Charge status
It is useful to know how discharged a battery is before
it is charged, to be able to charge it in the best manner.
The ambient temperature plays a part in both the
charging ability and capacity, not until at
+25 °C
does
the battery give 100 % of its capacity. The battery
cannot be charged especially well below
0 °C
, see
table.
The batteries must not be left uncharged. Every third
to fifth week, even a “charged” battery needs a
maintenance charge, due to self-discharge and possible
small consumers <40mA (clocks, tachograph etc.) if
the vehicle does not have a main switch. If there is a
main switch and a properly connected solution, one
can stretch to five weeks between maintenance
charging.
Temperature -18ºC 0ºC +25ºC
Capacity
20 h
(Ah)
50% 85% 100%
Charge acceptance (A) 6% 25% 100%
An alternator can never charge the battery to 100%; in
favourable circumstances a maximum level of 90%
can be achieved. Complete recharging can only be
done with a battery charger over a long period of time
(1-2 days). Increased power demand from the
alternator and battery may result in the battery being
discharged. The easiest way to check the charge is
with a voltmeter, but an aerometer (specific gravity
gauge) together with a voltmeter gives a more correct
result. The diagram below shows the rest potential and
state of charge compared with the specific gravity of
the acid.
550
Maintenance
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