Li-Po

HI,
It seems I've killed my first Kokam Li-po? I flew yesterday, my Wattage
Ultimate with a Cobalt 400 using a Kokam 7.4 volt 2000Ma battery pack.
Anyway, I only flew one 6 minute flight, normal for this setup and all was
well. I got home and tried to charge the battery. No luck, my Triton
charger say's battery voltage too low. Starts charge at 5.6 and goes to
5.78 in about 90 seconds, then sounds buzzer and advises battery voltage too
low.
I'm new to electric. Anyone know If I can save this li-po?
Thanks, Craig W.
Reply to
Craig
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| It seems I've killed my first Kokam Li-po? I flew yesterday, my Wattage | Ultimate with a Cobalt 400 using a Kokam 7.4 volt 2000Ma battery pack. | Anyway, I only flew one 6 minute flight, normal for this setup and all was | well. I got home and tried to charge the battery. No luck, my Triton | charger say's battery voltage too low. Starts charge at 5.6 and goes to | 5.78 in about 90 seconds, then sounds buzzer and advises battery voltage too | low. | | I'm new to electric. Anyone know If I can save this li-po?
Take your battery and charger outside in the driveway -- just in case you create a flaming inferno :) Keeping the battery at least a foot or two away from the charger would be prudent.
Put the charger on a NiCd charging program, charging at like 500 mA or so, and charge it for a few minutes. Yes, I did say NiCd -- this bypasses the safety routines built in for LiPo. NEVER do this for long, and never without paying very close attention. If you walk away and forget, you'll come back to a flaming mess.
Watch the voltage carefully -- once it gets above seven volts or so, switch over to the normal LiPo charging routine and see if it works. Hopefully this will take less than ten minutes to get back to seven volts. If it then charges correctly, great -- you got lucky. But do be extra careful about watching it for issues -- if it puffs out, or catches flame, it's time to discard the battery.
It would appear that you discharged your battery too deeply. Or maybe it went bad on it's own -- I don't know. What I'm telling you to do is dangerous, so that's why it's done out in the driveway, and don't let it out of your sight. If it does succeed in bringing your battery back to life, be sure to make sure you pay extra close attention to it while charging and discharging the first few times, to make sure it doesn't show any signs of self destruction. It could catch fire, so make SURE you charge somewhere where fire won't cause problems -- outside away from everything is best, but a fireproof container will do once you've verified that it's not a ticking time bomb after a few charges and flights.
I've never had to do this myself, but this is what I'd do.
And you should work out how it got so deeply discharged too. Can your ESC not stop running the motor at six volts, or does it have an lower cut-off voltage?
Reply to
Doug McLaren
You flew a motor that can draw 20A from a pack that flattened in 6 minutes...so you were AVERGAGING 10C discharge..and a pack that is buboous at much oiver 6C.
If it's not toaast today, it will be next time you fly it.
You need about 4000 mA/h to fly that plane RELIABLY.
Reply to
The Natural Philosopher
Brings up another point not often mentoned in Glow Vs. Elec. shootouts. If a gallon of fuel goes bad (almost never happens) you are out $14. If a Lipo pack goes bad (happens very very often), you are out much more. It's something I don't often see in the equation in those types of threads.
Reply to
Frank Costa
Frank,
Mainly happens to the nitwits who can't care for & use LiPo's properly. --
Jim L.
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Reply to
Jim Lilly
Or the one who accidentally set their chargers wrong and start a fire. Of course, humans beings are expected never to make mistakes...like accidentally leaving one in a hot car. Then there is the issue of crashing. You don't have to throw away the $1 worth of fuel that was on board after a crash. The LiPo on the other hand needs special care and supervision after every bump and jostle. Don't get me wrong, I love LiPos, I have 7 of them, I'm just being honest and bi-partisan here.
Reply to
Frank Costa
Read, "beginners???"??
Until I don't have to mess with flame proof boxes, esoteric chargers and horendously expensive motors and batteries, I'll stick with my glo stuff. Granted, electric has come a long way but it aint there yet IMHO.
Jim W
Reply to
Black Cloud
Black,
Read, lack of good old common sense!!! --
Jim L.
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Reply to
Jim Lilly
Frank,
That, or over-discharging them (just seen a club member do that one). Both rank in the nitwit department.
I'd have thought those clods to be glow flyers just coming into e-power, not so. It's most often seasoned e-power flyers going from NiCd/NiMh to LiPo, that are the worst abusers & misusers of LiPo's.
Not really, just the catastrophic crashes mainly. I've crashed several with LiPo's on-board, and just watch them for 15-20 minutes afterward & good to go or pack up.
I had 7, but cooked one when the ESC failed to shut down motor power @9v as it was supposed to:-(
Btw; I use Hobbico's Quick Field Charger MKII & their Elite Cycler for all my batteries. --
Jim L.
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Reply to
Jim Lilly
Hmm... A brand new technology that is still in the emergent stage and you throw rocks at those less educated on the subject than you. Remind me to send you some coal for Christmas!
Reply to
Six_O'Clock_High
Six_O'Clock_High,
Not MY fault that those giving LiPo's a bad rap, can't/won't/don't read & follow warnings & directions &/or use the wrong equipment/wrong settings with LiPo's.
The following info is almost always included with every LiPo pack. The fact that most of us follow these directions, yet a few don't, explains why those few are giving LiPo's a bad rap.
