Looking after your 120SR LiPo batteries.

[Imzzaudae]

There are many guys that charge there Lipo at 2 or even 3 times the C value on LiPo batteries.
But doing so significantly reduces the life span of the battery.

Charge you LiPo at no higher rate than .5 on the stock charger!


Don't over fly your LiPo!
Flying your helicopter until the light starts flashing on your 120SR will shorten the lifespan of your Flight batters dramatically.

Get a simple timer that you can stick to your transmitter. Set the timer 5 minutes and fly your 120SR until the timer rings. Land ASAP 10 - 15 seconds. Flying time may change as the batteries get older.


It is also important that you let the battery cool to room temperature,
before re charging.

[rojack]

Agreed that flying the heli until it can no longer lift off the ground is a good way to shorten battery life. Quick check: see what the voltage is when you stop flying. Don't fly the cell down lower than about 3.7 volts. (If the heli has a low-voltage cutoff, it may shut off the motor at around this voltage anyway.)

With a smart charger you can see how many milliamps you are putting back into the battery to charge it. Another accepted rule is not to take out more than 70% or 80% of the capacity of the battery.

There are a ton of threads about care of LiPo's, but two great and easy rules are don't over-discharge and don't store at full charge for a long time... like a few weeks...

As far as charge rate, the standard 1C rate is almost always safe. ...and if the manufacturer says you can go higher, then I would tend to believe them. In the case of the one in your post, I believe the little booklet says you can safely charge at 700 ma, which for this battery would be 1.4C instead of 1C. No harm in charging at 500ma of course, except it takes longer.

[dudeeg]

Originally Posted by Imzzaudae

There are many guys that charge there Lipo at 2 or even 3 times the S value on LiPo batteries.

Sorry for the lame question, but what does it mean "charge with 2 or 3 S value?"

AFAIK 1C means, the battery can be discharged with amount of current that is equal to capacity/1 hour, eg 700mAh 1C battery load can be maximum 700mA.

Or the 1C is a value for load, and the 1S is for charge rate?

Thanks!

[kc4sox]

I'm flying my 120 to 6 minutes and have never had the heli indicate a low voltage via the light on the board. And, I'm charging at the max rate on the stock charger. Batteries have 50+ flights on each. Just sayin.......YMMV

[ArchmageAU]

Originally Posted by dudeeg

Sorry for the lame question, but what does it mean "charge with 2 or 3 S value?"

AFAIK 1C means, the battery can be discharged with amount of current that is equal to capacity/1 hour, eg 700mAh 1C battery load can be maximum 700mA.

Or the 1C is a value for load, and the 1S is for charge rate?

I think Imzzaudae got the terminology was confused. I think 2C or 3C charge is what was meant.

The rest is correct:
- Do not over-discharge your LiPo (or fly to low voltage cutoff (LVC)). Get a timer and stick to it.
- Do not charge at a higher than recommended rate (it does shorten the LiPo's life).
- Let batteries "cool" between charge and flight (and flight and charge), even if not hot to the touch.
- Do not charge at an incorrect S rate.

The "life shortening" by charging at a hight than 1C rate is highly dependant on battery manufacture. There is a lot of discussion about this elsewhere. In short, most modern LiPo's life expectancy is shortened by less than 5% by using 3C change instead of 1C change. Over-discharge will kill them far quicker.

LiPo's have 4 significant numbers. S - Cells, mAh - milliamp hours, C - max dischange rate and C - max change rate. (Hang on, there are 2 C's )

S will equate to voltage 1S = 3.7v, 2S = 7.4v, 3S = 11.1v (Always use the correct S value when charging).

If C is listed as a number over 10, it is usually the discharge rate. The C is a multiple of the mAh rating of the battery. A 1S,25C,150mAh LiPo will discharge at a 3.7v (or up to 4.19v when full) at up to 25x150mA or 3.750 amps .

For charging some batteries also specify a max charge rate. The stock eFlights tend to take a 3C charge quite happily. If it is not specified, assume 1C charge.

To charge a LiPo, a reverse current is applied. This current must be modulated to not-over charge the LiPo. Recommended max current is usually the mAh rating of the battery. (for a 150mAh battery, this would be 150mA). This would be a 1C charge rate. At this rate, the battery should fully charge in 1 hour. Care must be taken to apply this at a voltage comparable with the S rating (or cell count) of a battery.

The stock Blade nano/mSRX charger charges at about 3C (up to 450mA) for a 150mAh LiPo. This is why a flown battery usually takes about 20 mins to charge.

If you charge parallel batteries (2 or more), you add the mAh together. 2x150mAh charged at 300mA is a 1C charge (900mA is a 3C charge). Balanced charging is not an issue here.

If you charge serial batteries (2 or more), you add to the S rating, but must balance the charging to ensure no battery is more changed than another.

Charging with too high an S rating is a great way to make LiPo's catch fire.

You sometimes see a P rating with the S rating (like 2S2P). This means the battery is 4 cells, but outputs 7.4v. Each LiPo output cell (3.7v outputs) is constructed of 2 base cells connected in parallel. Balanced charging occurs on each of the 2 parallel units.

Hopefully this has not confused people too much.

[Imzzaudae]

Sorry about the Typo. I fixed it.

I have also picked up 4 new Lipo and timed them to low voltage cutoff.
I guess the old ones where in worse shape than I thought.

I have also amended the flying time to 5 minutes rather than 3.

Out of 4 brand new freshly charged E-Flight 500mha LiPo the average was 6 minutes hovering around the living room when the light started flashing.

I'm sure flying time would shorten considerably in a gym or other large hall where a guy could toss the helicopter around a bit.

Once again thanks for the input guys.