Taken from the Hangtimes.com web site. Great info, great batteries.
Q: What's up with 'Formation Charging'? Can't I just charge and fly a new pack?
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A: The term 'Formation Charging'describes the initial charge/discharge 'forming'process that fully activates the 'chemical engine' and balances the cells in a new pack. NiMH packs have a particular need for repetitive c/10 charge/cycle conditioning, a 'break-in' procedureneeded to get them to full rated capacity.Both NiMH and Nicad packs benefit from the process and the intent is to make sure that any new pack has been verified to be fully operational and that a 'start-up' capacity number is established for the pack before it's put into service. To 'Form' a new NiMH packdo three10% 16-24 hour charges followed by a 300 to 500 ma discharge routine between each charge.In other words
oa slow charge at the slow charge rate (or as close to it as you can reasonably get with your equipment) as shown on the pack label. Charge till the pack is warm, followed by a controlled discharge with a cycler. Do it 3 times. The recommended Formation Charge/ Slow Charge rate for our packs is printed right on the label of the pack as well as on the data card the pack was shipped with. New Nicad packs should get at least oneslow charge followed by a 300 to 500ma discharge.Record the capacity numbers reported by your equipment for comparison cycling as the pack ages. Never check your brain at the door! As one respected modelerput it, "There's nothing more suspect than anew battery pack." Before you fly anybody'spack be certain it's fully operational and safe to fly.
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Q: How do I know if my pack is fully charged?
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Temperature is the key.. always, always, always! IF THE PACKAIN'T WARM AT THE END OF THE CHARGE ROUTINE, IT AIN'T CHARGED! NoteI said 'warm'. Not HOT! Hot is NEVER GOOD at the end of the charge routine.. but warm is OK. If using a temp probe, set it for 10 degrees above AMBIENT. If it's a peak controlled charger and the charger shuts down before the pack is slightly warm to the touch.. IT AIN'T FULLY CHARGED. If it's a timer controlled charger and at the end of the charge period the pack is not warm.. it's NOT fully charged yet! By far and away the biggest reason for low capacity numbers is undercharging.. if you have a 5 gallon pail with only 3 gallons in it, your only gonna get 3 gallons out of it. Engage your brain.. check temperature at the end of the charge routine!
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Q: Temperature??I thought voltage washow you could tell the pack was charged??
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A: More packs have been fried by guys looking for a 'number' instead of temperature on a chargerthan any other causeof premature battery failure. The 'finish' voltage of a pack will vary under an astounding number of variables.. but temperature rise ALWAYS signalsthat the cells arechargedin a slow charge routine.Why? Because when the cells can no longer absorb the energy being shoved at them by the charger, they begin to give the unstored energy off as heat.
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Taking the Temperature story to the next level.. fast charging. Here we can generate even more heat. Some high-impedance cells like AA NiMH's can get warm when being charged at 'normal' 1C (fast)or even 10% (slow) rates. They can get warm BEFORE they get to full charge.Why? Because high-impedance cells don't absorb energy as efficiently at high current levels.. just like they don't give up energy efficiently at higher discharge rates. So.. before you crank up the current on your charger on your new NiMHTxpack.. check the pack label on our packs.. and set the charge rate recommended; which is often LESS than the 'industry standard' forNiMH cells.
Finalword on temperature: Aside from being a key indicator for correct charge time, rate and final charge condition bear in mind that heat is the bitter enemy of NiMH Cells. Drive the pack into thermal overload (hot) on the charger andit's likely you'll ruin it. Pay attention to the temperature!