On Wed, 02 Jan 2019 16:24:58 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
T i m wrote:
On Wed, 02 Jan 2019 10:42:27 +0000 (GMT), "Dave Plowman (News)"
wrote:

snip

I have a Halfords charger - a few years old but claims to be automatic. On
the front says 11 amps. It takes longer to charge my car battery than the
14 quid Lidl one which only claims about 4 amps.

But that final time can depend on the time *it* takes to manage the
final phase?

Quite. I'd guess the Lidl one bashes in its full output 'till fully
charged.

I don't know any good (non faulty) LA charger that would work like
that, not without the potential to cook (/overgas) the battery that is
(depending on the ability of the charger and the capacity of the
battery). Even the charger for my EV (200Ah / 48V battery) only gives
full output (current) for the bulk charge phase before tapering down
to next to nothing.

Unlike the crude Halfords one that works on battery terminal
voltage.

Don't most chargers work that way, even straight transformer /
rectifier (taper) ones?


Like the Optimates go though a charge and leave stage at the end and
monitor how much the voltage drops when left. If it drops too much it
starts charging again and will only put up the 'Done' LED, once it
really is. Therefore, it might appear to take longer than a more basic
lower powered charger because it's more thorough?

(I'm not saying that IS the case with your chargers etc ...)

Basically, the old Rover has quite a high quiescent load on the battery
due to a 'sophisticated' alarm and other toys I've added. And the car may
not get regular use. So I charge the battery every three weeks, if it's
not been used. If one charger was doing a better job of fully charging the
battery, I'd guess I'd notice. ;-).

Funnily enough I was talking to a mate tonight about his desire to
automatically turn on various battery chargers for (say) 120 mins once
every month. He said he couldn't find a 30 day timer (?) so I was
thinking of one of the ESP / Arduino's might be handy?

Cheers, T i m