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LiPo replacement for Spektrum Tx Li-Ion - care and maintenance?

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Keith Miles 231/07/2020 01:17:16
501 forum posts
6 photos

Some time ago, I was persuaded, as others have done, to replace the original single-lead Spektrum 2S 2000mah Li-Ion in the Tx with a triple-lead 4000mah Li-Po, the latter seemingly only available from one source (a very reputable one) as far as I can tell.

The advantage of doing so being (a) greater capacity and (b) a 1 hour charge at 4A using a separate Lipo/Multi-charger as opposed to a slow charge, onboard, using the Tx jack and Spektrum adaptor supplied.

Flying mostly IC, aside from small indoor models plus a Riot, I’m now wondering (a bit late in the day!) if the Lipo conversion was such a great idea.

It seems, with only a few exceptions, that majority advice is not to leave Lipos sitting fully charged for more than about 3 days and, if doing so, to put them into storage charge. This is not, of course, necessary with Li-Ion.

So, I am now wondering , therefore, how many flyers who have done this Lipo conversion, regularly unplug and remove it from the Tx and put it into storage charge after a flying session and if they don’t expect to be using it again within 3 days i.e. treating it the same as a Lipo supplying motive power despite the fact that the Tx draws minimal current and will have lost much less capacity!

Whilst the original Li-Ion required an occasional traditional slow charge by just simply plugging the adaptor into the Tx, it seems that under general Lipo care advice, I should now be regularly removing the 4000mah Lipo, storage charging it, then fully charging it for 1 hour before EVERY flying session i.e. as one would for a Lipo flight battery.

Doing this in future would not only seem to defeat the object of the exercise but would also be less convenient, or am I missing something?

UPDATE! To add to the confusion, I now see that Spektrum offer 2S 4000mah Tx Lipo albeit, again, with a single lead. I understand that the Spektrum batteries, both Lipo and Li-Ion have inbuilt balancing. Still doesn’t explain the Lipo  “storage charge” anomaly, though, especially when that feature doesn’t exist in the Tx! 

 

 

Edited By Keith Miles 2 on 31/07/2020 01:57:16

Denis Watkins31/07/2020 07:17:19
4655 forum posts
132 photos

Just my take on it Keith, it is our own personal choice.

I fly mainly I/C, sport models, without telemetry and no " voice alerts "

And as I help others to maiden and instruct, I often don't get to fly my own models ! !.

On a good day, my personal experience is that I may use 300mah from my Tx pack.

This is not much use of a 4000mah pack, so some years ago I started to use 800mah in 1 Tx and 1000mah in the other.

This must be the 5th season for the 800mah which is still going strong leaving the field with 600mah usually.

It is then simpler to reach storage charge, or to charge prepared for the next day.

 

Edited By Denis Watkins on 31/07/2020 07:40:21

Dale Bradly31/07/2020 07:41:29
43 forum posts
13 photos

I will offer no recommendation either for or against, but here's my situation:

I replaced the factory NiCd in my JR Tx about 10 years ago with a HK lipo. Turnigy Zippy or similar labelling 3s, about 2200 or therabouts.

I give it a standard 1C full charge when it needs it, by removing it from the Tx so have access to the balance plug, on my normal Lipo charger.

I have never given this batt a store charge, removed from Tx for storage, precharged before flight, or any other process that we might consider standard operating procedure for a flight battery.

The end result:

Positives: This same batt has given faultess service, gives me at least half a season's flying between charges, and is one of the best simple things ive ever done in terms of model flying. The same battery will take me flying tomorrow, and i can't remember the last time i charged it...

Negatives: Because charging the Tx regularly isn't now part of the S.O.P, I of course will only hit the low batt alarm when i'm flying, so will have to stop flying for a bit to charge the Tx. But, it's a Lipo, so 20min break to charge will have me sorted for the rest of that day.

Will i do it again? Absolutely. When i get the next Tx, it will get the same upgrade at time of purchase if it does not come with a lipo as standard.The months between charges, for the tradeoff of having to remove the batt once every few months to charge, is absolutely worth it for me.

