You really don't want to trickle-charge the battery with high current..
that will cause the electrolyte to boil out and will kill the battery for
good. You want to use one of your wall warts to power a voltage regulator
such as a LM117 or LM217, so that you can adjust it to exactly the float
level of a lead-acid battery, that is, 13.6 - 13.8 volts.
Look up the data sheet for one of those regulators and build it to output
the float voltage. The battery will only demand the current that it needs
to stay fully charged. The LM117/217 can pass up to 1 amp, but more likely
will be limited by the capability of your wall-wart. Again, this is OK,
since the battery, once fully charged, will need only a few milliamps.
I recommend the LM117 or LM217 because of the low temperature extremes that
it may encounter in the midwest winter. The LM317 is rated for operation
down to 0degC, or 32F. I'll bet your winter will get down significantly
below that, so be safe and use a component that's rated to handle the
temperature extreme.
If you still need help after getting the data sheet for the regulator, come
back here with your questions.
Cheers!!!!
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Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)

Never take a laxative and a sleeping pill at the same time!!
"Bruce W...1" wrote in message
...
This is not ham radio related but I know you guys have the answer.

I need to store a car unattended for a winter in the midwest. And I
want to put a tricke charge on the battery.

I'd rather not buy a fancy trickle charger because it would probably get
stolen. On the other hand I have a vast array of wall wart
transformers.

If I connected one of these transformers how many milliamps should it
put out at 12V? Or rather what's the least current that would do the
job?

It seems that lead acid batteries can dissipate too much current as
heat. In other words I could probably feed it one amp continuously.
But would 100 mA at 12V do the job? I'd hate to lose a 1-Amp wall wart.

Thanks for your help.