Sparking Lipoly

[Kelly]

Now then,

I was fitting my lipo and oh no the wires on the lipo touched lots of sparks , have I ruined my lipo or will a re- charge save the day ???? aaaargh .

Advice please for a clumsy numpty

Cheers

Kelvin

[Tim Mackey]

Hi Kelvin. IF it was very brief, then I imagine you will be OK. I confess to having done something similar ( however I feel I am entitled to LOL, as I have around 50 LiPo packs now, and have used LiPo exclusively for almost 3 years )

I would leave it alone, outside on the concrete or whatever, in a fireproof dish. In the morning, assuming a cat or similar has not snacked on it , put it on a slow charge ( say .25C ) and then check to see what terminal voltage it reads at the end of the charge. It MAY have lost one or two life charges as it were....... but if thats all, consider yourself lucky...AND suitably chastised

PS what terminal connectors do have on the pack which allowed this to happen ?????

Any such connectors should be so arranged as to prevent this from happening. My incident occured with a new pack to which i was fitting connectors at the time.  I use 2 / 4mm gold, with a male on the positive lead, and a female on the negative, also I cut the neg lead a little shorter than the positive, so they cant normally touch each other. PLUS ensure that both connectors are properly heatshrinked, with the neg being completely shrouded. 

[Kelly]

Hi Timbo and Jetsome

Yes the contact was very brief , it has not burst into flames so I may try a slow charge.

The leads are the same length and the female is completely shrouded, the curve on the wires was just enough for the male to make slight contact  (sods law)  I will make one shorter in future.

I am using a short piece of un-shrunk heat shrink tubing over the exposed part of the male connector as protection when I am installing  the lipo until I get round to making one lead shorter.

Many thanks

Kelvin

[Steve Hargreaves - Moderator]

I think we have all done this at some time....certainly I have .....once!!! After that you make damn sure you don't do it again!!!!!!!!!

Just a quick point though.....if you find that there is absolutely zero voltage from the pack on your multimeter then do not despair as all may not be lost......some LiPos have "collector plates" which is basically a small pcb into which the individual cells are soldered to make the series connection. This plate has pretty thin copper/tin tracks on it to form the circuit & even a very brief overload will burn out the track thus breaking the series connection & showing a big fat zero on yer meter.........under no circumstances must you ask how I know this as I might have to lie ................

If you feel competent enough (or sufficiently skint!!) to attempt a repair the collector plate track can be bridged by soldering a short piece of cable or even some tin plate cut to resemble the track across the break.

BE VERY, VERY, VERY, VERY CAREFUL THOUGH....BY EXPOSING THE COLLECTOR PLATE YOU ARE EXPOSING THE CONNECTIONS TO EACH INDIVIDUAL LIPO CELL. IF ANY OF THESE ARE SHORTED OUT DURING THE REPAIR YOU COULD HAVE A VERY NASTY SITUATION/FIRE ON YOUR HANDS. DO NOT ATTEMPT THIS UNLESS YOU FEEL CONFIDENT IN YOUR SOLDERING ABILITIES & TRY NOT TO DO IT INDOORS IN CASE OF FIRE. I ACCEPT NO RESPONSIBILITY FOR ARC FLASH INJURIES OR BURNS AS A RESULT OF ATTEMPTING SUCH A REPAIR.

Here endeth the lesson......

[Kelly]

Hi

A quick update to this thread. The lipo in question has lost all power.

When ground running, the power fell off after a few minutes running at medium to full power, not  enough power left to  to move the servos. The lipo now refuses to charge up.

I will have a look at the collector plate as suggested.

I am now fitting a seperate Rx/servo battery to the Spitfire and Me109. The extra weight is worth the piece of mind if the lipo fails in flight.

Cheers

Kelvin.  

[Steve Hargreaves - Moderator]

Kelvin...if your intial short had popped the collector plate then the battery simply wouldn't work at all. You'd get zero volts at the connectors. If it has slowly lost power & now won't charge up then I think it is dead & a suitable funeral should be arranged (BMFA website has details of how to dispose of yer Lipos here )

[Kelly]

Hi Steve

Thanks I will dispose of it .  

The lipo had not been used very much,is it the shorting out damaging it or just a duff lipo or something else?????

It is a Flightpower Evo,a lot of money wasted

Cheers

Kelvin.

[Tim Mackey]

Can I just ask a few more Qs before you dispose of it.

You say and I quote - "When ground running, the power fell off after a few minutes running at medium to full power, not  enough power left to  to move the servos"

This begs the 1st question...

1) What exactly were you "ground running it on ? I am presuming a powertrain of some sort...involving an ESC - so

2) Why did the ESC not stop the motor BEFORE the servos stopped working? 

3) What exactly was the off load voltage reading of the battery pack before connecting it for this run?

4) You say you are now going to use a seperate battery for the radio  - why has this prompted this thinking ?

5) We asked you to measure and report on the terminal volts of each cell - have you done so ?

