Originally Posted by jnidd

Thanks guys. I had been a car racer for over 25 years before I quit. When I came back to the hobby I thought I would get into electric flight (I did fly nitro planes in the past)as I thought it was an easy transition. Getting used to Lipo batteries and hearing all the stories about fires and puffy packs has got me to read everything I can. While I agree with alot of the statements both PRO and Con I have to thank everyone for letting me know your views.

Now I am off to fly

Jeff

Originally Posted by OLD PRAIRIE RED NECK

My conclusions:
1: Stored batteries gradually loose their charge with time so the higher the charge when they are put away the longer it will be before they drop in voltage to below critical levels.

Originally Posted by Max

Sorry guys. I have to disagree with you 100%.
For the sake of the beginners reading this thread, I insist on providing an opposing view lest some of them believe you can leave fully charged batteries over the winter and expect them to perform well next season. THEY WILL NOT.

I have learned my lesson the hard way over years of electric flying. I did have a lot of packs go bad on me in the beginning because i left them charged for prolonged periods (usually over the winter) and many of them puffed.

I also have learned that fully charged batteries stored over prolonged periods suffer internal changes to chemistry that affect the batteries Internal Resistance (IR). This is when a battery is more likely to puff- If you fly it the same next year as you did last year, applying the same amount of load (current) as you did last year to the same battery, the higher IR of the battery effectively reduces your C rating.

For example: lets say last year you flew a 40C battery with no issues. Back then you were applying 30C on a 40 C battery. Next year, because you left your battery fully charged over the winter, the IR will increase and the true C rating will drop to 20C (there is a formula that allows you to calculate true C based on a batteies IR) After one or 2 flights, you battery will puff because you are still flying it on the same plane and style that used to put 30 C load on the battery, but it is now perfoming as a 20 C battery.

My advice: I STRONGLY recommend all batteries be discarged to storage voltage if you are not planning on using them for longer than 2 weeks (especiall during winter hibernation)

Originally Posted by OLD PRAIRIE RED NECK

Two weekends ago I pulled out 6 packs that have been in storage for about a year and a half. Four of them were put away fully charged as is my present habit. The other two were as they came out of the aircraft.
The fully charged ones checked out between 70 and 85% charge while the discharged ones were between 50 and 60%. That is the individual cell levels not as a pack. Note: none of them were puffed.

All were balance charged and used that weekend with no discernable difference in performance. None of them went puffy with use either.

These packs are Great Hobbies brand that I bought about 7 years ago and have been used a lot over the ensuing years. I have never given them any special attention nor have I ever used or charged them hard enough to get them any more than just barely warm.

My conclusions:
1: Stored batteries gradually loose their charge with time so the higher the charge when they are put away the longer it will be before they drop in voltage to below critical levels.
2: Respecting charge/discharge rates is far more important to battery life than storage voltage.
3: If there is a deterioration of capacity when not stored at "storage voltage" it is small enough to require a laboratory style study to determine how much.

Maybe I have good quality batteries? Maybe I'm just lucky? Don't know but it has worked for me for 7 years.

Use or discard my experience as you like.

Merv

Originally Posted by williame3590

Basically identical to my habits Merv. Same conclusions.

Bill