question on battery float charge, trickle chage, battery charger.
 

I have several betteries for those little kid's battery cars, some from the electrical lawn machine. I use the adapter type chargers (come with the car and the lawn machine) on them but they don't work. I brought them to Autozone to give it a try and it works.
Can I get those charger from Harbor Freight for this purpose? Also, I can use it on my 911 too.
Does the float charger (pic below) work or I have to have the bigger type (below)?
Thanks.
Automatic Battery Charger - 12V
2/6 Amp, 6/12 Volt Battery Charger

You cant go wrong with one of these

http://lh5.googleusercontent.com/pub...Ftwh127IPIvUWY

BatteryMINDer Plus

This is what the Harbor freight one does. It puts out just less than 1 amp until it reaches about 13.5 and then tapers off.

If you don't abuse the circuit board (shock or vib) it is pretty foolproof.

http://forums.pelicanparts.com/porsche-911-technical-forum/384280-harbor-freight-42292-battery-maintainer.html

I have had a couple for my motorcycles. This is the one I use right now. Cheap. Reliable. Works. And it actually charges up to about 14.7 volts before it floats down, which makes sure the battery really is fully charged. Put a voltmeter on other chargers--they usually go up to a max of13.6 or 13.7. I can't say that the more expensive ones I've purchased from other manufacturers have been any better (and often, they're not as good).

Schumacher SEM-1562A Battery Maintainer and Charger - Walmart.com

I find that these things "only" last 10-15 years or so.

Yes, use one.

for those from 1 to 2 amp, how long does it take you to charge a dead battery (let say 5v or 6v left) to full?
Thanks.

There's a formula for that depending on the amp hours of the battery. But, some are dead for another reason. Sometimes if you hit them with 70 amps for less than an hour and finish up on a trickle down system. they will hold.

On some at 2 amps you'll never get a proper charge. Keep 'em up until they die and then replace.

in that case, would 6amps be more proper to get full charge?

It still depends on the amp hour and where the battery stands before you charge it.
Battery Charger Calculator, Batteries Charge Time Calculation - Free Online Calculators

If you discharged the batteries too far, you may have damaged them. They might take a charge, but will generally not hold it for any length of time...

Vin

Reading some more specs from HF, I finally get the one below, a little better in amps. It says that at 55 amps, you can crank the car (as jump start). At 10 amps, you can charge the battery in 3-5 hours (same time range autozone usually told me when I bring them my dead battery. At 2 amps, it is trickle charge.
10/2/55 Amp, 6/12 Volt Battery Charger/Engine Starter

This is the one I use after too many dead car and motorcycle batteries. My 911 kills the battery in a month. I think it's the stereo installed in the car. This keeps the 3 bikes and 911 topped up.http://forums.pelicanparts.com/uploa...1333201338.jpg