6) We suggested a low rate trickle charge - again...have you done so ? 

If this is a failry large capacity F/P battery, then I find it very odd that it has not recovered form what you say was a  brief shorting out. If it WAS brief, then a large capacity pack would barely notice the short high current flow.

I await with interest.. more details of battery model, and answers to the above please before death certificate

[Kelly]

Hi Timbo

Thanks for your reply. I will re-check the charger etc and attempt to give you all the info(still on a learning curve). The shorting out was brief (just a touch).

I am as I say very new to EP flight ,if I am doing something wrong to cause the lipo failure then a seperate Rx battery means I  would still have control of my model if the same kind of failure occurs in flight 

The Spitfire flew fine with an identical lipo last wednesday no problems.

Back to the duff lipo. I fitted a smaller prop, charged the lipo as normal.

The motor ran for 2-3minutes at half to full throttle, then the motor cut out but the controls continued working, a brief spin of the prop then the power just seemed to drain away, the servos getting more sluggish and slower until the rudder was the only control showing any movement. all this occurred in several minutes.

Put the lipo back on charge ,the charger displayed  'check the battery open circuit'  message??

The charger works fine with my other lipos.

Hope to get back to you tonight .

Cheers

Kelvin

[Tim Mackey]

The "same kind of failure" will not happen in flight -unless you are sloppy with your wiring / connections / insulation etc, or of course if your careless fingers are still in there to touch the terminals together

It is not good practice to be running the motor on the ground like that anyway - lack of airflow can easily cause overheating. I generally only ever rum my powertrains on the ground for a maximum of 30 seconds -just long eneough to get a reading from my wattmeter of the vital statistics.

[Steve Hargreaves - Moderator]

Of course Timbo is right & a bit of extra investigation is called for here. If we don't understand why something failed then it may fail again at any time.

As Timbo says a relatively large battery should stand a very brief short & I assume since you are powering a Ripmax Spitfire this is a 2000mAh plus battery. Like Timbo I'm interested in why the ESC let the battery run down so far it wouldn't even power the servos......has this been happening regularly? if you let a 3S LiPo drop to about 8.25 volts you will surely kill it very quickly.....being a top drawer Flightpower pack it may be it has survived a couple of trips to "the dark side" (ie below 8 & a bit volts) & this would be a testament to the high quality cells in Flightpower batteries. If the ESC has allowed this to happen time & time again then no Lipo will survive for long.

Most ESCs allow you to set the power cut off voltage or define the cells in someway to prevent the batteries running right down to nothing...where is this set on your ESC?

[Tim Mackey]

Yep...still waiting for the data requested

[Jon]

Hi guy's Sorry to hear of the flash over....all this tech stuff is a bit over my head ....but only just today I was talking to Gary at BRC Hobbies about a new 2500 battery etc and he said without any prompting from me that I should be more than careful with it as any short circuit will cut its life by at least half and could kill it altogether.

Seems that some sort of very fast fuse is needed here..or is that just what the ESC should have done?

I'll sit back now and follow this thread to its conclusion.....

Once more, sorry to hear of it...best of luck....jon

[Kelly]

Hi Timbo and Steve,

Motor,

Thunder tiger Ripper outrunner 36/11-40A

Voltage range: 8~10 cells | 3x Li-poly

• KV rating: 1180 RPM/V
• Max efficient current: 20~45A
• Shaft diameter: 5mm / 0.197 in.
• Dimensions ø x L: 36 x 47.7 mm / 1.417 x 1.877 in.
• Weight: 165g / 5.82 oz.
• Propeller Recommended: 10 x 5 / 11 x 7 / 12 x 6

  Tornado Programmable 40 Amp brushless ESC ·  Programable 2 to 5 cell Li-po selection: ·  Low voltage cut-off set to 3.0 volts per cell ·  Features:

·  Soft cut off with BEC

Flightpower Evo 20

3300mAh    3s1p   11.1V

22c

When running the motor the low voltage cutt-off was set at 9v(3v per cell).

The lipo charged as normal.

The charger is a Pro peak SigmaAC/DC charger used with a Flight power V-balancer.

Hope this is what you need, this electrickery power  is still quite new to me ( I have just purchased a Watt meter- at last) . 

A lot of Don't's  and must do's in this EP game .

Kelvin 

[Tim Mackey]

I am very surprised that a 3.3A Evo 20 died so easily. Are you SURE that it charged correctly in the first place - did you confirm it s terminal voltage with a \dvm for instance. How much capacity ( in mah ) went back in after it "charged properly". I think we need to keep investigating this.

[Kelly]

Hi Timbo

So am I.

Yes

 No (what is a \dvm)?

Don't  Know.

Charged it , bleeped after 1hour 6 mins/   correct charger settings as per instruction book that came with the charger.

Kelvin

[Tim Mackey]

Well if it took just over an hour to charge thats about correct, and would suggest that at that point it was OK. I am still puzzled as to why the ESC did not cut the power before the battery appeared to get so low as to effectively die. Have you another ESC you could try? Could you cycle it on your particular charger?

