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what type of battery pack for i/c engine trainer

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Nigel R05/12/2019 09:38:56
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cymaz, to me that would be a red flag for that switch.

Peter Christy05/12/2019 09:43:15
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I agree! Although it could be the charge lead coming off the switch. In either case, for me, that would trigger further investigation!

--

Pete

gangster05/12/2019 09:46:42
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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

gangster05/12/2019 09:50:49
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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

Steve J05/12/2019 10:11:35
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Posted by gangster on 05/12/2019 09:46:42:

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 earliest Spektrum DSM2 receivers could take a few seconds to reacquire the signal following a reset. This was fixed over ten years ago. The reset voltage of Spektrum receivers is similar to that of most other microprocessor based receivers but still this 'you need 5 cells for Spektrum' nonsense goes on.

Steve J05/12/2019 10:21:28
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On the subject of checkers. I removed all the green/yellow/red LED bar type checkers from my models a fews years ago and replaced them with small voltmeters. If find the actual voltage more useful than a green light.

Nigel R05/12/2019 10:22:29
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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 205/12/2019 10:30:38
300 forum posts
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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

gangster05/12/2019 10:45:20
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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 Beeney05/12/2019 10:51:25
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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

Keith Miles 205/12/2019 12:18:57
300 forum posts
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Peter,

Firstly, there is no device that will accurately measure a battery’s state of charge. It is a misnomer for what is actually a voltage measurement. Also, as others have said, voltage needs to be measured on load to be meaningful. Furthermore, as previously stated (and as shown by graphs provided by SteveJ) NiMh voltage drops off dramatically as discharge approaches its lower limits. I maintain my cautionary position in respect of battery checkers.

Not knowing Richard’s level of experience, that would still be my advice to him, and, ironically, based on the very possible consequences that I was alluding to, examples of which are cited in your own most recent post!

So, one pilot had a flat battery and didn’t notice the red warning light that was fitted to his model for “safety” and others, who had no such warning device, crashed as a result of flat batteries and, as you appear to be inferring, due to a lack of a warning device!

A simple and basic question for you, then.

Why, were their batteries flat and why did one pilot not even notice the warning on his own safety device?

As is all too often the case in life, I might suggest to you that the failures in those cases were ones of complacency and/or the lack of due diligence in the use of the equipment.

It is a common human failing which no gadget or piece of technology has yet managed to eliminate entirely and, in some cases, it seems to make matters worse.

I rest my case.

smiley

 

 

Edited By Keith Miles 2 on 05/12/2019 12:39:48

Peter Beeney05/12/2019 15:39:38
1581 forum posts
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Keith,

I fell that we shall perhaps continue to look in different directions on this particular subject, maybe it’s just like the multiple types of Rx batteries on offer now, which ever one you choose is never really going to make much difference.

The simple answer to your question is I’ve no idea why their batteries were flat. A likely cause is that the batteries weren’t charged. It was quite a while back now but in the case of the Pitts as I remember the pilot had bought the model second hand with the checker already installed; it’s possible that he’d not used one before that and so he’d not taken that much notice anyway. However, it did highlight the installation’s shortcomings and it was suggested that the unit be placed in a more prominent position, generally in the line of sight at the front. In the other case the pilot noticed it when assembling the model. My humble opinion about this situation though, is that had both these devices NOT been present at the time then the final outcome, the inevitable and quick demise of the models, could have had a far more serious result! I personally would consider that a big model on full throttle with no radio power is potentially an uncontrolled lethal weapon.

The crashed model was actually a near example of this. Had this happened right out in the open country, as they usually do, fortunately, then I’m sure it would have been just one more crash and little or no attention paid to it. The fact that it happened rather closer to home quickly concentrated everyone’s thoughts. The gentleman is a very pleasant guy actually, but he is as he is. Just needs patience and some firm persuasion to mend his ways.

