Having noted that my trusty old B&D 12v drill/driver and 12v combi are
starting to lose some battery longevity I had a quick Google to see how much
a replacement might be.

About £30.

Since you can buy a new 18V combi (albeit not a particularly special one)
for under £40 this does not seem to make economic sense.

I also can't seem to find a fast/trickle charger which would allow me to eke
the best remaining performance out of the current batteries.

One major problem with lower end drills is the 3+ hours to charge plus the
requirement to then take them out of the charger after the 3 hours to avoid
damage.
Combined with the requirement to discharge the battery as far as possible
before recharging this does give all sorts of useability issues.

If I could find a reasonable trickle charger I might consider buying one
more batttery to keep two drills going as the batteries are interchangeable.
However I can't seem to find anything via Google so far.

It has been suggested that if I made up an adapter I could use my Site
(Makita) charger which is rated on the front as 7.2 - 18V.
Does anyone know how good these chargers are at sensing the fully charged
voltage of battery packs?
It looks feasible to cut the wire leading from the wallwart of one of my two
12V chargers (in the middle to allow reconnection if required) and then
connect to another lead which fits into the Site charger but I wouldn't want
to go through all the hassle of making up a connector to the Site charger
just to fry a battery.

I am assuming that the B&D 12V charger is a simple arrangement of a 240V/12V
wallwart and then a thin wire which takes the 12V to the adapter which fits
the battery pack.
If there is more intelligence in the adapter which the battery pack clips
into then the solution may not work.

Any information appreciated.

Also, would a motor cycle 12V trickle charger work if connected to the
battery pack?

Cheers

Dave R

--
No plan survives contact with the enemy.

Helmuth von Moltke the Elder