What is the silver covering on a lithium battery for?

[millsaw]

Hello all, one for the battery experts.

Background is - I bought some 1200mah batteries for my Syma X5SW. They fit snugly inside the battery compartment and extended my flight time loads (brilliant).

My X5SW is now about 50 feet up in a tree, looking like it is never coming down, also with mate808 camera attached, bye bye 50 quid  (brilliant).

So, I bought a X5C without controller or camera as I already have a controller and the X5C camera is awful. I didn';t realise that the X5C is actually a different model than the X5SC or X5SW. The 1200mah battery will not fit inside the different shaped battery compartment without some mods and a very tight squeeze (brilliant).

My question is, on these batteries there is this outer skin/covering thing made from silver material with pinstripe pattern, right? That doesn';t cover the battery completely tightly and can be compressed/manipulated with fingers? It doesn';t appear airtight because of the fold at the end where the connector wire comes out. Now, because the fit of the battery compartment is very snug, there will be friction and some force being applied to get the thing inside.

My question is, if this effort repeatedly over time does some damage/tears this outer covering of the battery (obviously an undesirable scenario that hopefully can be designed out), does it become dangerous or a fire hazard?

Thanks for help :) .

[hoverfly]

The covering will be come more inflated as the battery gets older as its releasing hydrogen, it';s not advisable to use a really puffed battery as if it does fail the fireworks are quite spectacular.

[millsaw]

Thank you for reply. Can you elaborate a bit more on its purpose?

[Two-Six]

I think that film is just plastic film and the lines are some kind of strengthening fibers, like reinforced sellotape has.  I don';t think they are conductive. 

It could be "Kapton tape".
https://en.wikipedia.org/wiki/Kapton

This is interesting:
https://learn.sparkfun.com/tutorials/how-lithium-polymer-batteries-are-made.

Perhaps if you got a long carbon fibre fishing pole you could poke your quad out the tree....Just don';t get it near any power lines, they conduct electricity.

[Powernumpty]

I';ll second the pole idea for recovery, search for "10M telescopic fibreglass pole".
When I bought mine it was about £25 but they look to be about £34 now.
That might sound a lot but I';ve recovered at least three planes with mine.

Don';t use the top two sections as they are so thin but then add (gaffa tape) a bit of extra waste pipe or something on/in the bottom, use it like a snooker cue rested against branches, if you can get a car under the tree you can stand on, then you are close to the height. 50ft is really quite a way up so you might be closer to 40 and that should be quite easy.

On the battery thing, the batteries with stripes are normally just about as thin as they will go, nothing to be gained removing an outer layer of thin heatshrink even if there is one. The chemical reaction needs to exclude oxygen or the thing runs away in a fiery mess so there is normally a plastic/foil bag with a small layer of protective heatshrink over the top and to hold more than one cell together, cells with just the foil may be OK inside sealed electronic devices but not being put in and out of models especially in a tight fit.

[millsaw]

Thank you for the advice. The batteries are wrapped in plastic over the silver foil. I';ve already poked a hole by accident (screwdriver, ******) through the plastic and foil on one of them so that one I';m scrapping. As long as I monitor the condition of them, make sure there are no punctures following insertion/removal I think it';s fine.

I';ve just tried the X5C and you know what? It flies better than the X5SW :) . It IS true that today there is mist and so very still air, so that could account for it, but the reports on X5SW and X5SC not responding too well in the wind seem to be accurate. I';ll fly on another day with light winds with the X5C to verify that. Sadly, no headless mode (which would have prevented tree-ing of the other one had I been using it) on X5C <shrug>.

The mods I made for the battery on X5C were as simple as using a small drill to drill out the peg thing inside the battery compartment at the back, thus creating space to slide the longer battery into. I also then drilled a couple holes at the front of the drone for the purpose of pushing something through to poke the battery out when you want to remove it. This is how I damaged the battery because like a fool I used a screwdriver. I shall be widening that hole so something broader and flatter can be used to push it out without fear of poking hole in battery lining.

[millsaw]

Thank you for the advice. The batteries are wrapped in plastic over the silver foil. I';ve already poked a hole by accident (screwdriver, ******) through the plastic and foil on one of them so that one I';m scrapping. For squeezing them in the X5C,  as long as I monitor the condition of them, make sure there are no punctures following insertion/removal I think it';s fine.

I';ve just tried the X5C and you know what? It flies better than the X5SW :) . It IS true that today there is mist and so very still air, so that could account for it, but the reports on X5SW and X5SC not responding too well in the wind seem to be accurate. I';ll fly on another day with light winds with the X5C to verify that. Sadly, no headless mode (which would have prevented tree-ing of the other one had I been using it) on X5C <shrug>.

The mods I made for the battery on X5C were as simple as using a small drill to drill out the peg thing inside the battery compartment at the back, thus creating space to slide the longer battery into. I also then drilled a couple holes at the front of the drone for the purpose of pushing something through to poke the battery out when you want to remove it. This is how I damaged the battery because like a fool I used a screwdriver. I shall be widening that hole so something broader and flatter can be used to push it out without fear of poking hole in battery lining.

[ched]

I have used a piece of electrical tape to create a sort of loop that you can make long enough to pull the battery back out of the compartment. That might make it easier to pull out?

[Skynet]

The silver covering is a metal foil which is laminated to the outside of the packs.