Lithium Polymer for Mag D

[chuck614]

I was in the hobby store the other day, and was shown a lithium polymer battery used by the RC helicopter guys that may be of some interest to our group. Lithium polymer cells have been around for some time, but don't seem to have caught on with the flashlight crowd like they have in RC. That may be because they are made in the shape of a wafer, and not a cylinder like our familiar C, D, AA, and various other cells.

I knew about Lipoly cells from this and other forums, but I couldn't seem to fit their "square pegs" into the round holes of a Maglite----until now. I bought two 11.1V, 800mAh cells that fit easily into the barrel of a 2D Mag with room to spare, and without boring the light or using a cell carrier.

The cells are made by e-fliterc.com, and are part no. EFLB0995. They are rated at 11.1V, but test at 12.45V off the charger. They are composed of three wrapped 3.7V lipoly cells, with JST taps and balancing leads attached. According to eflite's website, they are rated at 8C nominal, for a whopping 6.4 amps continuous (if only for short time). They also make a 7.4V model that is even thinner. Eflight makes yokes for wiring similar cells in parallel or series, and a super cheap charger/balancer for $20!! So I bought two, and took them home.

I soldered a stock Mag switch with female JST leads and threw on a G4 socket. I hooked one 11.1V battery up and slid it into the 2D Mag. It was like throwing it into a well, there was so much extra space! I put in a WA1185 and held my breath. POOF!! It sure was bright for a millisecond! Then I tried a higher voltage WA1166. A super nice smooth beam, with about one third the weight of 9AA's. And bright! I also tried a 12V 50W MR16 and it worked great, too. No runtimes yet.

What's not to like about Lipoly cells? I think that they will soon be the dominant paradigm in rechargable batteries. They are safer, lighter, quicker to charge and discharge, and smaller than anything else available. The only problem I see is that they are square. The RC guys are wearing them out. (some of their cells are up to 36V and over 20C!) Let's start using and writing up our experiences with them, and maybe we will see some shapes (cylinders) that are more useful to our hobby. What do you think?

 

[rizky_p]

Yeah Lipo packs that being use by Heli people are nice and can handle 10C and up. But the downside is they have very limited cycles before losing its capacity and very expensive as well. That is why i dont that kind of lithium.

thanks.

 

[SilverFox]

Hello Chuck,

I believe the big problem has to do with durability.

Your helicopter is designed to cushion the battery pack upon crashing. If the pack is deformed, you generally resign yourself to toss the pack. In a flashlight there is little protection. When you drop your flashlight, the force will be transfered to the pack. Now you have a pack that could possibly be shorting out, held within an aluminum sealed tube...

Tom

 

[chuck614]

Price is an issue today. It will not be an issue tomorrow. There is every reason to believe that Lipoly costs will be less that wet-solvent lithium ion batteries, (since there is no protection circuit built in) once the economy of scale catches up. From what I've read on the web, construction of lipoly cells is simpler and easier than any other chemistry, except maybe lead/acid. Further, they can be made in about any shape you can imagine. Everyone agrees they are safer in use than lithium ion, although they do require some care in recharging. My 11.1V cells cost $40 each. Twelve eneloops cost about $25. When you consider price as a function of weight or energy density, it looks to me like Lipoly has an advantage already. As for cycle life, they're subject to diminished capacity when abused like any other battery.

As for durability, I can't imagine cell phone manufacturers embracing these things if they thought they were fragile. I found an old (2001) complaint on the web citing mechanical shock as a concern, but it was in the context of broken tabs. At the current price of lipoly, I am inclined to believe durability would be a major cause for concern to RC fliers. Yet they are in love with lipoly. We should be, too.

I appreciate your ideas, and would like to hear more. I have ordered a 1D Mag from ledean for use as a 12V host. I will try two 7.4V cells in a 2D Mag with a 62138 bulb, before testing two 11.1V cells with a 24V (?) bulb. When I get a presentable light, I will take photos and solicit review. Thanks

 

[bob4apple]

Hi Chuck,
I like the idea of using some of the heli batts I have laying around in a mag. That bulb you mentioned (12V 50W MR16)- I just found it online on sale for for $3.00! at <http://www.bellacor.com/detail.cfm?ItemID=78571&partid=froogle-DataFeed>. I wonder- does that bulb fit in your mag easily without having to add parts to hold it in place?

Anyway, I can't imagine a safer place for this type of battery than inside a mag, especially since there's lots of room to pack some foam around it for additional cushioning. It would then take either a hand grenade or a 3 year old to put a dent in it.

