High mAh AAA pack

[Karl West]

I did a search on here for any info regarding high mAh AAA packs. I am needing to fit a smaller rx pack on a model and one way I can do this is by going for a AAA 5 cell (6V) rxr pack. I know that 800 - 950 mAh AAA packs are available and the thread from back in 2012 stated that the limitation for these packs going to higher mAh was the physical size. I know that there has been some development to reduce the thicknesses of internal components in NiMH cells and found some "advertised as" 2000mAh cells via the usual online auction site. Although the seller was a UK based seller I don't know the provenance of the cells (they are purely marked with their capacities) without any brand name. Knowing of the likely voltage sag under load I made these up into a 5 cell pack but I am wondering if anyone knows whether these will be OK as a rxr pack (also powering 4 std size servos) or whether there is some "commercial licence" being taken with the actual vs theoretical performance of such cells. I will of course run a ground based trial before committing to live aviation! Any thoughts gratefully received.

[Bob Cotsford]

Do you really need 2000mAHr? With 4 standard servos and a receiver even 500mAHr should give 2 or 3 hours of operation.

I know that with telemetry I can see a voltage drop of 0.5v or more using 2000+ AA packs with 5kg servos so I'd be very wary of trying AAA cells. Have you thought about trying 2S LiFe packs? I use the slightly larger 1100s on quite 5 and 6 servo setups without problems.

[Frank Skilbeck]

+1 for LiFe packs, I've replaced the 5 cell AAA Nimh with them in my 6 servo glider and the voltage under load is more stable. Unless you are going for a very low current draw I'd avoid high capacity small packs as the construction usually leads to a high internal resistance.

[Denis Watkins]

Please don't shoot me down. I am trying to use normal language and give you all options. The AAA battery size remains the same volume for both 500 mAh, and 2000 mAh, yes? OK, so the manufacturer has to fit in their AAA an electrolyte to store 500 ma, or 4 times as much, 2000 ma. Now imagine the electrolyte is a sheet of A5 paper to be rolled up and slid into the AAA pack. How thick would the electrolyte be at 500? But more importantly, how thin would the electrolyte be at 2000?, 4 times as thin is the answer… The same goes for AA. We have a longevity issue now, as the thinner electrolyte is used up more quickly in the volatile atmosphere within the cell. Please allow me this simplistic explanation. Us AA always when you can, and as low as you can buy, e.g. 600 - 800 - 1000 mAh , as there is simply more meat in them. We all think 2000 is wonderful, " charge it once per month ", but in general a lower mA rating has heck of a lot more punch. Conclusion, with standard servos use AA, and if room is an issue, odd shaped packs can be made up

[John Lee]

I've been using the same AAA 800Mah genuine enerloop 4 cell pack in a Blizzard with 2 analog & 2 digital servos since 2009 without issue. It has more than enough capacity for a day's flying.

[Karl West]

Thanks for the replies. Given the info above I will look at either going with a 5 cell of AAA 900mAh eneloops OR look at LiFe batteries. The only issue with the LiFe is that, as far as I can see, none of the 2s packs come in at a size comparable to a 5 cell flat AAA configuration, although happy to be proved wrong! I need the slimness to fit into the available space (want to leave the model as is rather than mess with hacking it about etc)

[Robin Colbourne]

Denis, Excellent post! That' a very interesting point, of which I wasn't even remotely aware. It probably explains why my old 500 to 650mah NiCad receiver batteries were so bulletproof and good for two or three hours of instruction, stopping only to refuel, when used every weekend (I did check before each flight on a battery condition meter), whereas modern 2000mah+ NiMH cells seem to be so unreliable.

[John Lee]

Karl As an alternative I've found these LiPo's with a regulator good if space is tight.

[Phil Francis]

Try component shop for 2000mah eneloop good prices and fast delivery.

Phil

[Denis Watkins]

Do watch out for Eneloop fakes. 1000 apologies to mention it, but they look real until you weigh a real one and a fake. Eneloops are expensive, sobdi your vest to stick to the true dealers, apologies again.

[Steve Hargreaves - Moderator]

I don't think you will find any 2000mAh AAA packs.....AA packs yes but AAA cells are rated to around 1100mAh.

As the others have mentioned 2S LiFe is a great alternative & will certainly pass more current than a AAA pack...

[Phil Francis]

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Edited By Phil Francis on 15/02/2016 18:27:07

[Don Fry]

Phil, hitting heads against walls is good for the soul. There is a fine Welsh phrase, "can't educate pork, boyo". I hope your constipation improves.

[Don Fry]

And I am REALLY sorry Phil, if I have raised your stress levels.

[Phil Francis]

I would not have posted if I did not trust said supplier. Apology accepted. Comment removed.

Phil

[Peter Android]

Purely my own experience for what it's worth . not preaching. not an expert .

Since I began using 2.4 Ghz Radio , being mistrustful of 4.8V Rx , I have had excellent results from the vapextech AAA 6 volt NIMH Rx Packs .

Both on Standard Futaba x 5 and Digi Spektrum x 5 servo's , ( same model) if anything the degradation per flight is less than my ( now defunct) same make - AA cells which was contra to expectations.

The ones I refer to are the Green Coloured Cells ,

NOT the Red ones which ( for me at least) had an appalling degradation rate and were subsequently junked .

I am now experimenting / monitoring with an 2S Life pack for Rx / Servo power , which I hope are as good as they read ?

I also use vapextech (Green ) NIMH in my TX's

**LINK**

One Caveat , beware when ordering via flea - pit , they sent me the red cells , twice .

now rectified ( monetarily - not electrical current )

P.