*A heavy electrolytic cap near the second battery might keep*




* the voltage up enough to pulse-charge the second battery. I'd use
something like 10,000+ Mfd at 25vdc or so, then make the pulses 1/3 to 1/4
duty cycle, which will allow the cap voltage to charge back up during the
off interval.*

-> Solar pulse charging advice sounds good.

Pedantic nit-picking:

I take it that 10,000 Mfd =3D =3D 10,000 micro-Farad.
Olin's head would probably explode on that one :-).
He loves to take mF as milli Farad when people write that and proceed as if
they meant it.
I'd take MF as mega-Farad.
I  tend to use uF for micro-Farad,  as it's generally well understood - but
of course that is informal.

In this case Olin's 10,000 mF =3D 10F is realisable albeit expensive at 25V=
,
so is an unlikely but possible interpretation.

20 of these in series (with balancing) at about $200 :-)
http://www.maxwell.com/products/ultracapacitors/docs/datasheet_d_cells_1017=
105.pdf

          Russell
--=20
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