!
Tom
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #2
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    Re: Watts up meter for monitoring?

    The little Wattsup/docwatson meters are nice... Their only "problem" is that they only "count up" -- So you cannot use them like a "real" battery monitor (which measures Amp*Hours in and Amp*Hours out for a battery).

    You could possibly place a switch in the system that allows you to switch the Amp*Hour meter from the load to the charging port or flip the direction of current so you can measure charging or discharging current with respect to the battery bank... Or, if you look up on their website, they have some circuits that allow you to reset the meter so you can log while you are discharging from the battery, then reset back to zero, and then log the recharging (note: while lead acid batteries are pretty close to 100% efficient in Amp*Hours while charging/discharging--They are only 80-90% efficient when measured as Watt*Hours--note a gain, if you are "bubbling the battery" or equalizing, that is pretty close to 0% efficiency as you are turning the excess charging current into gas).

    Watch the cooling on the battery and inverter--They could overheat (I cannot tell if the blank was restricting air flow or not.

    Also, I would look at the "idle current" of your inverter... That is a small battery and it will not take much power for an inverter to drain the battery of current in a relatively short time. Try not to run the battery much below 11.5 volts (~75F), if you take it too low, you run the risk of "reverse charging" a weak cell--which will permanently damage the battery.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #3
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    Re: Watts up meter for monitoring?

    The only thing I would add to Bill's response is "Welcome to the forum". --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • nc_tom
    nc_tom Registered Users Posts: 2
    #4
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    Re: Watts up meter for monitoring?

    Thanks for your input, I'm really learning a lot.

    Is there a better battery monitor that you would recommend?

    I have noticed a drain on the battery, I wonder if the inverter is a parasite. Would it drain even when the power switch is off? Maybe I should isolate the inverter with a switch.

    Is it ok to bring all of the inbound and outbound current together in that terminal block? (battery, charger, 12v outlet and inverter) It seems logical to me, but experience is better than my logic any day!

    Thanks again!
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #5
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    Re: Watts up meter for monitoring?
    nc_tom wrote: »
    Is there a better battery monitor that you would recommend?
    yes: http://www.solar-electric.com/tr20mosy.html
    nc_tom wrote: »
    I have noticed a drain on the battery, I wonder if the inverter is a parasite. Would it drain even when the power switch is off? Maybe I should isolate the inverter with a switch.
    Many inverters draw current when off. I don't know what inverter you are using.
    nc_tom wrote: »
    Is it ok to bring all of the inbound and outbound current together in that terminal block? (battery, charger, 12v outlet and inverter) It seems logical to me, but experience is better than my logic any day!
    I'm not sure how else you could do it. Of course, when you say 'inbound current' you are not referring to the solar panel output, and when you say 'outbound current' you are not referring to the inverter output.. Make sure that the battery is fused!
    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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