radio control dangers eg, lipos and ic

If you can find a spare microwave its ideal but I keep mine inside,however dont plug the microwave in.

Polyphilla wrote:

willowlea wrote: What do I need to buy to keep my lipos safe in a couple of weeks then?

A very important thing about Lipo safety that I haven't seen mentioned yet is about to hit us here in the UK with the onset of winter.
Many of us charge & store our batteries in an outdoor shed.... these sheds can get hot in the day & freezing at night.
The storage capacity of a Lipo varies according to its temperature. You could fully charge a 5000mAh lipo on a warm day & then leave it in a cold shed overnight ..... When its temperature drops, it suddenly becomes an overcharged 4000mAh battery & could be knackered.
This is one of the main reasons why decent chargers have a "Storage Charge" setting.

Pol.

I'm not entirely sure but it could be the other way round Phil, if you put a battery in a cold place it tends to loose it's efficiency, when you were a youngster did you ever warm torch batteries up to squeeze a bit more life out of them?
So it stands to reason that if you charge a battery in a cold place and then move it into a warm place then it will become over-charged.

I think your absolutely right.I think one of the most important selections when going electric is a decent charger.

Old Fart wrote: I'm not entirely sure but it could be the other way round Phil, if you put a battery in a cold place it tends to loose it's efficiency, when you were a youngster did you ever warm torch batteries up to squeeze a bit more life out of them?
So it stands to reason that if you charge a battery in a cold place and then move it into a warm place then it will become over-charged.

Maybe I wasn't clear O.F .... If you charge a lipo to full capacity in a warm shed during the day, ready for the next day's flying, it will be at it's maximum capacity...... If you then leave that lipo overnight & the shed gets cold .... the capacity of the battery is reduced & the excess charge is then the same as an overcharge.
In the example I used with a 5000mAh battery, .... you put into it the equivalent of 5 Amps for one hour & when it's warm it's quite happy to take that amount..... When it cools down it's capacity is less (say 4 Amp hours) .... but the energy from the initial charge is still there and will then appear as a 1 amp hour overcharge.

Pol.

What would be the result of this pol.

The Beard wrote: What would be the result of this pol.

Probably not a fire because the battery temperature wouldn't change suddenly .... but it could cause the cells to "Puff up" and be permanently damaged.

[/quote]
Maybe I wasn't clear O.F .... If you charge a lipo to full capacity in a warm shed during the day, ready for the next day's flying, it will be at it's maximum capacity...... If you then leave that lipo overnight & the shed gets cold .... the capacity of the battery is reduced & the excess charge is then the same as an overcharge.
In the example I used with a 5000mAh battery, .... you put into it the equivalent of 5 Amps for one hour & when it's warm it's quite happy to take that amount..... When it cools down it's capacity is less (say 4 Amp hours) .... but the energy from the initial charge is still there and will then appear as a 1 amp hour overcharge.

Pol.[/quote]

I don't think it quite works like that Phil, if you charge a battery in the cold the charger will charge it to full capacity but if you then move the lipo to a warm place then the fully charged lipo could then see itself as being over-charged and then the fire starts.

Old Fart wrote:
I don't think it quite works like that Phil, if you charge a battery in the cold the charger will charge it to full capacity but if you then move the lipo to a warm place then the fully charged lipo could then see itself as being over-charged and then the fire starts.

If the battery is cold its capacity is reduced. In my 5Ah example its capacity may drop to 4Ah when cold.
If you then charge it, the charger will cut off after 4 Amps have been pushed into it for 1 hour (mathematically speaking)
The battery may then warm up & its capacity increase back to 5Ah .... but it can't have that much charge in it because you only pushed 4Ah in .... it's then below full capacity.
Working in reverse ..... charge the battery when warm & its capacity is 5Ah .... the charger will allow 5 Amps to flow for 1 hour & will then cut out with the battery storing 5Ah worth of energy.
If the battery then gets cold & its capacity drops to 4Ah, ..... you end up with a 4Ah battery trying to hold 5Ah worth of charge ..... it's effectively overcharged.

I understand what your saying,its n ot a risk but when you get a cold attery out at the field its not as powerful,but if you keep it warm its more powerful hence why batteries are better in the summer,

www.4-max.co.uk/pdf/dos-and-donts-lipo.pdf

The Beard wrote: I understand what your saying,its n ot a risk but when you get a cold attery out at the field its not as powerful,but if you keep it warm its more powerful hence why batteries are better in the summer,

That's mostly because of the internal resistance of the battery increasing when it gets cold.
This means that if you're pulling umpteen Amps out of the battery, it's voltage will drop under load.
This does take some quite severe extremes of temperature .... but I have seen flyers in some bad conditions at the top of the Gt. Orme in the middle of winter & they have been affected.
You also need to take into account, if the internal resistance of the battery increases, & you still allow it to deliver the amps. .... it will them warm up & become fine ..... it's just it's capacity when cold that is the problem.
It's a bit like filling a bottle with water & then sticking it in the freezer ..... It may hold a pint at room temperature .... but when it turns to ice it'll bust the bottle.

Pol.

But you can store a fully charged Lipo in the fridge (not the freezer) for some weeks.

Old Fart wrote: But you can store a fully charged Lipo in the fridge (not the freezer) for some weeks.

Yes .... heat speeds up chemical reactions, including the ones that go on internally in any battery and cause natural decay ..... it's best to slow these down.
The basic rule is don't fully charge a battery at room temperature & then cool it ..... that's why modern chargers have the "Storage charge" function.

Is this a rule as fact or could it be your opinion?

just wondering Phil if it has been written anywhere.

Old Fart wrote: Is this a rule as fact or could it be your opinion?

just wondering Phil if it has been written anywhere.

Physics, Chemistry & Natural Sciences are my pet subjects, ( I skipped biology).... It's also been recorded by many modellers & if it's important I'll provide the links ..... I'd rather keep the forum to a down to Earth fun level & if you, or any member, want clarification of my explanations, I'll be glad to give it.

Pol.