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.



Discharge level:
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.

Handling :
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.

Cheap chargers :
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.

http://www.rcgroups.com/forums/showp...19&postcount=1

Break-in:

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.

http://www.rcgroups.com/forums/showp...1&postcount=10

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.



Added:2-26-2012

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.

Charles

Well said Charles.

Glen

Lines up with my beliefs pretty much perfectly.

Normally the battery storage at 40%capacity,however I 've received some batteries from hobbyking-1cell batteries -Turnigy 3,7V-160Mah and from China 3,7V-180mha which are both being storaged at 3,95V???

I agree with what you are saying Charles. For long term storage I have been using 3.7V/cell.

Question, would the 3.85V/cell apply for newer lipo's or for older lipo's as well (I put that not too well, I ment is there a difference in storage voltage for 10C-20C capable lipo's vs 25C and above?)

Michael.

This ought to be a sticky!

Originally Posted by bladefan

This ought to be a sticky!

Yes, but if it was nobody would read it. This info is pretty much covered in the existing stickies and it seems you have to drag newcomers there, kicking and screaming, to get them to read them.

Glen

I just got rid of a couple lipos and they seemed to charge ok but in the first place they were slightly puffy. second while the full charge was nearly 4.2 the performance was terrible and I time my flights and at the end of the flight the battery was discharged a little more than usual ..some guys will use them ..I figured given the number of cycles and overasll condition it was a safe bet they needed to go.some of flying buddies laugh at me cause I time my flights.at any rate I decided to drown them in salt water which is good inasmuchas I dont need all that sodium in my diet.

everyday are you saying you can charge a good lipo at higher than a 1c?? they dont necessarily need to be fast charge batteries.??can you clearthat up for me..

I have fast charged nimh and nicads but the chemistry was different.the reason I ask is that I am going to replace much of my inventory and purchase fast charge type lipos like the g3 hyperions and nano techs. whats your best advice?

Standard 1C charge rate has been around ever since the days of 3C discharge rate Lipolys.

When FMA first introduced the CelPro 4 around 6 or 7 years ago it had the option to set Auto C rate charges of 1,2 or 3C. Many used these to charge 6-15C LiPoly at Auto 3C rates for years and years now and I have not read of any isuues doing so in the past 5 or 6 years. Now the Cell Pro 4(and other FMA chargers set to Auto) will refuse to charge a cell which has very high internal resistence at a high rate.

I have charged Thunder Power Pro lites 13C dsc. rate at 3C for over 5 years. I have charged Hyperion 25 and 35C G3 Lipolys at 5c for over two years and some of the Thunder Power Pro Power series at between 5 and 10C for close to a year.

So what is a good summary? I feel that cells with low internal resistence have no problems being charged at greater than 1C. I feel that any 15C should be fine at 2C charge rates and that 20 C and above should be fine with 3C. This is assuming that a decent balancing charger is used and that the LiPolys are first charged at 1C and that charges are increased gradually and observed for any signs of problems.

Note there is at least on vendor who insist that their LiPolys not be charged at greater than 1C for the first 10 chceged even thought they rate them at up to 8C charge and 65C discharge.

There is another Vendor who says that this whole break-in business is BS and their's can be charged and discharged at the maxes. from the get go.

I tested some LiPolys for on vendor and he clearly stated not to charge at greater tan 3C. Well I charged them at 5C and 200 cycles latter they are stil doing great. Hint, some vendors do not know the products they sell.