lipo batt question for cp2

[wcairsoft3r]

I just got my HB cp2,and I was wondering..how do I know if the batt is ready to use,and when do I need to charge it?thanks!

[eddiemoth]

Hi wcairsoft3r,
This is a very good question. Since Esky Li Po charger does not have a volt meter built in, you need to time your fight. Do you have a voltmer? You can go ahead and charge it with the Li Po charger provided and when the red light is steady, it is fully charged. You can follow owner manual to test, adjust, balance and trim it. Once you can fly it, you need to time your flight from when your battery is freshly charged to when your heli begins to decrease its airspeed. There is not much info about a li po battery provided in the Esky Owner Manual, I strongly recommend that you also read this section for safety guidlines to avoid damanging your pack and any problems. http://www.helitown.com/forum/viewforum.php?f=35

By the way, I find that Esky does not do a good job with the owner manual and I would recomend that you download Blade CP owner manaul to use in addition to the manual provided.

[Ozzyeureka]

Basic guide with LiPo batteries- fly your heli until it will not hold its altitude, ie, your at full stick on the throttle and you are still losing altitude. Land asap and call it quits until you change or charge the battery. It is not fool proof, but it is safe to do it this way.

Do NOT run the batteries down by spinning the main rotors whilst the heli is on the ground after such a landing, nor persist in trying to take off if the heli doesn't want to - that will damage LiPo batteries very quickly.

[swatson144]

I'll 2nd Eddies statement and add my own emphasis on don't over discharge the lipo. It causes permanent irreversible damage. It's a shame the manual doesn't say much about that!

The HBee CP2 has no LVC (low voltage cutoff) and will go until the lipo won't trigger the charger. I'd get a timer and go for 8 mins even while using Radd's School of Rotary flight. You won't be depleting the pack, but it won't take as long to charge either. So it's pretty much a wash in flight time.

If you have a safe way to accurately measure the pack voltage here is a chart to estimate the percentage of charge from the resting voltage.

4.20v = 100%
4.03v = 76%
3.86v = 52%
3.83v = 42%
3.79v = 30%
3.70v = 11%
3.6?v = 0%

So for your 3S you should be able use the pack until it has no less than 11.3V after sitting for several mins, and enjoy a long pack life, with some margin for error. Please remember that as your skills change and put more demand on the pack your flight times will decrease. IE just scooting around on the floor your flight time may be > 30 mins, once you start hovering consistently it'll be more like 15 mins. etc. Much better to err on the conservative side than buy new packs.

Steve (who just said hmmm some of this should be in the LiPo basics and pasted it there)

[wcairsoft3r]

would it damage the lipo batt if I run the batt for aobut 5 minutes,then recharge the batt?Thanks for the info guys!

[swatson144]

would it damage the lipo batt if I run the batt for aobut 5 minutes,then recharge the batt?Thanks for the info guys!

Nope not at all IMO. There are 2 ways of thinking on this. That lipos have a determinate cycle life which is mostly true. They do have a rating but it's at like 1c and charging at a pretty low rate, and it's over 1000 cycles. There is no real data I can find on cycle life other than my own experience and of other people. When you think of it to get a real world none RC factual test it would take so long the info would be outdated by a new generation. 1 hour to discharge, .5 to cool, 2 hours to charge, and .5 to cool x 1000 it take 1/2 year to test.

The only thing I know for sure is in realistic usage I get between 100-150 cycles out of a good pack before they get "droopy" droopy being the voltage drops in use so my alarm is going on and off. I discharge Normally to about 75% allow to cool, and charge at .8C Sometimes I charge at 1C and rush the cooling a little because it's such a great day.

So I'd say recharging at 50% won't hurt and might make them last longer than disharging to 80%. They'll certainly last a lot longer than over discharging.

Assuming your charger doesn't have a LCD panel to tell you what went back in at recharge, and you don't have a good meter or wattsup etc, you could probably rough it by figuring if you are charging at 1c a typical charger will take about 1hr 15-20 mins to do a charge from 3v/cell under load with all the time consumed by trickling up and the constant voltage part of the cycle. So in theory you can run for 5 mins and recharge if it finishes in say 38mins you could add another min until it starts finishing just abit less than 1hr. You should be roughly at 75% and some margin for error. I haven't tested this but I sure as heck intend to now that it occured to me. Sounds like a good answer for the newly started Hbee CP2 crowd. That would only be accurate directly at 1C but the math wouldn't be staggering to calculate the time charging a 1300 mAh at 1000mAh rate. I'll look into it.

Steve

[eddiemoth]

So I'd say recharging at 50% won't hurt and might make them last longer than disharging to 80%. They'll certainly last a lot longer than over discharging.

This is another thing I like about a Li Po pack unlike Ni-MH attery that you have to completely discharge it before recharging.

[Ozzyeureka]

Actually, NiMH dont need to be completely discharged before charging, NiCds do. NiMh wont be damaged by going to 0, but they dont have a 'memory effect' , but they also have a poor shelf charge life (chareg teh battery, leave it on the shelf, within a few weeks the abttery is at 50% capacity)

LiPos dont suffer memory effect, do not like going to 0volts at all (irreversable damage if you do) and have a great shelf life, a couple of weeks after beinf charged, they will still show over 95% capacity available.
As for life cycle, if a battery is quoted as having a 1000 cycle life, then discharging to 50% before recharging to 100% will give you approx 2000 charges. We have been doing some life cycle testing on some HP pocket PCs, using different regimes, and so far the above theory is mapping out pretty close to true (1 year down the two year test)

[swatson144]

I just checked my theory and it proves out. Details on how to determine safe flight time on the RTFs simple and no extra equipment, until you feel like you need it. Can be found in the Lipo topic of batteries area.

Steve

[MAXXED]

I learned my lesson the hard way about li-pos, too.
When I ran the stock motor, I discharged my packs below 3 volts/cell and quickly killed two li-po packs. :x
When I switched to brushless, the ESC has a low voltage cutoff sensor, and I haven't killed a pack yet. :)
Li-pos aren't very forgiving on charging and discharging, but after a few expensive mistakes, you learn real quick. :lol: