> Linear charging is fine heat wise if you start from a "sensible" input
> voltage.
> 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.

But where do you get the 15V from? Mains transformer, rectifier and a cap? =
Then=20
you need to consider the tolerance of the mains power, that you have a ripp=
le=20
on the input to the regulator and that the voltage varies with load (perhap=
s=20
not a big problem here since you need quite a big transformer).

If the circuit needs to work with ripple free output voltage from the=20
regulators you will find that the input will be a lot more than 15V (peak) =
in=20
normal cases if it is also going to work at worst case.

/Ruben

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
Ruben J=F6nsson
AB Liros Electronic
Box 9124, 200 39 Malm=F6, Sweden
TEL INT +46 40142078
FAX INT +46 40947388
ruben@pp.sbbs.se
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D

--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.