On Feb 9, 5:07*am, Bob wrote:
* * * * I wanna know if I can hot wire my scooter battery to a regular
12v/60w soldering iron to do local soldering repairs

Why not? No more current will pass through the heating coil than the
resistance of said coil allows to pass.

If you're worried about damaging the soldering iron, put a 10 amp fuse
in the input wiring. 10 amps should be twice the normal maximum
current draw of the 12 volt iron. (1)

* * * * I know most soldering kits, you buy or build, usually require a
standard wall socket 120v/60w soldering iron and some 4AA batteries....

The AA batteries would provide half an amp of current to the heating
coil of the soldering iron, but wouldn't have the ampere hour capacity
to keep supplying the
1/2 an amp the iron draws.

* * * * So I was wondering what would happen if I used a 12volt SLA 8 amp
battery, since the wall outlet is a about 90watts

If your wall outlet has a 30 amp breaker or fuse, it will supply 3600
watts, not 90 watts.

and the 12volt SLA battery
is also some 96 watts although it drops quickly to an easy 11 volts because
of a burned cell I'm guessing....

Your battery may be old and could be dehydrated or has sulfated
plates.

Your fully charged 8 ampere hour battery should provide 8 amperes to a
load for
one hour without the voltage dropping below 12 volts. If it quickly
drops to 11 volts under load, it's not fully charged.

The resting voltage of a fully charged SLA battery half an hour after
charging should be 12.8 volts.

You can find battery state of charge charts online which will tell you
what the state of charge of a lead acid battery is, according to
resting voltage.

* * * * The math is there but some other factor is missing, I can't see the
power of a 12volt SLA battery to a mere 4 AAs ...........

The missing factor in your understanding seems to be the concept of
*ampere hour capacity*.

has anybody ever
tried this with a regular soldering iron for outdoor use???

No, I never tried that, but...

Work out the Ohm's law for your 120 volt soldering iron, or measure
the resistance of the coil and you'll see how many amps it draws from
a 12 volt battery.

The heating coil doesn't know what the source of power is, it just
heats up according to the current it receives.

(1) You might want to research the coefficient of resistance of
nichrome wire to see what the resistance is when the wire gets hot
enough to melt solder.