Discharged LiPo's

tango9

Hiya Guy's & Gal's

I know LIPO batteries are hightly volatile if left charging too long but heard from a fellow skirmisher last weekend that if a Lipo battery is discharged too much, it can also cause the battery to combust.


Interested to hear the facts on this if anyone knows.........:D

Private Snafu

Everything you need to know regarding LiPos is right here

extremetaz

tango9 wrote: »

if a Lipo battery is discharged too much, it can also cause the battery to combust.

I think the important thing to ask yourself here is this - if the Lipo is discharged - then where in god's earth is it possibly gonna get the energy to combust?

Won't happen.


Ever.

Puding

there are two man dangers from lipos in my eyes, physical damage to the cells and the cells being discharged to low, if they are discharged to low they can become chemicly unstable and a run away reaction can take place

this is why 11.1 are more dangeruse than a 7.4, a 7.4 lipo can not turn over the gearbox when it gets to that danger point where as a 11.1 can happy operat once the cells have discharged to that danger point and will carry on drawing from them, its the reason you get voltage monitors and alarms for your lipo

I think the important thing to ask yourself here is this - if the Lipo is discharged - then where in god's earth is it possibly gonna get the energy to combust?

Won't happen.

edit :
ignore me, wires crossed expert advice given by somone who knows that there talking about on this one bellow

extremetaz

Puding wrote: »

the problem is that you never discharge a cell to 0 , cells have an operating voltage once it drops bellow that it can not operate the device its powering but there is still energy within the cell

Electronic Engineer Pudin', I'm familiar.

If a cell is at zero volts unloaded, then it's dead - there's no charge in the cell and there's never likely to be again.

The issue with discharge and LiPo's is the minimum safe LOADED voltage. This is usually said to be about 3V/cell for safe margin but is actually closer to 2.7V/cell.

It's important to note that the loaded voltage is the voltage measured across the battery terminals whilst it is delivering current - you can't measure this by simply testing the battery out of the device it's powering, you have to measure it in use.

At this point, the chemical change that takes place is the formation of conductive material within the cell. More often than not this conductive material simply means that your battery won't hold a charge like it used to.

In rarer occasions, this material can build to the point of a short circuit. If this happens, your battery is finished. A short circuit within the pack will cause it to dump all of it's charge internally, this will cause the pack to heat up. How hot it gets depends on the amount of charge left in the pack but at 2.7V/cell before there's any chance of this happening, that's gonna be sweet f*ck all.

Most likely the first you'll know about it will be when you plug the battery into your charger and it won't charge - why? Because the charger know's that it's f*cked.


Bottom line - it still ain't gonna explode/combust/dance a jig

extremetaz

Puding wrote: »

this is why 11.1 are more dangeruse than a 7.4, a 7.4 lipo can not turn over the gearbox when it gets to that danger point where as a 11.1 can happy operat once the cells have discharged to that danger point and will carry on drawing from them, its the reason you get voltage monitors and alarms for your lipo

This point however is a fair one.

The info above would put the minimum safe loaded voltage at about 8.1V for an 11.1V pack.

An AEG will still turn over at this voltage.

Again, whilst this is highly unlikely to cause your battery to create any fireworks, it definitely isn't going to help it's longevity.

So Pudin' is spot on about the necessity for voltage alarms/cutouts when using the 11.1's

Puding

im sorry but im no expert in this area i can only go by what i;ve read and my experiance

the problem as i under stand it is that with a 3 cell pack , any single cell as you said can be safe up to 2.7 know that fine with a 7.4 2 cell lipo if the cells reach a danger point there only giving out 5.4 ( the aeg is going to stop way before this

the problem with the 3 cell lipos is if each cell reachs its danger point (using your figures hear as i have none of my own ) of 2.7 a 3 cell lipo is still kicking out 8.2 easly enough to operate the aeg and carry on draw current and discharging the cells bellow that safe point

this then generates heat which can cause a reaction in some cases not ever time but is a possibility

like i said im no expert im only going by what i;ve previously read thought research

edit : sorry just noticed your follow up post after i had posted this i got mixed up with the point you where making, i would stand corrected on the 0 energy comment i made, i was only putting two and two together with my research on the dangers of lipos and clearly got the wrong end of the stick

Masada

Its not a good idea to play down the dangers of lipo battery's in my opinion. I had one go from the size of a matchbox up to the size of a tennis ball in a couple of seconds on my desk once because it had become so low.

don't fuk around with these things.

extremetaz

Masada wrote: »

Its not a good idea to play down the dangers of lipo battery's in my opinion. I had one go from the size of a matchbox up to the size of a tennis ball in a couple of seconds on my desk once because it had become so low.

don't fuk around with these things.

It's called venting - it's a built in safety and it's what they do.

Point is it didn't explode or catch fire.

You are right though - batteries are not to be abused and particularly not Lithium chemistry batteries on account of just how much current they can dish out.

But all scaremongering aside, the only way these things catch fire is if they are shorted out whilst in a high state of charge.

Use a good balance charger (€30 on ebay), don't short them, and if you're using 11.1V in airsoft, fit a voltage cutout.

These things done, they're every bit as safe as any other chemistry.

Craigsy

Just on a related note, anyone use the Madbull Lithium Iron Phosphate Battery "life-po":D batteries. Apparently they're a lot safer to use then li-po's, but still do the job

Masada

Well, i wouldn't exactly call it safe, it was 5 times bigger than it was originally and it was hissing, only for the fact that i covered it and punctured it, i have no doubt it was going to rupture.

i had one burn out in the stocktube of one of my rifles too, It was there at least 2 weeks without me even knowing it had happened and it fried the wiring and plug. I stopped storing them in the gaf after that.,

extremetaz

Masada wrote: »

Well, i wouldn't exactly call it safe, it was 5 times bigger than it was originally and it was hissing, only for the fact that i covered it and punctured it, i have no doubt it was going to rupture.

i had one burn out in the stocktube of one of my rifles too, It was there at least 2 weeks without me even knowing it had happened and it fried the wiring and plug. I stopped storing them in the gaf after that.,

lol - sounds like you need to start looking after your batteries better - I've never had any hassle with any lithium chemistry battery I've ever used in any application... and I've been playing around with them in various forms since Nokia first started prototyping them in pre-production phones in '02.

It's a tad beyond me how you've managed to have two of them malfunction on you.

Point worth noting would be that your mobile phone and laptop use exactly the same batteries - you gonna store them outside the house too?

Masada

As far as i am aware my phone and laptop have Li-ion batterys, not lipo.,

Mine aren't the only cases i know of though, I know Doc and Moggser had some come in from hong kong that were all swolen too,

extremetaz

Masada wrote: »

As far as i am aware my phone and laptop have Li-ion batterys, not lipo.,

It's the same tech in both battery types.

Both require exactly the same charge/discharge precautions and both have the capacity to catch fire if shorted.

Only difference between the two is that LiPo has a higher safe discharge rate.

*edit: here's an interesting little write-up on the two you may be interested to look at.
clicky

**edit again: found a couple more.
clicky2
clicky3