Gotta make sure to zero those DC clamp on units before you use them. Seems like every time I use one it takes me a bit of time to get it to measure correctly.
From: George Skorup Sent: Thursday, January 25, 2018 9:45 AM To: [email protected] Subject: Re: [AFMUG] Watts and VA on DC vs AC Yeah. I guessed about 33 amps based on 13 volts. Could rise quite a bit as the battery drains, and I'd expect the inverter efficiency to drop as the battery voltage decreases. I like having my handy Craftsman AC/DC clamp-on ammeter to verify my poor attempts at math. On 1/25/2018 10:12 AM, [email protected] wrote: Your inverter is probably 90% efficient if you are lucky. 355 watts / .9 = perhaps 433 watts input 433/12 =37 amps input at 12 volts So, yeah, your guess between 30 and 60 amps is pretty accurate. You can also insert 1 foot of #10 wire in series with the 12 volt line. Measure the voltage from one end of the wire to the other. Millivolts = amps. You should have about 37 milliamps volt drop across that wire. From: Adam Moffett Sent: Thursday, January 25, 2018 8:49 AM To: [email protected] Subject: [AFMUG] Watts and VA on DC vs AC I wanted to rig up a load test for some batteries. I don't have a substantial 12V DC load, so I set up a 1000W inverter, a short extension cord, a Kill-a-Watt meter, and a heat gun. With the heat gun on low, The kill-a-watt reads 110v, 606 VA, and 355W. The question is how much load is this putting on the battery? Somewhere between 30 and 60amp I guess, and either way my multimeter can't measure more than 10A DC current, so I can't measure it directly. My Googling on the topic has failed to enlighten me. My instinct is to think that Watts is Watts, so I should probably use 355W in my calculation of battery capacity, but I'm not sure.
