Charging LiPo's for storage

[RC104ever]

So for sure it's the voltage you want to keep down, not the mAh?

To me the voltage seems like the zap. The punch. Whereas the mAh is the fuel in the tank.

Oh well. Easy enough to knock the top off with a bit of a run.

You are partially correct. Voltage is part of the equation but the 'C' rating is the other part for the 'punch'. Assuming all else is equal, the C rating is essentially the amount of current that the battery can push out either momentarily or continuously. So a 2s 5000 mah battery with a 40c rating vs a 2s 5000 mah battery with a 50c rating *should* feel different when driving. Both would be 7.4v rated (and would charge to 8.4v) but the 50c battery should feel 'punchier' in theory.

As for storing the lipo - just make sure it isn't at a full charge when you store it and you are good to go.

[Lonestar]

open-circuit voltage is about as good an indicator of what's left in a pack

Go for 3.85V/cell for storage. It's safe, no swelling. anything about 3.9V increases chances. Anything below 3.8V makes the pack age sooner.

Check every few months if not running the car

Paul

[justinspeed79]

Store them in the fridge, but make sure they can't freeze. Freezing them will ruin them, but keeping them cold will extend the life and performance, and will remove any swelling that might develope during use.

[Sixtysixdeuce]

a 6000 mAh battery will last twice as long as a 3000 mAh battery, but everything else will be the same. It won't be any more powerful.

Only true if the 3,000 mah has twice the discharge rating. At the same rating, the 6,000 can discharge twice as many amps as the 3,000. Hence it would be twice as powerful, since power is watts, and watts are volts*amps.

[Coelacanth]

mAh refers to a battery's storage capacity. All else being equal, a 6000 mAh battery will last twice as long as a 3000 mAh because it has twice the capacity. This is regardless of the watts because, as you said, volts * mAh = mWh (milliWatt-hours). 6000 mAh * 8.4V = twice as many mWh as 3000 mAh * 8.4V.

True, a battery with twice the discharge rate will theoretically discharge twice as fast, but I probably should've mentioned all else being equal in my earlier post.

[jxoco]

I cut this out of the instructions for a onyx charger:

NiCd, NiMH, LiPo, LiIon and LiFe cell manufacturers recommend applying a 40% full charge to the batteries before being
put in storage. To achieve this, setting the CAPACITY screen to a reduced level before charge will cause the charger to
deliver only a partial charge to the battery.
Multiply your battery’s rated capacity by 0.4 to find the proper value. Enter this value (or the closest available value) into
this screen. For example: The 40% full charge capacity of a battery rated at 3200mAh would be (3200  0.4) 1280mAh.
The closest possible setting for this would be 1300mAh. The 40% full charge capacity of a battery rated at 1600mAh would
be (1600  0.4) 640mAh. The closest possible setting for this would be 650mAh.
Once this value is set, proceed to charge the battery. When charge ends, you should notice that only about 40% of the
battery’s rated capacity was delivered during charge by looking at the “COMPLETE” screen as explained above.

[GodSpeed]

See, that speaks directly to my inquiry...and confusion.

You'll get 40% of your mAh that way, but you'll still get a full load of volts. Most of the discussion here has been towards limiting the voltage, for which, on an Onyx charger, you have to unplug early as there is no "storage" function.

[RC104ever]

Buddy, make it easy on yourself. Just run it until your ESC cuts off and then store it. Simple, and risk free. I have had zero issues doing it this way.

[Coelacanth]

Buddy, make it easy on yourself. Just run it until your ESC cuts off and then store it. Simple, and risk free. I have had zero issues doing it this way.

Just don't forget that it's discharged before running it the following year.

[smcleodvt]

Think of the mAH of a lipo as the size of your fuel tank. All lipos have the same V per cell. You don't want to go below 3.8 and you don't chatge above 4.2 V per cell. Storage is best between 3.8-3.85 per cell. If you have a balance charger when you plug it in there is a screen that will show you the cell voltage of each cell. You can also use a meter and touch the wires on the balance plug just to double check.

[THEYTOOKMYTHUMB]

Is there any kind of shelf life on stored lipos? I have some NIP ones that I bought probably a year+ ago. Obviously I will try them out and see, but just curious if anyone had any idea.

[DaveM]

Hi,

Quote,

"LiPo cells have a shelf-life and they basically begin to degrade on the day they're assembled"

Some interesting reading here,

http://www.oppoforums.com/threads/good-read-on-li-po-batteries.1363/

I think the figure in storage could be as low as 3 years.

That is why you should be buying LiPo's from a company that turns them over regularly.

Cheers, Dave.

[THEYTOOKMYTHUMB]

Thanks Dave. I need to get off my ass and get them plugged and ran... I always seem to find an excuse not to. I also really need to go thru all my lipos and get rid of a few old ones. They're laying around in various states of charge. Some of them I'm sure have been sitting around fully charged for a looong time. I cleaned up shortly after Rod had his incident, but haven't done so since.

[Coelacanth]

I think it's important to make a comparison, including NiCad & NiMH in the discussion of shelf-life.

NiCad & NiMH batteries don't take too long to lose their ability to take a charge. A fully charged NiMH battery soon loses it's charge; even a few months of storage and a NiMH battery will have no juice in it. They will also lose their ability to take a charge over time. Think of your cordless drills & tools. After a few years, you can plug the battery into the charger for hours and it'll only give you 20 minutes of use before the battery dies and needs to be charged again. That's probably the most annoying characteristic of NiCad & NiMH batteries.

Compared to NiMHs, LiPos at least retain their charge for MUCH longer, and I've read they can last in storage for several years without significantly losing their chargeability or capacity.

[limestang]

Battery charging would make a good sticky topic. Not sure if this has been posted before, but I found this article very informative.


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

- Limestang