At 09:54 AM 2/28/2002, lchase wrote:
>Automotive Electrical Lizards ..... ah Wizards on the list,
>
>Just a crazy brain storming idea;
>
>Four Optima Yellow Top Batteries wired in Parallel .... no separate starter
>battery.
>
>A " Off line" Portable Battery Jumper Starter" for emergency starting.
>
>Work ..... ?
>Not Work ..... ?
>Do Different .... ?

Sounds workable to me.  You're talking about roughly 200 amp-hours of
nominal capacity, which gives about 70 usable (85% >> 50%)  if you're
after  maximum cycle life; about 150 usable (85% >> 10%) if you're
balls-out* for capacity and don't care about cycle life.   Charging time
above 85% is so long (several hours) that it's uneconomical unless you're
running the motor anyway. But since you're talking about putting $700 into
batteries, why not put $300 or so into a smart regulator like the Ample
Power Next Step that will give you charges that are both fast and complete,
thus preserving your investment in the
batteries.  http://www.amplepower.com/ has lots of info and also a couple
of books on the subject.  Note that you may need to shift to a "hot-rated"
marine alternator or arrange extra cooling to avoid regulator failure with
these fast-charge regimes.

Rule of thumb for capacity is greater of four times your daily requirements
and four times your maximum load -- with gel or AGM batteries like the
Optima you can say three times max load.  That's maximum instantaneous
load, not average.

>Pertinent Assumptions
>
>1. Daily trip driving 2-4 hrs if that.

This would give you (assuming smart regulator) a charge recovery of
probably over 100 amp-hours assuming the batteries can accept that and
still be less than about 85% charged -- and you aren't using up the
alternator with A/C, headlights, foglights, blowers, gigantic stereos
etc.  Above 85% it will take at least that long to get the last fifteen per
cent.

david
* for the prurient (and curious) amongst us, this refers to a centrifugal
fly-ball governor as used on low-speed engines in the last century, not to
whatever <ahem> you may have been thinking.  Lord, I thank you that I am
not like these men Karl Wolz and Mike Miller, nor yet am I BenT (tho straight).

--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"