what type of battery pack for i/c engine trainer

[Keith Miles 2]

Bob and Peter,

Glad I’m not alone! The real world figures for digital are most enlightening and pretty much what I would have expected despite some of the questionable much higher figures quoted for digital that I’ve read in the past!

Are you still with us, Richard?

Sorting the wood from the chaff comes from experience and such debates/discussions are par for the course!

One hopes it will be more educational than totally baffling!

Do you already have a charger for a NiMh receiver pack as this might influence your choice, especially at this stage? If not, many modern chargers, even the lower priced ones will charge both Lipo/LiFe and NiMh and maybe Lead/Acid (Pb) as well.

On that subject, the big advantage these days is the availability, as previously mentioned, of fully featured and adjustable multi-type chargers which display all manner of information like charge current, voltage, elapsed charge times, capacity etc. So with these there is no guessing involved in order to ascertain the condition of your battery packs or to maintain them in good working order. Definitely worth investing in a decent charger if you intend to remain in the hobby. Only if you go for electric power do you need to consider spending a bit more money on a higher power one and a power supply for it as batteries for powering motors (almost exclusively Lipo type) need to be substantially more powerful than any battery which only powers low current radio gear. In turn, The charge current normally used for LiPos is relatively much higher than that used to charge a relatively low capacity NiMh receiver pack!

I should mention also that for charging of different battery types you will require various different connectors unless these are supplied with the charger otherwise they can be bought or made up, as required.

As said, nothing wrong with an equivalent Lipo (or maybe LiFe) for the radio gear as they have many advantages over NiMh but you will need that Lipo/LiFe charger and a regulator, as mentioned whereas the NiMh pack (1000-2000 mah) will drop straight in.

I assume that you have some building/assembly experience and need no help there but if you do, you will find no shortage of advice on here on that subject either!

 

 

Edited By Keith Miles 2 on 03/12/2019 19:28:26

[gangster]

If I was the op I would be totally confused by now. How complex does powering the flight pack of a toy aeroplane need to be?

Keep it simple use what the maker recommends. As a few have suggested use a proper 4.8 volt receive pack A few have suggested eneloop batterys, which is as good as it gets. But please,please change the switch harness. Even the most reputable radio uses cheap inferior switches . Probably the biggest cause of radio problems. The gear itself rarely fails and interference is probably non existant but power problems due to duff switch harnesses or black lead corrosion is a killer

[Peter Miller]

Poor bighter!! Richard asked such a simple question.

By the time he has read this lot he is probably so confused that he will give up and go back to rubber power or control line.

[Nigel R]

Hopefully the OP had the answer he needed before we all went off on a tangent!

Keith you are right, I do apologise for derailing things a little.

"I merely suggest, from my obtained figures, that a 2000mah Rx pack is probably overkill in your average sized model but, hey, yer’ pays yer’ money etc. etc"

2000mAh Eneloops get you the capability (i.e. C rating) to drive a handful of standard servos without sagging. The capacity (mAh) may be excessive, but capacity is only one of the battery's two main characteristics.

[Keith Miles 2]

Gangster,

The OP did not have a maker’s recommendation as he explained in the original post. I agree about the switch, especially on a second hand model although I have never personally experienced switch problems or black wire corrosion.

NigelR,

We all go off topic occasionally. I prefer to believe that it is usually for the right reasons! I’m sticking to my guns on the relative current capabilities, though, although for radio gear it is as I said very unlikely to be an issue in practice or any cause for concern.

As for sagging, I’ve measured a healthy non-sagging voltage with a 300ma load at 50% charge on my 4.8 v Eneloop 1000mah packs. I rarely do more than four of five 15 minute flights with any one model on a given day and I always charge ‘em back up when I get home. Another reason why I don’t feel a need for anything more than 1000mah.

So we are generally agreed that in Richard’s case, he will be fine with a 4.8v NiMh receiver pack, preferably Eneloop?

Perhaps we can also agree that we don’t usually NEED lithium batteries unless high power and/or very fast charging is required?

Maybe we should also have pointed out, as Richard has been away for a while, that we recommend Eneloop, as opposed to standard NiMh cells, because they lose very little charge when stored for long periods which makes them more user friendly and that NiMh don’t need to be recycled to avoid reducing their capacity (the legendary “memory” effect) as was the case in the old days of NiCd.

Do I hear the sound of someone snoring?

 

Edited By Keith Miles 2 on 03/12/2019 22:35:16

[David Davis]

Richard, there are some very knowledgable enthusiasts within our ranks who are keen on the technical aspects of electronics. They are usually people with a scientific background.

