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Old 03-09-2009, 12:52 AM   #1
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Default Lithyum Ploymer Battery

Why are Li-Po's so dangerous? are they really that bad? why do they catch fire? how do i properly maintain and charge a lithyum polymer battery? thank you for your time!
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Old 03-09-2009, 02:10 AM   #2
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Lipos are not that dangerous unless you do something REALLY stupid with them. If they were as dangerous as some seem to think, I would have burned my house down twice by now

Most lipo batteries come with instructions on how to properly charge them. Generally speaking, you charge them at 1C. That means that if you have a 4500mah lipo, you charge it at 4.5A. If you have a 3500mah lipo you charge it a 3.5A and so on.

You never discharge a lipo past 3.0V per cell. So you always want to run a low-voltage cutoff.

You also want to balance lipos. So if you want to keep your batteries in tip-top shape, get yourself a balance charger or you buy a balancing unit that plugs in between the battery and charger and that ensures that each cell of the battery is charged evenly to the same voltage.
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Old 03-09-2009, 11:18 AM   #3
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If LiPos were so dangerous, why would they exist in nearly every laptop and cell phone being made? They leaked into the R/C hobby as a result of the computer/mobile research and development efforts.

Any battery can be dangerous if not handled correctly. LiPos are no exception. Be sure to get a good charger, and keep reading up on them.

Using hard case batteries is a god idea. (any ROAR approved battery is hard cased) The actual LiPo cells are pretty soft, and are encased in a foil like envelope. They are very susceptible to physical damage. You should discard a physically dented or damaged pack, and never use or charge it. Spending a little extra for a hard case is like investing in good insurance.
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Old 03-09-2009, 12:11 PM   #4
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Must use a charger with a lipo mode!!!! CC/CV its commonly listed as too: Constant Current/Constant Voltage.

Fires are mostly by overcharging any cell over 4.2 volts. Good quality lipo charge with balancer pretty much takes care of that as mentioned.
Or puncturing the battery like also mentioned I believe.

Do some research, be aware, not scared. Nimh explode, so nothing is absolute.

To be fair, there were a bunch of burning laptops not so long ago. Wasn't that a charger issue???
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Old 03-09-2009, 04:12 PM   #5
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Why are Li-Po's so dangerous?
The same reason automobiles and bench saws are dangerous. If you misuse them you'll cause an accident.

are they really that bad?
No. They're not as bad as you might think. Naturally, the worst case scenarios are the one's told. You don't hear about the cases where someone has used them for years and never had a problem. Personally I've punctured lipos (on accident of course) short circuited a few, had one fly out of my car and hit a curb, causing it to loose voltage and have to be discarded eventually (just one cell of 5) and have never had a fire. I don't recommend those things of course. Just saying, it's not like you look at them wrong and they burst into flames.

why do they catch fire?
It has to do with the chemistry of lithium. Lithium is a very reactive alkali metal and readily reacts with nitrogen, oxygen, and especially water. Coincedentally these are the top 3 most common components in the air and thus the volitile reaction when there's any breach in the battery. If the breach is caused by the battery heating up due to overcharging then you have a perfect combination for fire. The lithium is both hot and exposed to a compound/element it can react to.

how do i properly maintain and charge a lithyum polymer battery?

1. Get a charger for lipo batteries. Don't go above 4.2V per cell and charge at 1C (the mAH rating of the pack divided by 1000). A quality charger has this built in and won't charge more than 4.2V per cell. Veterans never take this for granted though. Keep an eye on the battery when charging to make sure voltages are not exceeding the correct level.

2. Keep the cells above 3.0V. Your ESC should have a cutoff for when the cells reach this voltage. It will damage the cells if they get much below 3 volts. It won't necessarily cause any fire or anything of that nature, but may reduce the life or charge the batteries are able to take.

3. If storing the batteries for an extended period of time (months, not days), set the voltage of the cells to 3.7V/cell. This is better than having them fully charged suppsedly. I've never gone a month without using a pack so I've never really done this.

4. If you have soft case lipo's be careful not to damage them. Any impact or excessive stress, even strapping them down too hard in your car/truck could cause damage. Again, they're not likely to burst into a giant fireball but it could reduce the life or voltage of the pack if the soft cells are damaged.

Compared to NiMH and NiCD I actually favor LiPo batteries a ton. Aside from the fact that they have WAY more power and endurance than NiMH/NiCD and are much much lighter, they have no memory (you can recharge at any time without fully discharging) and they last just as long if not longer. No peaking, cycling, discharging, matching or zapping cells, and all that other garbage we had to deal with when it came to NiMH/NiCD. Just be careful with them and they'll treat you very well.
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Old 03-09-2009, 04:27 PM   #6
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Speaking of LiPo's, sort of, does anyone have a code for A-Main?

Am getting one of these:

And this:

Just so I have a good racing battery that is durable, as I use 2 NiMh's and it is rather annoying having them run down only 50% of the way after a race and having to recharge them.
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