Li-Po Batteries

Hey Guys,

As a newbie to RC Helis and assorted technology, I'd need some help to be brought up to speed on Li-Po.

When charging, do they have a memory like NiCad? That is, when re-charging a partially spent batt, will the discharge only go to the point where it was charged before?

Is there a deep discharge limit like lead-acid batts?

What limits the life of these batteries? i.e., what practices shorten the life?

What is generally the limit to the number of re-charges?

What happens when the battery is charged beyond 'fully charged?' (I've heard it can be catastrophic.)javascript:emoticonp('')

What can be done to 'refresh' the battery. (it's recommended to refresh my laptop battery by discharging it to zero charge once a month, then waiting 5 hrs to give it a 100% charge.)

Thanks,
Auteur47

I don't know the answer to all of your questions, but I can tell you this.

Try to never discharge your Lipo batts to below 3.8v per cell. To know the cell voltage, you will need some type of voltage tester or a charger that will display that info. I recommend the later. The main two ways to destroy a Lipo are impact from a crash or dropping the batt and overdischarging. (below 3.8v per cell. If you don't have a way to check cell voltage, limit flight times to between 5 and 7 minutes until you do. When you get a voltage tester or better charger, you will then be able to determine how long you can fly on a particular batt.

And lastly, never leave the batts unattended while charging. The better chargers will automaticly stop charging when the batt is full, but it is better to keep an eye on them.

Hope this helps,
Donnie D

Well guys, I gitta throw in my nickel. First the lipo's are 3.7 volts full charge. Therefore you could not use the 3.8volt limit. Use 3.1 volts as your low limit. Best way to keep an eye on them is using a voltwatch. This is a device that mounts on the heli and plugs into the balance lead, it has an LED to show full, then it changes color at a set voltage , then starts blinking, then blinking and beeping. This works great for us new guys since we don't fly to far away. As far as flight time, that will be determined by the mA of the battery.

I might be wrong on that FD, but I think the 3.7v is closer to the low limit voltage. When my charger finishes charging my batts have a cell voltage of about 4.15 to 4.16v per cell at full charge.

Just like a 12v car batt. When your voltage on a car batt gets down to just slightly below 12v, you'll need a jump start. I think normal voltage on a 12v car batt as somewhere between 13.5v and 14v.

But I may be wrong on this. won't be the first time.

Donnie D

Yes they will hold more just like a 12volt car batt. which when fully charged should be 13.5/13.8. Look at it this way a 3S is 11.1 volts, divide 11.1 by the 3 cells =3.7ea.
My 3s packs are about 12.6 when fully charged, but they are 11.1 volt packs!!
3.1 is the low limit, trust me,well you don't have to I'm sure there are web sites devoted to LiPo's.. Look at your ESC instructions. At the cutoff points you can pick. I think my HobbyWing uses 3.1 per as the middle c.o. point and low is bout 2.8which is to low IMO. If you do discharge to low, simply charge at .5 and the battery will recover.

Like I said, won't be the first time I'm wrong.

Donnie D

So, about how long do you fly average on an 11.1v, 2400mAh pak? Ballpark.

Well I don't have any 2400's I have 2200's and depending on the heli. My HBK2, I can easily get 10-12 before my alarm starts beeping. On my screamer 480, I get bout 6-8 min. I also fly the 480 using some 4S/2200 and get about the same times, way,way more power but bout the same times!!
With my EXI5 using the 6S 3000 I easily can get 15 min. But keep in mind that I mostly sorta hoover in motion to some slow forward forward flight.

Sounds like you and me fly about the same way, but if I did it for 15 minutes streight, I'd probably have a nervous breakdown.

Donnie D

Following link will give you just about all the answers you are looking for.
http://www.rcgroups.com/forums/showthread.php?t=209187

Everything shortly:
1. No lipo batteries doesn't have memory effect as nicd or nimh batts
2. Full charge is 4.2V per cell and it would be best if you don't go lower than 3V
3. If you discharge your battery too much you can ruin it
4. Charging and discharging at high currents lowers their lives. And it is best to store lipo with 3.2V - 3.7V per cell. Or fully charged lipo (4.2V per cell) in a fridge
5. If you over charge your battery it will puff or/and explode
6. To refresh lipo just charge and discharge your batteries at very low currents. But just don't put too much stress on battery and you will not need to refresh it

Yea dude I can see my old lady now!!!! Opens the fridge and there is a stack of heli batteries!!!!! She would be chasing me down the street with a stick!!!!!LOL

Fatdaddy wrote:

Yea dude I can see my old lady now!!!! Opens the fridge and there is a stack of heli batteries!!!!! She would be chasing me down the street with a stick!!!!!LOL

Yeah, I also don't do that. I keep them not fully charged

I didn't know about that!!! I do keep mine fully charged!!! I keep them in the baqsement but not the fridge!!

As I said it is best to store lipo with 3.2V - 3.7V per cell. But it won't hurt storing them fully charged for few days. But when you store you batteries for a week or more it is best to not fully charge them

Hey P3, Where do you get the LiPo info at. There is a lot to learn about these packs..
I've been worried bout keepin them from exploding or catching fire, now I got to figure out how to best store them. Cause some I don't use for a week or so at a time. I do rotate them so I use all of them and not just thew one on top(so to speak)
I've got a lot of money invested in battery's now and really don't want to lose any due to my lack of knowlage..

By the way bud, How did you make out with bidding on a DX6?

It is info gathered from many sites I don't remember them But there is a good site that Prel posted before
P.S. I lost auction. I'm thinking about turnigy 9x radio from hobbyking. I saw one (even used it) and it looked pretty good!

Get one of theese to check your battery voltage:

https://www.youtube.com/watch?v=1zleStIMkbY

I use a MaxPro I think they are called. I have one on each of my helis, got them from HeliDirect for around 5 bucks. Only problem I have is that I have one of my birds that I fly both 3S and 4S packs in. So I just time it when I use a 3S in that one.

On the lik posted by Prell, they have all the info there. The lowest voltage, storing etc.

http://www.rcgroups.com/forums/showthread.php?t=209187

Do you think HBFP 4in1 has a Low Voltage Cutoff (LVC) in it? I fly the bird until it only fly 30cm above the ground at full throtle. When I check the battery, it's +/-3.66 volt each cell. So I guess no need to have a timer. On the link above, it says: "It is important not to exceed both the high voltage of 4.2 volts and the low voltage of 3.0 volts.", or is it because that HBFP capable on handling a 11.1volt battery. So 7.4v is nothing for the bird.

The new HBFP is using 11.1v. But I don't have the info yet if the new HBFP using the same 4in1 and motor with the old one.

For pilots using 11.1v on stock 4in1 and motor, can you give us info on the HBFP LVC?

No, honey bee fp doesn't have low voltage cut off