NigelH Posted March 22, 2012 Share Posted March 22, 2012 When enquiring about Eneloop RX pack voltages, I also posted the same query here The responses are interesting in that people have suggested that Eneloops are unsuitable for use as flight packs, despite them being sold as such. What does anyone else think ? Thanks Edited By Biggles' Elder Brother - Moderator on 22/03/2012 14:01:51 Quote Link to comment Share on other sites More sharing options...
Ben B Posted March 22, 2012 Share Posted March 22, 2012 A bit of searching shows up this graphwhich looks about right to me. Doesn't look too scary unless pulling major amps but then you'ld probably want to use a lipo and a regulator in that case anyway because if you're pulling 5/10amps a 2000mAh rx battery isn't going to last long.... Edited By Ben B on 22/03/2012 12:26:37 Quote Link to comment Share on other sites More sharing options...
NigelH Posted March 22, 2012 Author Share Posted March 22, 2012 Thanks. Timbo did some DS821 current testing here Looks like four would be drawing about 800mAH. Four flights of ten minutes or so doesn't look unreasonable then but those guys were adamant that the packs were unsuitable for use as flight packs. Edited By Biggles' Elder Brother - Moderator on 22/03/2012 14:02:48 Quote Link to comment Share on other sites More sharing options...
Ben B Posted March 22, 2012 Share Posted March 22, 2012 Yes but they are on RCgroups They're applying a point blank "no good for flight packs" rule without specifying the plane being flown. The site they reference ("hangtime" ) is mostly IMAC planes. Clearly with a mahusive 3d plane with loads of servos using a 2Ah pack is a bad idea- but that's the case whether it's nicads, nimh's or LSD nimh's. I suspect it's a classic case of "my mate down the pub says....". Someone said that you shouldn't use a small rx pack for a big plane with loads of servos and high current draw and they've somehow tranformed this into "eneloop packs should never be used for rx packs". Actually, a large hole in their argument is the fact that the site they refer the OP to in order to "learn about cells" actually sell NiMH rx packs! And eneloops have a lower I.R. than many nimh cells. So the very site they are using as supporting evidence that you shouldn't use eneloop rx packs actually disagrees with them. Realistically if you're flying a small to medium plane and its not bristling with servos a 2Ah eneloop pack is fine. Unfortunately with their sweeping statement they also swept logic out of the way Edited By Ben B on 22/03/2012 13:20:40 Quote Link to comment Share on other sites More sharing options...
Ian Jones Posted March 22, 2012 Share Posted March 22, 2012 I may have missed it in all the speculation but have Sanyo & Overlander been specifically asked to comment on the issue of impedence and it's effect on the suitability of use of these batteries as flight packs? Quote Link to comment Share on other sites More sharing options...
NigelH Posted March 22, 2012 Author Share Posted March 22, 2012 Ian I didn't buy the pack from Overlander. As I've used them before, it was the just first place that I looked for a reference point. I'll speak with the place that I bought it from. I've just sent an enquiry to Sanyo. I'll report back. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted March 22, 2012 Share Posted March 22, 2012 Hi Nigel, re links; the new system works the other way round - type in your word ("here" for example) then highlight it, click the link button and paste the URL into the dialogue box. See here for a full tutorial and a sandpit area wereyou can test it out. Hope this is useful for you - and others that might be reading! BEB Quote Link to comment Share on other sites More sharing options...
Ben B Posted March 22, 2012 Share Posted March 22, 2012 The following make a move towards Rx packs other than 4-cell LSD NiMHs more likely 1) the change from 35Mhz (which would carry on receiving until the servos hardly moved) to 2.4Ghz which will brown out. 2) the increased use of digital servos with consequential higher current draws 3) the move towards bigger, more powerful planes 4) servos getting cheaper so people are more likely to use more (e.g. seperate airelon servos / elevator half servos) 5) the increased percentage of people flying 3d rather than regular "sports" flying 6) the move to NImhs from NIcads (which had lower IRs) All these mean you have to be more careful about rx pack choice but it's still not appropriate to say they're not suitable point blank. Certainly gone are the days you'ld stick a 4.8v rx pack in everything. Or to put it another way how about we have a poll? "If you use Eneloops battery packs, have you ever had an accident that you suspected was due to the LSD NiMH you were using?" Quote Link to comment Share on other sites More sharing options...
NigelH Posted March 22, 2012 Author Share Posted March 22, 2012 Inserting URLs - easy when you know how. I'll know next time. Thanks Quote Link to comment Share on other sites More sharing options...
NigelH Posted March 22, 2012 Author Share Posted March 22, 2012 I can't call the vender right now but they state 'These excellent Eneloop cells have an extremely low self discharge rate, higher current delivery, capability'. Quote Link to comment Share on other sites More sharing options...
nasa_steve Posted March 22, 2012 Share Posted March 22, 2012 ive been using Eneloop and Overlanders equivilant for a while now with absolutely no ill effects nasa. Quote Link to comment Share on other sites More sharing options...
John Cole Posted March 22, 2012 Share Posted March 22, 2012 If you look on the Eneloop info page you will see there's a reasonably-new high-capacity Eneloop cell and this might change some of the restrictions on the old ones. Look for the XX type Quote Link to comment Share on other sites More sharing options...
Andrew767 Posted March 22, 2012 Share Posted March 22, 2012 Posted by nasa_steve on 22/03/2012 16:32:57: ive been using Eneloop and Overlanders equivilant for a while now with absolutely no ill effects nasa. Steve....In what planes?....How many servos? Thanks Andrew Quote Link to comment Share on other sites More sharing options...
