On Tue, 21 Jul 2020 22:12:20 +0100, Theo wrote:

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.

I used an old 19v x 4A laptop power supply with a couple of 55W headlight
bulbs in series to charge my flat battery. It started at 2.5 amps and
dropped to 1.8 amps over a couple of days, giving a full charge.