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rickman

wrote on 10/14/2017 6:19 PM:
My old inverter worked flawlessly. It's rated at 300 watts (Peak), which
means it's really 150 or 200W. A local second hand store had a 400W
(RMS) inverter. The store owner said he's not sure if it works, and he
told me to take it out to my car and plug it in. I plugged it in, and
the moment I turned on it's power switch, it blew the 15A fuse to the
cig lighter in my car. (Nothing was plugged into the 110VAC output).

The store owner knows me, and he told me to take it home and see if I
can get it to work, and if it does, give him $5, if not, just bring it
back. I put a multimeter across the 12V input leads, and get around 500
ohms, which rises over time. I opened it up, and found it has a 25A
built in fuse. This makes me wonder if it requires 25A to work, even
with no load?????

You are probably looking at a surge current to charge caps somewhere. If
they aren't directly on the input, the unit won't draw much current until it
sees enough voltage to power up. Then it starts drawing a surge to charge
the caps and pop goes the fuse. I know appliance fuses come in slow blow
and fast blow, but I don't think I've ever seen a fast blow automotive fuse.
They have a lot less thermal mass to heat up. All the automotive fuses
I've seen had fairly fat links.

My question is this: How much current is required for these inverters,
depending on their wattage rating? I have never seen any of them with
the required input amperage listed on them?

While looking on ebay, I noticed a lot of then rated at 2000, 4000, and
even higher wattage. In fact I saw one listed at 16,000 watts. Obviously
these high powered ones need to be hard wired to the car battery (not
using the cig lighter socket), but I can not see how any car battery or
alternator could handle a 16,000 watt unit.

Do you believe everything you read? 16,000 watts is 21 horsepower. Really?
21 horsepower in an inverter? Is it as big as a suitcase and have a big
fan to keep it cool? From 12 volts that would be 1,333 amps. Yeah, right!

--

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998