Alan Cantwell Posted March 22, 2012 Share Posted March 22, 2012 i use a 5cell one, and its installed in an 81"span TA152, with 8 servos working away, 4 of them metal geared 645mgs, not noticed any ill efect, plenty in there after 5 flights, and i dont alf paste the thing!!! retracts though, being mechanical, have their own battery, just considering a switch to the much vaunted ABC cells, all the LMA boys are raving about them, the eneloops dont come in high capacity sub C size, i asked sanyo if this was going to alter, and they have no intention of making sub Cs Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 22, 2012 Share Posted March 22, 2012 A real can of worms this Nigel......I, like many other use these LSD cells & have had no issues with them so far. The problem appears to be that they cannot supply "high" currents without a significant drop in the output voltage. Such a drop in voltage can lead to problems with 2.4GHz receivers dropping out due to the low voltage. What is difficult is establishing what the current drain is in an installation in your model......obviously the current taken from the battery will vary depending on the load on the servos, knowing what this peaks at is very difficult to acertain & hence we don't know if we are drawing a "high" current from our batteries. I don't think this is a specifically LSD battery issue...I think it probably applies to all AA cells to a certain extent...the shape of an AA cell (long & thin) is not conducive to high current flow. But then we need to ask ourselves what is "high" current in our application.....frankly I think you'd be unlikely to see a total current drain much over 1A in a typical 40-60 powered sport model & even this would only be for a very short period of time. In this sort of application I believe that the LSD cells will be fine. Of course if you are looking to use a much larger model with many more servos...possibly digital...then you may draw lots more current & this may be where the LSD cells break down. In this case we probably need to look at sub C cells or the like. These can supply much more current without the voltage sagging. Also it is very important not to confuse capacity with the ability to supply high currents....often a high capacity pack will be less able to supply high currents at a consistent voltage than one of a lower capacity..... There have been many threads devoted to this issue on the forum....I'll see if I can find some & post the links Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 22, 2012 Share Posted March 22, 2012 @Alan 4 Vapex "Instants" are available in C cells......see here....I'm sure they would make them into an RX pack if you wanted... Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 22, 2012 Share Posted March 22, 2012 Servo Current Consumption How much current do servos use? Interesting stuff.... Quote Link to comment Share on other sites More sharing options...
John Cole Posted March 22, 2012 Share Posted March 22, 2012 Steve: if you read the Eneloop info page you'll see that the XX series has been brought out specifically for high-drain devices. They AREN'T just high-capacity. But Sanyo don't quote a design-max discharge rate. Also: the cell outer format gives little indication of what's inside: think Swiss Roll! NiCds of this format could deliver massive current. Quote Link to comment Share on other sites More sharing options...
Trevor Crook Posted March 22, 2012 Share Posted March 22, 2012 I was chatting to our club chairman a couple of weeks ago and he was telling me he'd made some measurements on an Eneloop Rx pack under load. He said that the results were very impressive, better than most cells he'd tested. Unfortunately, although he told me the various figures he obtained, I've forgotten them! Sorry that this is such a vague contribution, but I'd be confident of using them as a pack in my modest (up to 6' sport and sport/scale models. Quote Link to comment Share on other sites More sharing options...
Trevor Crook Posted March 22, 2012 Share Posted March 22, 2012 Hmm, don't know where the winking face came from! Quote Link to comment Share on other sites More sharing options...
Ben B Posted March 23, 2012 Share Posted March 23, 2012 It's because you've put 6" " ) and the " ) without the gap inbetween is the shorthand for a winking face comme ca Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 23, 2012 Share Posted March 23, 2012 Hi John.....I wonder why Sanyo don't state a max discharge current? Interesting...... They may offer them for high drain devices but what does this mean? Is it merely marketing speak.....? A "high drain" device might just be consuming 0.5A or so....this is high drain compared with say 150mA & I would expect AA cells to cope quite happily with either.....the higher capacity ones will obviously last longer in either situation. Construction wise then yes I think your swiss roll analogy is spot on....two thin plates rolled together like a swiss roll.....to get the greater capacity they usually use thinner plates so they can pack more surface area into the cell......this can often lead to a higher internal resistance however & makes the voltage more susceptible to dropping under load. As you say NiCds were capable of delivering larger currents but these batteries were often much lower capacity......thicker internal plates = lower internal resistance = the ability to supply more current....plus of course its a different chemistry but I've absolutlely no idea if thats relevant or makes a difference!!! I have to say though that for my part much of this is speculation based on a little knowledge....& that can be very dangerous..... I do believe however that for a standard 40-60 type sport model with standard analogue servos a 4 cell LSD battery pack is more than adequate & very hard to beat in terms of reliability & simplicity.... Quote Link to comment Share on other sites More sharing options...
PatMc Posted March 23, 2012 Share Posted March 23, 2012 The Sanyo website has this graph that IMO gives enough performance info to show that they are suitable for use with most models. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 23, 2012 Share Posted March 23, 2012 Agreed Pat.....even at 4A they are holding up pretty well...& these are continuous loads.......our models will only put intermittant loads on them..... Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted March 23, 2012 Share Posted March 23, 2012 PatMc & Steve Interesting graph to put my mind at ease after all the hoo hah .Two points - 1 I see it was done at 25 degrees C does a lower temp affect the performance much ?& 2 are Vapex Instants the same do you think ? I use them and have had no problems with 5 or 6 standard servo set ups using Futaba 6ex 2.4 setup with a four cell Rx battery for approx four flights per session Quote Link to comment Share on other sites More sharing options...
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