Linear charging is fine heat wise if you start from a "sensible" input volt=
age.
The highest you need charge to is a shade over 14v in some modes and
for a basic charger you probably don't need over about 13.6.
So, say you have a 15 V feed. If you charge at 1C max then at 12V
battery you need 15 Watt total energy and you lose (15-12) x 1 =3D 3
Watts in the regulator. If each regulator has a TO220 or DPAK size
device with individual heat sinking this is not too hard to handle -
and the average dissipation will be lower both per channel and
overall. 12/15 =3D 80% and at the top end its say 13.5/15 =3D 90% so say
85% mean for a linear regulator and in practice end to end many
switchers may give you no better than tat. A switcher at 92%
dissipates only half the heat.

Most efficient of all is probably a buck regulator from a 15V rail.
You can hope to get 95% from this.

If "rolling your own" is acceptable then there is an old lead acid
charger IC that was much used say a decade ago (name escapes me L6620
rings  a bell but probably wrong). It has app notes available that
show its internal working and describe in intimate detail what it does
and why - emulation of that in software using a PIC with a few ADCs
would be a breeze [tm].

     Russell
--=20
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