Agree entirely with you about the ‘complacency and/or the lack of due diligence’ bit. I’d generally put it under the umbrella of pilot error. But I also have to say that I also could very easily forget to charge my Rx battery too, especially these days. However, I also like to think that when I got to to the patch and the checker, which I couldn’t forget, was indicating something was different this time then I couldn’t ignore it either. It would be my personal safety lock.

I reckon a debate about the pros and cons of on load checkers could go on a bit but I can give my opinion if you wish. But the one observation I can make with some certainty is that if I switch my LiFe battery powered model on and the red led is gleaming forth then the battery is close to it’s flat voltage of 5 volts. One exception might be the fact that the checker is faulty but either way I’m most definitely not going flying until I’ve sorted it out. I’d be very interested indeed in any argument that says I should do otherwise.

Keep on flyin’ Keith.

PB

Keith Miles 205/12/2019 18:31:08
300 forum posts
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Peter,

I have no intention whatsoever to cause any offence. You seem to be a sensible chap.

You say, however, that you have no idea why those batteries were flat. Yes, you do have an idea, and you are probably right, because you confessed to having failed to charge your own batteries before flight and that others might have done the same!

So, the clear lesson there, if safety is a primary concern, is to always ensure that batteries are fully charged before flight and to make full use of the features of modern chargers to regularly determine their condition rather than putting faith in a not necessarily trustworthy “wicket keeper “ who might fail to catch the ball!

As I and others have pointed out, NiMh cells and their NiCd predecessors will hold a healthy and safe voltage before dropping off very quickly if pushed to their charge limits. I would again suggest that, in that situation, a battery checker might merely encourage some to do precisely that leading to them then scratching their heads wondering why their model crashed. Furthermore they may then adopt a mindset of believing what the checker had been telling them and then repeat the same mistake and then blaming it on “radio interference” or on the radio manufacturer.

And you are quite right to point out pilot error as an issue.

I have held a PPL for 15 years. The same type of issues crop up in full size aviation as well where pilot error is the cause of most accidents rather than the technology itself.

Running out of fuel, for example, is generally considered to be inexcusable!

A useful analogy might be that, insofar as light aircraft are concerned, we PPLs are taught never to rely on panel mounted fuel gauges but to calculate the fuel required before flight, to always visually inspect the fuel tank and to then either fill up to a known marker within the tank or measure quantity with a calibrated dipstick!

I have never run out fuel and have never had a battery go flat in a model aircraft because I always know the state of my batteries BEFORE I even leave the house or turn on my transmitter!

Edited By Keith Miles 2 on 05/12/2019 18:44:55

Edited By Keith Miles 2 on 05/12/2019 18:48:37

Edited By Keith Miles 2 on 05/12/2019 19:08:02

Peter Beeney05/12/2019 22:24:25
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Fear not, Keith, I’m not offended in the least and never likely to be. I merely meant that we are always likely to see this in a different light.

The simple reason I don’t know why the batteries weren’t charged is just that I didn’t ask the pilots at the time. It was a long time ago and not a very significant incident anyway.

Sorry if I gave you the impression that I’ve said that I’ve forgotten to charge my batteries at some point, I did say “could forget’ when perhaps I really meant to say ‘IF I forgot’ to charge, simply just using this as an example.

Also I do have some experience with cells as it happens. Perviously I’ve spent many years checking and testing battery packs for members of two busy clubs. I used a Schulze Chamäleon isl 8-936g Charger, this had a large screen on which you would get a perfect display of all the charge/discharge curves. I could take a photo, show the owner and explain any discrepancies. There are a few examples in my photo albums in the White Light folder and one in the Transmitter Battery Discharge. Again this was a long time ago, as I remember the owner had a problem with the low volt alarm coming up soon after he started flying. Pretty obvious when you look at it.

I’ve had very little dealings with the plug in load resistor plug in type checker, I’ve had little reason to. And I’ve never seen a situation such as you describe, with folks getting confused with the readings; again I’ve seen very little use of these anyway. I personally have no problems with the onboard type faithfully following the discharge curve, though, and that’s very easy to prove with a volt meter and a variable DC voltage supply.

