Which settings on my new charger should I use to charge my batteries?

Dear Car Talk

Dear Car Talk | Jul 01, 1997

Dear Tom and Ray:

I have received a battery charger as a gift. It has the following settings
on it: 6-volt/6 amp; 12-volt/2 amp; 12-volt/6 amp. I have a 1982
Oldsmobile, a '77 Chevy pickup truck and a Snapper rider mower. Which of
the above settings should be used to charge the batteries on each of these
vehicles? -- Bob

TOM: Well, for the first two vehicles, the Olds and the Chevy, you should
use the 12-volt/6 amp setting. The first number, the voltage, is determined
by the battery. And all modern cars use 12-volt electrical systems.

RAY: The second number, amperage, is a measure of how much electricity can
flow through the charger's wires at any given time. And even your highest
setting, 6 amps, is not very much. A 6-amp charger would take all night to
transfer enough electricity to charge your car's battery. That's why they
call your device a "trickle charger," because the electricity trickles in

TOM: It'll work perfectly well overnight, but it's not strong enough to
provide an instant charge to a dead battery. For comparison, the charger in
our garage is 12-volt/100 amp! That'll charge a dead car battery in an hour
or less -- about as long as it takes to have your shirts Martinized.

RAY: As for your riding mower, I don't know for certain what kind of
electrical system it has. Many of them use 12-volt systems, but without
knowing the age of the mower, I can't say for sure. The voltage should be
written right on the battery (or you can always call the company to be
sure). And as long as the voltage is set correctly, I think either amperage
setting would be OK.

TOM: But just to be safe, have your brother make the last connection to the
terminal. Good luck, Bob.

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