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Do I need to replace my 6v Eneloop Rx pack?

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propogandhi26/12/2011 13:35:08
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359 forum posts
273 photos
Just a quick one gents. This is my first Eneloop pack and its being used in an electric model as power for the radio eletronics (alierons, elevator, rudder, flaps, eflite retracts). Fresh off my 750mah delta peak wall charger my DX8 tells me its at 7.5v (which I assume is fully charged at 1.5v per cell?). What I am seeing though is that after being on for say 15-20 mins (whilst I'm setting up the model, cycleing retracts/servo's etc), the pack voltage is falling down to around 6.5v, or 85% according to my bettery checker.
 
My question is, is this normal for Eneloop cells? I know they are meant to stay at 85% for a long time without use, but is this also the level the pack falls back to rather quickley with regular use? The pack was brought off ebay and now I'm wondering if I've now discovered the reason it was sold, but then I'm thinking it could just be the way these cells behave.
 
Any input on this would be greatly apprceicated.
 
season greetings to all,
 
prop.
Frank Skilbeck26/12/2011 18:01:22
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4728 forum posts
101 photos
No. look here you'll see that a drop off to below 1.3v per cell is pretty normal shortly off charge.
Barry Ensten30/01/2012 18:21:44
8 forum posts
You are putting FAR too much load on the ENELOOPS as they have a high internal resistance. Each cell has an internal resistance of 0.1R when new, so a 5cell pack will drop 0.5V @1A. If you operate Flaps and gear together you could quite easily pull 2A, meaning a 1V drop.
 
It's lucky you have been using 5 cells, as if you had been using 4 you would be getting brown outs (and crashing).
 
Eneloops are great for TX's (only take 200mA ish) but useless for all but small models.
 
A trainer with an LA46 is as big as I would go with them.
 
 
 
Barry
 
 
 
Tim Mackey30/01/2012 18:44:09
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20920 forum posts
304 photos
15 articles
With respect -I dont agree. Servo current consumption is far less than most folk believe, and I have seen ( and flown myself ) pretty large models that are powered by eneloop AA cells.
I also dont agree on the brown out - Spektrum gear actually has a very good tolerance to low voltages, and with the "Quick Connect" system built into every receiver, a brown out is actually not a likely cause for a crash - in fact the only way you're likely to know you suffered one is via the flashing led upon landing.
All these staemnets are backed up by plenty of experience with spektrum gear ( 4years + ) and also documented real world testing.
 
Obviously Im not condoning flying with below par batteries, or suggesting that brown outs are to be ignored, but I just think your rather sweeping statement is a little OTT
Mark R30/01/2012 19:05:36
279 forum posts
44 photos
Have to say i agree with Tim...very sweeping statement, been using eneloops for awhile now. Got 1 in my travel air 4 servos, 1 in my Maachi 4 servos and 1 retract, they seem to last me well and allow all day flying, tho as a matter of caution upon landing i use a battery checker and before i fly again i check again. Not techincally minded so cant give fact n figures just real world flying.
Codename-John30/01/2012 20:26:44
1087 forum posts
18 photos
I used 1 eneloop 4 cell pack in a kyosho spitfire 50 while setting it all up, operating everything retracts, flaps, twin aileron servo`s etc was testing it all for at least half an hour cycling everything back and forth checking for snags etc and no problems what so ever, and i like mark use them in lots of models
 
 
 
Lee Smalley30/01/2012 23:05:55
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2125 forum posts
68 photos
2 articles
barry yet again misleading information based on old stories and technology, i use eneloops in all my models even 30cc petrol, tim is correct, they are more than able to handle normal flight loads
John Cole31/01/2012 11:18:55
615 forum posts
24 photos
When referring to Eneloop documentation and reports you should be aware that a new version was introduced a couple of years ago with better performance and rechargeable 1500 times.  These can be identified by the part number HR-3UTGA; the old one was HR-3UTG.
 
Also there is a newer version, referred to as the Eneloop XX. This has been specifically designed for high-drain use and has more capacity - 2500 maH.See the press release accessed from the News section (bottom left) of EneloopInfo where you will find lots of useful info and data.
 

Edited By John Cole on 31/01/2012 11:27:53

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