"Tracy Crook wrote:
Probably only a couple of amps. Right Tracy?

This may be understating the requirement.  You need:
4 - 7 amps for EFI pump
4 - 6 amps for ignition ignitors
5 - 7 amps for injectors
1/4 amp for EFI controller (EC2 type)
13 - 20 amps total depending on exact parts & RPM of engine.

I use a 22 AH motorcycle battery.  That would last a little over 1 hour.  I
test it for capacity at 6 months old & replace it at 1 year.
Tracy"

This dates from 08/29/1999
Looks like the injectors are of the peak and hold type.
Don't know what type of pump for sure but I think
he was using Walbro's in those days.
The ignition sounds like inductive.

Paul Lamar

Hi Paul,
Be careful with lead/acid battery spec's. Battery manufacturers would
like to have you do the quick math as you [Tracy]  have done, but the reality is
different. You can probably deplete a 22 AH battery in 22 hours with a
ONE AMP draw. But if you apply a 22 amp draw that same battery that you
would expect to last ONE HOUR may only last 20 or 30 minutes, depending
on the internal structure and quality. There are various "standard"
reporting points manufacturers use and some manufacturers will provide
useage graphs upon request, but really they'd rather you didn't know the
truth.

An elusive point is what a particular manufacturer calls a
depleted battery. This is usually referenced to an electrolyte specific
gravity but if converted to a voltage may be far less than needed to
meet the minimun operating threshhold voltage of the equipment it's
intended to operate. Remember also as voltage drops amperage goes up to
supply the load with the same wattage it needs so things like wiring and
motor coils begin to heat up. Without manufacturer's data, I would not
hesitate to apply a 50% reduction to battery life expectancy
calculations to be on the safe side, more reduction if the battery has
been in service over a year since a battery never 100% recovers from
discharge/recharge cycles. Use it in your lawn mower if it is over two
years old. Dave M