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Model Forum / Radio Controlled / Land Models / October 2003LiPoly cells
I saw the thread about the Las Vegas show and the mention of LiPoly cells. I did a google search on them and I see that there are some retailers selling the LiPoly cells. However, all of the dealers I came across were from overseas (I am in the US). Does anybody know where LiPoly sub c cells can be obtained here in the US? Also, where can I find a good explanation of LiPoly? The google search came up with a whole lot of hits but very little info I can actually use. Thanks, --Dan > I saw the thread about the Las Vegas show and the mention of LiPoly cells. > I did a google search on them and I see that there are some retailers [quoted text clipped - 6 lines] > Thanks, > --Dan I don't think they are sub c cells. I think it's a new type of packaging...sort of a flat like a Hershey bar kinda thing stacked together. Some RC aviation guys are trying them.....google european RC aviation and see what you come up with. There was a tidbit in last months RC Car Action or RC Extreme mag about the new technology. They may also need to be approved by ROAR for sanctioned racing yet. >>I saw the thread about the Las Vegas show and the mention of LiPoly cells. >>I did a google search on them and I see that there are some retailers [quoted text clipped - 16 lines] > There was a tidbit in last months RC Car Action or RC Extreme mag about > the new technology. LiPoly may not come in Sub-C cells. I'm not entirely familiar with them, but I think they give about 3 volts per cell anyway. Most people that I hear from say they lack the current delivery for RC applictions.  SignatureJustin Mahn remove Panties to e-mail > I saw the thread about the Las Vegas show and the mention of LiPoly cells. > I did a google search on them and I see that there are some retailers [quoted text clipped - 6 lines] > Thanks, > --Dan > LiPoly may not come in Sub-C cells. I'm not entirely familiar with them, > but I think they give about 3 volts per cell anyway. Most people that I > hear from say they lack the current delivery for RC applictions. http://www.kokam.com/english/product/battery_main.html Signatureftupet is as ftupet does I took a look at that site, one question I have (maybe somebody can answer) is what is "1.0C" or "5.0C" when talking about the max current draw? Other web sites dealing with LiPoly cells also use this terminology. Thanks, --Dan > > LiPoly may not come in Sub-C cells. I'm not entirely familiar with them, > > but I think they give about 3 volts per cell anyway. Most people that I > > hear from say they lack the current delivery for RC applictions. > > http://www.kokam.com/english/product/battery_main.html 1.0C refers to 1 x the rated capacity of the pack e.g for a 2100 mAh cell 1.0C is 2.1A. The biggest problem with these cells is they need careful handling... they need a special Li-Poly charger, don't discharge below about 2v per cell and be very certain about the C rating and maximum current draw in whatever application you are using it in. A typical car motor will draw well over 30A running under load so you will need lots of cells in parallel to spread the current load , exactly the same reason for putting mutiple FET's into a speedo! Chris > I took a look at that site, one question I have (maybe somebody can answer) > is what is "1.0C" or "5.0C" when talking about the max current draw? Other [quoted text clipped - 12 lines] > > -- > > ftupet is as ftupet does I think they are looking quite good really. The chargers are probably available somewhere. If not, Digikey proably sells an IC with all the lipoly charging inteligence built in, building one would be a snap for anybody willing to look at the datasheet. Take a look at the site mentioned, battery SLPB 75216216. 30,000 mAh with a 5.0C max discharge rate. Thats a 150A discharge rate if I understand things correctly. The nominal cell voltage is 3.7V, so we are talking a 2 cell pack with 7.4V, which can be discharged down to 4V. Thats better than our current 7.2V packs discharging down to 6V. Holy moly, thats like 10 really good modern RC packs wrapped up into 1. The real only problem I see with *this* particular example is the weight. 670 grams per cell. For us in the US, I think that is about 2.95 pounds. I don't know what a standard 6 cell 7.2V pack weighs, but it probably isn't 2.95 pounds. But hey, I'll take a 15,000mAh pack at 1.5 pounds. From the way the mentioned site looks, Lipoly may be the way to go in the near future. --Dan > 1.0C refers to 1 x the rated capacity of the pack e.g for a 2100 mAh cell > 1.0C is 2.1A. [quoted text clipped - 32 lines] > Checked by AVG anti-virus system (http://www.grisoft.com). > Version: 6.0.530 / Virus Database: 325 - Release Date: 22/10/2003 Oh yeah, that 2.95 pounds was a calc for 2 cells at 670 grams each. --Dan > I think they are looking quite good really. The chargers are probably > available somewhere. If not, Digikey proably sells an IC with all the [quoted text clipped - 54 lines] > > Checked by AVG anti-virus system (http://www.grisoft.com). > > Version: 6.0.530 / Virus Database: 325 - Release Date: 22/10/2003 That SLB 603870H cell is looking pretty sweet. Put four of them in parallel to get 6000mah and 60A discharge rate. Then take four more, put them in parallel, and hook both mini-packs up in series to get 7.2V. Each cell only weighs 32.5 grams. 