WARNING Safety precautions for Lithium Polymer cells/packs stocked by Model Flight
1. Never fast-charge any battery type unattended. 2. Never charge LiPo cells/packs at any rate unattended. 3. Only charge LiPo cells/packs with a charger designed specifically for lithium polymer chemistry. Example chargers include the Kokam LIPO 402, and Schulze chargers with lithium charging capability. 4. LiPo cells can ignite because of unmatched cell capacity or voltage, cell damage, charger failure, incorrect charger settings and other factors. 5. Always use the correct charging voltage. LiPo cells/packs may ignite if connected to a charger supplying more than 6 volts per cell. 6. Always assure the charger is working properly. 7. Always charge LiPo cells/packs where no harm can result, no matter what happens. 8. Never charge a cell/pack in a model. A hot pack may ignite wood, foam or plastic. 9. Never charge a cell/pack inside a motor vehicle, or in a vehicle?s engine compartment. 10. Never charge a cell/pack on a wooden workbench, or on any flammable material. 11. If a cell/pack is involved in a crash:
a. Remove the cell/pack from the model. b. Carefully inspect the cell/pack for shorts in the wiring or connections. If in doubt, cut all wires from the cell/pack. c. Disassemble the pack. d. Inspect cells for dents, cracks and splits. Dispose of damaged cells (see below).
12. Dispose of cells/packs as follows:
a. Discharge: with the cell/pack in a safe area, connect a moderate resistance across the terminals until the cell/pack is discharged. CAUTION: cell/pack may be hot! b. Discard:
- NiMH: place in regular trash. - NiCd: recycle (cadmium is toxic). - LiPo: puncture plastic envelope, immerse in salt water for several hours, place in regular trash.
13. Handle all cells/packs with care, as they can deliver high currents if shorted. Shorting by a ring, for example, will remove a finger. 14. Always store cells/packs in a secure location where they cannot be shorted or handled by children. 15. When constructing a pack, use only cells of the same capacity (mAh).
--
Jim L.
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Reply to
Jim Lilly
I think that your complicated list of warnings is exactly the problem, because the general concensus amoung the anointed modelers is "I will read the instructions if there is a problem." Hard to change that. Would you accept an alternative? I am not sure (based on something Red Scholefield said) that ANY currently on the market hobby charger does the job well enough to be left alone while chargine LiPo's. That brings us back to the emergent techonology bit again. . .
Reply to
Six_O'Clock_High
You don't have to if you treat them gently.
Its the stupes who abuse them that get the fires.
Aided and abetted by competitive marketing that makes unrealistic claims about their capabilities.
And then sell some safety device to stop the customer killing himself.
Reply to
The Natural Philosopher
In news:cg06ta$rcs$2$ snipped-for-privacy@news.demon.co.uk, The Natural Philos>
It's interesting that those afraid of Li-Po batteries probably run around all day with one strapped to their waist thinking nothing of it. Just about every cell phone built in the last 5 years has either a Lion or Lipo battery.
Why don't they explode and burn up? The battery packs and chargers are intelligently built with safeguard circuits built in. Until the Model industry takes heed and offers packs and chargers with the equivelant safety systems, we will continue to have people hurt themselves because they are too stupid to pay attention.
-- Dave Thompson
Reply to
Dave Thompson
Six_O'Clock_High,
Sure, how's about we take responsibility for our actions. That's really the bottom line here. --
Jim L.
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Reply to
Jim Lilly
I'm not afraid of new technology. In fact, I am part of a team that uses massive Lipo batteries in an unmanned underwater vehicle. It uses 2 60 lb Lipo battery packs that I can put on the charger and forget. All charging and discharging is regulated by circuitry built into the batteries. I can even balance the individual cells if the voltage between them becomes too great. The chargers are run by a regular PC running specific software to handle the job. We can get up to a 17 hour "flight" out of our packs and I won't even comment on the price as it's in the multiple 10s of thousands.
That being said, how hard would it be for the smaller Lipo manufacturers to include the same type of circuitry into the packs used in our AC today? If cell phones, pagers, and UUV's can do it, why not Kokam and the like? Heaven knows we don't need any excuses for the ambulance chasers to file yet another costly class action lawsuit over "unsafe" batteries.
As far as reading instructions and warnings- until the "real men don't read instructions" attitude goes away, there will be those who think they know it all and will of course destroy what ever it is they were playing with.
My .02
Jim W
Reply to
Black Cloud
Black,
Impressive! Those LiPo's probably just barely get warm too.
It needs to be done, but hobbyists will argue the price is too steep then.
Sad, but so very true. --
Jim L.
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Reply to
Jim Lilly
Actually, Kokam has a 2000mAh pack that can do 15C, or 30 Amps. I've got four of them.
Still, he ran the pack down too far, plain and simple.
Reply to
Mathew Kirsch
Black hit the spot with ALL the correct answers. There really are TWO problems with getting hobby packs properly built (probes, circuits, and logical chargers properly wired for them). The first is acknowledgement of the fact that proper charging can only be safely accomplished with those parts added to the system. The cost issue is transparent to real modelers.
Reply to
Six_O'Clock_High
Whaddya think of the new Accucycler elite? looks interesting. Field reports anyone?
Reply to
MikeF

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