When is a storage charge required?

[Jason Hyland]

OK, so I know I should bring my LIPO's to a storage charge, but my question is when? So, my 4S has about 4v per cell currently after a flight, and I probably won't need it for a couple of weeks - should I take it down to 3.8v per cell or is that just a wasted discharge ( please, dont )?

[Former Member]

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[Jason Hyland]

Posted by Percy Verance on 08/05/2016 16:20:31:

I wonder if shops take lipos down to their correct storage charge, or do they just stack them on the shelf until sold?

My very limited experience with quad lipos is they all arrive at storage charge.

[Former Member]

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[Geoff S]

All the LiPos I get from HK arrive with a storage charge. However, I never storage charge my LiPos. Perhaps I should but I leave them fully charged ready to fly when the weather's suitable.

Geoff

[Former Member]

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[Capt Kremen]

Last year due personal circumstances and not least rubbish weather co-inciding with the rare times I was able to fly, my LiPo remained untouched but in a fully charged state.

This year, I expected a lot of 'duff' packs and expense buying replacements before I flew.

'Touch-wood' etc ... I've made best use of the good weather days and opportunities to fly.

So far, no apparent issues.

OK, I'm not flying many high current EDF or other pack straining types of model which might put the packs to ultimate test but they are giving me the same flight times and performance as in previous years,

I date my packs and some are now 5 years old and still giving good service.

In previous years, I always 'storage charged' packs, balanced and generally gave them the utmost attention.

Without doing anything 'silly' and keeping to the prudent safety practices of use, for a 'general sport flier' such as i consider myself, it seems LiPo are quite forgiving of being 'forgotton' for a while!

[KiwiKid]

Yes, you can get away with it if you are not flying high drain systems and the batteries are of reasonable quality. I am still flying 7 year old Hyperion lipos in a couple of gliders.

However, it is good practice to discharge batteries down to storage levels (particularly large expensive ones) to prolong their efficient lifespan.Borrowed the below from another site:

"LiPos lose about 20% of their charge capacity per year when stored at room temperature with a full charge. When capacity is lost IR goes up as well since it effectively makes the battery smaller. "They lose about 5% per year when stored with a charge 50% or less at room temperature. That 5% can be reduced a couple percent by storing in a refrigerator. Though it's not a good idea to store them any colder than that. It actually degrades the electrolyte when temperatures are below the freezing point of water. The electrolyte itself doesn't freeze until about -20F. "Batteries typically ship with a 40% charge from the factory (3.80V per cell), though sometimes you see them with a 50% charge (3.85V per cell). It's been found that a charge level of 30% is ideal for minimizing risk of fire during storage or transport (3.75V per cell). Carriers may be requiring that level of charge for transport in the future. It does not reduce shelf life wear a lot, but it is a little lower at 30% compared 50% SOC (state of charge). Personally I store my batteries at 30% SOC for safety reasons. "If you look at the daily cost of storing batteries at full charge you can evaluate the penalty. On a daily basis it's going to be 20%/365 versus 5%/365. If I want to store with a full charge a couple days it's not too much of a hit in shelf life wear. Though I usually won't go as long as a week."

[Cuban8]

If you can remember to install a storage charge then that's fine. I've never bothered myself and have several lipos that are still perfectly adequate after six years of regular use in a 500 heli.

I wouldn't lose sleep over it if you forget or can't be bothered to faff about. Use them well within their capability, balance charge regularly and limit charging rates to 1.5 or 2C (check specifications though).

Might be luck, but I've never ever lost a cell in a pack and those that I've got rid of were simply worn out after prolonged use.

Edited By Cuban8 on 09/05/2016 08:38:36

[Allan Bennett]

I work on the basis that the less charge there is in the battery the safer it is -- subject of course to the charge not being so low that it will self-discharge itself below a safe value before you look at it again.

So at the end of a flying day I do nothing to my used packs since they'll be at anything between 20% and 30% charged; and I storage-discharge any packs that I didn't use, so that they're down to 50%.

Edited By Allan Bennett on 09/05/2016 08:35:16

[The Wright Stuff]

Posted by Allan Bennett on 09/05/2016 08:34:38:

I work on the basis that the less charge there is in the battery the safer it is -- subject of course to the charge not being so low that it will self-discharge itself below a safe value before you look at it again.

So at the end of a flying day I do nothing to my used packs since they'll be at anything between 20% and 30% charged; and I storage-discharge any packs that I didn't use, so that they're down to 50%.

Edited By Allan Bennett on 09/05/2016 08:35:16

Absolutely, I do exactly the same as Allan. I only bother about storing them exactly at storage charge over long winter lay offs...