COACH BATTERIES

[hippieforever3]

> As others have pointed out, there are some technical issues with
your comments. I think if you research the topic you will find a
steady stream of "Lead-acid is not subject to memory' on technical
sites. Rule-of-thumb is to avoid discharge below 50% whenever
possible. I wouldn't personally go so far as to say a 100% discharge
will destroy a battery, but it will definitely shorten life.

I misused the term memory for simplicity but you guys are sticklers
for details.

Please read:
http://www.udel.edu/igert/pvcdrom/BATTERY/charlead.htm


> One other issue is this part:
> >Price vs. performance vs. reliability.
> >Two $75 55ah 12 volt batteries will be more reliable than one $150
> >100ah battery but take up twice the space
>
> As you noted correctly "sheer lead volume determines capacity" so
it is not possible to have a 100AH battery that is the same size as a
55AH battery unless the latter has an extreme amount of wasted space.

Yes atomic physics makes "sheer lead volume determines capacity" true
but characteristics like charge and discharge rates determine "useful
capacity". A good example is that a well designed and built battery
with EXACTLY the same lead weight may have double the "cranking
capacity" as a poorer designed and built battery.

Charge and discharge rates and efficiency are also effected by design
and workmanship.

After looking up the prices of the super premium DEEP CYCLE (don't
buy ANY that aren't deep cycle) and doing a cost benefit analysis, I
would recomment the following;

Buy enough good quality, (not necessarily the highest quality or
price) 12 volt deep cycle batteries that you can start the coach if
one battery shorts a cell (99% of all failures) and replace your
batteries on a periodic rotation basis WHETHER THEY FAIL OR NOT.

EX: If you buy 48 month warrantee batteries and you have 4 replace
the oldest one every year. If you can start the coach on three
batteries, you have a 100% redundant system. Reliability exceeds
99.99% by mathematical proof.

The cost benefit method would be to figure the cost per ampere hour
(a pretty good indicator of overall $ to performance) and then buy
the lowest total cost batteries that have sufficient cranking power
capacity to start the coach with a 10% margin, WITH one battery out
of the system.

I'm guessing that this would result in a system of $100-175 12 volt
batteries, maybe adding one additional spare somewhere.

Regards,
GPSGary