I have no doubt that this battery has suffered degredation compared to other batts that might be better cared for (e.g. most flight batteries), but as Denis aludes to in his post, the demands placed on the battery by the Tx are so low, that any degredation of the batt are not in any way a problem or concern to me.

Or in other words, I'm starting to be more concerned about the 12 year old computer that i use to steer my planes around the sky, than i am about that computer's power source.

brokenenglish31/07/2020 08:45:56
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605 forum posts
30 photos

My own opinion is simply "Why change something that has been working perfectly OK for years?"

8 years ago, when starting to teach myself to fly, I purchased an rtf Radian/Spektrum combo which was a great start.

8 years later, now with 4 Spektrum transmitters, after a lot of flying hours, I'm still using 4 eneloops in the Tx and I've never had the slightest problem, so why change???

I sometimes consider "upgrading", but it couldn't give a materially better result than the performance I've been reliably getting for the last 8 years...

Edit: Reading my own post, here, and Dale's post, above, it's clear that there are several (or even many) ways of getting a result that satisfies each person individually.
For me, the bottom line is that there's not much point in wasting time trying to improve something that has always worked perfectly OK!

Edited By brokenenglish on 31/07/2020 08:56:14

Edited By brokenenglish on 31/07/2020 08:57:17

Peter Christy31/07/2020 09:15:17
1921 forum posts

One thing that a lot of folks overlook is that 2.4 GHz transmitters use a LOT less power than the old 35 MHz gear.

Both are restricted to 100mW ERP (Effective Radiated Power). To achieve 100mw erp on 27 or 35 Mhz needed an input to the RF stage of around 1 watt, because of the inefficiencies of a telescopic aerial in a hand-held box. On the other hand, a 2.4 GHz Tx only puts out 60mW to achieve 100mW erp, due to the "gain" of the aerial.

In other words, a 2.4 GHz transmitter only requires .06 as much power in to produce the same power out!

In the days of 35 MHz, the RF board consumed the vast majority of the power. The encoder - even computerised ones - took only a small fraction of the total power consumption.

Even the most complex modern transmitters only draw a comparatively tiny amount of power into the encoder, so a 4000 mAH pack is severe overkill, to put it mildly! You could probably fly for a whole year on that without re-charging!

Also, bear in mind that most 2.4 GHz transmitters run at a much lower voltage than in days of yore, typically 5V or less. Admittedly the regulators need a bit of headroom, but most operate quite happily at 6 or 7V input. (A 2-cell Li-ion pack is typically 7.2V - 3.6V per cell). Using a higher voltage pack will simply cause the regulators to dissipate the excess power as heat! This might keep your hands a bit warmer in winter, but serves no other useful purpose! wink

My personal preference is to use LiFe cells in transmitters. A 3-cell LiFe comes in at 9.9V, and makes a perfect substitute for an 8-cell NiXX pack. A 2-cell Life settles at 6.6V, which should be quite adequate for most 2.4 GHz gear - but check the manufacturers voltage recommendations before rushing out to do this!

LiFe cells can be fast charged in the same way as LiPos - provided your charger has a LiFe setting (most modern ones do), they do not suffer from "memory" effect, and can be left charged for long periods without deterioration.

They cannot provide the extremely high currents that LiPos do, but this is unnecessary in a transmitter.

So please, use LiFe cells in transmitters, NOT LiPos!

--

Pete

Richard Clark 231/07/2020 09:31:19
424 forum posts
Posted by Keith Miles 2 on 31/07/2020 01:17:16:

Some time ago, I was persuaded, as others have done, to replace the original single-lead Spektrum 2S 2000mah Li-Ion in the Tx with a triple-lead 4000mah Li-Po, the latter seemingly only available from one source (a very reputable one) as far as I can tell.

The advantage of doing so being (a) greater capacity and (b) a 1 hour charge at 4A using a separate Lipo/Multi-charger as opposed to a slow charge, onboard, using the Tx jack and Spektrum adaptor supplied.

Flying mostly IC, aside from small indoor models plus a Riot, I’m now wondering (a bit late in the day!) if the Lipo conversion was such a great idea.

