To build one is not that hard though a beefy bridge rectifier and a
transformer salvaged from some high power low voltage device, probably find
something at a boot sale.
Brian

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The Sofa of Brian Gaff...

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Note this Signature is meaningless.!
"Theo" wrote in message
...
I think I might need a new car battery charger. However I'm failing to
find
anything suitable and wonder if the team can recommend any models.

Requirement #1 is to be able to charge flat batteries.
My boot lid sometimes doesn't latch properly and leaves a dim little light
on - which if you don't drive for a week or two empties the battery. My
current 1980s dumb-charger can't handle delivering current into a low
voltage battery for more than a few seconds before the thermal trip
goes[1].
I've seen smart chargers say 'we handle flat batteries 7.5V' which is no
use when the voltage drops below that.[2]

I would expect that mode to be a constant current mode, although they
could
pulse or do other fancy things. But it should be able to deliver it
continuously without tripping out.

Requirement #2 is a display of voltage and current so I can see what's
going
on. Little LEDs saying 'half' or 'full' do not cut it.

Nice-to-have #3 is a means of terminating charge when it's full, but I
could
live without that.


Are there any 'smart' chargers that aren't also 'too clever for their own
good' chargers?

Thanks
Theo


[1] Instead I've been using a old 32V 2A bench PSU in constant current
mode,
but 2A isn't very much and the case gets very hot (suspect a linear PSU).
It also isn't great to leave in the engine bay as it isn't weatherproofed
in
any way.

[2] You might say the battery has had it by this point, but it's an AGM
battery in a hybrid so it lives an easy life. It only needs to provide
20A
for a few seconds to open contactors, it isn't used to start the car. I
might look at a LiFePO4 SLA-replacement next time.