Blimey that was a close shave

[Adrian Smith 1]

As a matter of course I now fly my big aerobats with a PowerBox units mainly for battery redundancy safeguards. Well yesterday flying my trusty Inverza 62 I noticed on landing after the second flight the external red warning lights winked when twiddling the sticks. Which means no more flying until cause investigated. Believe me the lights are bright so you won't miss 'em. Now the two Nimh batteries are quite new so I did wonder if it was a loose connection to the PowerBox. Well Nah! It wasn't that, not directly anyway.

Well that's clearly not right so back to the workshop, flying curtailed for day.

As a matter of course I cycled both batteries and they showed above 90% capacity at "full" charge. Presumably the chafing on the wire, which was no doubt caused by my inattention to the way I stowed them when putting cover back on. (never leave batteries in the plane after flying), did enough to make the PowerBox feel not happy and something was wrong. Would that make the PowerBox react? Anyway can the situation be resolved? As the cells appear to be ok I did wonder about just replacing the lead with a new one or just reinsulate the scuffs with heat shrink. Last resort is a new battery I guess, but I want to see if I can avoid that.

Edited By Adrian Smith 1 on 29/09/2015 09:00:32

[Dave Hopkin]

I wouldnt have thought the scuff on the insulation would cause that sort of problem, if they shorted a much bigger and more apparent issue would have happened!! While you should replace/repair that insulation I would be looking for the cause elsewhere.... I think digging deeper might be a good idea looking for a bad joint/connection somewhere maybe

[perttime]

Looks worse than minor scuff in the photo. What is that bright spot to the left of the photo?

Try replacing the wires, and see if you still get warnings.

[MattyB]

The external damage doesn't look too bad, but I guess the most likely root cause is that there is some kind of partial fracture of the wires internally. I would simply replace the wire and connector and retest on the ground thoroughly.

[Jon H]

I agree with MattyB. I had a similar situation with my 1/8th scale nitro car. The vibration had snapped the wires inside the insulation. I only fount the problem by giving the lead a bit of a pull to stretch it out. Clearly copper wont stretch but the insulation will so it should be clear if its broken

[Adrian Smith 1]

Well perttime the shiny bit is exposed wire which ain't good. DaveH you have set me thinking now. Firstly I didn't believe there was anything wrong with the PowerBox, but certainly connections need to be tested thoroughly. It's quite possibly a wire fracture within the insulation not helped by vibration on the battery lead as you guys have helpfully suggested. I am going to try 2 different batteries and see if I get the same effect.

[Phil Green]

Unpleasant as it sounds, It looks to me like you have small visitors in your workshop. They love to nibble wiring, they make a bee line for it in preference to anything else.

Cheers
Phil

[Adrian Smith 1]

As entertaining as your suggestion may be Phil, it is incorrect! The batteries and not left in the workshop or in the plane after flying, they come home with me and sit in a drawer ahead of charging again before flying. Unless of course they are hidden pilots flying the aircraft without my knowledge!

[Martin Harris - Moderator]

What was it chafing on where the shiny bit is? If it was against something metallic there could be a possibility that it shorted via that point and the power box detected it...I'm assuming that is the battery lead?

Did you get the fault indications after the cover was removed?

To be safe, replace the wires but a bit of heatshrink would probably be almost as good - but you'd need to assess it in real life to decide properly.

 

Edited By Martin Harris on 29/09/2015 15:38:17

[J D 8]

Having had much experience with vehicle wiring I would replace one's that are so pinched.

[john stones 1 - Moderator]

Get some spiral wrap on them when you've sorted it Adrian.

John

[Adrian Smith 1]

There is chafing in two parts Martin, one where the wire is showing, and yes it's the battery lead. The fault indication was before the cover was removed. I think a replacement lead is the answer I guess. John, spiral wrap is a great idea for all my leads, question is where would I source that stuff for those size leads do you reckon?

[john stones 1 - Moderator]

Sell it umpteen places should be easy found ebay, Maplins etc

John

[Adrian Smith 1]

Got it John, from Amazon and they have a selection of sizes.

[Shaunie]

Definitely copper showing on the black wire on the very left but also if you look closely at the right most of the four big ridges on the red wire I think copper is visible there too. You don't use convoluted sleeving do you? That horrible stuff is the frequent cause of damage similar to that in car wiring looms.

Shaunie.

[Adrian Smith 1]

Well Shaunie I have never heard of convoluted sleeving so I am guessing I haven't. Up until now I haven't used anything for protection, hence trying spiral wrap to see the effect.

[Vecchio Austriaco]

My son had this problem on a glow heli- battery cable was in contact with carbon frame because of vibration/friction - the frame is on ground potential because of an on board glow system - and of course the frame is conductive. The radio battery was shortened. The result was approximately 120£ - new blades - new main shaft, new main gear, some of the linkages in the head etc....

There is a tubular braid from a very stiff plastic (Nylon?) existing which cures the friction problems. It's been used ever after that experience...

Just found that one: http://www.fast-lad.co.uk/store/expand_braid_black_2-6mm_b002-p-1688.html to give you an idea what I am speaking about. The explanation "to make the wiring neat" is bu......t. the reason is clearly to protect wiring from being damaged by rubbing on the edge of the frame.

 

VA

 

 

Edited By Vecchio Austriaco on 01/10/2015 13:27:19