It seems, with only a few exceptions, that majority advice is not to leave Lipos sitting fully charged for more than about 3 days and, if doing so, to put them into storage charge. This is not, of course, necessary with Li-Ion.

So, I am now wondering , therefore, how many flyers who have done this Lipo conversion, regularly unplug and remove it from the Tx and put it into storage charge after a flying session and if they don’t expect to be using it again within 3 days i.e. treating it the same as a Lipo supplying motive power despite the fact that the Tx draws minimal current and will have lost much less capacity!

Whilst the original Li-Ion required an occasional traditional slow charge by just simply plugging the adaptor into the Tx, it seems that under general Lipo care advice, I should now be regularly removing the 4000mah Lipo, storage charging it, then fully charging it for 1 hour before EVERY flying session i.e. as one would for a Lipo flight battery.

Doing this in future would not only seem to defeat the object of the exercise but would also be less convenient, or am I missing something?

UPDATE! To add to the confusion, I now see that Spektrum offer 2S 4000mah Tx Lipo albeit, again, with a single lead. I understand that the Spektrum batteries, both Lipo and Li-Ion have inbuilt balancing. Still doesn’t explain the Lipo “storage charge” anomaly, though, especially when that feature doesn’t exist in the Tx!

Actually although the chemistry (lithium oxide with phosphates, iron, or cobalt) and voltage may vary from manufacturer to manufacturer (cobalt gives 4.2 volts) Lipo and Li-ion are the same thing. Only the packaging is different. and that is the only thing 'Lipo' refers to. Nothing else at all.

So all the 'storage voltage', avoid storing at full charge etc. stuff is ideal for them all, though essential for none. It extends their lifetime somewhat.

As for are they worth the faffing around? I think not. I use Multiplex rc and untl their very latest transmitter they used 2200 'Eneloop' Nimh cells. They hold their charge for a very long time, last all day, maybe two, on the field, and never need to be balanced.

So some years ago I changed all my transmitters (and all my planes radio batteries) to those. Yesterday I used an old JR transmitter with Eneloops that I put in a cupboard unattended for three years, I just switched it on straight out of the cupboard yesterday lunchtime and it's still running this morning, and it's still showing a good voltage

What else is needed?

Keith Miles 231/07/2020 13:03:45
501 forum posts
6 photos

Some interesting contributions, there.

So, would it be reasonable to assume, then, that the constant Li-Po “mantra” requiring storage charging is not absolute and can, in fact, for practical purposes, be completely ignored in certain circumstances as it has nothing to do with safety but only about maximising battery life?

Referring to my earlier post, it is, nevertheless, noteworthy that Li-Ion seems to be the preferred technology for the vast majority of consumer electronics and, perhaps, because it is less “fussy” and less volatile than Li-Po?

I must say that I have been more than happy with the Tx conversion, it was just the “storage charge” issue that was bugging me!

Actually, I recently built a Super Chipmunk (IC) and as it uses 7 servos, I opted to use, instead of my usual 4 cell 1000mah NiMh Rx packs, a 1000mah 2S Lipo and 6v regulator. It is certainly easier to unplug and re-connect for charging purposes than the Tx Li-Po, the latter being slightly fiddly and requiring a little more care!

Not sure why Spektrum are now offering a Li-Po Tx battery option albeit with the same single lead, dedicated two-pin plug and internal circuitry, or maybe I could offer a reason? Again, they ain’t cheap and seem to be primarily, or entirely, intended for use with the Tx and the supplied mains adaptor, though I could be wrong. But, hey, that’s another matter! 

 

Edited By Keith Miles 2 on 31/07/2020 13:32:49

Steve J31/07/2020 13:44:44
avatar
2105 forum posts
61 photos

As and when I decide that the 2S Li-Ion pack in my DX9 is approaching the end of it's useful life, I shall take it apart and replace the two cells with new ones.

All my LiPo's are stored fully charged. I may be losing a some cycles, but I really can't be bothered keeping them at their storage voltage and charging before I go flying.

