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.

There were two switches in the trunk of my previous car.

A three position slide switch. A trunk-closed switch.

The three position switch had:

Always ON
Gated by trunk-closed switch
Always OFF

as the three positions. If you wanted to lock an elf in the
trunk and have the light ON, you could do that.

You should check and make sure your "option" switch is set
in the best position.

One of my door switches on the old car was
intermittent, but, the system is normally open,
and the intermittent switch means it doesn't
come on when the door is open. Fiddling with the
switch would bring it on. Closing the door always
turned if off. Just ON was a problem. Again, the courtesy
light had control switch had:

Always ON
Gated by door switch(es) - wired OR
Always OFF

I would work on my vampire loads, before giving in
to the appetites of the car.

My current car has vampire loads of less than 20mA.
The meter I used, can't give readings better than that
(that's the clamp-on ammeter reading). I would need
leads with banana plugs on the end, to be making a current
measurement without disturbing the electrical system.

My charger has no problem handling the 20mA vampire load.
And, it automatically cycles when the Vbatt drops low
enough. The only thing my charger doesn't do, is there
is no temperature compensation. The voltages it uses,
correspond to operation at 25C. If the air temperature
was somewhat different, the battery would be under-charged
or over-charged accordingly. There is a least one
commercial charger, where the "temperature measurement lead"
is a separate item, and you can place the lead where ever
seems appropriate.

If you change battery chemistries, then it's possible
some charger details will change too.

Paul