By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by CML

NiMh Rx pack check report! ( And a warning?)

All Topics | Latest Posts

Search for:  in Thread Title in  
Peter Christy14/08/2020 14:06:40
1871 forum posts

Barrie: Well, the JR servos have been exceptionally reliable, many of them in service for years without issue! And as you say, a long way from when dismantling servos and cleaning the pots was almost a weekly occurrence! The only downside is that they are strictly 5V devices, and running of 5-cells or equivalent is asking for trouble!

I've had varying experiences with LiPos! I've had Overlanders, Zippy's, ThunderPower, you name it! I think the ThunderPowers (which came highly recommended!) were the worst! Expensive, and puffed up very quickly, despite only ever being charged at 1C. My first set of Zippys were good, but subsequent purchases not so. I've got a couple of Turnigy Graphite packs, which so far are holding up well, but on recent experience, the Overlanders are the best. (There! That's done it! Watch them puff up on the next charge, now!)

I only ever charge LiPos at 1C, rarely discharge them below 25-30%, and over the long winter / lockdown period, made sure they were all on a "storage" charge. Perhaps I need to abuse them more! It certainly seemed to work with NiCads! wink

As far as safety goes, whilst I've heard of - and seen - plenty of LiPo fires and explosions (one took out a whole hotel suite at an international heli contest, and got ALL the competitors banned from the hotel!), I've never heard of a LiFe going up in flames!

The thing is that it doesn't take much - a moments inattention is sufficient - to set off a LiPo. Not so a LiFe, and that's aside from any tendency to spontaneously go off!

For traction motors, LiPos are a necessary evil and should be treated with respect. But I won't use them where there is a practical alternative.

I'm probably being over-fussy, but I do have quite a few very old models. The Cobra I mentioned earlier belonged to John Haytree, and is believed to be one of the first in the UK (around 1970/1). I do try and look after them, as they are like the exhibits at Old Warden, reminders of where we came from! I would hate to lose one due to something avoidable!

--

Pete

Barrie Lever14/08/2020 14:26:43
avatar
320 forum posts
53 photos

Pete

Thanks for your insight into LiFe and LiPo, I may look at LiFe for the next Rx power packs.

I like to keep these things simple and that seems like a good route.

I was a bit tongue in cheek with the JR servo's, I think they were very well made but I was aware of the sensitivity to more than 5V. I strongly disliked the Tx and Rx from the early days around 1983, I had too many models crash and it was all down to the ceramic filter breaking in the Rx, this did not happen with the Futaba FM Rx, I have not really forgiven them and there are good or better alternatives out there.

The old days was not only cleaning pots but also those Mitsumi motors with the nice little aluminium end can.

Thanks

Barrie

Peter Christy14/08/2020 15:19:30
1871 forum posts

Posted by Barrie Lever on 14/08/2020 14:26:43:

The old days was not only cleaning pots but also those Mitsumi motors with the nice little aluminium end can.

Thanks

Barrie

This was my first set of proportional radio:

A Bonner Digimite-8 (Circa 1966 - I bought it in 68, 2nd hand)

Inside the servos looked like this:

If you look carefully in this image, you can see the pot track and wiper on the vertical sub-board:

The output rack had 15 or 16 ball bearings down each side, and the case was held together by spring clips! You had to be VERY careful opening them, as otherwise ball bearings would fly everywhere!

The pots needed regular cleaning, so I got quite adept at it!

The transmitter output about 1 watt on 27 MHz (AM). It was powered by a 600mAH 12volt GE Nicad. The receiver ran off a 7-cell 600mAH GE Nicad with several tappings on it! Each servo had seven wires connecting it to the receiver, and it was an 8-channel system. The servos were symmetrical, and reversing was achieved by taking the servo out, turning it around, and replacing it!

It was designed by a couple of guys from the Jet Propulsion Lab in California, and still works today, but I had to replace the original Nicads sometime in the 90s. Black wire corrosion eventually did for them!

The Tx now runs off a 4-cell LiFe (12V), and the receiver off a 7-cell NiMh pack.

