martin collins 1 Posted March 31 Share Posted March 31 One of the models i am working on at the moment is going to need a RX pack for the receiver and one for the Ignition, i am looking at either a 2s LiFe pack or a 6v Eneloop, what are the benefits/drawbacks of either in this choice, which one would you pick and why? Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted March 31 Share Posted March 31 Would depend on the size of the model, for larger models I prefer Sub C cells rather than AA for their ability to maintain voltage underload. Other than that I've used both Life and Nimhs for Rx/Servos and ignition. Don't leave Life cells on, if the voltage drops too low they are toast, so remember to make sure they are switched off after a days flying. Quote Link to comment Share on other sites More sharing options...
steve too Posted March 31 Share Posted March 31 I use 4 cell AA Eneloop packs for ignition service and see no benefits in using anything else. I have some models with 2S LiFe packs, but I may go back to subC for my bigger models and Eneloop (or LiPo and UBEC) for the smaller ones as I don't like the flat discharge curve of the LiFe. Quote Link to comment Share on other sites More sharing options...
Dale Bradly Posted March 31 Share Posted March 31 I use LiFe for Rx and ignitions in all new stuff for the last several years. A couple of legacy models remain on Nixx tech. Reasons for LiFe preference: availability, cost, and also a statistical basis that the more items (i.e. cells and joins between those cells) you have the more chance of a failure somewhere in the system. Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted April 1 Share Posted April 1 I use Tamiya 7.2 sub C stick packs, the Rx run off of 5 elements and the ignition from the end at 7.2 volts, no radio interference and no problems with 2 separate battery's. Quote Link to comment Share on other sites More sharing options...
Peter Christy Posted April 1 Share Posted April 1 I had issues using eneloops on ignition systems. It was in a large scale Bell 47 helicopter and could barely get daylight under the skids! Switching to sub-C cells brought it back to life, and it flies fine on those, with no other changes. The AA cells have a higher internal resistance, which is fine for receiver use - even with power hungry servos (though not if you have more than four, I would suggest!) - but the ignition system I was using was a capacitor discharge type. The higher internal resistance meant the capacitor couldn't fully charge between strokes, resulting in a loss of power. I couldn't use LiFe's on it, as it was restricted to 5V, with dire warnings for the consequences of exceeding that! I believe the later versions are more tolerant! Similarly, the servos in the heli were JR, which don't like more than 5V. I ended up using 4-cell sub-C packs for both, which proved more than adequate and reliable. If your servos and ignition system will tolerate higher voltages, then LiFe cells are good. Just remember that although the nominal voltage is 6.6 volts for a 2-cell LiFe, fresh off charge, they can exceed 7V! Make sure your servos/ignition will tolerate this - however brief it may be! 1 Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted April 1 Share Posted April 1 I have pairs of Spektrum Life receiver batteries in two of my warbirds and they infuriate me. If I try to charge them simultaneously on the A & B ports on my Overlander V2 charger 9 times out of 10 I get a Bad connection warning. If I charge them one at a time they are usually ok. As mentioned the flat discharge means you never really know what capacity they have left. I chose them because of the reputable brand and fact that Life batteries can be charged in the model, unlike Lipo’s and warbirds generally have batteries tucked away up front within the cowl area as ballast. To add a battery type to the opening question, what about LiIon? I put three in my FW190 (2 x receiver and 1 for ignition). So far I have been happy with the choice as they are simple to charge and can stay in the model, though not so re the cost. Quote Link to comment Share on other sites More sharing options...
Peter Christy Posted April 1 Share Posted April 1 (edited) Nick: I've never had an issue with LiFe cells and Overlander chargers. All mine came from Hobbyking (yeah, I know!) mainly because, at the time, nobody else seemed to stock them. Even now, they are the only source of 3-cell LiFe packs, which make very good substitutes for "Old School" transmitters that run on 8-cell NiMhs, as the voltages are almost identical. I would suggest you get someone to try and charge your packs on their charger, to see if the issue is the cells or the charger. It sounds like one or the other is faulty to me. I've never come across Spektrum LiFe packs, but I would assume they buy them in from a supplier, and put their own stickers on them - just like everyone else! 😉 LiIon is the same chemistry as LiPo, the primary difference being the packaging. They are somewhat less prone to physical damage, but can be more sensitive to abuse. The metal case can't "puff up" to help relieve the pressure if they are abused! I believe they do have vents for such situations, but in a severe situation, these could become clogged. Basically LiIon has no significant advantages over LiPo, and will probably be heavier for the same capacity. They are quite often found in modern transmitters, where they are well protected both physically and electrically. In a model they may be more exposed to both! Edited April 1 by Peter Christy Typo Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted April 1 Share Posted April 1 IMHO I would not use either. Technology has moved on. Lipo's that I use as a flight packs as they get a harder life and if they can't support powered flight they go for recycling that way they are always good enough for RX duties. Don't like cheap/unreliable switches so go for a switch/UBEC that has sufficient current rating to deal with a failed/jammed servo and not brown the RX out. Better go and hide in a BatSafe box now! 😉 1 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted April 1 Share Posted April 1 Simultaneous charging of installed batteries often fails due to the charger’s “intelligent” features finding leakage paths or something similar through the common “earth” connections on the model which appear to confuse them and cause early charge termination. This can occur when using multiple chargers as well. I’ve found that using separate power supplies (e.g. mains on one and batteries for others to ensure separation) can allow the use of two or more chargers simultaneously - e.g. dual receiver batteries and onboard glow. The excessive freshly charged LiFe voltage can be tamed by means of a decently rated silicon diode in series with the supply lead (beyond the charge point). This typically drops @ 0.6V with a very good reliability risk - 2 additional solder joints versus multiple components and connectors in a BEC solution. While LiFe do have a flattish discharge curve, their state of charge can be discerned from an accurate voltage reading but given their energy density, can usually be over specified by a large factor compared with nickel based batteries giving a huge margin over the 700mAh packs which would give a comfortable day’s flying in years gone by. 1 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted April 1 Share Posted April 1 Never had issues with any of them, tend to use Life mostly now though, in truth it's on cost basis. Quote Link to comment Share on other sites More sharing options...
