Victron energy Blue Smart IP67 12/7 Anleitung Seite 13

3.6 High internal resistance
When a battery reaches the end of its cycle- or float life, or when
it dies prematurely due to sulfation or corrosion, capacity will
dramatically drop and internal resistance will increase. The
charger will not recognise such a battery during the test phase (it
could as well be a nearly fully charged battery).
A very short bulk phase when charging a supposedly discharged
battery does however indicate that the battery has reached the
end of its useful life.
Remark: sulfation can sometimes be partially reversed by
repeated application of the RECONDITION MODE.
3.7 Can be used as a power supply
The charger will supply DC loads when no battery is connected.