Edited By Steve J on 31/07/2020 13:45:24

Paul C.31/07/2020 13:56:23
avatar
697 forum posts
165 photos

Interesting thread , I purchased a spektrum dx8 gen1 brand new about 8 years ago . At the time of purchase also had the genuine Spektrum lipo battery, a bit expensive but my mate recommended I get one to save having to charge so frequently easy to install and change the to lipo battery in the tx menu. The standard spektrum charger could still be used just found that it took a little longer that's all, I must admit I was a little surprised that there was no ballance lead and that I should use the standard charger. Not had the slightest problem with either the battery or the transmitter and have not noticed any reduced battery life. my knowledge of batteries is less than not a lot but this does appear to be at odds to how we are told to handle lipo flight packs.

Richard Clark 231/07/2020 14:28:32
424 forum posts
Posted by Keith Miles 2 on 31/07/2020 13:03:45:

Some interesting contributions, there.

So, would it be reasonable to assume, then, that the constant Li-Po “mantra” requiring storage charging is not absolute and can, in fact, for practical purposes, be completely ignored in certain circumstances as it has nothing to do with safety but only about maximising battery life?

Referring to my earlier post, it is, nevertheless, noteworthy that Li-Ion seems to be the preferred technology for the vast majority of consumer electronics and, perhaps, because it is less “fussy” and less volatile than Li-Po?

I must say that I have been more than happy with the Tx conversion, it was just the “storage charge” issue that was bugging me!

Actually, I recently built a Super Chipmunk (IC) and as it uses 7 servos, I opted to use, instead of my usual 4 cell 1000mah NiMh Rx packs, a 1000mah 2S Lipo and 6v regulator. It is certainly easier to unplug and re-connect for charging purposes than the Tx Li-Po, the latter being slightly fiddly and requiring a little more care!

Not sure why Spektrum are now offering a Li-Po Tx battery option albeit with the same single lead and dedicated two-pin plug or maybe I could offer a reason? Again, they ain’t cheap, presumably because of the apparent inbuilt (and dedicated?) circuitry.

Edited By Keith Miles 2 on 31/07/2020 13:26:02

Yes, it is just a 'mantra'. It was unheard of a few of years ago. But it's a trade off. Can you be bothered to go though the storage charge routine or just leave them in whatever state they happened to end up in after you last used them? (Which is what I do, be it a model plane, a transmitter, or a garden hedge trimmer.)

The concept of it is that no lithium based battery of ANY type likes to be completely flat for long. (That's equally true of Lead-acid and Nimh too.) So make sure it isn't by charging it up a bit. But then we usually don't keep going until the equipment stops anyway so 'completely flat' doesn't often happen.

Safety. I personally leave them in any state of charge even fully charged . But I am NOT going to formally state that it's as safe as leaving them in a lower state of charge.

"it is nevertheless noteworthy that Li-Ion.......preferred.....less fussy..."

Despite what I previously posted you continue to 'believe' that Lipos are diffeent. They are all  lithium ion. The only difference is the packaging. 'Lipo' refers to the POLYmer (plastic) case and that's all. It's not any kind of formal 'definition'.

Your Super Chipmunk. A 1000 ma battery is VERY (I could say dangerously) small for a 7 servo plane, even a quire small one. I assume your plane is 'medium size'. I suggest you change it for a 2200, it doesn't matter whether it's lithium or Nimh. But if you choose Nimh use Eneloops.

Edited By Richard Clark 2 on 31/07/2020 14:30:37

Paul C.31/07/2020 14:41:36
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697 forum posts
165 photos

Actually although the chemistry (lithium oxide with phosphates, iron, or cobalt) and voltage may vary from manufacturer to manufacturer (cobalt gives 4.2 volts) Lipo and Li-ion are the same thing. Only the packaging is different. and that is the only thing 'Lipo' refers to. Nothing else at all.

I didn't know this ! Thought that lipo and liion were two totally different things, never too old to learn something new 👍

Paul.

Richard Clark 231/07/2020 17:06:00
424 forum posts
Posted by Paul C. on 31/07/2020 14:41:36:

Actually although the chemistry (lithium oxide with phosphates, iron, or cobalt) and voltage may vary from manufacturer to manufacturer (cobalt gives 4.2 volts) Lipo and Li-ion are the same thing. Only the packaging is different. and that is the only thing 'Lipo' refers to. Nothing else at all.

