At home I charge my NiMH AA cells for everyday use.

I have an rapid "intelligent charger" which senses delta-V and it
measures current/voltage/whatever.

Let's say I start to charge some cells. After an hour, they are not
fully charged but I take them out and immediately replace them with some
different cells.

(1) Would the charger still remember the first set of cells and seek to
find delta-V based on its reading of the previous cells?

(2) How long should I leave an intelligent charger when swappig
batteries like this to make it forget the previous cells?

(3) Would I need to actually disconnect the charger from the mains power
to make it forget?

Alex Coleman wrote:
At home I charge my NiMH AA cells for everyday use.

I have an rapid "intelligent charger" which senses delta-V and it
measures current/voltage/whatever.

Let's say I start to charge some cells. After an hour, they are not
fully charged but I take them out and immediately replace them with some
different cells.

(1) Would the charger still remember the first set of cells and seek to
find delta-V based on its reading of the previous cells?

(2) How long should I leave an intelligent charger when swappig
batteries like this to make it forget the previous cells?

(3) Would I need to actually disconnect the charger from the mains power
to make it forget?

Sensible designs will detect the removal of the cells and reset the
charger.

Many (most?) use standard chips that do this.

However, if you don't like assumptions, either take measurements, open
the thing up and see what chip is used, or go for (3).

--
Sue

Alex Coleman wrote:
At home I charge my NiMH AA cells for everyday use.

I have an rapid "intelligent charger" which senses delta-V and it
measures current/voltage/whatever.

Let's say I start to charge some cells. After an hour, they are not
fully charged but I take them out and immediately replace them with some
different cells.

(1) Would the charger still remember the first set of cells and seek to
find delta-V based on its reading of the previous cells?

No.


(2) How long should I leave an intelligent charger when swappig
batteries like this to make it forget the previous cells?

a millisecond.

(3) Would I need to actually disconnect the charger from the mains power
to make it forget?

No.

Chargers have no memory. Normally there is a 'fast charge' button, which
initates the charge - the machine simply waits to see when the output
voltage falls by a few mV instead of rising. Normally it then goes to
'trickle current' mode.

If you disconect the battery, it should sense that and go to trickle
anyway when a new battery is connected. You normally restart the fast
charge with a button.

In the case of a charger that is dedicated to a particular pack, (e.g.
for a cordless) I suspect that there is a combination of voltage and
delta V sensing..fast charge will be applied below a certain level,.
otherwise its trickle charging. IN that sense its merely using the pack
voltage to 'push' the notional 'restart button'.

(3) Would I need to actually disconnect the charger from the mains power
to make it forget?

I would go for this option, having just destroyed 4 NimH AA cells on a
Goodman's intelligent charger, that now all read about 10 Mohms in both
directions, plus its psu has failed.
So I think its chip was a couple of cells short of a full battery.


john2