Recently, I ran across some good information on battery charging. This is good beneficial info so, I thought I would pass it along to you.

The heart of any R/C system, no matter how sophisticated, is the batteries. If they are rechargeable ni-cd type batteries, there are some basics to know about charging to insure dependable and long life. Since battery failure causes most of the crashes that occur due to radio failure it is important that this information be known by any R/C'er.

When charging ni-cd batteries, we are concerned about the charge rate, or the amount of electrical energy flow (current) that is going into the batteries while being charged. This amount of energy flow, the charge rate, is measured in milliampers (ma). Fixed rate chargers are set up to provide a constant rate for a given voltage pack; i.e. 50 ma at 4.8 volts. If a higher voltage pack is charged with this charger, less current will be provided. Variable rate chargers provide adjustment to set the desired charging rate. As long as the charger is capable, the voltage of the pack being charged is not a factor because the rate can be adjusted as need- ed. (NOTE) Ni-Cds are always charged in series, never in parallel.

There are four different charge rates for ni-cds: overnight, quick, fast and trickle. Let's take them one at a time.

OVERNIGHT: When charger at the overnight rate, discharged ni-cds will reach 100% of charge in 14-16 hours. This rate is determined by the formula C/10, or the rated capacity of the batteries divided by 10. So, if we are charging 500 milliampere hour (mah) batteries at the overnight rate, the rate would be 50 ma. For 900 mah cells it would be 90 ma; 1200 mah, 120 ma; etc. this rate is the most commonly used in R/C. It is also the safest because ni-cd batteries can be left on charge at this rate for extended periods (days, even weeks) without damage. We are talking ni-cd batteries only, not lead-acid.

QUICK: Discharged batteries charges at the Quick Rate will reach full charge in 4-6 hours. This is determined by the formula C/3, or the battery capacity divided by 3. For 500 mah batteries it would be 166 am; 900 mah would be 300 ma; 1200 mah, 400 ma; etc. It is not recommended that the batteries be left on beyond the 6 hour period or overcharge might result. Most ni-cd used in modern radios will accept a quick charge but, it is not recommended to quick charge the cells on a routine basis because it can degrade the life of the battery.

FAST: The Fast Rate will charge ni-cds in 15 minutes or less. This is determined by the formula 3C or three times the capacity of the battery. For 500 mah batteries, it would be 1500 ma or 1.5 amps. Most ni-cds used today will accept a fast charge but, it is not recommended for R/C receiver and transmitter batteries because the charge time is very critical to prevent overcharge and damage. Only specialized chargers for fast charging should be used.

TRICKLE: The Trickle (or float) rate replaces the energy that ni-cds lose through shelf life. It is defined by C/50; for 500 mah batteries, it would be 10 ma; for 1200 mah, 24 ma; etc. Ni-cds can be left on trickle indefinitely without damage and always be 100% charged. Realize that the batteries can't be charged up at this rate, only maintained. If you use the Trickle Rate, do so only after the batteries have been fully charged. Preferably at the Overnight rate.

If you wish to measure the charge rate so you know what is going on when the batteries are being charged, it is necessary to have an ammeter capable of measuring 150 ma or so. A small, inexpensive Radio Shack multimeter is fine. You need to hook it in the charge circuit so that it is in series; i.e., the current flows through the meter. A suggested procedure is illustrated to perform this task. Always be careful not to short the batteries or charger out or damage can result! Also, when dealing with batteries, always maintain the proper polarity.

	To sum it up: (Where C = battery capacity) 
	Overnight charge = C/10 
	Quick charge = C/3 
	Fast charge = 3C 
	Trickle charge = C/50 

Note: Thanks ACE RIC for the above information.