The main point is not so much, that a battery last 30 minutes.
It is the electrical current, what is important.
If you consume power from your battery, then the electrical system runs at
12-11.5V.
If your charger is in action your system runs on 13.5-14.5V.
This means, the ignition output is a lot higher and the engine makes more
power.
Cheers
Chris
-----Urspr?ngliche Nachricht-----
Von: Fot [mailto:fot-bounces at autox.team.net] Im Auftrag von Rocky Entriken
via Fot
Gesendet: Sonntag, 29. Januar 2017 06:55
An: Bud Rolofson; FOT
Betreff: Re: [Fot] How much electrical power is needed for a 30 minute race.
I never bothered with the lightweight battery in my Spitfire (no
generator/alternator) because I needed the ballast anyway, so I moved mine
to the right side of the shelf behind the seat for better weight balance. In
fact, I got a heavier marine battery for the extra storage. My car has
electronic ignition, starter, two fuel pumps, tach, transponder, four brake
lights (none of my other gauges are electric)
That said, I found a fully charged battery would last me about a day and a
half. So for a weekend I had two batteries and I'd change it out overnight.
A two-day autocross weekend seemed to use it up more than a two-day race
weekend.
Actually, for a race weekend, one battery would probably last, but why take
chances? Hitting the starter sucks the most juice and I sure didn't want it
to fail to start just when I got the 2-minute warning for Sunday's race
(it's done that)! OTOH I've found that once started it'll do the whole race
with nearly no charge -- did that once when I had to get a push start off
the grid. None of the other stuff including sparkplugs suck much juice.
--Rocky Entriken
-----Original Message-----
From: Bud Rolofson via Fot
Sent: Saturday, January 28, 2017 11:02 PM
To: FOT
Subject: [Fot] How much electrical power is needed for a 30 minute race.
How much battery is needed to run a Spitfire for a 30 minute race without an
alternator, in terms of amps, or current needed.
I've been looking at lighter weight batteries like the Braile and don't have
a good idea of what reserve capacity is needed. Is 35 minutes enough with a
battery capacity of (C/20 rate): 21 amp/hr.
Fuel pump, ignition, some Gage's, and LED brake lights are the biggest draws
on the battery.
Thanks for any suggestions.
Bud
Sent from my Commodore 64
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