Originally Posted by
CarbonJoe
All lithium based chemistries (except the nanophosphate A123 chemistry) have the potential for thermal runaway. There have been many documented cases of Sony and Dell laptops catching fire.
What is different between the electronic circuitry in the cell phone, laptop, or iPod that is so much better than that in a Pulsar or ICE charger? Don't they charge using the same CC-CV charging method? The thermal runaway is due to over voltage, right?
Almost all household lipo chargers (Laptop, cell phone, ect...) cut off when the pack reaches 4.2V per cell. They do not keeep charging the last 10% that our hobby chargers can. Thermal runaway can also be caused by physical damage shorting out the internals.
Originally Posted by
ratherBracin
aren't every cellphone charger basically a wallplug trickle charge type of unit, whereas all the RC-based chargers are going at a much higher amperage rating?
Cell phone as ,most other household chargers are not really chargers they are just power supplies. The charger is built into the unit. I would guess that most are able to charge close to the 1C rating and a cell phone pack is pretty small.
Originally Posted by
CarbonJoe
I've seen one LiPo fire, due to someone trying to make a last minute adjustment to a 4wd buggy, and puncture the battery with a screwdriver. It started smoking, but luckily he was able to rip the pack out of the car before it was damaged. But there is a big difference in dead shorting a pack through physical abuse causing the issue than using a Li compatible charger in a normal manner. Why doesn't ROAR also mandate use of a thermal cutoff in every charger as well?
Interestingly, the label on the bottom of the Orion 3800 states "do not charge at less than 1C or more than 2C". What's up with the less than part?
How many LiPo charging fires have there been? Maybe the airplane guys can help with this one, as they have been using LiPo a lot longer than car guys have. Almost every large race has had reports of NiMH packs blowing up. Heck, even certain NiMH packs were banned for a while in Europe for this specific reason.
I agree I have had more than 10 packs puff up on me but only one fire (That I didn't cause for my own pleasure
) almost all have been from charging a damaged pack. I have had a couple puff for no real known reason. One pack was a brand new brand name pack the other a pack only used a couple times, also from a well known manufacturer. Both during charging and I caught them before anthing bad happened. (Also all happened to be airplane packs, IE no hard case)
I would guess that orion states that because most good lipo chargers have a time cutoff and if you charge at .5C it will timeout before it is done.
I also agree about the NiMH packs if I was running the cells that everyone has been having trouble with I would put them in something. I have to say though in 25+ years of racing I have only seen one pack explode and it was a NiCd 20 years ago.
Originally Posted by
CarbonJoe
A specific question... other than the YouTube videos where people purposely destroy a LiPo pack by cooking them with overvoltage, are there any documented examples of LiPo fires specifically from following recommended charging practices? Just playing the part of the sceptic. Given the big issues in Europe about some NiMH batteries being banned because of pack blow ups earlier this year, I would have expected so see the same stories for LiPo.
Even for off-road nitro, I would have expected to see stories about LiPo Rx packs flaming up, given the close proximity to 250 degree .21 buggy engines, especially in hour long mains. Not much air flow inside a sealed battery box under a lexan body. Look at where the XRAY battery compartment is in relation to the engine.
If it eases your mind to charge in a "bunker", save yourself some money and get a surplus 50 cal ammo box for less than $10.
I don't think there are many fires from undamaged packs being charged correctly but at the track the ones I have seen have been from racers charging in the wrong mode, such as NiMH mode for a Lipo. That is when a battery bunker comes in, in my opinion. Just a saftey precaution for idiots and us that try charging damaged packs.
another thing industrial lipos, such as used in houshold devices are made to be much more tolerant of our abuse, be it heat, physical damage or overcharging, their trade off is that they can't supply the kind of amps at the low weight we demand.
That is also why some companies have better lipos than others, they can be made to take more than 4.2V per cell and many of the top brands can, that is why sanctioning bodies have put in place voltage rules. To keep guys from pushing the limits.
In closing, I have been using lipos for 5 years now and my problems with them have gone down every year, companies make better cell and better chargers. I saw a real drop when it became norm to leave 20% in the packs and balance chargers became available. If A123 systems could make cells that fit in cars and had a more normal voltage they would be selling tons with almost no chance of fire. In air they are taking over.
Lockhart