"Andrew Gabriel" wrote in message
...
In article ,
"newshound" writes:
Sorry, I really should have given more details. I've got a couple of 9W,
a
16W, and a 4 foot tube on a switched spreader so that I can be very
sparing
with the load. I do know how to do the sums (but I didn't make that
obvious!!). The inverter's claiming low voltage after a few minutes use
on
an ex-diesel battery (80 AH I think) that was used, but still working
fine

Measure what voltage drops to just before the inverter cuts out.
10.5V is pretty typical - if it's significantly higher, then the
inverter is faulty. If the battery is falling to 10.5V in a few
minutes of low load, then the battery is dead (or possibly needing
maintenance such as topping up, depending on type).

Yesterday, the inverter wouldn't fire up with a single 9W CFL. Today, when I
had my DVM, it worked fine with a 16 watt one. Battery initial voltage,
12.8. When drawing 2 amps, 12.6 v. So looks like a fairly healthy battery to
me. I wonder if I have an intermittent bad connection and was losing volts
somewhere yesterday.

on the car when I retired it. I know about deep cycling and a couple of
my
other fencer batteries have a dodgy cell, but I think this main lighting
battery is still pretty good (it will run a fencer for weeks). I suppose
I
should stick a few amps load on it and plot the discharge curve with my
data
logger!

Fencer will probably work well on 10V, if the battery has a dead
cell.

My point really was, are some cheap inverters fussy about CFL loads?

Not that I've noticed. You almost certainly have to use the VA
rating rather than the Watts rating to calculate max load on the
inverter though.

I'm not looking for more than about 20 "watts" out of a 300 watt inverter so
I guess I'd be OK even with a nasty load.

Although the simpler answer would be to follow Andrew's suggestion and
stick
in some "caravan" bulbs.

Bear in mind these probably don't include any protection against
deep discharging a battery, and that can wreck both the battery,
and the fluorescent tube control gear. So you probably want to
add a deep discharge protection circuit. That would be easy to
build if you're in to electronics, or you might be able to get
one from elsewhere, such as an alarm system one.

Valid point. I guess it might be just such a circuit which is making my
inverter fussy. I keep thinking about getting a proper deep discharge
battery, but never quite get round to it. Here's protection a circuit for
Li-Ion

http://www.ultimate-electronics.co.u...204.5%20Ah.pdf
--
Andrew Gabriel
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