Minutes or mah (milliamp hours) By James Goss      When you are cycling your batteries most cyclers will allow you to select the results to be stated in minutes or either mah (milliamp hours). This may be confusing to some new pilots in our hobby so I thought I would give you a little background on the subject. Both mah and minutes will tell you what you want to know about your battery pack's condition. You are trying to find out how much energy your battery will store so you will know how long to expect the battery to last during a day at the field. For example, if you have a 600-milliamp battery and it is fully charged when you place it on the cycler and it takes 120 minutes to discharge down to the point where your cycler starts to charge the battery again, then you can expect to get 120 minutes of actual work from the battery.      You have got to remember that the cycler is discharging at the rate you have selected, this may be 50 milliamps or it could be 250 milliamps or any value your cycler will allow. I like to use 250 milliamps on all packs less than 1200 milliamps. 250 milliamps is a good reference because this is about what an average transmitter draws in current. Some PCM radios will pull a little more, but by and large 250 is a good value to use. With this in mind lets say you have cycled your 600 mah flight pack and it shows 120 minutes of time required to discharge the battery to the point where it drops below 4.8 volts. This is what happens when the battery uses up its stored energy, its rated voltage starts to decrease. With nicads the voltage drops very fast when this point is reached. How long you actually have to fly on this battery depends on the actual load on the battery, and that load may be greater that 250 milliamps. So you may not have the full 120 minutes of flight time even though the cycler said you have 120 minutes.  Under some conditions you may only get 60 minutes instead of the 120 you expected. So using minutes is good if you have the same discharge rate on your cycler as you will have in an actual flight, but this is not likely. Your flight discharge rate for the flight pack is constantly changing as your plane goes through its many maneuvers.      Milliamp hours is a little more confusing than minutes, we all understand time so this is why the manufacturer has the discharge rated in minutes or mah. Even I know that there is 60 minutes in one hour. A lot of modelers find it easier to read the discharge in minutes and there is nothing wrong with this. It doesn't have to be 100% anyway. For the more technical minded people the mah rating will tell you the whole story about your battery and it is very accurate. The term mah gets its name because it is current referenced to time. If you have a 1200 mah battery, you should be able to get a current flow of 1200 milliamps (1.2 amps) for a time of one hour before the battery's terminal voltage starts to drop. This same battery should also furnish 100 milliamps for 12 hours, or 600 ma for two hours, or any combination of milliamps and hours that equal 1200 mah. Since your battery is rated in mah and not minutes, this is the only logical unit of measurement to use. Having the same unit rating means you can look at the battery rating and compare it to the cycled mah value. A new battery's cycled value should be equal to or greater than the battery rating.      There is a relationship between minute's discharge and mah discharge. It is easy to understand if you look at it this way. Lets say you have a discharge of 120 minutes and you were using a discharge value of 250 ma. This means that 250 ma were flowing through a load resistance for 120 minutes. To convert this to mah simply change the 120 minutes to hours, 2 hours, so we have 250 ma flowing for 2 hours. Now multiply the 250 ma times two hours to get 500 mah. Both minutes and mah are useful, but I think I like mah better because the battery is rated in mah. Minutes will work ok especially if you have a good record of the cycle time on a battery and you notice a sudden fall off in discharge time, this flags you that something is wrong. Cycling is a good way to spot a trouble in advance of total failure, but you must cycle on a regular basis if you want it to work for you.