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Old 07-26-2006, 07:50 PM
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Jay Florida
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?? about Lipos

Hey Guys,
I dont have much experience with electrics except for a few foamies,so here goes. How hot should a lipo get while discharging? I am running a TP 2100 on a Extreme Flight Torque 2818T/900 with a 35amp Airboss speed control and a APC 12-6 E. After a flight (pretty aggresive), the battery is hot to the touch but not hot enough to hurt if you hold it tight. Also, what do you use to balance the cells with? One more question, What size E-flight motor is the 2818/900 equivalent to?
Thanks,
Brian
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Old 07-26-2006, 08:59 PM
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Re: ?? about Lipos

Sounds like you are drawing too many amps from the battery. Have you measured the current?

To answer you question they shouldn't be hot at all. A tad warm perhaps but you don't want them getting too warm.

I've seen a lot of guys run 2 2100s in that power class. Not only does it help the batteries but they were actually seeing more power. Enough to make up for the extra weight.
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Old 07-26-2006, 09:08 PM
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Re: ?? about Lipos

Hey Brian
You should try to keep your lipos under 120 degrees. Most Mfg's. say 140 degrees but IMO that's too hot, heat is what kills lipos. Also you shouldn't fly untill cut-off on the ESC. You want around 3.7 volts per cell resting with no load i.e. 11.1 V. That should leave about 20% left in your battery. It's that last 20% where the battery really starts to heat up because of internal resistance. Since you don't want to fly untill the ESC cut-off what you need to do is fly for about 6 min. land and check the battery with a wattmeter or multimeter. That will tell you how much is left in the pack and you can adjust from there. As far as balancing goes, there's a bunch of good, inexpensive balancers out there. I own several different types but one that's good and cheap is the Astro Blinky, they're around $25, just order the right adapter for your batteries ( TP, Tanic, Polyquest etc.)
The Hacker A30/16M is roughly the same as the 2818/900 except the Hacker has a 160 Kv more than the Torque motor so it will pull a little more power and a little more amps
Hope this helps
dook
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Old 07-26-2006, 09:37 PM
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Re: ?? about Lipos

Thanks, you would think that when you buy a package deal you should be OK. I have not checked current yet. I don't have a whattmeter. Looks like more stuff to buy. Sounds like I need a smaller prop. What is recommended for the EF Extra that will lower current draw without killing performance? Are there batteries that will allow more current draw without adding more weight? Theres no way I'm adding another 5.5 oz. battery to a 32 oz. plane.
Thanks,
Brian
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Old 07-26-2006, 09:39 PM
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Re: ?? about Lipos

Dook I just realized what you are saying. The battery heats up towards the end of the charge. I'll cut a flight short tommorow and check temps. That's gonna be tuff because this thing is a blast.
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Old 07-26-2006, 10:52 PM
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Re: ?? about Lipos

OK... get one of these...
http://www2.towerhobbies.com/cgi-bin...&I=LXEMG5&P=ML

If it is like an external 3 cell pack, and the ambient is say 80'ish....
temps around 120 degrees after a 10 minute flight are OK... try not to use more then say... 80% of the capacity... (1680 mah from a 2100 mah pack for example)...
But remember.. they say that 160 is MAX temp... (Give'r'take).... so if the outside surface of the pack is 160, then the middle of the center cell is at about 200 degrees!!! BAD DEAL!!!!... I have been told that the mechanism of degradation (Other then erupting into flames ) is that the gelatinous substance in the cell becomes runny, thin like alcohol and the layered plates in the pack become closer together from the pressure of the mounting straps.... Keep all temps under 120, (ESC, Motor and LiPo's) and you have a good long term robust system... it is OK to pre-heat the LiPo's to about 100 degrees before a flight though... they perform better when warmed up a bit!!!

Hope this helps....
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Old 07-27-2006, 09:45 AM
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Re: ?? about Lipos

Brian....a wattmeter is a pretty important piece of equipment if your going to fly electrics. With it you can check the amp draw and adjust with different props or different gear ratios in a gearbox to get the amps where you want. You can also check how much power (watts) the motor is putting out and check how many miliamps are left in the pack. A 15C 2100 mAh battery will be rated at 31.5 amps continuous. The 2818/900 with an APC 12/6E prop draws around 32-34 amps @ sealevel so you have to use some throttle management to avoid overheating. You could drop to a 11/5.5E prop to drop the amps but on a 32 oz plane you might not like the performance for 3D, for sport flying it's fine. Just remember; Throttle management.
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Old 07-27-2006, 06:57 PM
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Re: ?? about Lipos

Thanks Guys.
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