At 05:33 PM 12/27/2000 -0000, Simon Matthews wrote:
>A PO of my "A" extended one battery tray and put in a group 24 battery --
it is enormous (and difficult to get into place)!
As long as you actually can get it in, that's not such a bad deal.
>I really doubt that the capacity of a 6V battery would be greater than my
group-24 battery (remember that the total capacity of 2x6v batteries in
series is the same as one 6v battery, just at a higher voltage).
The total storage capacity of two small 6V batteries might be very close to
the capacity of a single group-24 12V battery. The new tech 12V battery
will have considerably more Cold Cranking Amps capacity.
When you put two 6V batteries in series you get 12V at the same cranking
amps capacity. If the 6V battery is rated 350 CCA, then two in series will
yield 350 CCA at 12V. A new tech 12V group 24 battery may well be rated at
600 CCA or even higher.
Do not confuse CCA, which is a short term high current draw, with storage
capacity, which is a measure of how long you can draw a specified current
from the battery before it runs down. Storage capacity, usually specified
in Amper Hours, is directly related to the physical size of the battery, or
more particularly the number of plates and the mass of the working material
inside.
A group 24 battery may have about 62 AH capacity (when new). If you leave
all the lights on when you park the car, and they draw 10 amps, You might
still be able to start the car after 5 hours. A smaller 12V battery that
fits in the battery box of an MGB may only have 36 AH storage capacity.
Two 6V bateries being substantially more internal working mass, may have a
storage capacity around 60 AH (30 for each battery), and so would last
considerably longer with the lights on than would one small 12V battery.
When I had two 6V batteries in my MGA It could stand for at least 4 hours
with the lights on and still start. With the one small 12V battery I have
in there now it cranks better in cold weather, but can hardly stand two
hours with the lights on before it won't crank over at all. That's why we
have this discussion about the practicality of installing two 12V batteries
in parallel.
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
|