Finally, on the batteries we use in the airplane, car, portable radio, GPS, cell phones, etc., we want the hottest (most powerful) battery available. But, there is no reason to go overboard , pay more money than necessary, if you have unnecessary capacity that you don't use.
You airplane / car / mower/ motorcycle/ etc. battery will be rated in CCA (cold cranking amps). That indicates how many amps the battery can deliver for 30 seconds in 0 degree F temp before the voltage drops to 7.4 volts. Rule of thumb is 1 CCA for each cubic inch displacement of the engine. More is generally better but no need to pay double for twice as much as you need. The benefit of excessive CCA in our airplane is there will be more reserve capacity if the alternator quits and possibly the excess capacity will keep the electronic ignition working to the nearest airport or with magnetos keep our radio or flat screens running to a safe landing.
Smaller cells / battery packs are generally rated in MaH (Milli-amp hour = 1/1000 amp) or amp hours or they seem to be going to watts on newer batteries. With these cells / packs more is almost always better unless the price is outrageous. A/AA/AAA/ nickel metal and the smaller lithium type cells will always list MaH as in 1.2 volts / 800 mah or on lithium 3.6v / 2800 mah or on some drill packs they may list in amps, 2.0 , 3.0 etc. 18 volt 2.5 amp. Those listing watts is still and indication of power (P=IxE ), power in watts = volts X amps) and you can compare one to the other. An 18 volt X 2.0 amps would be 2000 mah and an 18 volt pack rated at 36 watts (watts / volts) would equal 2 amps or 2000 mah.
One example of more is not always needed is a customer bringing in AA battery packs used in emergency lights that are rated at 500 mah for me to rebuild. I can rebuild with 800 mah cells and the customer is getting a pack with 50% more energy that when the lights were installed years ago. There is no reason for me to rebuild the packs with 2700 mah cells and cost the customer several times more than necessary. Understanding how batteries and cells are rated lets you decide what your needs are and spend accordingly. With you buns on the seat at 5000 feet, more is almost always better.
Larry Flesner -- KRnet mailing list KRnet@list.krnet.org https://list.krnet.org/mailman/listinfo/krnet
