[C320-list] Word on small inverter

[Gary Guilbeaux]

Hi Warren,

As an electrical engineer but novice sailor, it’s important to understand
that amps (A) doesn’t say much about the power consumed or provided by a
device unless the voltage (V) is also specified. Power or Wattage (W) is
equal to the voltage times the current (P = VI), so 30A at 12V equals
360W.  A TV that uses 3A at 110V consumes 330 watts of power, so an
inverter would pull around 27.5A at 12V to power that TV, not accounting
for the efficiency of the inverter.

Given that information, it’s pretty easy to understand why the inverter
either didn’t work or got very hot.  Also, the 12V lighter type outlets are
typically only rated for around 15-20A. They can generally handle more than
that, but it’s not a good idea to rely on it.

Gary Guilbeaux
1999 Lil’ Bit of Paradise
C320 #634


Some years ago I bought a small inverter, maybe 600 or 800W, don't remember
> exactly. I connected it via a 12V outlet on the main panel. For some
> reason, I felt it wasn't putting out so I called the company. They told me
> that the unit can detect if connected directly to the battery and would
> only provide more than 400W when connected directly (or close to) the
> battery. I don't remember seeing anything in the instructions about that
> limitation. I returned the unit in exchange for a 400W unit. 400W should be
> close to 30A which is more than enough for TV, laptop, etc.: small loads. I
> wouldn't pull more than 20-25A for very long as the unit will overheat.
> (This is just from personal experience. I am not an Elec-engineer. Just an
> old boat hack.)
>
> Warren and Pattie Updike
> 1994 C320 "Warr de Mar" #62
> Middle River, MD (Chesapeake Bay)
>
>
>
>
> --
Gary Guilbeaux
C: 512-799-4383
gguilbeaux at gmail.com