Those were the days.....! laugh

--

Pete

 

Edited By Peter Christy on 14/08/2020 15:20:31

Edited By Peter Christy on 14/08/2020 15:21:23

Martin McIntosh14/08/2020 15:31:38
avatar
3540 forum posts
1220 photos

Barrie, I saw a Smog Hog with that stuff at Sutton Park. It went in full bore and there were ball bearings strewn everywhere.

Cleaning pots and motor coms was a regular chore but then they did away with the motor screws and crimped them together so I was stuffed. Sorry to go so far off thread.

Martin McIntosh14/08/2020 15:38:46
avatar
3540 forum posts
1220 photos

I would never dream of putting Lipos in an i/c model having had so many puff up, lose capacity and a cell failing. OK on electric since on 2s plus, the BEC will still supply the airborne bits should a failure occur.

Barrie Lever14/08/2020 15:56:52
avatar
320 forum posts
53 photos

Pete

Here is my first proportional radio a Skyleader SL, mine was actually a 6 chanel, this an SL4 that I got off of Ebay as I try to collect up an example of every radio that I have owned (Jr excepted). I have an immaculate Futaba M series which I still think was the game changer radio with it's price and reliability.

I think the Skyleader SL was a next generation radio after your Bonner, as a matter of interest how similar were RCS to the Bonner?

I flew a Kraft series 75 some of the time, I borrowed it off of a friend, that was the bench mark for me and the Futaba did not exceed the Kraft in my opinion, but was close to half the price, I think the Kraft had cost close to £300 when shortly after the M series was £165.

I am listening to what you and Martin are saying about LiFe V LiPo, I do see that LiFe are more mechanically robust than LiPo, I think that may swing it for me.

Thanks

Barrie

dsc_1237.jpg

Peter Christy14/08/2020 16:31:52
1871 forum posts

Hi Barrie,

We're drifting a bit off thread here, so I'll try and make this quick - and maybe we ought to start a new thread on historic radios?

That Skyleader is a couple of generations (at least!) after my Digimite! The first Skyleader proportional was a 3+1 system in a blue anodized case that looked like a re-badged F&M system! (F&M were one of the biggest American manufacturers back in the day). IIRC it used the Bonner Digimite servos.

The first RCS digital proportional also used Bonner servos. Indeed one of the servos I later acquired as a spare has RCS stickers on it! The Digimite used a somewhat different pulse train to modern systems, which makes me think that those early RCS systems were also "clones" of the Digimite!

--

Pete

Keith Miles 214/08/2020 16:33:47
464 forum posts
6 photos

First off, I’ve only ever used, with one recent exception, 4-cell NiCd or NiMh received wisdom having been that higher voltage can upset servos as seems to have been confirmed in this thread. I have never had cause to test my present collection on 5-cell nor, until very recently, any reason not to to stick with 4.8v (nominal, of course!).

Martin,

I’ve never had the need over the years, in my models, to use anything larger than 1500mah and more recently, it seemed that 1000mah were sufficient for my purposes and, as said, and whilst perhaps not a significant factor in practice, the lower capacity for a given physical size will, nevertheless, have comparatively lower internal resistance and should be less susceptible to volt drop at a given load. My current (!) concerns are unrelated to capacity, which has been proved to be perfectly adequate, but an apparent premature deterioration in the point at which a volt drop occurs at 0.5C ((500mA). I don’t own any digital servos either or a re-think would certainly be needed!

Pete,

I certainly echo the dubious longevity and inconsistencies with Lipos. I have certainly had this experience with my indoor models with all E-Flite, of various sizes, being not only the most expensive but the least durable! Flying field chat also tends to suggest a lack of consistency even, occasionally, between supposedly identical packs!

Nigel,

Yes, saw the 2000 NiMhs on Component Shop as well as a few other sites. As for the “Lites”, I only bought these because they seemed to predominate and weren’t as I recall, specifically identified as such nor did I have cause to search for anything more specialised. By the way, what does “YMMV” mean?

smiley

Keith Miles 214/08/2020 21:18:45
464 forum posts
6 photos

Ah, yes, Digimite.

Not to everyone’s taste.

You either love it or hate it.

smiley

Keith Miles 215/08/2020 01:51:40
464 forum posts
6 photos

One more thought before bedtime!

