Proper (?) LiPoly management.
So this subject comes up often and I wrote this post on another User's group over a year ago.
Note close to 3 year ago now. 2-26-12
The following are my opinions and have worked for myself and many others.
Proper storage :
Approx. 3.85 volts per cell in a cool location. IMO with today's fast charge capable LiPolys and high rate capable chargers there is little sense in leaving LiPolys charged just in case the weather turns nice.
I have used 80% depth of discharge as my standard for years and it works extremely well. There is mounting evidence that the latest high quality LiPolys can endure deeper discharges much better than prior ones but testing is still limited.
LiPolys are fragile. I have been called crazy for suggesting the be handled like an unboiled egg or fine china. Every crease,bing,bump,etc. creates a pressure point which leads to accelerated salt crystals growth.
My advise is not to use them. An accurate high quality charger / balancer will extend the life of your LiPolys and in conjunction with high quality fast charge (3-6C) capable LiPolys will reduce the number of batteries you need,make LiPoly management much simpler and greatly increase your flying time and enjoyment.
High C rate charging:
I have charged at 3C and higher for close to 4 years now. I have proven to myself that quality LiPolys charged and balanced on quality equipment does not adversely reduce their life. I am currently charging at 5C and replacing over 80% capacity in under 15 minutes on many of my LiPolys.
<Added> I keep reading post that charging at greater than 1C reduces life and that the slower charges are always best. I am not going to do extended cycle testing at 1C charge rates but all the proof I need that 5c charging with high quality LiPolys and eauipment is not damaging is right here.
I start with 1C charges and moderate max. loads.I try and stay under 60% of claimed max. cont. C rating and keep flight times short to insure not exceeding 80% capacity used.
Example A 20C 2200 is rated for 44 amps. cont . but I would stay under 26A (12C) average. Short burst to 35-40 amp. are fine but the practice of charging a new LiPoly and then seeing how much power it has does a new LiPoly no good.
Added 5-4-12: As noted above I charage at multi C rates routinely however:
I work up to this on a gradual basis.First charge is at 1C perhaps even two at 1C depending on the LiPoly and charger used. Observe the cell's balance and do not charge faster if they are drifting about much.
Next up is 2 or 3 2C charges then a 2 or 3 C rate ones. Once the LiPoly has 10 to 15 charges I have worked up to 5C (for so rated LiPolys) and from then on I charge based on how fast(soon) I will need it charged again.
Post here with fairly detailed charge and discharge cycles working up to 5C charge rate.
First sign of a LiPoly going south.
Most often the first signs of a LiPoly starting to go down hill will be cells not staying balanced as well,more time being taken in the CV stage of charging / balancing.
If the battery is marginal to begin with you could also notice a decline in power but often this is so gradual that it is not noticed until it gets really bad or you happen to fly a newer / better battery.
Efficient use of charging time:
This example based on charging 3S3300 at 12.5A (3.78C) and while not linear are representative of other rates. Each person will have to conduct their own equalization as chargers/balancers and LiPolys will vary.
Total charge time 18 min. capacity replaced 2896 for an average of 160.9 mAh per min..
During the first 12:30 while rate was holding at 12.5A
2600 mAh for an average of 208 mAh per minute.
Between 12:30 and 14 min . 200 mAh or 133.3 mAh per minute.
First 12:30 or 69.4% of total time 2600 mAh or 89.8% of capacity achieved.
C rate in simple terms
OK now C in simple terms.
C rate as used by most is C apacity in Ah times a number.
A 2200 mAh LiPoly is 2.2 Ah as 2200 mAh / 1,000 mAh = 2.2 Ah.
A 1C charge rate is the A rate required to fully charge the battery in one hour.
2.2 Ah to be replaced in 1 hour equals a 2.2A charge rate.
Greater than 1C
If discharged at 10C then 2.2A X 10 = 22Amps.
also 60 min . / 10 = 6 minute fligjht.
If Charged at 3C then 3 X 2.2A = 6.6 Amps.