LIPO storage: 3.7 Volts?

[JIM MARCUM]

Where is a good thread on storing LIPOs properly? Just read a thread stating storing a LIPO fully charged will degrade at max amp output. i.e, storing a 40C fully charged will degrade them down to <20C. Fact or fiction? If that's true, I've got a lot of LIPOs to discharge JIM

[Stinger9D9]

I've heard the same thing too, don't really have any backup on it, but I guess it sounds reasonable. I always left mine topped up...and some of my older packs have noticeably lost their punch, but you could probably just chalk that up to them being cheapo packs are a year or so too old.

It sure is nice to have the packs ready when I have time to run to the pond though (without waiting to charge them up on the day). It makes a spontaneous fun run a lot easier, and sometimes, I just don't have much time to go play around a bit.

That said, anything to get more life out of my packs is welcome. I don't race and I don't have the budget to swap out all my packs for new ones each year.

[lectriglide]

Jim - here's a good discussion. Stored fully charged, the IR internal resistance of the battery increases, which effectively lowers the output available resulting in a lower "c" rating if you will. Good thread.

http://www.rcgroups.com/forums/showthread.php?t=1477091

[Remmie81]

From what I have read on the internet about lipo storage im not getting hard answers.
There is a lot of same information copied to different communities without hard facts.

Lets say someone points out that his lipo that was always stored fully charged, after a year doesnt supply the power it used to have.
I dont see the brand, the type, and how he used it. I mean you cant compare the use of a lipo in the boats we have and an airplane.
There are just to many variables. Even the batch were the battery pack came from could be a bad batch of batteries.
Or was the C rating of the pack just on the limit of your use? How many cycles has the pack already on it?

In our boats we are pushing our packs and they are giving the power we want and we like it. We all want to go as fast as possible, otherwise we would be driving the tugboats with Pb batteries.
I think the most important thing to enjoy the most out of your lipos is that your setup is correctly and you dont discharge them to far.
Everything has a life time. They have to be replaced sometime.

I dont have the skills/tools to do though tests, but if I would be able to do that with a pack and could give an answer next year, that will then be for that specific pack that I probably can not buy anymore next year.

I take into account that I have to replace my lipo after a year of use. They are much cheaper then the old style Nimh batteries, have much more punch and I can run longer on them.

Grtz,
Remmie

[785boats]

Jim.
Just about every article you read about Lipos will state not to store them fully charged. It's sort of a universal rule from users & manufacturers alike.
It's exactly as lectriglide stated in his post. The longer a pack is in a fully charged state, the higher the rate of degradation & increased internal resistance.
But 3.8V - 3.9V/cell is more the accepted storage which is around 50% capacity. That's why most chargers have a 'Storage Mode' setting of 3.85 V. And that's the voltage that most manufacturers store & ship their packs.

Remmie.
You shouldn't have to replace your packs every year if you treat them correctly. We have guys in our club still racing with packs 3 years old.

Here's another article about the treatment & care of Lipo's. You guys may have read it already but it's worth absorbing the info for a better understanding on Lipo batteries.

https://sites.google.com/site/tjinguytech/charging-how-tos

[Fluid]

3.7 volts is too low, that's almost fully discharged. To me the "authority" is the LiPo pack assembler. All major LiPo brands I've used specifically say in the pack instructions to store the pack between 3.85 and 3.96 volts per cell. One reason is the potential for cell damage if stored fully charged. The other is safety - the packs have half the energy available. I store at ~3.85 volts per cell.

You shouldn't have to replace your packs every year if you treat them correctly.

I find this is not correct if you are using cheap cells, at least club members have discovered this. I am on my third season on the Hyperion packs in my P race boats, they are still fast (although perhaps ~2 mph slower than when the packs were brand new).



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[LiPo Power]

Most chargers out there will storage charge to 32-35%
So in my opinion this function of any good lipo charger was
design for the proper reason and that is why I always
storage my lipos using this function. Also, storage charge will
balance your cells properly.

[Fluid]

Most chargers out there will storage charge to 32-35%.

What? I have no idea where the poster came up with this "fact". Two of the more popular top-end chargers from LiPo battery suppliers say this:

Hyperion DUO: STORE MODE for LiPo, LiFe, and LiIo allows fast and simple charge/discharge to 60%~70% capacity for proper storage of Lithium Batteries = long battery life.

ThunderPower 1430: Storage Mode. In the case of LiPo/LiIon batteries, the charger will automatically charge or discharge the battery to approximately 3.85V per cell.



Don't believe everything you read in forums....well-meaning or not.



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[LiPo Power]

The poster was just reading the EOS display after storage charging 4S lipo ( see picture )
Also, 3.85V on 4S IMO is close to 50% of the lipo capacity..... ( Thunder Power 1430 )
From what I see not all the chargers are set to 60-70% storage charge, well the 1430 isn't...
Just because one quoted top popular charger do 60-70% storage charge does not mean it's the golden template or ,,fact,, for storage.
There are few more chargers other than 2 quoted above available on the market, so there is no solid standard since the setting on each for storage may be diferent.
I do get new batteries charged by manufacturers to little over 50%....
I think if someone would like to storage lipos at 50-70% that is no problem... Not to me anyways....

Cool quote from RC groups:

I fly timed flights, to leave 20% in my packs. I don't bother charging them up to storage after flights because my interpretation of the "rules" about storage charge is that less % is better for storage -- 50% is the oft-quoted figure for long life, but it's a compromise between storing them too full, and running the risk of them self-discharging below a safe voltage. Manufacturers ship at 50% because they don't know how long the pack is going to be stored before use, so they have to be on the safe side with respect to self-discharge.

Good read here:

http://www.rchelicopterfun.com/rc-lipo-batteries.html

http://www.rctech.net/forum/radio-electronics/443091-lipo-storage-mode-question.html

...and so on...

What? I have no idea where the poster came up with this "fact". Two of the more popular top-end chargers from LiPo battery suppliers say this:

Hyperion DUO: STORE MODE for LiPo, LiFe, and LiIo allows fast and simple charge/discharge to 60%~70% capacity for proper storage of Lithium Batteries = long battery life.

ThunderPower 1430: Storage Mode. In the case of LiPo/LiIon batteries, the charger will automatically charge or discharge the battery to approximately 3.85V per cell.



Don't believe everything you read in forums....well-meaning or not.



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