I’ve always doubted the usefulness of so-called battery “capacity” checkers which, unless I’m very much mistaken are, in essence, off-load voltmeters and which, unless I’m again mistaken are only capable of giving a rough guide to capacity and, even then, only if used on a battery in otherwise known good condition.

This is probably not an issue with motor power but I’m wondering how many flyers might be using these “checkers” on Rx packs.

For example, my seemingly worst 4- cell Eneloop pack, fully charged, was at 5.5v before being subjected to a 0.5C load which dropped it to 4.8v, on load, within just 1 minute!

By comparison, the best cell, also at 5.5v, using the same test process, lasted 70 minutes.

I would be surprised to learn that Lithium, or any other chemistry, for that matter, was incapable of exhibiting a similar characteristic and therefore any less likely to giving a user a false sense of security when using an inexpensive “checker” or even a more expensive one!

It seems to me that the only battery test or “check” that can be fully trusted is one that, at least, mimics the operating conditions. Modern chargers have certainly made such a process much easier to do than was the case in years past unless, of course, you had a job in an electronics laboratory!

Oh my gawd, is that the time....?

moon

Nigel R15/08/2020 07:07:26
avatar
4081 forum posts
694 photos

A thought occurred to me, have you investigated what sort of condition the leads and connections are in, for your worst packs, in case of black wire or similar?

Nigel R15/08/2020 07:09:14
avatar
4081 forum posts
694 photos

I use those widgets to tell me if I've charged a pack or not. I would take the "% full" figure with a large punch of salt.

PeterF15/08/2020 08:16:43
avatar
569 forum posts
740 photos

When I used to fly with NiCad or Nimh Rx cells I purchased a Hitec Powermate II battery checker, this had a 7.5 ohm high power resistor built in so it put a 4 cell pack under a load of about 0.5 to 0.7 amp when measuring the voltage, and commensuratly higher for a 5 cell pack. This was much better than a straightforward off load voltage measurement. Alas, I do not believe that these are sold any more but they do come up from time to time on ebay.

s-l1600.jpg

Edited By PeterF on 15/08/2020 08:17:22

Keith Miles 215/08/2020 08:46:20
464 forum posts
6 photos

Nigel,

You make a good point about black wire corrosion, something that, I confess, is something I’ve only heard about but never looked for. I would be surprised, however, if it was affecting more than one of my batteries although it’s always a possibility, I suppose.

I sense that we agree on the appropriate use of checkers, especially where we might not be sure about when a battery was last used. Unlike motors, receivers are, of course, less able to give an alternative early warning of impending battery demise!

Interesting to note that my servo specs, at least, seem based on NiCd/NiMh 4/5 cell nominal voltage (4.8/6.0v) and the HV ones on that of 2S Lipo (7.4v).

And I take due note of the higher fully charged voltages for each which, presumably, servo manufacturers will have, or should have, made sufficient allowance for? Receivers do seem to have long had wider quoted voltage tolerances.

A very interesting thread, thus far, and it’s certainly improving my thought process!

Jonathan M15/08/2020 08:50:16
avatar
816 forum posts
316 photos

Interesting thread.

I've learnt to get to 'know' my (Eneloop) NiMh batteries individually in each model. Battery load-checkers are just one part of the kit, telemetry readings are another (as long as you've calibrated the TX to the exact voltage first), and typical re-charge times the third. Model type and servos/control-surface deflections will make a big difference, as will flying style and wind conditions (thinking slope-soarers in particular). I periodically re-cycle them for good measure.

A slightly different issue, but lots of club members run their LiPos too low, then leave them in random discharged states until they're ready to re-charge for the next session - then complain that the brand isn't good enough! I almost never run mine below appx 35-45% charge (often just 50-55%), then restore them all to the same 'storage' level on the Quad Charger as soon I get home, and only re-charge to full just before going flying again. Each LiPo is labelled with the date of purchase and letter (A, B, C, etc) and I sometimes reverse or mix up the order in which I use them, especially as I don't always use the last fully-charged battery. That way a set of four 4250mAh 4 cells costing nearly £240 is going to last and last, and each LiPo should be as reliable as the next in the set.

