Charging a Parked Car's Battery, with the Engine Off!
Before starting the charging cycle on your batteries, please read the battery manual and follow the manufacturer's instructions for their batteries. Next familiarize yourself with the operations manual for your particular battery charger. Finally go over the safety section for your own sake. Attorneys satisfied, it is time to get busy charging that battery...
Check the battery terminals, posts, lugs, and connections in general. Make sure the connections are solid, and clean enough to contact the charger clamps. IF the battery terminals are beyond reproach, just replace the battery.
If the terminals are good, bring out the battery charger, and place it in a safe, stable location. Ensure you have adequate AC cord to make the power outlet on the wall, and DC cabling to reach the battery without a fight. Make sure to move
cords away from any pulleys, belts, fan blades and other moving parts under the hood of
the vehicle. Leaning on a fan belt is a bad way to cut a battery charger cable...
Assuming a Negatively Grounded Vehicle - Negative to Chassis
(Battery Charger connection configuration should be...)
* Connect the negative battery charger clamp (black clamp) to a good grounding area on the
engine. Do not connect the battery charger to any vehicle fuel line as it may lead to a quick fire. Do not connect this clamp to any sheet metal or body panel. The body panels and sheet metal can fail during the charge as they may not be fully grounded, the amount of electricity can melt the panel, or the current can damage the paint.
* Connect the positive battery charger clamp (red) to the positive battery terminal.
* Connect the AC cord to the wall socket.
* An alarm, indication light, or beep from the battery charger will indicate a battery is connected
in reverse polarity on higher end battery chargers. Lesser chargers may not operate at all, or fail when connected in a reverse configuration.
* When disconnecting the charger, make sure to disconnect the AC cord from the wall first. Then remove the battery charger's clamp from the battery terminal. Finally, remove
the charger clamp from the vehicle chassis and move any leftover tools from under the hood.
Determining the Positive and Negative Terminals on your battery.
If you can not determine the positive and negative posts with the markings of the battery itself, there is another method. The positive terminal or post should be a bit larger diameter then the negative terminal post. When making this assumption (larger post is positive), do check with a voltmeter prior to hooking up the charger to avoid inverted wiring. Another method for determining positive and negative is the grounded chassis, and general lack of resistance to test with. Since most vehicle applications have the negative battery post connected to the chassis via thick ground straps, "grounding" the frame, there will be very little resistance between the frame and the negative terminal on the battery. Any voltmeter will be able to test for this continuity.
Battery Charger Warnings:
Always read and follow the manufacturer's battery charging instructions prior to
connecting your battery, or trying to charge a battery bank. Do not attempt to charge batteries
in a confined environment. Explosive and hazardous gases are an inherent byproduct of
battery charging, do think ahead. Batteries contain sulphuric acid, and lead, both of which are hazardous material if removed from the battery, or disposed of improperly, do take care to be
environmentally responsible. Batteries are useful, just be safe.