Winter storage- lipos

[Frank v B]

Could someone please post an idiot's guide on "How to store lipo's for winter"... in plain english with words no more difficult than "see Spot run"*.  This is both for new members and old ones like me.

Frank

* that should pretty well eliminate Andy on two counts- he flies in winter and is a walking dictionary.... not containing any simple words.

[mawz]

Discharge to storage voltage - 3.8-3.85V per cell. Most chargers will have a discharge setting to do this. Note if they're already discharged beyond that, you may need to charge first.

Store in a secure, contained storage, preferably fireproof. A BatBox or ammo can is good, or in your lipo bags. If using an ammo can, do make sure it's not airtight. Don't store near flammable items (especially not that half a jug of glow fuel that's been sitting since you discovered the joy of Lipo's)

[bweaver]

The article I always refer to found at https://www.rchelicopterfun.com/lipo-batteries.html, is the most informative I have read on the subject of 'lipos do's and don'ts', including guidance on storage and charging practices. 

I think it is a must read, even you could understand @Frank v B . (Because I can - I think)

[Andy Hoffer]

The article I always refer to found at https://www.rchelicopterfun.com/lipo-batteries.html, is the most informative I have read on the subject of 'lipos do's and don'ts', including guidance on storage and charging practices. 

I think it is a must read, even you could understand @Frank v B . (Because I can - I think)

Excellent article @bweaver .  But I do fear for the impact on @Frank v B due to all the multi-syllable words. 

ANdy

[bweaver]

Re: Excellent article @bweaver .  But I do fear for the impact on @Frank v B due to all the multi-syllable words. 

ANdy

There are pictures in the article too. 

[Andy Hoffer]

Re: Excellent article @bweaver .  But I do fear for the impact on @Frank v B due to all the multi-syllable words. 

ANdy

There are pictures in the article too. 

Whew!!  Thanks @bweaver . I feel much better now!!  I'm sure @Frank v B  will too!! 

Andy

[AlexShao]

Usually, I use the storage mode to charge all the LiPo batteries every month.

[MarcV]

As I understand it, the lower the charge level the better for storage.
I've stored my lipos as low as 5 or 10% (3.7V/cell) over the winter.
The disadvantage of that is that if you have a poor quality lipo, it will self discharge to below 0% over the winter and be damaged.
Or if you don't use that lipo the next summer, it will eventually self discharge to below 0%.

I now store my lipos at the 25% level (3.75V/cell) over the winter.
The lipos that I stored over the winter at 25% and don't use during the summer,still have enough charge to make it through the next winter.

How much better it is for the lipo to be stored at the 25% (3.7V/cell) level compared to the 50% level (3.80 to 3.85V/cell) I don't know.

Marc

[mawz]

As I understand it, the lower the charge level the better for storage.
I've stored my lipos as low as 5 or 10% (3.7V/cell) over the winter.
The disadvantage of that is that if you have a poor quality lipo, it will self discharge to below 0% over the winter and be damaged.
Or if you don't use that lipo the next summer, it will eventually self discharge to below 0%.

I now store my lipos at the 25% level (3.75V/cell) over the winter.
The lipos that I stored over the winter at 25% and don't use during the summer,still have enough charge to make it through the next winter.

How much better it is for the lipo to be stored at the 25% (3.7V/cell) level compared to the 50% level (3.80 to 3.85V/cell) I don't know.

Marc

That's not the case, storing discharged lipo's is just as bad for them as storing fully charged lipos.

You want to as close to 50% charge as possible for a long shelf life. 25% is not terrible for them, but you'll get better results and a longer lifespan at 50%.

[Frank v B]

Hey, @Andy Hoffer,

You can now translate Mawz's simple English instructions into a Websterian masterpiece:

Please translate the following:
Discharge to storage voltage - 3.8-3.85V per cell. Most chargers will have a discharge setting to do this. Note if they're already discharged beyond that, you may need to charge first.

Store in a secure, contained storage, preferably fireproof. A BatBox or ammo can is good, or in your lipo bags. If using an ammo can, do make sure it's not airtight. Don't store near flammable items (especially not that half a jug of glow fuel that's been sitting since you discovered the joy of Lipo's)


Frank

[MarcV]

Adam, do you have the source of information for the 50% storage value?

I got my information from Sony's Lithium Ion Rechargeable Batteries Technical Handbook.  I enclose the relevant section that shows that storing a battery at "0% (3.3V)" is slightly superior then at "50% (3.8V)".

This is also backed up by personal correspondence with Walter Van Schalkwijk Ph.D. (who's written a few books on lithium ion batteries) and is a user of my battery analyzers.

Marc

[mawz]

Marc,

Probably the best source is the following paper.

https://pdfs.semanticscholar.org/3ed3/04146557a1904030e3365dfe5a90527013d8.pdf

That clearly demonstrates the issues with storage at overly high voltages. Lower voltages really don't increase the risk in terms of damage to the battery itself from storage voltage

The real issue with storing at 25% or lower is the risk of a cell failing from self-discharge to overly low levels. The closer you get to cascading cell failure voltage as a starting point, the higher the risk of losing a cell. That's largely why manufacturers ship at 50% charge, it gives the maximum shelf life for the cells without risking damage from storing with overly high charge.

Realistically, for short-term storage (3-6 months maximum), 25% is just fine. 50% simply gives you the headroom to know the battery can be stored long-term without worries, while being a low enough voltage to not run into the well-documented issues with storing fully charged batteries.

I do store my batteries discharged during the flying season (storing between 20 and 50% charge).

Just to be clear, when I say 'storing fully discharged batteries', I'm talking 5% or less of nominal capacity. At that level you are risking damage from the low state of charge even before storing.

[bweaver]

 

[sihinch]

Bruce - not until Thursday!!!

[cpaine]

neat little tip i learned from some ef1 guys at the Nats, once discharged to storage voltage of 3.7v (25-30%?) is to store them in the fridge. im no electrical expert, but the theory is, the cold temps slow down the electrons in the packs... like hibernation so to speak, therefor extending life of the pack....
problem is, they take away room for my beer in my beer fridge!!!