On Tue, 24 Feb 2004 02:05:39 GMT, U wrote:

Solar panels and all that stuff is quite expensive, but old car batteries
("old" is when it doesn't get my Diesel started in subzero temps) are not.

While a cold diesel is hard to start, the capacity of a car battery
drops drastically at cold temperatures and assuming you are referring
to temperatures below 0 F (not 0 C), the capacity of the "old" battery
is well below nominal even in warm conditions.

So even if you can get those cheaply, you may have to have two to get
to the nominal capacity. The optimal float charging voltage may be
different for different old batteries and this can be a problem when
connecting multiple batteries in parallel.

Batteries designed for car starter duty often expect some amount of
vibration, which they do not get when in stationary use.

Unless you get several batteries for free, it is not such a big
bargain as it would look like. I don't know about the car battery
final disposal costs, but if they are high, collecting a large number
of reduced capacity old batteries might be quite expensive when they
are finally disposed.

Paul OH3LWR