|David Davis||25/02/2019 05:52:36|
3590 forum posts
The weather has been unbelievably gorgeous for late February for much of the last ten days so I charged up my Fun-Fly's battery overnight, put it into the van and drove the short distance to the flying field where some of the guys were stripped down to tee shirts and jeans; it was not quite hot enough for shorts! The charger is a Robbe Lader 6 and the rx battery a Sanyo Enelope 2000 mAH nimh. It was charged at 60 mAH.
The OS 40 FP proved to be a little reluctant to start but with the help of a clubmate's finger over the intake venturi the engine burst into life. My clubmate carried it to the runway and off it went.
For several minutes the model flew perfectly. I was trying to perfect aerobatic manouevres when the engine suddenly cut which was unusual as it had always performed faultlessly in the past. I was preparing for a dead stick landing when I found that I had no control whatsoever and the model dived to earth and completely re-kitted itself. I will not have to clean that one again and I now have plenty of kindling for the wood burner!
When we examined the wreckage we found that the battery was completely flat.
The photograph below was taken on 12th April 2016 shortly after the maiden flight and I assume that I had fitted a new battery to the model when I built it, so the battery must have been about two years and ten months old.
I will certainly take to labelling my batteries with their purchase date from now on but any advice to prevent a re-occurrence of this incident will be appreciated.
|Percy Verance||25/02/2019 07:17:12|
8108 forum posts
Is there a reason you charge an Eneloop at just 60mah David? I ask as I charge mine usually at 400 to 500mah, and have done for years.
I suspect you thought you had plenty of juice in the pack when in fact you hadn't. I'd investigate the pack further ( not that you'll probably use it again). It may well have had a dodgy cell or something...... There may also be the possibility of a false peak. It's not unheard of with nimh packs. I've never personally found their claims of 80% charge after a year in storage to hold up too well either........
Edited By Percy Verance on 25/02/2019 07:19:14
|Maurice Dyer||25/02/2019 07:33:35|
|64 forum posts|
Charge at 10 percent for at least 10 hours. The Robbie later six is not peak detect.
Nice looking Fun Fly. I have had three. Build another, good luck.
|Don Fry||25/02/2019 07:41:00|
4557 forum posts
From memory the Lader 6 charger is a old fashioned constant charge unit without delta peak detection. Therefore you should have had, assuming overnight is 12 hours on charge, at least IRO, 700 mAh in the battery. So if the battery is flat, it's duff, or the charger is duff, or remote possibility, a short somewhere.
but bottom line you need a modern charger, a cheap standard 4 button unit will do, which will allow you to check capacity, test the cell under load for voltage sag.
A cell with some age in it is not necessarily worse than a new one, but a means to test them is vital
|SIMON CRAGG||25/02/2019 08:03:40|
|544 forum posts|
David, sorry for your loss, but at least it did not anything or anybody.
I would suggest that you change to LifePo4 batteries.
I ditched all my NIMH packs at least three years ago, and have never looked back.
IMHO Life packs are excellent.
Hope this helps.
|David Davis||25/02/2019 08:23:54|
3590 forum posts
Thank you for the advice gentlemen.
I suppose that I normally charge batteries up on only 60 mah because I started r/c flight with nicads. My understanding of batteries is pretty limited but I understood that it is better to charge a receiver battery slowly over a long period than to put a lot of current into it over a shorter time period.
As well as the Robbe, I own a Hobby King X120DC charger which I use to charge electric flight batteries. At the flying field we plugged the battery into a battery capacity checker and could not get a reading of any sort. Having got the wreckage home, I tried to charge the battery using the Robbe but could not get the little red light to come on so I plugged it into the X120DC and got an an immediate message that there was a disconnection. I then plugged another eneloop battery into both chargers and they operated normally. That is enough evidence for me to conclude that the Fun-Fly's battery is no longer serviceable.
Nice model thought the Fun-Fly was, I've too many incomplete models and unstarted kits in the workshop as well as a couple which need small repairs so I'm going to concentrate on those before entertaining the idea of building another Fun-Fly.
The way I see it I've now got plenty of kindling for the wood burner!
I normally get quite annoyed and upset with myself when I crash a model, especially one I've built myself so I don't know why I feel so positive. Then again, there has been a new lady in my life since 12th January. I expect that has something to do with it!
Edited By David Davis on 25/02/2019 08:27:12
|Percy Verance||25/02/2019 08:40:23|
8108 forum posts
I must admit I have pretty much moved on from using nimh battery packs to operate models regularly. I have a couple of Eneloop packs which get used to set up models on the bench ( I rely on the bec for flight) and a pack or two used in a couple of old model boats I tinker with occasionally.
As Simon points out above, there are now genuinely superior alternatives to nicad/nimh. It's just a shame a nice model was lost.......
|Jon - Laser Engines||25/02/2019 08:42:37|
|5205 forum posts|
I am currently doing the winter maintenance on my La7. The model is 9 years old now and so i was giving it a thorough check over.
Part of that check is the battery and i fully charged it on the peak charger saturday afternoon and tomorrow (it was supposed to be today but i forgot) im going to bring it to work and do a full discharge-recharge to see how many mah i get out and how many go back in. The battery is a 3000mah so if i see less than about 2500mah out then im going to boot it to 2nd line duty as a power pack for electric retracts.
I do this with all of my batteries periodically to get an idea of how healthy they are and so far i have not suffered any battery problems.
|Piers Bowlan||25/02/2019 08:57:12|
2045 forum posts
Commiserations David. Have you pulled the battery apart by way of a post mortem and tested the cells individually- also the solder connections between the cells? Odd that you are getting nothing at all from the capacity checker. I would take a close look at the charger you used to charge it with, just to be sure.