I didn't know this ! Thought that lipo and liion were two totally different things, never too old to learn something new 👍

 

Paul.

I'm not any kind of 'professional' in the subject just an interested model plane flyer with a vaguely relevant technical background..

My first electric rc plane was in the early 1970s when we only had nicads (plus a few other sorts such as silver-zinc which were better but never made in 'consumer' quantities so were very expensive). I did it simply because it was quite hard to get good performance. Or sometimes any performance at all .

Edited By Richard Clark 2 on 31/07/2020 17:07:24

Steve J31/07/2020 17:21:00
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2105 forum posts
61 photos
Posted by Paul C. on 31/07/2020 13:56:23:

my knowledge of batteries is less than not a lot but this does appear to be at odds to how we are told to handle lipo flight packs.

Transmitter batteries have a lot easier life than most LiPo flight packs and the LiPo pack in your DX8 will have a little board in it to look after the cells.

Paul C.31/07/2020 17:59:43
avatar
697 forum posts
165 photos

Thanks for the info chaps 👍 very informative.

Paul.

Keith Miles 231/07/2020 18:04:00
501 forum posts
6 photos
Posted by Richard Clark 2 on 31/07/2020 14:28:32

Yes, it is just a 'mantra'. It was unheard of a few of years ago. But it's a trade off.

Despite what I previously posted you continue to 'believe' that Lipos are diffeent. They are all lithium ion. The only difference is the packaging. 'Lipo' refers to the POLYmer (plastic) case and that's all. It's not any kind of formal 'definition'.

Your Super Chipmunk. A 1000 ma battery is VERY (I could say dangerously) small for a 7 servo plane, even a quire small one. I assume your plane is 'medium size'. I suggest you change it for a 2200, it doesn't matter whether it's lithium or Nimh. But if you choose Nimh use Eneloops.

Glad to have my “mantra” suspicions endorsed.

On the matter of “belief” you are overstating a little but no big deal. That said, I would take an educated guess that Paul C and I are by no means alone in thinking that the 3 Lithium types are/were different chemistries as opposed to same chemistry in different packaging. Not arguing with you but might research that further, purely out of interest.

As for my 1000mah Rx packs, at one time a 500mah NiCd pack was common in a 4-servo set up in an average sized model (and included in many radio sets). I would regularly have four or five flights, no problems, and had nothing more than a basic Futaba charger with just an LED for Tx and another for Rx. My Rx packs were never less than 4.8v before recharging. Despite that, and to provide additional “headroom”, I moved to 1500mah packs, occasionally 2000mah. Overkill, it has transpired.

Fast forward to more modern times and a fancy charger with charging information displayed and I discover that my current similar 4-servo models (Wot4, Wots Wot, PT19) are using an average of only 60-70 mah per 15 minutes operation, i.e. start up/flight/shutdown. So five or six flights (75-90 minutes of operation) would use only 300- 400mah, in round figures. I have, therefore, and for some considerable time now, been using Eneloop NiMh 1000mah and find them more than adequate for the job. I also took this “real world” data into account before choosing a suitable Lipo for the Chipmunk and am confident of a safe 45-60 minutes of use to around 50% discharge. And I bought a spare!

As for higher capacity cells, it is also my understanding that there is a greater voltage drop at a given current the higher the capacity of NiMh/NiCd cells of a given physical size e.g. AA 2000mah versus AA 1000mah. Usually, of course, the higher the capacity of a battery, the greater it’s size, otherwise there has to be a trade-off.

This is why it seemed to me, contrary to your suggestion, that one should perhaps be prioritising power/voltage over capacity when dealing with seven servos of similar specification to my usual four. In my view, the former is more important, in safety terms than the latter. Higher battery capacity in this particular context is more about convenience in terms of endurance and recharge intervals and could, in theory at least, create a danger as opposed to avoiding one!

Oh, and I even operated all seven servos at once, on the bench, and I never saw more than a brief blip of 200mA.