On the other hand there are people like me who have some difficulty understanding the difference between current and voltage and what's more I don't much care about the technicalities. This morning for example, I had to check whether an Eneloop was a NiMh or something else! It is a NiMh.

I have been flying r/c models since 1988, so that's thirty-one years, and have only used either NiCads and NiMhs in my models because other batteries seemed to require regulators and/or soldering or a different charger and that put me off! It was much simpler to unplug a Nicad and replace it with a Nimh!

I have crashed on many occasions, but on only one occasion was the crash caused by a receiver battery problem. Right at the start of my r/c model flying career I had neglected to charge my rx NiCad overnight and the model ran out of electricity and crashed from a great height.

Despite dire warnings of Nimhs suddenly running out of electricity I now only use NiMhs and I've never had a problem with them.

I am going flying later today. Currently the i/c models which I have in flying condition are as follows: my club's trainer, an ARTF trainer called a Primary 40 powered by an Irvine 40; two Barons, these are French three channel trainers with 1.6 metre wingspans which I use in a daft competition, "La Coupe Des Barons" each summer; a WOT 4 Mark 3; a 1/6 scale BE2e; a Senior Telemaster, an eight foot wingspan trainer powered by a 90 fourstroke and a Flair Harvard.

They are all fitted with 2000 mAh 5 cell NiMhs and guided by a Spektrum radio. Do like wise with your trainer without a qualm.

I use an X120 DC charger from Hobby King powered by a 12 volt source. It is capable of charging many different types of batteries.

PS. I have always used 5 cell rx batteries with my Spektrum equipment because everybody else used 5 cell battery packs. If the equipment will function adequately with a 4 cell Nimh, good! I have a couple of new 4 cell packs which I was going to give away.

[Keith Miles 2]

David,

Whilst in broad agreement with your post, I would counter your comment about “everybody else” using 5-cell packs( i.e. 6 volt) packs.

I have been flying models for even longer and have found 4-cell 4.8 volt to be the ones most commonly used.

Maybe it’s a regional “Pied Piper” phenomenon?

That said, I’m now regionally outnumbered by the Leccy and Lipo brigade!

[Peter Beeney]

Perhaps some of the confusion is simply caused by the fact that we are now rather spoilt for choice these days; 4 or 5 cell NiMh or 2 cell LiFe, just take your pick because they will all do the job ok. Even a 2 cell Lipo with a £1 6V 1A voltage regulator soldered into the switch harness works perfectly well, I gave that one a bit of a bashing when lithiums first appeared on the scene; it was simply the fact that the very early batteries themselves were not too reliable, one went open circuit overnight without warning, that was of greater concern and subsequently bought those proceedings to a standstill. A standard trainer model with 4 x 148 servo types controlling it is not going to be very power hungry either, so just about any capacity size will cover it.

Good luck with whatever you choose, Richard, the only piece of useful advice I may be able to offer is to invest in the appropriate onboard Rx battery checker at the same time…

PB

[Nigel R]

"If the equipment will function adequately with a 4 cell Nimh, good!"

Indeed it will.

Caveat is, make sure they low discharge nimhs, such as Eneloop. Or, Vapex Instant, GP Recyko (I think).

If they are "standard" nimhs, if they have been left idle for a long time, are probably completely discharged, and will now be dead as a post, and will not recover.

Any recent and decent battery charger will provide a discharge function with capacity measurement.

"as for sagging, I’ve measured a healthy non-sagging voltage with a 300ma load at 50% charge on my 4.8 v Eneloop 1000mah packs. "

The ever helpful Hitec website lists the "no load operating current" for a standard (HS425) servo as 150mA.

300mA is only movement of two servos of this type, if they are not connected to anything.

My own take:

Hitec's quoted stall current is 800mA, for the same standard servo.

5 standard servos, 800mA x 5 = 4A.

Eneloops are rated for 2C discharge rate, i.e. 4A for a 4xAA pack.

The AA discharge curve posted by Steve above shows they will happily hold 1.1V under those conditions.

Nimh packs also self-balance when trickle charged - simple solution.

As the saying goes - all bases covered. With some to spare, as the worst case is rather contrived, and the in-flight maximum draw will be somewhere between the no-load case and full current case.

However. Personally, I like a bit of headroom on a critical component. An AAA pack doesn't provide it (my opinion). YMMV.

 

Edited By Nigel R on 04/12/2019 14:03:49

[Keith Miles 2]

Peter,

A fully charged battery will not suddenly fail nor use it’s charge on the way to the flying field. Also, with reference to other posts in this thread about battery capacity choice and useage, there should be absolutely no need to fit a battery checker unless you don’t trust yourself or your battery or you just like adding gadgets with pretty lights.

