> I have a potential project (awaiting go ahead) that requires 24V @ 2.5A
> (60W) to drive an LED strip. =A0The LED voltage and current parameters ar=
e
> fixed. ...

2 x 12V is easiest.

Use a DPDT changeover switch or relay to convert from parallel for
charging to series for operation.
You can add series diodes and/or balancing resistors for charging.
Probably work OK enough in hard parallel - naughty but ...  .

OR use two chargers - one per battery. As long as Vout is isolated (as
it probably is, it should work well. :-)

Batteries: Bigger AH the better for long life.
12 x 1.2Ah =3D 14 WH
Load =3D 5 Wh or say 40%+ of capacity. OK but getting deep-dischargish.
If you can tolerate larger it will thrash them less.
(365 cycles/year will destroy basic SLA at deep discharge. Don't know
at 40% but ...).

There are numerous laptop from 12V power supplies around. Some are
switchable. Available at your rating and above.
These are liable to be able to be changed from eg max 19V as typically
sold to 24V by changing or adjusting one resistor. YMMV.
Noise will vary and may be a problem.

Efficiency from 12 to 24 V real world probably won't be too much over
80% so you may get 20% + more runtime using two batteries directly.


                 Russell

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