 

Edited By Keith Miles 2 on 31/07/2020 18:10:43

Trevor Crook31/07/2020 19:57:34
1026 forum posts
71 photos

I don't think its all "mantra" although lipos seem a lot more tolerant of storage regime than often thought.

However, in the electric car world, some manufacturers now quote a gross battery capacity and a usable capacity, which differ by a few kWh. This is because the battery management system in the car prevents full charge, or full discharge, to prolong cycle life. The manufacturers have an interest in doing this as batteries have typically 7 or 8 year warranties.

Keith Miles 231/07/2020 21:47:07
501 forum posts
6 photos

UPDATE (for those who might be interested!).

Just been doing some further research and firstly, "Battery University" states, in concert with Richard's comment:

"As far as the user is concerned, lithium-polymer is essentially the same as lithium-ion".

BUT, for me, there seemed to be two key phrases there, so did some further checking in order to confirm my suspicions and to justify my doubts.

My I-Charger 208B, in the base settings menu, has separate provisions for Li-Po, Li-Ion and Li-Fe and the manual for it also quotes significantly different parameters for each cell type in terms of nominal voltage, maximum charge voltage, storage voltage, allowable fast charge and minimum discharge voltage cut-off level.

I won't waste time and space by quoting all of them here but, if interested, you will find the manual online and the aforementioned differing battery parameters are listed on Page 6.

I will, however, from the Spektrum DX9 manual, quote the recommended (but adjustable) cut-off level of 6.4 v for a 2S Li-Po/Li-Ion battery i.e. 3.2 v per cell.

Interestingly, but understandably, this common value for both is higher than that quoted in the I-charger manual by 0.2v and 0.7v respectively.

So, with due respect to present company, I can only again conclude that Lithium cells are NOT all the same and that a level of caution is required in terms of perhaps understandably accepting such statements or in making assumptions.

As for the original subject of this thread, a positive outcome is that I am now somewhat less concerned about storage charging of any LI-Po batteries, especially ones that are only used for very light duty in a transmitter or relatively light duty in only powering a receiver and servos!

It seems to me that storage charging is more a matter of getting the maximum life out of the batteries as opposed to a safety issue, something which seems to be pervasive where Li-Po cells are concerned and perhaps, therefore, open to misunderstanding (I include myself!) of what is important and what isn't!

As for a need to balance charge, as opposed to a recommendation..............?

A subject for another thread, perhaps?

smiley

 

 

Edited By Keith Miles 2 on 31/07/2020 21:53:57

Steve J31/07/2020 22:03:33
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2105 forum posts
61 photos
Posted by Keith Miles 2 on 31/07/2020 21:47:07:

I will, however, from the Spektrum DX9 manual, quote the recommended (but adjustable) cut-off level of 6.4 v for a 2S Li-Po/Li-Ion battery i.e. 3.2 v per cell.

I understand that the manual is wrong and the protection circuit in the battery pack will shut off above this voltage.

Steve J31/07/2020 22:09:25
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2105 forum posts
61 photos

Posted by Keith Miles 2 on 31/07/2020 18:04:00:

... at one time a 500mah NiCd pack was common in a 4-servo set up in an average sized model ... My Rx packs were never less than 4.8v before recharging.

1.2V/cell off load is a long way down a AA NiCd discharge curve.

... As for higher capacity cells, it is also my understanding that there is a greater voltage drop at a given current the higher the capacity of NiMh/NiCd cells of a given physical size e.g. AA 2000mah versus AA 1000mah...

I suggest checking the datasheets.

If your seven servo (flaps or retracts?) model with the 1000mAh battery stops responding and goes in, please don't blame the radio.

Keith Miles 231/07/2020 22:13:48
501 forum posts
6 photos
Posted by Peter Christy on 31/07/2020 09:15:17:

LiFe cells can be fast charged in the same way as LiPos - provided your charger has a LiFe setting..

.

The same way?

Another quote (sorry) from my charger manual suggests that Li-Po be fast charged at 1C and Li-Fe at 4C.

Unless I misunderstood your post, a bit of a difference there, I would suggest!

Edited By Keith Miles 2 on 31/07/2020 22:15:25

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