One chap who used to be a bit casual now does the same, and he also marks each LiPo with a stroke from a Sharpie each time its been used...

...some of his LiPos have been banged up in their 'cells' for years!! wink

Keith Miles 215/08/2020 09:25:52
464 forum posts
6 photos

Jonathan,

I like your style!

I’m sure that if we were all as disciplined about care and maintenance the number of “mysterious” problems or premature failures would probably be significantly reduced.

Keith Miles 217/08/2020 12:24:36
464 forum posts
6 photos

Adding to my confusion, I have just noted, with reference to Panasonic EU website, that they only list the following single Eneloop cells:

Standard: AA 1900 and AAA 750.

Lite: AAA 550

Pro: AA 2500 and AAA 930.

During my LiFe search, I also note that Futaba seem to do a LiFe Rx pack for the princely sum of £75!

That’s waaaaay more expensive than alternative equivalents!

My brain hurts!

Bob Cotsford17/08/2020 12:47:44
avatar
8744 forum posts
487 photos

My experience with using those universal battery checkers is that they are good to check that a LiPo is fully charged before flying with it, but with other chemistries you don't get such a clear indication of charge state from resting voltage. Even with LiPos those checkers seem to work in large steps below 50% ie a LiPo might report 28%, 14% or 5% but nothing in between. Basically, flat or very flat.

I gave up on Nixx batteries after getting unending false peaks on various chargers when attempting 0.5 or 1C charges. LiFe packs all the way for me, though even these lose capacity with age. Metal can versions such as A123 do seem more resilient but you do pay for that. As for the Futaba price, you would have to assume it has extremely complex proprietary built-in balancing and charge protection circuitry as a similar Zippy pack would only cost a fraction of that price.

Peter Christy17/08/2020 13:00:06
1871 forum posts

Posted by Keith Miles 2 on 17/08/2020 12:24:36:

During my LiFe search, I also note that Futaba seem to do a LiFe Rx pack for the princely sum of £75!

That’s waaaaay more expensive than alternative equivalents!

My brain hurts!

RC Japan list the Futaba LiFe Rx pack at 4400 Yen = £31.64! Probably tells you something about UK markups! (Yes, I know about VAT and freight charges, but over 100%?!?)

Turnigy sell a similar pack for £11.90! Component Shop £10-£15 depending on capacity.

Lots of good deals out there...

--

Pete

Keith Miles 217/08/2020 13:26:29
464 forum posts
6 photos

CORRECTION!

Contrary to my earlier comment that Overlander’s stock of 4 cell NiMh packs had significantly reduced, Seems that it might be a “link” issue as I just checked again and my 1000 Lites ARE still listed as are 2000 (standard?) and numerous other options. My apologies to Overlander!

Bob,

Yes, I see some limited value in checking motor Lipos prior to and after flight. In the first case, in case you have mixed up your known charged batteries with ones that you have just used but there are other simpler and safer ways of dealing with that than using a checker, I reckon!

On the false peak issue, there does appear to be some debate over this and charging preference but I suppose it comes down to personal experience, hence this thread!

As for that Futaba battery, unlike Spektrum options, the advert I saw did not state that it was an “intelligent” battery which, of course, might explain the high price. I will have another look.

P.S. One thing I do like about NiMh is their standard dimensions!

Edited By Keith Miles 2 on 17/08/2020 13:29:36

All Topics | Latest Posts

Please login to post a reply.

Latest Forum Posts
Support Our Partners
Sussex Model Centre
CML
Slec
electricwingman 2017
Sarik
Advertise With Us
Latest "For Sale" Ads
NEW POLL - has the pandemic altered your event safety perceptions?
Q: Has the covid pandemic deterred you from attending shows and events in 2021?

 No, I'll be attending just as many as I usually do
 No, but I'll choose my event with greater care
 Yes, I'll attend fewer events going forward
 Yes, I wont attend any where previously I have

Latest Reviews
Digital Back Issues

RCM&E Digital Back Issues

Contact us

Contact us

Magazine Locator

Want the latest issue of RCM&E? Use our magazine locator link to find your nearest stockist!

Find RCM&E!