Suggestions for measuring daily watts used

[off-grid-geeks]

I have a WBJr connected to my Classic 200, so I know that the data should be available to determine how many watts (Wh) are consumed in a day.

It is easy for me to see how many Wh have come IN from my panels and into the battery bank.
But I'd also like to know how many Wh came OUT from the batteries (and obviously through the WBJr) to be consumed by my house.

However, I have a feeling that not all Watts used by the house are measured by the WBJr.
If there is enough power coming in from the panels to both charge the batteries AND also send some to the house loads, then I believe that the energy going to the loads directly from the Classic would not be seen by the WBJr.
I believe the WBJr only sees outgoing (load) power usage that comes from the battery bank (i.e. after dark).

So perhaps the WBJr is not the way to approach this.
Perhaps I need an additional watt meter sitting just before the feed to the house, which would see all power going to loads, both from the battery bank AND from the solar panels when they can provide extra power.

Thoughts?

Thanks!

[mike90045]

some of the larger inverters have internal metering, or you will have to get another whiz bang to meter the loads.

[toothy]

I don't know if you want an on going daily reading or a once in a while thing... You could just turn off the solar for 24 hours and get an idea of one days usage.

[kitestrings]

Hi geeks,

I would think the log data from the Classic would be most useful.  Granted the Wh, or kWh produced isn't all "useful", a portion of it goes to losses mainly in the batteries, but also the inverter and line losses...but in the end you need both the beer and the foam to have a full glass (boy that makes me thirsty).

If you are trying to quantify the losses and all of the load goes through an inverter then there are a couple choices.  The low-tech, dirt-cheap approach would be to just install a regular kWh meter (1S if 120V, 2S if 240V).

Otherwise, if your batteries are fully charged on a nice sunny day, the load needed to float the batteries with no load(s) on is what you need for battery maintenance.

~ks

[zoneblue]

Yes you can do this. The classic measures two (3 incl pv) sets of current: classic output amps, and WbJr amps. This tells you all you need to know. Take the classic amps, and subtract the whizbang amps, that tells your total system load amps.

The classic amps are positive, and the WBJr amps are positive for charging, negative for discharging. Thus:
-->  Iload=Icc + (-Iwb)

Multiply by Vbat and hence, Pload.

Caveats, there are slight differences in the way that those currents are sampled and averaged, thus there will be very minor spikes but overall it works well.

[Westbranch]

ZB, I think you have a typo .... first you say ''subtract'' and then you typed ILoad = Icc + (-Iwb)...

I believe you meant

ILoad = Icc - (-Iwb)..
so that when the WB is indicating as  -,   power is flowing FROM the battery to the load. Thus that power is in addition to any output from the Classic... and the sum, a neg. negative difference, of the two is the total load being powered... Make sense?  easy to show in a formula, tough to put to words...

[zoneblue]

Yeah confusing. Well i add it then subtract it to show that from common sense perspective the load gets power from two sources, the controller and the battery, except that the battery current is denominated negatively wrt to the load. Hence Iload= Icc + ( - Iwb). Make sense?

[off-grid-geeks]

Thanks for all the replies! Appreciate it!