Date: Sun, 29 Jul 2007 18:42:09 -0700
Reply-To: Michael Elliott <camping.elliott@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Michael Elliott <camping.elliott@GMAIL.COM>
Subject: Re: Deep Cycle Batteries
In-Reply-To: <vanagon%2007072920395069@GERRY.VANAGON.COM>
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The highest power appliance I've ever used in our trips is a Sevylor
kayak inflator that pulled 17A from the battery for about 20 minutes.
That's 17 x 12 ~ 200 watts. Well within the max current draw
capabilities of our East Penn (West Marine) group 27 even though it's
not a high-quality deep cycle.
As for what a 1200W inverter is for -- giant batteries? 110 lb women who
think they need a huge SUV to get groceries, or guys who reckon an
F-350 is just the ticket to drive to work in? Hats on backwards and
giant tires?
Because the inverter people can build them and sell them. Advertising.
Some appliances, motorized ones, for example, pull a hefty whack of
current on startup. Our coffee bean grinder (coffee thread!!!! Duck!)
won't start with the little 200W inverter which goes into Protect when I
hit the "go" button, though it will with the 800W one. When running it
draws about 10A, or 120W, so here's a case where a bigger inverter is
(momentarily) better.
But running an 800W appliance off a smallish battery is asking for
trouble. What's the manufacturer's recommended maximum discharge current?
Appliances that heat stuff are extremely power-hungry. Use propane or
some other fuel.
--
Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR
Geza Polony typed:
> Dennis, Michael,
>
> Thanks for replies.
>
> Michael, I have a 4AWG wire feeding the 1250W inverter, and it's only about
> 2 feet long, so it ought to be large enough. I charged the aux battery with
> no load on it (fridge and inverter are the only things wired to it) for
> about 45 minutes to get to 12.30 volts. In an hour and a half of using the
> fridge it dropped from 12.3 to 10.62 volts, about the lower limit for any
> cooling. Seemed to bounce back some when I turned the fridge off.
>
> Dennis, if 800 watts at 120 volts fried the battery--then what the h**l do
> they sell 1200 watt inverters for? I thought you were supposed to be able to
> use Skilsaws etc. with the larger inverters. These are designed to go into
> normal cars and trucks with normal batteries, no? Or was it the length of
> time using it that whacked the Optima (maybe five minutes, no frothy milk on
> the coffee) ?
>
> So what I'm hearing is that the aux battery isn't holding a charge, which
> explains why the voltage during charging is lower than on the vehicle battery.
>
> Next time I get a degree, it's going to be electrical engineering.
>
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