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Doc Wattson (net?) Meter
By valterra, Section Diaries Posted on Sun Aug 3rd, 2008 at 09:50:25 PM MST
Does the meter run backward?

I am considering getting a Doc Wattson meter. Being able to tell how many Ah were either generated or consumed would be great. Also, I'd love to be able to just glance and see my system voltage without flipping on my DMM.
I'm wondering if the meter will run backward or count down if appropriate.
Right now I have -50/+50 Ammeter hooked up between the Negative battery terminal and my system bus. EVERYTHING is hooked up to that copper bus on the other side of the meter - wind, solar, grid battery charger, and all my loads. If I run an appliance, the meter dips into the red (negative). If I power up the battery charger to my bus, the meter tips to the green (positive). If I am using as much as I'm generating, even those amounts are zero, of course it sits in the middle.
If I hooked up that Doc Wattson meter in the same location, would the Ah count go up AND down? I figured a mechanical meter of some kind would give me a net result. For example, we all talk about "spinning the meter backward" on grid-tie applications. But would this meter also accomplish the same task?
Anyone have any knowledge or experience with this?
I guess if you are making more than you use, and dumping on a daily basis, you'd always read right around zero. But those of us who go days between dumps, would I be able to see a negative number?

Doc Wattson (net?) Meter | 3 comments (3 topical, 0 editorial)

Re: Doc Wattson (net?) Meter (3.00 / 0) (#1)
by pvale (pvale at pvale dot com) on Sun Aug 3rd, 2008 at 07:12:11 PM MST
(User Info)

Sorry, no the "Doc Wattsun" or "Watts Up" meters are not bi-directional. I have an old E-meter that does this. The E-Meter is sold as the Xantrex "Link 10" meter now. These meters keep track of AH into and out of the batteries. I do use a Watts Up meter on my solar input to see what the total generated AH and Watt/Hrs were generated. Since my small 12V loads are 24/7, some of my solar input goes directly to the loads without any net charge to the batteries. The E-meter lets me see the large picture from my batteries viewpoint, and the Watts Up lets me see the total power generated by the solar array. I have several other DMM's that I use from time to time in various parts of the system. Even the little $12 Harbor Freight DMM's will directly measure up to 10A DC. I have a 10mv/A shunt connected directly in line with my solar panels, and I'll clip the little HF meter set on 200mv DC across it to directly read the solar input, especially if I'm using the Watt's Up meter for something else at the time. You can't beat the bang-for-the buck of those little red HF meters. I won't feel too bad if I accidently blow one. Better that than one of my Fluke meters. Good luck, the Watts Up meter is good for reading a load, but the Link 10/E-meter is a much better system meter.

Re: Doc Wattson (net?) Meter (3.00 / 0) (#2)
by valterra on Sun Aug 3rd, 2008 at 09:03:07 PM MST
(User Info)

Make that a $2.99 HF meter - I have 5. lol. :-)

For anyone interested - they're on sale again right now.

Thanks for the tip. I guess I can't look to it for that. The Good Doctor then would keep track of how much energy I've created then.

As for the HF Meters - My wind and solar both run THROUGH their own meter, so I can measure the current of each input individually. With 3A wind and 2A solar, the +/- 50A gauge is overkill. But for TOTAL loads versus charge, especially when "cheating" with a grid-powered charger, the big analog meter does move.

[ Parent ]

Re: Doc Wattson (net?) Meter (3.00 / 0) (#3)
by Bruce S (bruce(dot)stahl <at>gmail (dot)(com)) on Mon Aug 4th, 2008 at 07:59:13 AM MST
(User Info)

You are correct , they are not bi-directional.
BUT they can be run two together, with one backwards of the other.
They can also be left in place for charging . It doesn't bother them at all.
When we switched out the SLA's for NiCd packs in the e-tike, we had to go to using two of these due to the on-board unit being set for SLAs.

Bruce S

[ Parent ]

Doc Wattson (net?) Meter | 3 comments (3 topical, 0 editorial)

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