It looks like it's closer to 50 amp. My inverter must be very
inefficient.
Thanks everyone for the input.
------ Original Message ------
From: [email protected]
To: [email protected]
Sent: 1/25/2018 11:57:27 AM
Subject: Re: [AFMUG] Watts and VA on DC vs AC
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.
