ok guys here is another one to chew on. I was at a airshow a couple of weeks ago. they have a new battery out there called lipo. lithum-polimur. these batteries are powerfull and light. for all of us who are looking to save wieght . maybe we should look into this. 1 battery was just 2/8 GRAMS. about the same weight as one of our cells
what do you people think
cougar:tophat:
hi,
I also fly with rc planes and i fly with those Lipo batteries i can’t imagine to fly whith out them. The are light and powerfull but you have to be more carefull when charging them with special charger, the could explode or burn when you charge them to long.
I used them in my 1.20m sailboat and it went verywell, just look for the right voltage and mAh.
the weight saving is on small boats considerable.
greetzz Robert
I dont remember where I read about it, but I remember this:
LiPos + water = no good!!
Lithium batteries offer a huge weight and space savings. They are no more unsafe around water than any other batteries. The chemistry of lithium batteries( the potential to burn voilently if charged wrong or damaged ) is what makes them potentialy dangerous.
Most small electronics, including cell phones now use lithium batteries.
There have been some fires( car and house) from either overcharging them or trying to charge batteries that were damaged in crashes.
They work great but you cant abuse them.
Be careful!
There are 2 types of Lithium cells on the market right now.
Lithium ion, (Li-Ion) and lithium polymer (Li-Po)
The lithium in a Li-Poly cell is hazardous and will react violently with water. (go ahead, ask me how I know. let me know if you want pictures?)
Li-ion cells are a bit more stable and can be used around water, but care should be taken to keep them dry.
Never wrap either type of cell in plastic, or dip in a waterproof coating. The cells have built in vents that must remain open to allow the safety features of the cell to operate properly.
Unless you know exactly what you are doing, it is probably best if you do not use any kind of lithium cells in a boat at this point.
If you have insurance, check it closely, most will not cover a Li-Po fire, or damage caused from a LiPo cell.
Peter Richards
I have used Li-poly batteries for a few years now , in planes and boats. Its simply not true that li-poly batteries react violently with water. Infact one of the safe way to dispose of them is to discharge them as much as you can( you can use a resistor), drop them in salt water and let the battery discharge from one terminal to the other through the conductive salt water, till they reach zero volts. They will slowly discharge creating small oxygen and hydrogen bubbles. Even fully charged li-polys disposed of in highly concentrated salt water will do nothing but bubble and slowly discharge.
If you over charge them, short them out or damage them causing an internal short , the chance of a fire is very real. Look here for info http://www.rcgroups.com/forums/showthread.php?t=209187
After rereading those threads, I dont see any real benfit to using Lipolys in most sailboat classes. Unless you are fanatical about weight(like US1M), I think the risks outweigh the benifits for the average person, even if it is just for peace of mind.
I will still use them, as they make a huge difference in airplanes and I take every precaution when using them.
Robert,
I would kindly suggest that you do some more research on this subject before you make blanket statements like you have. Other people on this board may read your comments and believe them to be 100% fact.
Here are some things to think about:
~ Not a single battery “manufacturer” recommends getting their lithium cells anywhere near any kind of water. (Fresh or salt)
~ No recognized model insurance coverage will accept a claim for damages from LiPo cells used in boat.
~ Putting water on a LiPo fire WILL make it worse! [SIZE=2](Been there, done that. Got the scars to prove it.)
I am not saying that you have not had good luck with your packs. It is good to hear you like them, and have used them responsibly.
I do think it is prudent to let others know that there are risks, and that precautions must be followed.
Peter Richards
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I have done my research, and have had much personal experience with lipoly batteries. I dont know the details of your accident with lithiums,but we are talking a normal and practical application of lipolys ,no? To make the statment that the lithium in lipolys is hazardous and will react violently with water, is giving the impression that the intact battery is hazardous and will react violently with water( which is wrong).
Now, you need to do some more research before making blanket statments. Check the link I provided.
[SIZE=2]You?re right Robert.
By the way, here are some of my credentials:
Electronics Engineering degree. (Thesis on modern cell technology.)
7 years of record setting speed trial runs (with all types of cells incl. LiPo’s)
Designer of the fastest commercially available LiPo boat kit (70+ MPH)
Designer of several very popular “Parkflier” aircraft (all LiPo powered)
I was one of the first people to use LiPo cells in a marine application. (Where they work very well but have had problems if they are damaged or were immersed.)
I am currently lobbying several major modeling organizations to accept new cell technology and insure them.
I don?t know if any of this qualifies me to know what I am talking about or not? I will readily admit that I still have a lot to learn.
I will say that if anyone is thinking about using LiPo power in any application, (air, water, or anything else) certain precautions must be observed to prevent injury or property damage.
#1 use a high quality LiPo charger.
#2 check your cell condition all the time.
#3 If a cell looks damaged, or irregular, DO NOT USE IT!
#4 A voltage cut off device is a good idea.
Peter Richards
PS. I helped Jim McPherson (also an Electronics Engineer) test his Lightenna before it was commercially available.
I have used it in marine applications and it works well. I highly recommend it.
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i too have learned that li.po batteries dont like water. dont know what happends. but since most of us . put are batteries in a bag. i cant see the problem. but i have seen IOM guys put in corrector wieght. just to get close. now most of us. cant get that light. so maybe we should look at lossing the wieght. and after seeing the airplane guys using them. just a thought . this would be a good idea. lots of power and lite wieght too. soo far a good discussion. thanks rob, and peter. we can use all the information we can get
what happend to batteries if they get wet? what about damp?
cougar
anybody else thinking the same way
I’m old to airplanes and new to sailboats. I’ve used Lipos for years in electric float/sea planes, flying hydros, hydro foils, electric boats, and now my sailboat. I’ve never had a problem with them with regards to water exposure, and they’ve been submerged plenty of times. The only problems I’ve had are high current applications with mis-matched cells in parallel, and I’ve seen problems due to overcharging and damaged cells due to violent plane crashes.
…just my experiences
Mike
lipos are also usd in fullscale sail boats, such as PDQ"s 44i Antares #21, i believe. it’s using motors with lipos, instead of the yanmar 3ym 30’s
http://www.youtube.com/watch?v=z3o_2mwRPdw&feature=related :scared:
Not trying to spook anyone, but could ya imgine your boat with this inside?
I’ll personally stick to designing around the heavier power sources. 