On a brighter note, have you thought about which model you might replace it with .
|Tim Flyer||25/02/2019 09:04:36|
1219 forum posts
That looks like a battery charger that does not tel you what currently is actually flowing into the battery. All good modern “computer” programmable type chargers have a digital readout showing what current has actually gone in . Without that you can’t see if a battery is actually taken in charge. With a readout you can clearly see an NIMH aging as it will slowly reduce capacity and take less charge. As batteries age internal resistance increases. Old NIMH batteries need cylcling occasionaly ( discharging and recharging) . Buying a multi output computer charger really makes sense even if you only fly I.C models . I use a 6 output carger so I can charge transmitter and glow sticks etc together. Also 80ma is a very low rate for that battery. You could charge it at a much higher rate 300mah would be fine on a receiver battery with that capacity. Sorry if I repeated above ... I started writing early this morning ... commiserations too on the loss of a nice plane ...
Edited By Tim Flyer on 25/02/2019 09:07:32
996 forum posts
Sorry to hear about the write off. Never nice. Battery’s are funny things. Personally I would trust a 60mA charge more than I would a delta peak charger that could false peak when one cell may have no capacity Having said that as someone said it’s nic to see what is actually going in. Technically a post-mortem is purely academic if you are totally happy that it’s not the switch harness or the charger. Ie was it charging for the full time.
|David Davis||25/02/2019 09:42:55|
3590 forum posts
Incidentally gentlemen, what I forgot to mention in the OP was that having walked over to the crash site with my transmitter, a Spektrum DX9, I glanced at its screen and instead of finding "Fun-Fly" on the screen, I found the monitor screen. May this have had something to do with the crash?
Piers, I may well take the battery round to my clubmate Francois, a retired ship's engineer, who understands these things better than me.
The Robbe charger seemed to work when I plugged another NiMH battery into it but I am using the peak detecting X120DC to charge it as I type this.
As for its replacement I have a Flair Harvard which I bought second-hand, an ARTF AcroWot which I need to finish off, a WOT 4 XL which needs re-covering and a WOT 4 Mark 3 with a lose motor mount. Guess I'll get on with one of those!
|Don Fry||25/02/2019 09:53:15|
4557 forum posts
No David, I also have the DX9, the monitor screen is not an issue. If you had telemetry you might want to fly on the telemetry screen, to monitor flight data. The transmitter does not care.
|Steve J||25/02/2019 09:55:00|
1774 forum posts
Cycle nickel batteries regularly with a decent charger. I do conventional NiMHs every three months and Eneloops at the start of the season.
|3523 forum posts|
My first Precedent FunFly (foam wing version) met its demise for a similar reason several years ago. That, too was an unexpected fine winter day and I gave the battery (probably a NiCad) a quick charge before setting off to fly.
The model was in the vertically down phase of a stall turn and never recovered! I used the wing in an own-design model that looked much like a Vertigo but the fuselage was toast - the engine, a ST 34, survived.
The lesson I learned was that a fast, quick charge, sometimes gives a false reading. I also acquired a better charger that told me how much energy had been replaced in the battery so giving an extra level of certainty.
|Bob Cotsford||25/02/2019 10:30:43|
8255 forum posts
If the pack shows 0v and the charger doesn't recognise it then it looks to be open circuit. That could be a dodgy plug, a broken wire, a failed solder joint at the cell, a fractured connector between cells or a cell that has failed open circuit.
I'd agree with previous posters though, 60mA isn't enough for 2000mAh cells, it really needs to be 200mA for an overnight charge. At 60mA it would take a day and a half on charge from flat.
I've never had much of a liking for peak detect chargers with NiMh packs, they seem to forever be getting false peaks. I like the 2S LiFe packs from HK, or for bigger models 2S A123 metal can LiFes. Just don't try charging them on a LiPo setting, they don't like that
|Maurice Dyer||25/02/2019 10:38:04|
|64 forum posts|
I know there is a problem if you peak detect Nicad/Nimh, They will give a false reading. Unless somebody with more knowledge than this enthusiastic amateur knows of a better alternative, I plug the batteries into a standard 10 percent charger and leave for a minimum of 10 hours. Then use a battery checker at the field before flying .
If somebody knows of a better charger that shows the true under load capacity of my Nimhs, and gets around the false peak detect issue, please point me in their direction.
|David Davis||25/02/2019 10:55:07|
3590 forum posts
Gentlemen I have found out the cause of the crash and it's much simpler than we all expected!
Having decided that I was not going to use that battery again I thought that I could do no more harm if I cut away the covering and tested each cell with a multi meter. To my surprise I found that every cell was giving a reading of over 1.4 volts but if I put the prongs onto the exposed copper bits of the plug I still had a zero reading.
I then noticed a kink in the negative wire. Keeping the positive prong against the postive terminal of the plug while pushing the negative prong against the exposed copper wire in the black wire gave a reading of 7.12 volts.
Precisely how that wire became broken is a mystery.
|Don Fry||25/02/2019 11:00:35|
4557 forum posts
Maurice, if you discharge a pack through a standard 4 button charger, set the discharge rate, and whatever the pack gives is its capacity under THAT load. A battery checker measures pack volts. It won't detect increased internal cell resistance. Like the people have said, packs need load testing, to check they do what it says on the tin.
Edited By Don Fry on 25/02/2019 11:01:15
Edited By Don Fry on 25/02/2019 11:02:00
|Denis Watkins||25/02/2019 11:22:14|
|4181 forum posts|
At Wheelspin Maurice
Battery Load Tester 4.8/6V NiCd + NiMH
PART NUMBER: P-FS-BC04
£9.49 Web Price
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