In fourty years, I’ve never fitted a battery checker to a model and have even less reason to consider it now given the sophistication of modern chargers which will clearly display information that should priovide a warning beforehand if a battery is dodgy. Also, in those fourty years, I have very rarely seen others using one.

It should also be borne in mind that it could lead some into a false sense of security because the discharge to an unsafe state of NiMh cells (as with NiCd) is not gradual but quite sudden (see NigelR’s graphs) and therefore the checker could read an apparent healthy voltage on the ground, especially if off-load, only for the voltage to then drop during flight with obvious consequences!

I would be worried, personally, about the possible consequences of placing too much faith in a battery checker!

 

Nigel R,

I’m with you all the way, there!

I only quoted my 300ma load test as an example based on my observations of total peak current measured .when all the sticks were being moved at once on my Wot4.

You will probably also agree that servo current peaks only briefly on initial stick movement before settling back to a relatively low level and is never constant.

The best ultimate test, therefore, as the Leccy and Lipo flyers regularly do, is to fly the model then check the battery useage although, on that score, I similarly take the view, as in my reply to Peter, that a checker (of capacity in that case) is less accurate than a monitored recharging of the battery!

Edited By Keith Miles 2 on 04/12/2019 15:43:39

[Keith Miles 2]

Peter And SteveJ

My apologies for attributing the aforementioned graphs to NigelR!

😊

[Richard Elvin 1]

Well chaps, my post seems to sparked some lively debate!! Once again thank you all for your responses to my question and again a lot to consider and take in.

Keith Miles 2: Keith I do have a charger, a Ripmax Sigma Eq 2x50 watt that i used to charge the LiPo's on the much missed Wot4 and it will charge all the other different types of battery.

All for now

Richard.

[Keith Miles 2]

Richard,

Looks like an excellent choice of charger!

With hindsight, 50 watts might have suited me better than my i208 and 500w power supply. I was thinking ahead, at the time, with a view to charging larger LiPos but as yet, have never needed to use it to it’s full potential as I still fly mainly IC, all with those 1000mah 4.8v AA NiMh packs! With the exception of a very recently bought (and yet to be flown!) Riot, all my electric models and LiPos are small ones, most being helicopters and mostly for indoors. Also, my charger is only single channel which, of course, means charging one battery at a time.

On that point, you may hear, or may already have heard, of a technique called parallel charging, used by dedicated electric flyers for their numerous LiPos where such restrictions can be overcome and allow charging of several batteries at a time from one output

You really need to know what you’re doing to use that technique or, amongst other things, like damaging batteries, you could burn the house down!

You are aware, also, of the charging current limits of different types of battery, I assume?

Hope I’m not teaching grandma to suck eggs, as they say!

[David Davis]

Posted by Keith Miles 2 on 04/12/2019 11:06:23:

David,

Whilst in broad agreement with your post, I would counter your comment about “everybody else” using 5-cell packs( i.e. 6 volt) packs.

I have been flying models for even longer and have found 4-cell 4.8 volt to be the ones most commonly used.

Maybe it’s a regional “Pied Piper” phenomenon?

That said, I’m now regionally outnumbered by the Leccy and Lipo brigade!

Do you use a Spektrum radio Keith? I meant to refer only to those who use Spektrum.

[cymaz]

Also, just bear in mind when using a battery checker through the charge port on a switch, that the readings aren’t always true.

Live found that the reading is lower through a switch than plugging the checker direct into the battery. I assume it’s the switch circuitry and resistance

[Nigel R]

cymaz, to me that would be a red flag for that switch.

[Peter Christy]

I agree! Although it could be the charge lead coming off the switch. In either case, for me, that would trigger further investigation!

--

Pete

[gangster]

I have never seen a failure due to using 4.8 volt battery which is usually what the makers call for. I have however seen problems including crashes due to the use of 6 volts. Some earlier Futaba servos and many JR don’t like it. I take the point re Spektrum but believe it was due to some earlier DSM2 receivers taking too long to recover from volt drops. Probably due to poor installation lossy switch harnesses black lead etc Running on an extra cell is only papering over the cracks (unless there is a high servo count or power hungry servos). I bench tested the “brown out” phenomina” on a number of DSMX receivers and found no issue. Instant recovery this included an Orange dsm2 which was also fine unfortunately the reputation has lived to this day

[gangster]

I wish you could get the old Flair on board battery checkers. They latch a high intensity flashing light if they see even a short volt I still have two would love to have more

[Former Member]

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[Former Member]

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[Nigel R]

Onboard telemetry records minimum voltage seen, I think. Take that with a pinch of salt.