32.5 * 8 = 260g = 9.1oz. That's two or three ounces less than a regular Sub C pack. Rick R. There is a company called "Thunder Power" that makes packs for R/C applications but I only know of electric planes using them now. I have one of the 3s4p packs (10 cell equivalent) that is 16oz and 8000mah. I use them in a 3D plane called an "E3D" it draws 36 amps at full throttle and can hover up until 30 min when it drops off and I have to land. They are about 1/4 to 1/2 in taller than the sub"C" but much lighter. -- Scott MacAfee ----------------------------------------------------------------------------------- Posted from the RCGroups.com Discussion Forums. Visit us at http://www.rcgroups.com <------- Win free R/C Gear! View this thread at rcgroups.com: http://www.rcgroups.com/forums/showthread.php?threadid=162165 >The chargers are probably >available somewhere. If not, Digikey proably sells an IC with all the >lipoly charging inteligence built in, building one would be a snap for >anybody willing to look at the datasheet. Didnt investigate the finer points of the differences between Lithium Polymer and Lithium Ion chemistries (Kokam's chinglish was a bit much for me;), but I suspect theyre similar enough to require/use the same charging regime. If so, chargers / charger IC's arent hard to find - check out the TEA1102 chip, it handles NiCd, NMH, lead acid (both wet-cell and SLA) and Lithium Ion cells... can handle just about any number of cells youre likely to want to charge at once, and uses an external regulator element, so charge current can be milliamps to tens of amps - pretty much limited only by the power supply's ability to provide current and the cell/battery's ability to swallow it. http://www.semiconductors.philips.com/pip/TEA1102TS_N3.html >The nominal cell voltage is 3.7V, so we are talking a 2 cell pack with 7.4V, >which can be discharged down to 4V. Thats better than our current 7.2V >packs discharging down to 6V. The terminal voltage is pretty high when fully charged, yes. Just like NiCd/NMH cells though, they have a peak at commencement of discharge, after which the V(t) (terminal voltage) drops dramatically before starting a steady decline to the point where the pack "dumps". From the discharge V(t) graphs on Kokam's site, that peak is most noticeable under high discharge conditions (above 1C to 2C), much the same as NiCd/NMH cells. At 5C, the peak is quite dramatic, and V(t) after that peak is rather low - low enough to make me suspect using a pack of LiPoly cells would leave you feeling like the pack was right on the verge of dumping, even though it was still 95% charged. Between the low V(t) and low maximum discharge rate, I think I'll pass for now. I look forward to seeing the next generation of Lithium technology though... those Lithium Polymer cells are a clear step forward compared to earlier Lithium Ion technologies, so the future would appear bright. --- standard anti-spam measures taken email sundevil ... at ... iprimus , com , au to contact me privately sorry for the inconvenience --- best use for low power toys etc. cell phones, parkflyers, > LiPoly may not come in Sub-C cells. I'm not entirely familiar with them, > but I think they give about 3 volts per cell anyway. Most people that I [quoted text clipped - 15 lines] > > Thanks, > > --Dan > LiPoly may not come in Sub-C cells... > but I think they give about 3 volts per cell anyway. Three of them might make a good Transmitter pack, though. 3.6V * 3 = 11.8V. Rick R. yeah its the OCT 03 XtremeRC Cars mag that has the test of these. From their tests looks like these li-po cells kick a.s. Li-po 8000 vs a GP3300 pack. weight Li-Po is 10.2 oz the GP 3300 is 12.95 oz RUNTIME-- Li-po 20min. gp300 9min. ACCELERATION 0-60 feet Li-po 1.67 seconds @ 39.8 mph gp3300 1.82 seconds @ 32.8 mph no lack of punch there TOP-SPEED Li-po 47.2mph gp 3300 41.2 mph test vehicle Super RS4. Motor 5-turn Hacker brushless motor. LiPoly's are showing up in the model airplane arena, I suspect it's only a matter of time before they filter into the R/C hobbies. I know some airplane guys that are using them in full size airplanes. They are not yet available in sub-C forms, take a look at http://www.kokam.com, they are a major manufacturer of these new batteries. What is nice about LiPoly, they are much more rugged than the older Lithium Ion technology. As far a current draw, they are on par with NiMH, and they don't have overheating and bursting problems that LiIon had. There are two things stopping me from trying them out for now: 1. The price is higher than NiMH, but on a dollars per capacity scale, it's really not bad. 2. They still are sensitive to over-discharging like LiIon was. Some ESCs are now comming equipped with LiPoly low battery detection, but the only one's I've seen are designed for airplanes. Not many chargers support Lithium yet either. Hopefully we'll see some LiPoly compatible equipment for cars/trucks soon... > I saw the thread about the Las Vegas show and the mention of LiPoly cells. > I did a google search on them and I see that there are some retailers [quoted text clipped - 6 lines] > Thanks, > --Dan LiPo should make a nice, light receiver pack for nitro cars. Always nice to cut weight wherever possible. > LiPoly's are showing up in the model airplane arena, I suspect it's > only a matter of time before they filter into the R/C hobbies. I know [quoted text clipped - 31 lines] > > Thanks, > > --Dan |
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