diy solar

diy solar

How to measure DC current?


New Member
Feb 20, 2023
What device can I use to measure the current and voltage at the output of solar panels and deduce the power?

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In order to calculate wattage you need both voltage and amperage. Typically you do not hook directly to an inverter unless grid tie. Instead your panels connect to a SCC. often that SCC will give readouts of incoming PV voltage and either incoming amps or charging amps with battery voltage. Some give incoming watts.

You can get amperage with a DC clamp on meter or a shunt. Voltage can be measured with a volt meter and some shunts have a meter that calculate watts from reading both amps and volts. W=VA
A clamp meter like this one. You need the place the clamp around either the positive or negative wire, but not both at once.

Digital Clamp Meter, Multimeter Voltage Tester Auto-ranging, Measures Current Voltage Temperature Capacitance Resistance Diodes Continuity (AC/DC Curr

I just bought this one, on the recommendation of someone on this forum. They said they tested it against their much more expensive Klein meters and it’s quite close in similar readings. Most of the budget ones cost $60-90, so at $32 it’sa good deal. Price has gone up about $5 since I bought it in July.
an inverter that includes a solar controller would have a screen item showing incoming solar watts. you may have to click around through the various things that can display and it may or may not let you set that as a default item for the screen.
There are plenty of meters like this which give you watts at the moment, voltage, total watts and amp hours. This one even gives you how long even a minor amount of current was present. I use the external temperature probe to measure hot water tank temp or it could be helpful to know how hot a charge controller or inverter get. full scale current ranges are from a0A to 100A.
My system is first and foremost something for me to learn with. Then it is a great big expensive toy.

Because it is a toy and analog is cool:

View attachment 167195
Analog is cool. It’s 12:47 PM and my batteries are all charged up so the current is low. If anyone is looking for a clamp on amp meter, this is a good one from Amazon.
Here's the ammeter I bought. Harbor Freight Ames 1000A.

Advantage of this one is 0.01A resolution, so better for comparing PV strings than one with 0.1A resolution.
It also has inrush, good to test motor loads.

The KEWEISI meter I bought on AliExpress for $10 shipped. It only takes about 12 days to get here from China. Lots of vendors with this and similar items. Prices keep changing so shop around and carefully watch shipping costs and times. Fast shipping over $5 and with some cheap things shipping costs take an instant jump at $5 in stuff. I've become like an old lady watching QVC on Ali buying stuff every week!