 

[chuck614]

Thanks---I really am trying to draw attention to lipoly applications for our hobby. Of course, most of the lipoly cells made today won't fit in a Mag, but the eFlite part number I cited fits with room to spare.

As for the MR16 bulb, I bought one of fivemega's MR16 drop-in sockets. Easy as pie. My bulb was from Lowe's; a GE Reveal 50 with reflector and lens built in. The Mag bezel screws right down on the bulb rim.

The only real PITA was soldering the wires to the Mag switch. See what you can throw together and give us a report.

 

[Fallingwater]

LiPos have no protection whatsoever.
In a RC helicopter you usually know when they're nearing the you'd-better-charge-me-now point because the heli starts losing power, but in a flashlight you might well go past that point without noticing.
Install some sort of voltmeter with a beeper that'll tell you when you're nearing the point of no return.

About the life of LiPos: they only last less when they're discharged hard.
Use a RC LiPo in a low-current gadget and it's very likely to last as long as a standard cell.

Oh, and they're not safer than LiIons. Actually, due to the soft casing, higher energy density and much faster discharge rating, they're considerably more dangerous.

 

[Wattnot]

Wow. This is so weird. I JUST NOW finished explaining the characteristics of lithium ions in another thread (people don't understand why their low voltage warning goes off, and the voltage reads higher AFTER they take it out and measure it with no load).

For some odd reason, I ended the post mentioning how fortunate you guys are not to have to mess with lithium polymer and BAM . . . I see this! LOL!

Just be careful with these . . . REALLY careful!! They are soft sided and easily damaged. The shock from dropping a Maglight on a hard surface could potentially be enough to make a nice pipe bomb explosion for yourself! I'm guessing but I believe the reason these are not made into hard, enclosed cases is for the reason I just described above. If you think the videos of lithium ions with a nail in them are fun, check out some with lithium polymers!! They can throw burning goo 4 feet in all directions with a direct short. Several people have lost their models just for charging them, and IIRC at least two garages and/or homes were burned.

Lithium polymers have to be the most dangerous of the lithium family. If you discharge them too much, you can ruin them (or they can puff up and explode). If you charge them too much you can ruin them (or they can puff up and explode). An okay charger starts at around 100 bucks, a good one (like the heli guys mentioned above use) is at least $250. They like the cold even less than lithium ions. I flew my plane this past Saturday in 30 degree weather and lost power after 4 minutes and had to dead stick her in. I normally land on my own after 8 minutes to keep from stressing them out.

I would just steer clear of them for flashlights if it were me!! Their big advantage is available current. How badly do you need 20, 40 or even 60 amps?

As for the helicopter thing, I've been doing that since 2003. I'm a member of several RC forums as well! My hobbies are colliding!! oo:

 

[bob4apple]

Oh, OK, I see...a drop-in socket is needed, or some other method to wire in the current. But that's so cool that the reflector fits so well. Please ignore the bulb I linked to, it's a flood which most people wouldn't want. They also have a 9 degree spot bulb in 20 watts, maybe that would be better. But since I go to Lowe's often, I'll be sure to look at those Reveals.

About the price for lipolys, I agree that they'll come down when more people discover that the new electric helis are easier to fly, that is, the models with the dual counterrotating blades.

Definitly don't be waiting for a report on anything I could throw together...if I did any soldering, it would be only my second time. But I'm going to keep learning and trying and tinkering because it's F U N.

WOW- about those warnings. I understand fires happen, and exploding hard enough to throw hot goo 4 feet, but I find it very difficult to believe it could explode with mag-shredding PIPE BOMB force! If true, the things should be illegal- kids are playing with these all over, probably flying one over a gas station somewhere right now.

 

[Wattnot]

Here's what I found in just a few seconds of searching. The first two show the 4 feet of flying, burning goo and the third link from a guy who burned down his garage because he mistakenly set his charger for FIVE cells instead of FOUR. Only another 4 volts did all that.


http://www.helihobby.com/videos/LithiumBattery.wmv

http://www.youtube.com/watch?v=z3o_2mwRPdw

http://www.rcgroups.com/forums/showthread.php?t=463115

The pipe bomb possibility is just that . . . Likely? Maybe not so much . . . . but why take a chance? You want to stuff these in a home made pipe sealed on both ends and toss it around? Go ahead, have fun! Just know what you're dealing with.


There's plenty more on youtube I didn't bother linking because I figured you'd get the idea. I've noticed sometimes links get removed so if that happens, just go to youtube and search for "lithium polymer battery."

 

[Fallingwater]

About the price for lipolys, I agree that they'll come down when more people discover that the new electric helis are easier to fly, that is, the models with the dual counterrotating blades.

