Inverters

Arthur Marshall wrote:
> I've just picked up a cheap (very) inverter from Gizoo, and if anyone
> can advise as to how much battery this is going to use up, powering a
> 40 watt appliance, it would help as I haven't used one of these
> before.
>
> Basic question is whether they drain the battery really fast, in which
> case it will only really be any use when I've got the engine running,
> which I don't like doing of an evening.

I'd suggest it will draw between 4 and 5 Amps from the battery, depending on
the inverter's effficiency. If it is a really cheap design maybe even 6
Amps.

Paul

> Even if the inverter draws 5
> Amp (unlikely) you could run it for 20 hours on a standard 100Ah
> leisure battery.
>

Not if you want the battery to last for a few years. More like 6 hours.

On Thu, 26 Jun 2008 19:14:27 +0100, Arthur Marshall
<arthurm@zetnet.co.uk> wrote:

>I've just picked up a cheap (very) inverter from Gizoo, and if anyone
>can advise as to how much battery this is going to use up, powering a 40
>watt appliance, it would help as I haven't used one of these before.
>
>Basic question is whether they drain the battery really fast, in which
>case it will only really be any use when I've got the engine running,
>which I don't like doing of an evening.

P=IV

or transformed (because we want current (I);

P/V = I

We actually need to factor in efficiency of the inverter.

Assuming a cheapish inverter, we can allow 0.5 amp + 10% of load
current for wastage, so

(1.1(P/V))+0.5 = I

so for a 40 W appliance

(1.1(40/12))+0.5=I

So, about 4.2 Amps