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Aug 13, 2019, 08:05 PM
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CR2 and CR123A receiver packs


Hey guys,

I asked this in the battery forum, but haven't received a response yet so I will ask it here.

Have any of you made and used receiver packs out of either CR2 (3v) or CR123A (3.3v) batteries? I just received 40 each of Tenergy CR2 non-rechargeable and Tenergy CR123A rechargeable batteries. I am thinking to make non-rechargeable packs out of the CR2's and also some rechargeable packs out of the CR123's. They are both very small and lightweight batteries and if they can handle the load of 4-5 micro or mini servos then I think they would be awesome. The CR2's are 800 mAh and the others are 1500 mAh, so I may just use the CR2's R/E/T planes and the CR123's in other full house planes up to .25 size.

Thoughts or experience?

Mike
Last edited by gmwahl; Aug 14, 2019 at 09:30 PM.
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Aug 14, 2019, 09:35 PM
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Would pictures help? These look promising if they will last at least 6-8 flights each. I could then remove the connector and solder it onto another pack and fly again...no charging. The packs are free at this point, but I looked on amazon and I can get these for about $1.50 a piece, so $3.00 for a disposable pack divided by 6 flights minimum is about .50 cents per flight....quite affordable. The weight and dimensions are great for 1/2A planes too.

Mike
Aug 14, 2019, 09:42 PM
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Oops, here are the pictures.
Aug 14, 2019, 11:46 PM
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Once upon a time, in a galaxy far, far away (back in 2010? maybe not that far away), I played around with similar batteries to provide power for some small RC rocket gliders.

And it worked. I just had to make sure the batteries had sufficient power (no recharging). As I recall, I was surprised how long the batteries did last (month or more).

For my 1/2A models, I use a 6.6v 300 mah Li-Fe. And it has plenty of power.

For my rocket gliders, I use a 1s (3.3v) 500 mah Lipo. A fully charged 1s Lipo is around 4.2 volts, and supplies enough power for a couple of flights.
Aug 15, 2019, 12:26 AM
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How much flying time do you usually get out of the 300mAh LiFe pack?

Mike
Aug 15, 2019, 07:43 PM
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Quote:
Originally Posted by gmwahl
How much flying time do you usually get out of the 300mAh LiFe pack?

Mike
Gosh. With the 6.6v 300mAh, I get 3 or 4 flights in a day, and I may fly 2 or 3 times before I recharge.

In other words, I have all kinds of power. Usually with 3 to 5 servos.

Frankly, seems like a challenge to get the battery down to 6 volts.

https://www.towerhobbies.com/cgi-bin...p?I=LXHCKV&P=7
Aug 15, 2019, 11:17 PM
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Some of us racing the EF1 electric event have tried using a separate battery for the receiver, and servos. I gave it a try last year, and I raced 6 times without recharging. Servos are all Hitec; two HS225's and one HS82. Average flight times were probably 2 to 3 minutes. It was a day later that I recharged, and I had used less then 1/2 of the capacity, but bare in mind that these batteries may "rebound" some after a rest. I was using the Specktrum 300mAh life pack.
Aug 16, 2019, 03:27 PM
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Quote:
Originally Posted by crawf56
Gosh. With the 6.6v 300mAh, I get 3 or 4 flights in a day, and I may fly 2 or 3 times before I recharge.

In other words, I have all kinds of power. Usually with 3 to 5 servos.

Frankly, seems like a challenge to get the battery down to 6 volts.

https://www.towerhobbies.com/cgi-bin...p?I=LXHCKV&P=7

Nice! Sounds like the LiFe batteries are the bees knees!

Well, I've made up two CR2 packs and two CR123 packs and will test them to see how far I can safely push them. Without knowing how many mAh I'm pulling out I guess I will just try them until I hear a servo start slowing down. I'm also considering making a couple of transmitter packs for a few of my 72 MHz radios.

Mike
Aug 17, 2019, 07:13 AM
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Don't try fling a Life pack till the system slows down, that will lead to a crash. The only problem with Life batteries is there is a knee in their discharge curve. Until it hits that knee, it puts out current at the same rate, but once past that knee, the voltage drops very quickly. The Life packs that I have are in models that usually only get a few flights at a time. If used on a model that gets flown a lot on a single day, you will have to determine how much current used per flight and , by experimenting, how many mah the pack actually puts our before it hits that knee, then stop well short of that point.
Aug 17, 2019, 02:58 PM
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Quote:
Originally Posted by Allen Dye
Don't try fling a Life pack till the system slows down, that will lead to a crash. The only problem with Life batteries is there is a knee in their discharge curve. Until it hits that knee, it puts out current at the same rate, but once past that knee, the voltage drops very quickly. The Life packs that I have are in models that usually only get a few flights at a time. If used on a model that gets flown a lot on a single day, you will have to determine how much current used per flight and , by experimenting, how many mah the pack actually puts our before it hits that knee, then stop well short of that point.
Huh?

What do these terms mean: "system slows down"; "knee in their discharge curve"

Are these cases where the Li-Fe battery is also powering an electric motor?

I am NOT a battery expert. But I have been flying Li-Fe batteries in small aircraft for receiver/servo power for a couple of years, and I don't think I have seen this phenomena.
Aug 17, 2019, 03:51 PM
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On older nicads you could fly until the volts drop to the point you feel the servos slowing down. They have a very shallow volts curve as they discharge. With Life the battery will hold its volt up to the very end and drop off almost instantly..the volt curve has a sharp drop off near the end. looks like a knee...
A wee bit o slang in Allen's description
Latest blog entry: In flight
Aug 17, 2019, 08:38 PM
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Quote:
Originally Posted by turbonut
On older nicads you could fly until the volts drop to the point you feel the servos slowing down. They have a very shallow volts curve as they discharge. With Life the battery will hold its volt up to the very end and drop off almost instantly..the volt curve has a sharp drop off near the end. looks like a knee...
A wee bit o slang in Allen's description
Thanks. I know more than I did.

I have been flying RC since 1982, and I had never heard of the "slowing down" phenomena. Always learning.
Aug 17, 2019, 09:14 PM
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Not something I would ever do...
Latest blog entry: In flight
Aug 18, 2019, 06:16 AM
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Sorry for any confusion. The term "knee", as used in the discharged curve of Life batteries is a common term, because of the sudden straight down voltage drop when they reach their discharged state. Because of this, you can't use an ESV (expanded scale voltmeter) to check charge level like you can with NiCad or NiMah batteries. as the ESV will still show normal voltage, even if the Life battery is just minutes from being totally discharged. Only flying them for a few flights and determining how many Mah has been used, compaired to how many the battery is rated for, can give you an idea of how many flights you will get out of a given pack. Even then it is best to err on the conservative side.
Aug 18, 2019, 03:22 PM
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Good comments. I'm assuming that I can use the LiFe battery for a few flights and then recharge them to see him many mAh's I'm putting back in and then I can estimate total flying time available to me. Not sure how to tell how much capacity is left in the non-rechargeable CR2 and CR123 batteries. I'm assuming they have that same "knee" phenomenon?

Mike


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