If you weren't going to fly your heli for a long period, say 3 or 4 weeks, is it best to store the batteries discharged or fully charged. Can't find much info on the e-flite website related to storage (other than to not store it above 150 degrees????)

I have heard to store them half charged.

Is not flying for 3-4 weeks a problem for LiPos? At what point should one worry about duration of storage? And what's the easiest way to discharge them? How do you tell they're halfway discharged (what voltage? 10V)? I always charge mine after they've been out of their bird for a few minutes, and then toss them back into my storage box (i.e. tackle box) for next time. But with the weather lately, it's been sometimes 2-3 weeks before I can fly. I think my 1800 mAh battery has seen a little hovering, but the 2 2100 mAh batteries have been fully charged and unused for at least 2 weeks now.

maybe toss them into a freezer? I've heard of people storing alkaline batteries there, but I'm not sure if that works on Li-Po's and recharables.

I also just charge them up and leave them sitting until I can fly again.

Just yestarday i was sitting on my couch with my heli shelf located on teh wall behind me and I heard this buzzing sound. i checked it out and it turns out it was my CX2's servo in a death throw. I had left the lipo plugged in for more than 24 hrs. The red light was on and it wouldn;t even sink to my radio at all. The battery was 100% depleted. I took it out and plugged it into the charger but of course the light just blinked green. Great, I wasted one of my batteries so I tossed it into the recycling bin. A couple hours later I tried it again and this time it took a charge, not only that but it didn't seem to effect the life much at all. I can still get about 10 mins out of it. Sort of off topic but I thought I would share.

I read in a book that if you leave batteries sitting for awhile they can actually get a small charge back on them.

I think that was relevent and good to know

IMO,

Do:

Store Lipo's, long term, at about half charge if possible.
Keep them in a cool environment.


Do Not:

Over discharge below 3.0-3.5V per cell.
Store fully charged for long periods of time (several weeks or more).
Freeze.
Drop or puncture.

So do not freeze them. do you know why not?

Sorry, I don't.

I know I have seen it here that refrigeration is good, freezing is not.
I think there was some information in the DN Power batteries that said store in a cool area and mentioned not freezing but I will have to check that tomorrow when I'm home.

If I'm wrong, that's OK too.
If you find information to the contrary let me know.

No. you are right, cool is good, frozen is bad.

Thanks, got it

This is true I think with Lipo's too.

Try this, fly your heli until you'd normally pull out the pack.
Check the voltage immediately on the 2 individual cells.
Check the same again after about an hour and I bet my chocolate pudding you'll get very different results!


(I don't mind losing this bet, 'cause I don't like chocolate pudding anyway)

But let's see what result everyone else gets.

Some info on LiPo's;

- Nominal Voltage: 3.7V (used to calculate total pack voltage 2S=8.4V, 3S=11.1V, 4S=14.8V and so on )
- Minimum discharge voltage: 2.8V (on HQ cells! Just keep above 3 or 3.2 to be certain, especially without a good charger)
- Maximum charge voltage: 4.2V (actually 4.23V)

LiPo's can approximately store 300% more energy with the same volume and that volume weighs about 15% less. The S-rating stands for the number of cells connected in series (hence the S), some have a P-rating, which stands for parallel! So 4S2P stands for 2 Parallel connected packs each with 4 cells connected in series.

Never (not even the HQ/HighSpec cells) charge on over 1C. 1C is 1x the total capacity of the pack, which is the same as the capacity of one cell. (For example NiMH should preferably be charged at 0.1C or C/10 to ensure lifetime of your packs) If any cell starts to swell up, disconnect and store in a fire-proof container. Also if the pack feels 'soft'/mushy, please don't use it! If you do, keep checking on it. LiPo's dont really explode, but they burst into flames...

When crashed, check the LiPo for marks, dents, scratches and so on. This may cause you're LiPo to slowly start disintegrating itself, heating up and causing a chain reaction to the other cells. Heat kills these things.

It's recommended to charge them to about 50/60% when you store them for longer periods. LiPo's have a slow self discharge around their nominal voltage, but a quite high one on the max and minimum voltages. This is caused by the chemical compounds used.

As you can see, i've been reading up to batteries in general. Since the NiMH in my DX7 blew up due to improper charging (caused by myself, listening to the wrong people, not knowing a thing). Be sure to keep yourself away from such havok and gain as much knowledge as you can/like. It'll save your batteries, equipment and yourself!
(Whohooo, didn't that last centance sound mature/all grown-up?! )