I think I will continue to use such a checker and you will continue to just charge your batteries. Probably the story of aeromodelling clubs all over. Although within our club if anyone now crashes soon after takeoff with a flat battery there may well be some very odd looks thrown at the pilot responsible; …to say the very least…

Happy flying…in both disciplines…

PB

Keith Miles 206/12/2019 00:04:29
300 forum posts
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Peter,

No problem.

I sent you a private message but in view of your response here most of it, it seems, may well be a case of teaching grandma etc etc. Sorry about that.

By the way, I’m a retired sparky albeit having dealt mostly with higher voltages!

Stay out of those trees!

smiley

Edited By Keith Miles 2 on 06/12/2019 00:07:15

ken anderson.06/12/2019 08:53:59
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back to the lad who set the thread away (Richard)… bet you didn't think you would get as many replies/answers as you have......you shouldn't need to ask another Q about batteries for a while..or ever.. emotion

ken anderson...ne...1..question time dept.

Piers Bowlan06/12/2019 12:41:33
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People can argue ad nausium about the benefits/disbenefits of an on-board battery checker as opposed to ensuring that batterys are always fully charged before flight. Having or doing both is even better perhaps but in either case if the health of the battery is not known neither will necessarily save you from an expensive and potentially dangerous crash. In PB's earlier post regarding the model Pitts crash, the model was purchased second hand apparently so was the Rx battery replaced, if not, was it's age and condition determined? I wonder how many models have crashed over the years from black wire corrosion as a result of being stored in a cold damp shed over winter?

Could be for a case for having two batteries (with schottky diodes) or some form of battery backer?

Steve J06/12/2019 13:44:13
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Posted by Piers Bowlan on 06/12/2019 12:41:33:

Could be for a case for having two batteries (with schottky diodes) or some form of battery backer?

Having two power sources for the receiver and servos is all well and good, but if you do so you need to make sure that you have system and testing regime that ensures that you have actually improved things and not just increased the number of failure points.

Keith Miles 206/12/2019 17:30:56
300 forum posts
6 photos

Piers,

On your point about the condition of a battery not being known, I totally agree, but the full use of a decent and not necessarily expensive modern charger should be able to take care of that issue.

I fully recycle my receiver NiMh packs every six to twelve months using the discharge and charge functions separately, rather than auto recycle, in order to note what comes out and what goes back in. One can also set a high-ish discharge current to check the on-load voltage. After checking, I also mark them up by making a little flag to go around the cable using a small bit of paper, with the test date on it, and a bit of sellotape. In addition, for maximum peace of mind and user friendliness, all of my NiMh packs are Eneloop.

A 7.4volt Rx Lipo with regulator is certainly an option worth considering (I have recently done this with a Seagull Chipmunk) especially if the convenience of fast charging is preferred. Indeed, since my earlier responses to Richard, I now see that Etronix produce 3 5A regulators and two of them, at least, now seem to have the JR/Spektrum connectors fitted which was not the case when I bought mine. So, no need now for any soldering in of a sacrificial servo lead! Hurrah!

On that point, why do Etronix seem to be the only company supplying such an obviously useful device, given the availability of small 2s LiPos, including ones with the JR/Spektrum connector? Are others missing a trick or did I miss something in my previous searches?

Keith Miles 206/12/2019 17:44:38
300 forum posts
6 photos
Posted by Steve J on 06/12/2019 13:44:13:
Posted by Piers Bowlan on 06/12/2019 12:41:33:

Could be for a case for having two batteries (with schottky diodes) or some form of battery backer?

Having two power sources for the receiver and servos is all well and good, but if you do so you need to make sure that you have system and testing regime that ensures that you have actually improved things and not just increased the number of failure points.

Or to put it another way, with added complexity cometh the need for increased vigilance and the likely onset of migraine?

smiley

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