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View Poll Results: Do Li-ions fail faster then other chem make ups based on vibration / fatigue?
yes 4 16.67%
no 11 45.83%
This is a stupid poll 4 16.67%
I dont know ask Judge 6 25.00%
Multiple Choice Poll. Voters: 24. You may not vote on this poll

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Old 04-16-2012, 08:47 PM   #46
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Quote: Originally Posted by Fromeco
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Lithium Ion and Lithium Polymer cells are both LiCoO2 or Lithium Cobalt Oxide cathode. With Graphite Carbon Anode. Some years back the Anode on Lithium Ion cells used to be made of Coke, this is gave the cell voltage of 3.6 instead of what we have now which is 3.7. This is why you still see chargers with a Lithium Ion setting and a Lithium Polymer setting. The difference is the termination based on the 3.6 volt cell chemistry. So the base chemistry for a Poly and an Ion are exactly the same. It is the construction that is different, this is where you get difference in amperage output.

Hope that helps a little bit

Quote: Originally Posted by Shaker
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. It's different for each type of battery by the way.

Li-Poly - 3.7v per cell
Li-Ion - 3.6v per cell

I found my charger was actually about 1/2 volt over as shipped and had to recalibrate it to get the correct output.
not true with current LiIon.. that was true a few years back.. but not true now....
see above...

nominal voltage of current LiIon and LiPo are the same
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Old 04-16-2012, 11:01 PM   #47
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Quote: Originally Posted by Zeeb
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Even though you don't get the torque you would from unregulated Li-Ion/Li-Po's
Zeeb, always enjoy your responses to things/problems/etc.

But I have to disagree with you on unregulated lithiums. I ran regulated lithiums for over a year (6.5v) and later decided to dump the regs (Hitec 7950's) and found that the plane didn't fly as well. What I found out at the time using an Aurora9 (yuck) radio and its telemetry was the lithiums sag pretty bad.

They basically drop to 6.7 to 6.5 volts. The whole HV thing to me is a gimmick. Now if they start making regulators that regulate to 7.2 volts and allow us to run 3s lithiums on our rx's it's just not going to work.

I guess basically what I'm saying is 2s lithiums don't have much headroom.
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Old 04-17-2012, 12:06 AM   #48
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Here's an interesting story. This was posted by the father of 3D heli sensation Kyle Dahl:

No, unless just going 2S is for convenience reasons (which is valid).

My son (Kyle Dahl), has competed nationally and internationally for the past few years, with about the highest performing helis available, and has yet to go "HV" to power his on-board electronics. Always 6V or less.

The one exception is the Logo XXtremes (800 class 3D heli), that Kyle flew this season, which were set-up with HV systems and servos.

But interestingly enough, for about 30 flights on one of the three XXtremes Kyle has, the selectable output voltage BEC was mistakenly set to 5.2V, with the other two machines set at an "HV" setting of 8.4V.

All three machines were flown in rotation during preparation practice for the 2011 XFC. Kyle never discerned any difference in how the three machines flew. We discovered that one machine set @ 5.2V later during some maintenance.

I know there's guys who rave about how much better their helis fly with HV set-ups, and I know the electronics manufacturers love to hear that. But...
(-: Dave Dahl
So I'm thinking that if one of the best heli pilots around could not the tell the difference there is a better than even chance that most of us cannot either. Except maybe in our own minds.
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Old 04-17-2012, 10:46 AM   #49
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Quote: Originally Posted by plane
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I guess basically what I'm saying is 2s lithiums don't have much headroom.
Are you talking about Li-Ions? If so I completely agree with you as I mentioned the issue with those batteries is you have to get a really big mah rating number battery to deliver decent current and even then it's far below what an A123 or Li-Po can put out.

So the "don't have much headroom." would NOT be the case with a Li-Po and while some guys use those for rx packs, as I've mentioned before the chemistry makes me nervous and I only use Li-Po's for my electric powered stuff since there's really no suitable substitute.
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