( overpriced and under spec'd charger IMO )

A DVM = digital voltmeter. Maplins are doing 2 for 6 quid at the moment buy one ( 2 even )

I still think there is more to this than meets the eye, and I do not think you should bin it ...yet. I would like some tests done across eacgh cell, using the balance plug and a DVM. Also anohter charge...preferably on a diufferent better charger. I can do this for you if you wish. I just hate the idea of you throwing away what may be a good battery.

Going back the ESC....if it is duff ( and I personally do not rate the tornado stuff ...sorry but I have had bad experiences with it ) it may well have allowed your pack to drop below a safe minimum. If so, and we can show it...then you may have a case for compo.

Let me know what you think.

PS I also returned the F/P V balancer to them as it was rubbish when coupled with certain chargers.

[Kelly]

Hi Timbo,

I will get a DVM or two ,at the weekend.

I have the Hacker motor and esc combo in the Me109, might do the maiden this weekend .

The balancer when connected on its own shows 2green and 1 orange light on the display,according to the info the green is 75-100% the orange is 20-50% very strange.

Now I have my watt meter I will do a check on the 109 before flying.

Thankyou for the offer of charging, I may buy another charger and a balancer to be on the safe side . Which do you recommend? also advice on a good esc if  mine is duff.

Thanks Timbo

Kelvin

[Tim Mackey]

I dont like to endorse a particular brand or supplier normally...please PM me via the forum button and I will advise.

Having said that: re chargers ...well I take it you have seen this ?review

If you want to send me the pack, I will happily do a thorough test on all aspects of it for you. No charge of course

[Kelly]

Cheers Timbo, will get back to you later.

Kelvin

[Myron Beaumont]

Kelvin   Very interesting thread for me to follow now I know a lot more than I did a week ago & now understand the lingo ie things to do & things not to do & what the maths/figures all mean .Have had so much help here & from magazine articles about lekky stuff I'd never read before & ignored.Thanks for the index by the way David .Invaluable in my case!  I am getting hooked on this aspect of our hobby -For one thing it has woken up some of the brain cells (3 maybe) that I've not used in this sort of context for sometime. I just hope my eyes are good enough to fly after looking at all the things to do with lekky stuff for about 10 hours a day on this laptop

Grumpy?

[Kelly]

Hi Myron,

Yep this electrickery needs a bit of reading. just got my DVM and still trying to work out what all the numbers and symbols mean .

I enjoy a challenge and  this lipo failure has spurred me on to read and look at all aspects of EP.

My P-40 is definitely on hold until I sort this out.

I will have a fiddle with the DVM tonight and find all the articles  relating to lipo failure on the other forums.

My thanks to  Timbo who is  brilliant on this thread.

Timbo I will be in touch later .

Kelvin

[Tim Mackey]

Just remember that if you "find all the articles  relating to lipo failure on the other forums" - there has never been a single incident of lipo failure regarding meltdown/fire/ collapse and all the other scaremongery stories that was not eventually traced back to user error or charger failure of some sort.

[Kelly]

Hi Timbo,

During my re-checking I realised that the V balancer was flashing red indicating low chage on one of the cells,so the V  balancer was preventing the charger from charging hence the no circuit warning.

I decided to connect straight to the charger on a low charge, the charger showed 8.28 v at the start, I let it charge until the voltage was showing at 9.6 v.

I reconnected the V balancer and the Lipo began charging as normal. After the charging cycle The final voltage was showing at 12.26 volts.

I think the next step would be to check the power train with this Lipo connected. My question is would the Watt meter show any fault with the ESC/BEC.

It may well be my fault if I programmed the BEC to cut off at a too lower voltage, the BEC is programmed using a series of beeps,  just 1beep is for 2c Lipo cut off at 6volts, 2beeps is the setting for 3c Lipo cut off at 9volts.  I may have set it at one beep  . It may well be as you say,  user error .

Cheers

Kelvin.

[Tim Mackey]

lets hope so Kelvin.... good job you listened to me then and didnt write it off just yet eh

Not completely out of the woods....but sounding more promising.

I ditched the V balancer a while back - gave tooo many erroneous warnings and was incompatible with my Astro flight LiPo charger. If I were you, I would now discharge the battery slowly at say around 1 A or so - using maybe a car bulb or similar. You can use the wattmeter to check the current, unless of course your charger can do a discharge /cycle. Then when its down to 9V and no lower, take it off, leave it to rest for a an hour or so, then re-charge again checking at the end of the charge eactly how many milliamps went back in.

You should be acheiving 12.4V - 12.6V and close to 3000+ m/a for a charge from empty.The wattmeter will only read current drawn, and will NOT identify a BEC problem ( why are you bothered about the BEC function ? - this is nothing to do with the low voltage cutoff )

I reckon you have as you say....probably had the ESC LVC set to 2 cells not 3. To the naughty step young man!

PS it is the LVC you program NOT the BEC