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batman
08-01-2005, 03:42 PM
I have been holding off going into LIPOs in the hope that some new, safer technology might come along to rival it in performance. I have read about Saphions but they seem to havegone by the wayside also the new Li-ions that Milwaulkee Tools have, but we don't see anything about them anymore. And there have been one or two others that may have been vapourware. So, can anyone enlighten us as to the possibility of a new miracle cell in the pipeline?

SargentM
08-01-2005, 10:47 PM
I am comfortable in the fact that the manufacturers of Lipo cells are working to increase the rate at which we can charge these cells safely and with no reduced lifetime. But I look foward to trying hte next 'wonder cell' and a new charger to go with :D

ragbag
08-02-2005, 02:52 AM
I use lipos.
Somewhere a while back I read that the Lion's come in a metal case and are sealed. When they go, they go big time because of the pressure that is created in the can.

And that isn't beer or soda that is going off!!!!

I haven't seen that refered to in quite a while, so it might be missinformation. Often wonder if these are the spectacular fireworks we see from time to time.
Seems with the new chargers and the warning's we aren't getting as many "bad" reports as we did in the "begining".

Last year at SEFF there were a few, haven't heard of one incedent this year. Maybe we were just getting negative press last year and not this year.
George
Gainesville Fl

Matt Kirsch
08-02-2005, 03:28 PM
Education and advances in "smart" charging technology have gone a long way in nipping the LiPoly fire issue in the bud. Fires still happen from time to time, but not nearly as often, unless people just aren't 'fessing up like they used to.

If you follow the rules and take proper care of the batteries, there is absolutely no reason to fear LiPoly technology. Even if a pack fails and catches fire, you've taken the proper precautions so the damage is limited to the pack itself.

Sometimes the reason people fear LiPoly technology is because of a myth. For example, many people believe that LiPolys are little bombs just waiting to shoot fire all over the house the second you're not looking. LiPolys do not spontaneously combust just sitting there on the shelf. If you look at every LiPoly fire, you'll see that it can be traced back to a charging issue or a short circuit.

Charging issues include blatant overcharging, like using the wrong cell count, or a cell imbalance issue where one cell's voltage has dropped below the others, causing one or more of the "strong" cells to become overcharged.

Shorts can be external, like a screwdriver across the terminals, or internal, like ones caused by crash damage.

batman
08-04-2005, 04:18 AM
I have a couple of Lipos but have not taken the plunge to all Lipo yet. I realize that if precautions are taken they should be quite safe. However, they are not as robust as Nimh or Nicd and there have been a few " events " for which there is no explanation. A couple tht come to mind have involved fires in cars from Lipos that had not been recently charged or discharged. It is possible that thermal runaway may have occurred because high temps in the cars but I have not heard of that happening with Nixx batteries. The Li-ions that are being used in Milwaulkee tools 28 volt systems sound very robust with fast charging as a bonus but those cells are not yet available to us. There was talk of those cells being sold separately in about 12 months time, of course we will need new chargers for them :confused:. I am just reluctent to dive into Lipos big time if there is a safer technology coming soon.

SargentM
08-04-2005, 07:35 AM
There should be no reason that you cannot charge Li ion cells on your polymer charger, unless there is a different nominal cell voltage.

Matt Kirsch
08-04-2005, 07:07 PM
I'd put money on these Milwaukee tools having LiPoly packs, not much different than the current-generation LiPolys we use in larger planes. Technically, LiPoly is Li-Ion chemistry. The difference is in the packaging.

Contrary to popular belief, it's not the cell technology that's preventing "fast charge," as much as the charging and protection circuit technology. The faster you charge, the quicker the cells get out of balance. Without a balancing circuit, fast charging is just a dangerous proposition. People were doing it, and getting away with it to a point, but as soon as one cell got a little weak, the strong cell would get overcharged, go overvoltage, overheat, and well... you know the rest.

Without sounding too much like a commercial here, that's what FMA is attempting to remedy with the BalancePro (available now) and SkyVolt (in September) systems. I'm evaluating a SkyVolt right now in my P-40 conversion. FMA says 80% capacity in 20 minutes, 90% in an hour. These are just their standard 2100mAh and 3200mAh 20C cells, with taps on each cell, an onboard protection circuit, and a special charger that also monitors each cell individually.

Commander_Drake
08-04-2005, 07:16 PM
FMA says 80% capacity in 20 minutes, 90% in an hour.

Sounds great! 80% is plenty for most of the flying I do.

Unbalanced prop
08-08-2005, 03:12 PM
I'm evaluating a SkyVolt right now in my P-40 conversion. FMA says 80% capacity in 20 minutes, 90% in an hour. These are just their standard 2100mAh and 3200mAh 20C cells, with taps on each cell, an onboard protection circuit, and a special charger that also monitors each cell individually.

