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e-Electric Batteries & Chargers > LiPos Dropping Like Flies!
 
 
smokin
Senior Heliman
Location: Glenwood, Iowa - USA

I am at wits end! I have been watching my LiPos die at a phenominal rate and can't seem to figure out why. I puffed several packs last season. In recent weeks I have lost one near new TP 3S 2100 Prolite and one brand spanking new TP 3S V2 Extreme 2200 to overdischarging. The Extreme pack lost significant power approximately 3 minutes into it's first flight attempt in an MX-400. Neither of these packs shows any visible signs of damage (no dents, cuts, burns or puffing of any kind).

I metered the Prolite, and all three cells are below 3.3v so I know this one's a deader. I metered the Extreme after that first flight attempt and the cells read 3.68v, 3.67v and 3.68v respectively. According to everything I've read, LiPo batteries must have at least 3.3v on each cell to safely charge. I should be able to charge this pack. When I plug it into my charger, the charger signals a "low voltage" alert and refuses to begin charging.

I always charge batteries after they've cooled using a Multiplex LN 2010 charger and a TP-205 cell balancer. I limit flight times to 7 minutes. I'm just doing basic hover and mild forward flight.

I suspect my charger is not actually fully charging anymore for some reason, but no way to be sure so I just ordered a new Thunder Power TP425C charger.

I have another new TP 3S 2100 Prolite battery on the way but I'm gun shy about using it till I'm sure I have a full charge on it. Any advise is welcome.
09-09-2008 02:27 PM
 
 
USNAviationjay
Senior Heliman
Location: Sugar Land Tx USA

thats why I love my Cellpro 4S best small charger I've ever had. I can rely on it to give a full accurate charge every time.
09-09-2008 02:32 PM
 
 
helimatt
Elite Veteran
Location: Lafayette, IN

Help us help you:

What motor, esc, pinion, and blades are you running? Always on the MX400 (different main gear tooth count than the Trex 450, right, so pinion/headspeed relationship is different).

It simply sounds like you are over-discharging the packs by flying too long on your setup. I don't know that charger, but does it read out the mAh put back during recharge? Limit yourself to 80% of the pack's capacity, or approx 1700mAh. I fly 5 minutes of 3D on my Trex 450, and put in ~1600 to 1650mAh regularly. My packs hold up well, but the ProLites 15C might puff under higher power setups like mine. I fly min 20C packs.

Trick: set for NiMh or NiCd on the charger, 1 amp, and charge your lipo for a bit until the voltage comes up. Don't worry! The Lithium charge cycle is constant amps to start anyhow, so you will not harm the packs. I had to do this all the time on my AirThunder 6S packs because I would fly them longer (they can handle the deeper discharge), and the ThunderPower 1010C charger would not start the cycle if they were below approx 20V.

Never, ever, ever, ever give up.
09-09-2008 02:43 PM
 
 
kcordell
Veteran
Location: O Fallon, MO

Ditto on the 80% usage. That's the key, also conditioning new packs, starting out at about 50% of capacity and working your way up to 80% over about 6-8 flights. I have done this with all of my packs and all are performing well. I start a new pack at 2 1/2 minutes and then go up 1/2 minute each flight until I hit the 80% number. Seems to work well for me.

Team Futaba, Miniature Aircraft Pilot, YS Engines, VelTye
09-09-2008 04:54 PM
 
 
fenderstrat
Elite Veteran
Location: Aston,Pa

you havent said if you are using a timer,this is critical with lipos,as said earlier you should not be putting back more than 1680mah into a 2100 mah battery

if you think your charger is not functioning properly first BE CAREFUL,second get a DVM and check cell and pack V at the end of a charge and see exactly whats going on,your packs, 3S,should be about 4.2 V per cell or around 12.6V(+/- .02) for the pack,a little less is ok and normal for many packs,over these numbers is never ok,as overcharging a lipo is very dangerous

PerformancePlusRC field rep
COMPASS helis field rep
Mini Titan/SE
HBK2
Futaba FASST
09-09-2008 11:29 PM
 
 
kcordell
Veteran
Location: O Fallon, MO

I use the timer in my 14MZ for my flights. I have it activating on throttle stick use. As soon as I advance the throttle, the timer starts on a countdown. It beeps every minute then at 30 seconds then countdown beeps at 10 seconds. The 5 1/2 minute time is working just about the same for my 5S 3700mah packs in my Razor and my 3S 2500 mah packs in my Furion.
I also record every charge with flight time, date, mah put back in for every battery since new.

Team Futaba, Miniature Aircraft Pilot, YS Engines, VelTye
09-10-2008 12:15 AM
 
 
rexxigpilot
Senior Heliman
Location: florida

Smokin,

You have gotten good advice so far. But the best thing for you to do is what you're already doing - getting a better charger! I had many lipos fail over the past few years. I was pulling my hair out trying to figure what I was doing wrong. Turned out it was not my doing. It was faulty firmware in my very expensive charger.
09-10-2008 02:23 AM
 
 
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