I am finally getting back to a project which will require a=20
rechargeable battery inside...  Because of cost, apparent reliability,=20
ability to obtain replacements easily, etc., I'm likely going to end up=20
with a battery made up of multiple NiMH AA cells.

I would like to charge the pack from A roughly 12V source (I.E. be able=20
to plug it into a automotive lighter outlet, which is typically=20
somewhere between 12 and 14 volts).

I need around 20Watt-hours.  This means I need around 8 good quality=20
cells, or a 9.6V pack, which should be fairly easy to charge from 12V...=20
however....

My application also requires around 18VDC out - so a 9.6V pack would=20
require a step-up DC-DC converter for the output....  So, a 15 or 16=20
cell pack would eliminate that part, but perhaps make the charger=20
circuit more complicated, depending on the charge versus load current=20
requirements.

I also prefer to avoid having to heatsink in any meaningful way the=20
'output stages' of the charge controller - that is, a linear charger=20
probably isn't what I'm looking for.

In an ideal world, there would be a switchmode charge controler that=20
with the IC and a half-dozen fairly non-critical external components, it=20
would magically take around 12V in and charge an 18V NiMH battery  pack=20
reliably and correctly.   Unfortunately doesn't seem to exist.

So, I guess my question is... did I miss a 'perfect one'?  And if not,=20
what is your favorite 'pack charging' NiMH charge controller?

-forrest
--=20
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