This is already happening.

WOW- about those warnings. I understand fires happen, and exploding hard enough to throw hot goo 4 feet, but I find it very difficult to believe it could explode with mag-shredding PIPE BOMB force!

A LiPo blowing creates a hell of a lot of gas. Lots of gas inside an enclosed space = high pressure = bang.
It probably wouldn't have pipe-bomb force, but I wouldn't want it near me.

If true, the things should be illegal- kids are playing with these all over, probably flying one over a gas station somewhere right now.

The risk of people flying LiPo planes over gas stations is practically irrelevant compared to the risk of people who smoke around gas stations.

 

[VidPro]

because you can only wedge so much bagged cells into a round tube, your bettter off with round canned cells, even say li-fe-po ones , for what you can get in there of a bagged cell, a li-fe-po would have as much capacity, and they now come in the larger sizes.

so what i am saying is when putting square batts in round holes, and limiting capacity because of shape, you might as well use the lesser capacity li-fe-po battery in round. it would be of similar capacity, and safe. or put a real canned li-ion in and get max capacity.

li-poly can be melded a bit, to shove even larger bagged cells into mag holes, tested it a few ways, but there was no way to get full capacity of materials in , unless the materials were more of the shape of the item your putting them into. if they made a round bagged cell, it would have more capacity, but they dont. While li-polys can be rounded, and bent a bit and still work, there is a point where the electrolyte roll internal will kink and , it just isnt worth trying to Bend one , to get a decent capacity one in it.

isnt the better question: not! , why wont flat batteries fit in round tubes, but Why does a flashlight have to be round

i can think of many uses for a flat flashlight, lantern styles, front pocket light, work light, head light, a big flat based light with swivel heads could have many usefull purposes, and adapts well to flat battereis,.

 

[chuck614]

You're right, flashlights don't have to be round. But the Maglite, like Harley-Davidson, has become something of an icon, with tons of aftermarket trinkets that we use to customize them. The tube flashlight is a paradigm that is not going to go away, but with the average width of most lipoly cells being about 34 mm, they're not going into a Mag. I just wish our chatter on this forum might lead manufacturers to make lipoly batteries that are tailored to consumer-level use, like D, C, and AA sizes. Of course, the same impediments exist that keeps li-ion from broad consumer acceptance, like safety and compatiblity. Time and the market place will tell.

I appreciate the cautionary comments. I will continue working with lipoly, with the idea that if it's safe enough for the RC people, it's safe enough for me, but with a heightened sense of concern for safety in handling. I have read several of the cautions and disclaimers that are on the sales websites, and keep them in the front of my mind when working with these cells. I will report to you my successes and failures as they occur.

 

[IMSabbel]

Hello Chuck,

I believe the big problem has to do with durability.

Your helicopter is designed to cushion the battery pack upon crashing. If the pack is deformed, you generally resign yourself to toss the pack. In a flashlight there is little protection. When you drop your flashlight, the force will be transfered to the pack. Now you have a pack that could possibly be shorting out, held within an aluminum sealed tube...

Tom

Oh, i am pretty sure that inside a nice thick aluminium tube, those cells are much better protected than falling out of the sky with an RC helicopter.

Just assure that they are a tight fit (dont have room to accelerate), and they should easily withstand those 50-100g spikes an impact can produce.

 

[2xTrinity]

You're right, flashlights don't have to be round. But the Maglite, like Harley-Davidson, has become something of an icon, with tons of aftermarket trinkets that we use to customize them. The tube flashlight is a paradigm that is not going to go away, but with the average width of most lipoly cells being about 34 mm, they're not going into a Mag. I just wish our chatter on this forum might lead manufacturers to make lipoly batteries that are tailored to consumer-level use, like D, C, and AA sizes. Of course, the same impediments exist that keeps li-ion from broad consumer acceptance, like safety and compatiblity. Time and the market place will tell.

LiFePO4 has much better potential for consumer-level use due to the fact that the chemistry is much safer and less finnicky about charging/discharging than other LiXX chemistries. This chemistry is also in its infancy as far as development goes, so there is a great deal of room for improvement. There are already some cells available in 18650, 26650 (Long C), 32600 (D) and 32900 (F) form factors, although at this point power density is awesome, but energy desnity by volume is still poor.

LiPoly, or any prismatic cell for that matter is better suited for "lantern" mods which traditionally use square packs -- either old school alkaline lantern batteries, or now, rechargeable SLA packs. Replacing SLA with a LiPo pack in a lantern/spotlight could lead to some great performance.