"I take the point re Spektrum but believe it was due to some earlier DSM2 receivers taking too long to recover from volt drops."

The supply voltage minimum quoted in the Spektrum manuals is 3.5V minimum - that's quite a drop from 4.8V nominal pack voltage. Tests performed (there are one or two filmed on youtube) seem to show the real world minimum voltage closer to 3.0V.

The "quick connect" feature, present in the RX for a long long time now, drops the recovery time to (I think) 1/20th of a second after input power comes good following a brownout.

edit: Steve beat me to it while I was typing

Edited By Nigel R on 05/12/2019 10:23:03

[Keith Miles 2]

David,

Yes I do use Spektrum, as do other IC flyers I know who also use 4.8 volt NiMh Rx packs. I have also used 4.8;AAA on a small IC model without problems.

I have only one model on 6v, a 1000/2s LiPo with regulator but have only flown it twice so too early to assess it. At 9lbs with 7 servos, I figured that it might be a better choice and just felt like experimenting!

Cymaz,

That’s interesting and maybe another good reason for not bothering with on board checkers! I maintain that the best, and safest, way to check a battery for flight is by using a decent charger and noting, after having fully charged it, how much charge then goes back in after a flying session. Given the features of modern chargers plus timers on transmitters it should be easy to both keep an eye on battery condition and work out how much flying can be safely made on a given battery (allowing a healthy safety margin) especially, as you point out, if the checker itself cannot be trusted!

P.S. I can see the advantages of telemetry, perhaps, especially for thermal soarer devotees with somewhat more flexible flight times! Then again, if you can comfortably get more than two hours of receiver/servo power from a 1000mah battery......? 

 

 

Edited By Keith Miles 2 on 05/12/2019 11:17:28

[gangster]

Whilst We have moved on to checkers it is probably still pertinent to the op. It is essential for most cell chemistry’s to measure the voltage on load. The plug in checkers have or should have a built in load. We have become used to lipos where the voltage acts as a fairly accurate fuel gauge This is certainly not the case with NiMh or nicad or dry cells. I cringe when I see someone look at the on board checker and declare oh its 60% that will be fine for another flight. Perhaps the comment that we are better off without them has some validity’s

[Peter Beeney]

Keith Miles 2 @ 04/12/2019 15:14:18

Keith,

If you do not wish fit an onboard battery checker on your models then I guess that is your personal choice and I certainly wouldn’t have any issues with that at all. All I can say is that I was just offering Richard my advice based on many years of observing modellers together with their sometimes little foibles and misconceptions; and that’s more often than not about things electrical. He most certainly doesn’t have to heed it in any way, shape or form. It’s not a case that that I don’t trust myself particularly, rather more in that anyone else that’s interested can instantly see the state of charge of my battery if they want. But of course if it were not in place or not working then I would certainly miss it. I certainly think that if anyone used one for a while they would not want to be without it.

It’s all about safety for me. I know for certain sure that these things have prevented two models taking off with flat batteries. In one case, a large Pitts, the pretty red light was spotted in the cockpit by another pilot casually standing behind the model, the engine was already running. Quite a while back now a large warbird went in at full chat two minutes after take off due to a flat battery, much too close for comfort. Despite being advised to the contrary the pilot had decided an onboard checker was unnecessary. In the event this became a loud wake up call all round and he certainly uses one now. No harm done as it happens but I think we can all make mistakes, especially when we least expect it…

Just to be pedantic for a moment, and relating specifically to the 7 led 6.6 volt LiFe checker, I have played about with these quite a bit in the past. At one stage I paralleled 4 together in a Rx and wound the voltage up and down to compare the actual visual difference between leds. There was a very slight variation between greens but all the reds came on simultaneously; that’s as in exactly together. Can’t really get better than that. Also the last one is very bright; it would be difficult not to see it, even from some distance away. You mentioned a Fluke multimeter in another thread; on another occasion to get a really firm grip on the operating range I also used a Fluke to measure accurately the millivolt rises, and falls, between leds. I related all the gory details of this stuff in a post way back in the mists of a time long ago.

Just as an aside, my meter, like me, is now very old; and it’s not been calibrated for a while either. but even so I’m happy that it’s sufficient for modelling purposes.

Can I also say that I think I would place just as much faith and trust in the monitors as I would in any other piece of model flying equipment.

Stay safe…

PB

Edited By Peter Beeney on 05/12/2019 10:55:13