How do car battery chargers work?

OK, so let's talk about car battery charger first. A car battery charger comes in handy in many situations -- and not just involving car. Maybe you have a lawn tractor with a 12V battery that sits all winter long in the shed. Or a boat that sit parked 9 months out of the year? Any motorized device (ATV, lawn mowers, etc) that uses a battery to get it started can end up with a dead battery and in need of a battery charger. Most car battery chargers plug into a regular electrical outlet (say on the wall of your garage) and then connect to the battery terminals via two cables. Some slowly charge the battery while others act like an instant jump start. Some popular models include those made by Black and Decker, like the VEC1095ABD Smart Battery 25/10/2 Amp Battery Charger. This little unit runs about $75. It has to be plugged into an electrical outlet, and you then connect the jumper style clamps to the dead battery (it even warns you if you connect the leads incorrectly and is designed to be spark resistant). There are 3 different charging rates you can choose from (2/10/25 amps), but for car batteries, you can usually get enough charge within just 1-3 minutes to be able to start the car (a complete charge can take up to 2.5 hours). A few other companies make similar chargers, but to be honest we've been so satisfied with the B&D brand (and have heard almost unanimous good reports in our research) that we recommend you just go with a Black and Decker model. You can expect to pay from $35 to $130 depending on the model you pick (see all Black and Decker models here). If you want to look at other models, try Sears and the DieHard brand they sell - we've seen battery chargers there for about $45 to $65. The Black and Decker Simple Start 12V Battery Booster is another pretty cool product. It works like a portable spare battery in your glove box or under your seat. It plugs into your cigarette lighter and charges your car battery in about 10-20 minutes (a light will come on to tell you when it is ready) - no need to open the hood or use jumper cables. It can also be used to power devices like cellphones and laptops -- you'll just need to plug it back in at home to recharge IT once it gets drained.