battery storage: how long?

[Crunchy409]

I was wondering if it is ok to, say, fully charge a batter at noon one day and use it around noon the next. Is that too long to leave a battery fully charged?

thanks

[r40734]

I'll leave mine fully charged for more than two weeks sometimes and have never had a problem. At the most, they bleed off a couple tenths of a volt. Leaving them fully charged over night is perfectly acceptable.

[Pinecone]

I will leave my packs fully charged up to 2 - 3 weeks. Over night is fine.

[redgiki]

Permanent loss of capacity at room temperature (70 degrees F) is 20-40% per year if the pack is fully-charged. At normal storage voltage, LiPos lose 1/10 of that amount. Worst-case, you're losing 0.77% capacity per week keeping it fully charged, or 0.11% capacity per day.

What's that in real-world numbers? Let's assume you have a 2200mAh 3S LiPo. Storing it fully-charged for 24 hours at 70 degrees equals a maximum of 2.42mAh per day capacity loss as a result. If it's colder, it's less than that; if it's warmer, it can be much more.

You'll occasionally hear stories about people leaving a pack fully-charged for a week or two and it comes back "gutless"... what they leave out is that usually that pack was also left in a hot garage, which dramatically accelerated the separator degradation which is at the heart of LiPo capacity loss. If we assume that twenty degrees warmer doubles the speed of separator failure, then you could lose upwards of 70mAh capacity on a 2200mAh LiPo by storing it in a hot garage fully-charged for two weeks.

Moral of the story: Yeah, go ahead and charge your LiPos the night before you're going flying. If it turns out to be several days, pop the fully-charged batteries in the freezer and defrost them the night before you plan to fly.

[bonmot]

Then for long term (1 year) storage, what voltage should it be?

[redgiki]

http://www.batteryuniversity.com/partone-19.htm

3.75-3.8v/cell, stored at around 32F (0C) is ideal for long-term storage with minimal loss of battery life.