So Matt...............what are your thoughts on the "skyvolt" system? How is it performing for you?

Doug

batman
08-08-2005, 06:20 PM
The batteries that Wilwaulkee use are an advancement on the old li-Ion cells. What they have done is incorporated nano technology into the cells so that they can be fast charged and discharged safely. If I remember right they can be fully charged in 15 minutes and will hold up to a discharge similar to what we currently achieve with Nixx cells. I believe the nano thechnology keeps everything in place so that no migration takes place with in the cell therefore making them safe to use the way we need to. Of course the only way to get some at the moment is to buy the Milwaulkee 28V replacement batteries and pull them apart because the company that produce these cells have their produce fully commited to Milwaulkee for the next year. Unfortunately I can't find the links to the sites where all this info is available but I hope that someone who reads this will have them and post them for us to check.

Matt Kirsch
08-08-2005, 06:23 PM
Two flights, three charges, all flawless as far as the SkyVolt system is concerned. The SkyVolt charger is almost like a Ron Popeil rotisserie oven, you just "set it and... DON'T forget it," but it's not nearly as twitchy as setting my Astro 109. Close enough is close enough because the system allows up to 3C charge rates. I could literally "redline" the charger and not hurt a thing.


It's amazing to be able to fly a .60-size warbird on a single 6S pack that weighs half as much as the equivalent 20-cell pack of GP3300 NiMH.

skyvolt12
08-08-2005, 10:17 PM
Hi I was interested in a statement you made concerning the Astro 109 charger. You said it was "twichy". I was about to buy one, but twitchy caused me to think about it. Could you maybe be more detailed. thankyou
skyvolt12

Tweet
08-09-2005, 11:29 AM
The Astro 109 is a good charger. However, you do have to set the charging current on your own. If your last battery charged was a 5S4P 8000 mah battery and you set to charge at 8 Amps on the next battery you charge is the 3S1P 730mah battery for your Shock Flyer and you forget to dial the current back then bye-bye 730mah pack and hello fire. So, the Astro 109 is not as idiot proof as some, but it does work well and I recommend it. I try to make a habit of turing down the charge current to 0 when I finish a batter and also to double check the cell count and the charge current when I put a new battery on. However, people do get distracted although I haven't yet...

Unbalanced prop
08-09-2005, 01:55 PM
Tweet

From all I've read, you won't start a fire by charging with too many amps, only too much voltage. You will probably ruin the battery or at least damage it, but it will not flame up like charging with the wrong cell count selected. Lipols flame when charging with more then 4.2 volts per cell. On the 109, you can only adjust the amps and not the voltage.
Kokam and TP (may be others) are working on cells that will take a 3C charge rate.:eek: That will make 20 minute charges a reality.:cool: I agree that the 109 is an excellent charger, just turn the knob down before you start charging.

Doug

skyvolt12
08-09-2005, 03:01 PM
Greetings, I had a hunch that would be the ans. to the twichy's I thank you for the quick response. That could be a problem allright especially if you have a " brain fart" as my 40 year old son likes to call it. Thanks again.
skyvolt12

Unbalanced prop
08-09-2005, 03:21 PM
The "twitchy " part to me is the knob is hard to adjust amps exactly. Just a small amount of turning the knob can make the amperage jump a lot. This happens worse at lower amperage settings but is not a big problem. Just make sure and turn the knob off, plug in the battery, make sure it selects the correct cells and then set the charge rate to a 1C rate or less according to the battery being charged. After three minutes the charger goes to phase two of the charge and will not change the number of cells selected. Be sure and check after three minutes for cell count and all should be OK from there. After many charges of 2,3 and 4 S packs, my 109 has never seklected the wrong cell count.

Doug

skyvolt12
08-09-2005, 06:20 PM
Hi Doug,
Thanks for the imput, that dosn't seem like a big problem.
skyvolt12

stuff
08-09-2005, 09:34 PM
Batman ooo sorry my candle just went out. you snooze you loose Stuff

GeraldRosebery
08-10-2005, 02:43 AM
The LiPo fooforah is exactly the same as the beginning of the major use of gas engines. Way back then we were required to have a fire extinguisher handy when we used a gas engine. It seems laughable today doesn't it? The same is true of LiPo's. Once people realized that you have to use specialized constant current-constant voltage chargers, the whole exploding battery thing has just sort of gone away as a major issue. Sure be careful, but don't panic! Cell phones use LiPo's and exploding cell phones have largely gone away as well. The cells are better made as are the chargers.