Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: TrickyNekro on November 24, 2008, 01:33:03 PM
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Well, I just did it... I mistakenly shorted my 11.1V battery...
It burned a wire to hell and did a nice spark... but is she dead now...
When I took reading after the incident... The voltage didn't dropped it's at 11.7...
And now she is charging nicely at 1C...
It also seems to have drawn less that 15A cause the fuse is ok...
And 15A is it's limit with peak at ~20A...
The shorting time was less that some fragments of second...
I hope she's ok cause a 11.1V @ 1.5Ah here is 40Euro!!!
Please answer guys....
I want both my money and house...
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Ok... I've seen no one replied, so I guess nobody knows...
Short circuiting LiPo batteries IS dangerous... It can destroy the cells but also cause an explosion... But for this to happen you need to have the battery connected for a minute or so...
LiPo batteries can deliver huge currents, that's true! When short circuiting they great a huge spark and burn almost everything instantly... So you will have no problem... In most cases, they burn the circuit and the cell survives...
That's very good, cause such cells are more than expensive... I feel sorry others' other losses...
I was preparing a smart low voltage kill switch, and I wanted to set the amperometer at my multimeter...
Unfortunately, I forgot to disconnect the ground, so I burned some wire....... ;D ;D ;D
Still, I'm happy cause the cell is all right!!!
The kill switch is for a small RC heli... So I better upload it for all you guys...
Best Regards, Lefteris
GReece
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I would keep the LiPo pack within your sight when you charge, you never know what will happen. Plenty of RC modelers need to remodel their homes or garages after a little $30 lipo battery exploded while they were away.
Even though it was a tiny spark, it did kill the battery a little on the inside. I accidently shorted one of my batteries for my Blade CX2 and I immediately noticed a drop in performance.
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In fact, I think it's better... The batteries are off the self...really...
I also use a smart charger and so... Although I never charge unattended...
Usually, problems occur if you are charging quickly. For example I have 2C batteries, but I can wait
for 1C...
And charger plays a big role. For example, I heard many LiPo cellphone batteries explode if charged
with wrong charger... A smart charger will stop charging at all... if the cell is full on charge.
And so on...
LiPo cells, are nice cells, durable... but they need respect... Respect many don't show, thus losing their home and garage... 8)
Best Regards, Lefteris
GReece
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fuses are something I should probably preach more at SoR:
http://www.societyofrobots.com/electronics_fuse_tutorial.shtml
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fuses are something I should probably preach more at SoR:
http://www.societyofrobots.com/electronics_fuse_tutorial.shtml
I used a 20A fuse which was at battery current limit and never broke ;D ;D ;D ;D
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lol . . . why would you use a fuse that only blows at equal or greater than the current your battery can supply? :P
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Basically, I was trying to use the amperometer of my multimeter, but I forgot to disconnect the ground :P :P :P :P :P
So, It went poof!!! ;D ;D ;D ;D ;D ;D
The fuse was the multimeter fuse...
I won't cry for a wire that's sure! I measured the capacity of the battery and it seems to be all right (you know certain drain over time)
Actually it gives me 1500mAh from 12.6V to ~10V, below 10V it drops quickly!!!
Also charging time is the same... so no capacity errors....
I also read somewhere on RC groups, that, such things, simply happen.... There is no problem at all...
But I guess when playing with these batteries, you need a 10A fuse...
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What is the C ratting of your battery? Many Li-po batteries have at lease 20C meaning they can output 20 times their capacity. I have a 11.1 volt 2200mAh 25C continuous 55C burst Li-Po for my helicopter. That means it can output 99A bursts without being damaged. Usually the problem with LiPos shorting is over heating and blowing up. As yours only shorted for a short amount of time it is probably fine, but better safe than sorry. Watch it to make sure it does not swell while charging or discharging it. If it does you need to stop using it immediately and never charge it again.
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What is the C ratting of your battery? Many Li-po batteries have at lease 20C meaning they can output 20 times their capacity. I have a 11.1 volt 2200mAh 25C continuous 55C burst Li-Po for my helicopter. That means it can output 99A bursts without being damaged. Usually the problem with LiPos shorting is over heating and blowing up. As yours only shorted for a short amount of time it is probably fine, but better safe than sorry. Watch it to make sure it does not swell while charging or discharging it. If it does you need to stop using it immediately and never charge it again.
About overheating... it didn't even sweat...
It's peak is 20A for 20sec... So the battery is ok... Man are you sure about the ~100A draw... It's hell too much... Must be Amps....
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About overheating... it didn't even sweat...
It's peak is 20A for 20sec... So the battery is ok... Man are you sure about the ~100A draw... It's hell too much... Must be Amps....
Take it you meant watts here.Actually no CommanderBob meant amps (Multiply the 2200mAh by 55 then allow for losses).
As for the pack not breaking a sweat, It didn't need to. Shorting a lithium cell no matter for how long can affect the cell chemistry. I had a pack i shorted and it didn't show any sign of degradation for more than a dozen chg/dschg cycles.
Just be careful, even with a 'smart'charger things can go wrong.
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Ok, I just had a walk by some RC forums... All said that the LiPo may loose some of her live or capacity....
Well... I have done the capacity test...
At full charge it goes from 12.6V to 9.6V under a computer fan (~100mA draw) in about well....
15 - 16 Hours, and the battery is a 1500mAh capacity one... So I guess this is more than fulfilling...
What else.... I charged it 2 - 3 times... at 1C and it's OK...
Yesterday, I did big current draw with my RC heli motor and ESC... And hell she is all right...
Ok, someone here may argue what's the use of so many posts, well
LiPo batteries, are the best consumer available batteries up to now... (weight - capacity ratio, energy output......)
So, it's good if some info exists here on the forum, for everyone...
Best Regards, Lefteris
Greece
And thanks to all replies!