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Old Feb 22, 2012, 07:44 AM
Taranis Tyro...
MattyB's Avatar
United Kingdom, England, Hitchin
Joined Jan 2004
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Question
Evo 9 battery options?

I'm just about to convert my old Evo 9 to FrSky 2.4 with the DHT-U module, and while I'm there I want to replace my TX battery which has been getting a little tired of late. Having done some online research I'm now thoroughly confused - can anyone de-muddy the waters? As I see it there are 3 options that are an upgrade over my current NiMHs, but each have strengths and weaknesses...
  1. Low self discharge NiMHs (Eneloop etc) - Low self discharge, can charge through TX but only slightly slower, more expensive, larger number of charge cycles(?), heaviest option
  2. 2S LiPo - Cheapest option, low self discharge, low weight, quick charge capability (outside TX), can't charge through TX or use TX charge monitoring, fewer charge cycles from battery.
  3. 2S Li-ion - Even lower self discharge, bit more expensive and heavy than LiPo, space could be tight (according to this post I have only 20mm of depth to play with), can't charge through TX or use TX charge monitoring, not sure about charge cycles on this option!
One other point to note - I fly mostly slope, and that means operating a lot in cold conditions. Which of these cell chemistries performs best in low temperatures?

Many thanks!

PS - Although I am a newbie to electric flight and lithium batteries I am pretty experienced pilot. As a result I've read up on the dangers of charging LiPos in situ and will only be charging them outside the TX! I have a decent balance charger already so I'm comfortable from a safety persepective.
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Last edited by MattyB; Feb 22, 2012 at 08:00 AM.
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Old Feb 22, 2012, 08:38 AM
Guz
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Tempe, AZ
Joined Dec 2005
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I went the way of LSD NiMh, and haven't looked back.

I like it because I can still charge in Tx, or out. If you charge outside Tx, remember to reset the capacity value in the Tx setup screen when you put them back in. They do hold a charge quite well, compared to normal NiMh. Weight isn't that much of an issue, it's a light Tx to begin with. They fit perfectly, no internal modifications needed.

I had my LSD NiMh pack made up at Batteries Plus. I took the battery lead off my old pack and had them re-use it. They only charged me for the batteries which I bought from them (my shop is kind to R/C people, other shops may not be).

If you do go with LiXx (or any type of battery) batteries, make sure you use a keyed connector so you can't plug in the battery backwards. Everyone has a brain fade sometime and you will plug in the battery backwards once, and only once. Then it's off to be repaired.
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Old Feb 22, 2012, 10:27 AM
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United States, TN, Jamestown
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I used to have 2 EVOs and one had 2s LiPo, the other with a 2s LiIon. Both of them would last forever between charges.
When the original batteries started going bad I just used what I had available, without any extra cost.
About the cold, I don't think a LiPo will be affected much in a transmitter as they are when you use them as flight packs, since the transmitter pulls very little current. In my experience, the cold just makes the batteries not able to deliver a lot of amps, but I could be wrong.
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Old Feb 22, 2012, 12:22 PM
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The Fens, Britain
Joined Nov 2005
227 Posts
I have a 6-cell Eneloop battery from Overlander - sold specifically for the Evo though I think I had to solder the old battery's connector on. Enough capacity for dawn to dusk flying with the FrSky module.
Voltage seems OK in cold weather.

A 2S LiPo would suit the Evo voltage-wise, but I thought the Eneloops were less faff, and safer.

Brian
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Old Feb 24, 2012, 09:10 AM
Taranis Tyro...
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United Kingdom, England, Hitchin
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Thanks guys, much appreciated! I have decided to experiment with a 2S LiPo on a Deans polarised connector for the fast charging capability, and because the Eneloop option was a lot more spendy - lets see how it goes...
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Old Feb 24, 2012, 11:59 AM
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Originally Posted by MattyB View Post
Thanks guys, much appreciated! I have decided to experiment with a 2S LiPo on a Deans polarised connector for the fast charging capability, and because the Eneloop option was a lot more spendy - lets see how it goes...
It will go fine, just don't charge it through the radio's charging circuitry. The best would be to charge it through a balance connector on the battery. That way the cells are charged and balanced correctly.
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Old Feb 24, 2012, 04:00 PM
Taranis Tyro...
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United Kingdom, England, Hitchin
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Yep, don't worry - it will only be charged on the balance charger whilst safely tucked up in a LiPosack!
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