[Fot] How much electrical power is needed for a 30 minute race.

[Rocky Entriken]

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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