steve too Posted April 1 Share Posted April 1 1 hour ago, Peter Christy said: I've never come across Spektrum LiFe packs, but I would assume they buy them in from a supplier, and put their own stickers on them - just like everyone else! Spektrum's Smart LiPo and LiFe batteries have integrated management boards. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted April 1 Share Posted April 1 I use LiFe. Both chemistries are bulletproof, but LiFe can be charged really quick if you want a surprise model, or a surprise session, as in 20 minutes and out the door. If you want more load capacity, use a bigger LiFe pack. Note NiMh to me equals Enloop cells. The rest I have concluded over the last couple of decades are rubbish. 1 Quote Link to comment Share on other sites More sharing options...
Peter Christy Posted April 1 Share Posted April 1 35 minutes ago, steve too said: Spektrum's Smart LiPo and LiFe batteries have integrated management boards. That could well explain why they don't play nicely with Nick's Overlander charger! -- Pete Quote Link to comment Share on other sites More sharing options...
Nick Somerville Posted April 1 Share Posted April 1 Thanks for thoughts chaps. My Spektrum Life batteries are not the Smart type. My Overlander D100 V2 doesn’t baulk at charging 2 Lipos at the same time or 2 Liions! Interesting point about the earthing though. I did have an earlier D100 without the voice prompts but that went bang when charging the same life batteries simultaneously. Quite scary as I was working close by at the time. Interestingly if I go down to 0.5 amp charging it does sometimes behave. Interesting comment about Liion batteries being no better than LiPo. If you google LiIon the blurb always comes up as superior to Lipo on several fronts. Also Powerbox and Jeti, both high end radios, market them as preferred Rx and ignition batteries. I assume there must be a reason. Quote Link to comment Share on other sites More sharing options...
GrumpyGnome Posted April 1 Share Posted April 1 Typically, if a manufacturer is 'pushing' something, it's because they can make money. Cynical? Moi? Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted April 1 Share Posted April 1 It's not a bad reason to go into business. However, most profit on batteries comes from sticking a label on the package so in these cases, function and reputation probably take precedence. Quote Link to comment Share on other sites More sharing options...
steve too Posted April 1 Share Posted April 1 2 hours ago, Nick Somerville said: Interesting comment about Liion batteries being no better than LiPo. My understanding is that LiPo and LiFePO4 are both types of lithium ion batteries. Quote Link to comment Share on other sites More sharing options...
Peter Christy Posted April 2 Share Posted April 2 Its not a question of LiPo being better/worse than LiIon. Its horses for courses, and each has its merits and disadvantages. Its true that LiFe cells are also Lithium based, but the internal chemistry is quite different. LiFe cells are much less prone to combusting when abused, making them more suitable for installation in hard-to-get-at places. However, they have slightly less capacity for a given size. They also can't deliver quite the same peak current as LiPo/LiIon cells, which is why they are rarely used for traction motors. -- Pete Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted April 2 Share Posted April 2 Pete, have a look at the Li-ion Molicels being offered, some EDF guys are using them, not quite the same punch as Lipos but mah per mah they are lighter. We've put 2 x 2s ones to power the Rx and servos in my mates FW190 to replace 2off 2200 mah 2s lipos, note model has all HV servos. Quote Link to comment Share on other sites More sharing options...
Peter Christy Posted April 2 Share Posted April 2 (edited) I've have actually used LiFe cells to power the motor on an electric glider I've got. Its a 3-cell 2200MAh pack. The power plant in the glider is a geared Graupner Speed something or other (bigger than a 600). It was designed to run on 8-cell nicads, but the 3-cell LiFe is the right voltage, but lighter and smaller! Performance is - er - leisurely! 🤣 But its great on calm summer evenings - if we ever get any again....! -- Pete Edited April 2 by Peter Christy Typo Quote Link to comment Share on other sites More sharing options...
Nigel R Posted April 3 Share Posted April 3 On 31/03/2024 at 20:01, martin collins 1 said: One of the models i am working on at the moment is going to need a RX pack for the receiver and one for the Ignition, i am looking at either a 2s LiFe pack or a 6v Eneloop, what are the benefits/drawbacks of either in this choice, which one would you pick and why? Depends. How big is your model? How many servos? What kind of servos? What is the engine - single cylinder 2 stroke? Seven cylinder radial? Quote Link to comment Share on other sites More sharing options...
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