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Old 07-31-2012, 05:27 PM   #1 (permalink)
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Default quick question lipo or nimh for a transmitter?

about to head to the hobby shop....

should i get a stock 9.6v nimh (i think 9.6) or a 3 cell transmitter lipo?

will the higher voltage damage my dx7? i just got it brand new from my boss. its an old dx7 but i got it new in the box never used
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Old 07-31-2012, 05:58 PM   #2 (permalink)
 

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Good question and i look forward to the responces..All i know is that i have run both and only change i can tell is that the lipo last a heck of alot longer bettween charge ups.
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Old 07-31-2012, 06:14 PM   #3 (permalink)
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I've run both on my DX8 and prefer the lipos. By a large margin. Longer between charges as mentioned and surplus power for the vibe/tone timer alert I use.
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Old 07-31-2012, 07:35 PM   #4 (permalink)
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If the DX7 isnt made for lipos you can buy a Tx lipo pack and solder 2 diodes together on the battery so the Tx will only see 11.2v fully charged.

I have been doing that for over a year on my JR 9303 2.4 Tx with no problems. You have to take the battery pack out to charge but that is a minor inconvience.

The packs are pretty cheap, roughly $20-25 and the best part for me is that they charge quickly.
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Old 07-31-2012, 08:29 PM   #5 (permalink)
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Quote:
Originally Posted by Blueram View Post
Good question and i look forward to the responces..All i know is that i have run both and only change i can tell is that the lipo last a heck of alot longer bettween charge ups.
Quote:
Originally Posted by Maypole View Post
I've run both on my DX8 and prefer the lipos. By a large margin. Longer between charges as mentioned and surplus power for the vibe/tone timer alert I use.
I've been wondering about LiPo's in a TX also... I just got a DX8 which can take a LiPo. So what am I missing here? A LiPo will last longer in the TX between charges, but I thought that you weren't supposed to leave LiPo's charged. It's supposed to be bad for them. What am I missing?
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Old 07-31-2012, 09:25 PM   #6 (permalink)
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Quote:
Originally Posted by hANDYman View Post
I've been wondering about LiPo's in a TX also... I just got a DX8 which can take a LiPo. So what am I missing here? A LiPo will last longer in the TX between charges, but I thought that you weren't supposed to leave LiPo's charged. It's supposed to be bad for them. What am I missing?
To get a long life out of your lipos the best option is to always keep them at storage voltage but you'll still get years of use out of them by using them like you would normally do in a TX.
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Old 07-31-2012, 10:06 PM   #7 (permalink)
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If your Tx use 9.6v NiCad battery, you can use LiFe battery. The voltage close to 9.6v NiCad batt.
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Old 07-31-2012, 10:14 PM   #8 (permalink)
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Originally Posted by hANDYman View Post
but I thought that you weren't supposed to leave LiPo's charged. It's supposed to be bad for them. What am I missing?
2 things:
Leaving a LiPo charged increases its internal resistance, this is bad when you are trying to suck 50A from it, not an issue when you only need 100mA.
LiPo's designed for low discharge rates (TXs phones laptops etc.) are damaged much more slowly by being kept full, compared to the high-C LiPos used for flight packs. So the damage will be slower.

You will get several years out of a TX LiPo, or longer, especially if you dont mind that it only holds half what it did when new (for the DX8 that would put it around the same place as the stock NiMH pack at ~2Ah).
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Old 07-31-2012, 10:42 PM   #9 (permalink)
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Cool... good info, thanks guys. I may have to look into getting one.
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Old 07-31-2012, 11:29 PM   #10 (permalink)
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I use Eneloop NiMH packs in my DX7 and X9303. You can use the stock charger and they hold their charge a lot (months) longer than regular NiMH.
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Old 07-31-2012, 11:41 PM   #11 (permalink)
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Quote:
Originally Posted by TheBum View Post
I use Eneloop NiMH packs in my DX7 and X9303. You can use the stock charger and they hold their charge a lot (months) longer than regular NiMH.
I use eneloops as well for my DX7SE. All 8 of em!

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Old 08-01-2012, 12:58 AM   #12 (permalink)
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Quote:
Originally Posted by pinguin View Post
If your Tx use 9.6v NiCad battery, you can use LiFe battery. The voltage close to 9.6v NiCad batt.
I use a Hyperion 3S LiFe Pack and get 4x the life per charge as the NiMh pack that came with it, plus no modifications to avoid overvoltage damage.
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Old 08-01-2012, 01:07 AM   #13 (permalink)
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Quote:
Originally Posted by backburner1955 View Post
I use a Hyperion 3S LiFe Pack and get 4x the life per charge as the NiMh pack that came with it, plus no modifications to avoid overvoltage damage.
Are you saying you can actually use the stock charger? I tried to do that, believing Hyperion's claim that it was safe, and I ended up with two puffed packs: the one I bought and the warranty replacement.
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Old 08-01-2012, 01:17 AM   #14 (permalink)
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My understanding from reading FMA multi-chemistry charger manual is that LiFe charging is pretty much governed by the same rules as for LiPos, so nope, no trickle chargers.
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Old 08-01-2012, 08:47 AM   #15 (permalink)
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Quote:
Originally Posted by jperkosk View Post
My understanding from reading FMA multi-chemistry charger manual is that LiFe charging is pretty much governed by the same rules as for LiPos, so nope, no trickle chargers.
Hyperion advertises the following:

Quote:
The pack includes Safety PCM circuits to allow charging inside Transmitter, using standard wall NiMH charger.
In my experience, those circuits aren't as safe as they say.
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Old 08-01-2012, 11:39 AM   #16 (permalink)
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What is a life pack? They are safer for the tx? Stronger than a nimh?

What about these eneloops? You put them in a 8 AA harness that fits in the stock battery tray?
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Old 08-01-2012, 11:49 AM   #17 (permalink)
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Quote:
Originally Posted by nickypoo View Post
What is a life pack? They are safer for the tx? Stronger than a nimh?
It's a lithium battery of a different formulation than lipos. The full name is LiFePO4 (lithium iron phosphate). The main advantages are their flat voltage discharge curve and nominal 3.3V/cell output, making them especially attractive as a receiver pack for LV servo setups without a regulator. The same goes for transmitter packs because there's less "excess" voltage vs. lipos when used in place of NiMH. They also tend to be less volatile than lipos.

Quote:
What about these eneloops? You put them in a 8 AA harness that fits in the stock battery tray?
You can do that or get premade packs (or get tabbed cells and solder and shrink wrap your own pack). I have a Radio Shack 8-cell battery holder with AA Eneloop cells in my DX7. In my X9303, I have a premade pack I bought here:

http://store.batteriesamerica.com/sa...eadytouse.aspx
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Old 08-01-2012, 12:01 PM   #18 (permalink)
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Life or Sanyo?
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Old 08-01-2012, 12:18 PM   #19 (permalink)
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Quote:
Originally Posted by nickypoo View Post
Life or Sanyo?
My link is to Sanyo packs. I don't trust lithium of any sort in transmitters anymore.
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Old 08-01-2012, 12:23 PM   #20 (permalink)
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MMV.
I have been using the same lipo in my DX7 since end 2007. I never discharge more than 3,8V and never charge inside the tx . Same goes for my 2 sons
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