Storing Li Po batteries in plane, bad?

I'm sure that there will be answers to the contrary, but if your batteries have never been crash damaged, and are disconnected, I'd feel fairly safe leaving them in the plane. I never charge mine in the plane.

PCPhill

No more jeopardy than storing them with NiCds or other batteries. LiPos have been around for a while now and there haven't been masses of stories on the evening news about fires caused by them.

Abuse NiCds and you can get explosions. They can also generate more than enough current to start fires. I have seen several electric powered sailplanes that went up in flames from shorted wires.

Thanks for the reassurance. My batteries qualified for the conditions you specify. Unless I hear otherwise, I will leave them in my plane until better flying weather.

Wan

As I pointed out in the oher thread, probably no worse than having a can of paint thinners in there.

If they are not likley to short, they are not going to burn.

All the fires reported have been wehn (over?) charging, or as a result of a short - usually some time after a crash had damaged a pack.

Charging in the plane means you lose the plane as well as the batteries, and your hpuse, when it catches fire :-)

Thanks again.

I have read and re-read both threads on Li Pos, and I think I got it. These are my first 3 Li Po battery packs and I've heard so many comments about their hazards. I found disclaimers by vendors of Li Poly batteries and horror stories by modelers that set me in paranoia.

A story about how a car was burned by a crash damaged battery, and how shorting will cause fires, may be isolated incidences, but perhaps they cite things that were exciting but happens infrequently?

At the local indoor fly, there were at least 20 or more flyers flying for 2 1/2 hours all using Li Po batteries and there were no cases of accidents except for the mid-airs and hard landings. Nothing caused by battery failures. Multiply the number of flights by the number of places where Li Polies were used and I get the picture that they're rather safe. Don't you?

Sorry for being long winded, Wan

Remember the litigious nature of Western culture. If you fail to inform, you cvan be held responsible for misuse. No one wanst a suit for a mllion dollars against them on behalf of an insurance com-pany forfailing to point out that LIPOS when abused by complete fuckwits, can burn your house down.

Leaglly it is reaonsable to suppose that most people know that throwing a can of gas on a bonfire will cause a bigger one.

Its less reasonable to suppose that if someone sticks their LIPOS on a Nicad chager and sets fire to their house, they ought to have known it would. THAT is why all the disclaimers.

The nerds themn come along and pretend to know more than they really do, having read it soemwhere in a marketing document.

My other half relates the story of some psychology and arts students, who got togeher to advertise a non existent product on the sides of busses. Withon weeks people were telling them how good it was because person X had personally used it etc etc.

Yes, but don't get complacent. If you over cahrge a Nicad, it oozes muck. If you over charge a LIPO it goes pop and burns HOT. There is a difference. If you short a nicad tho, the wiring generally catches fire, and the battery gaasses and may in fact explode, but its a little less drastic than a pack going up like a magnesium flare.

the persception of risk is modified by ignorance.

It is also modified by the gravity of the downside.

We consider that one chance in a thousand of getting killed in a car an acceptable risk.

We consider that one chance in a million of a nuclear accident unacceptable.

We seem to cionsider that an expenditure of - what - $30Bn plus, and the loss of - what - over 2000 coalition lives and possibly 40,000 iraqi lives is acceptable.

But not the loss of a what? a $1bn pair of buildings and aircraft and

3000 lives....the future occurrence of which the above $30bn was spent...

Sorry for being political. :-)

I just have cost/benefit analysis as my second nature, and, spending as much time managing investments as I do, risk/reward ratios and guesstimating them is my meat and drink.

SNIP

unacceptable.

Hey D.H.,

Why didn't YOU move to Iraq? I understand they are crying in need of CBA folks and they seem to be your kind of people.

Since you cannot take any balanced views, please take your political horse manure and pound sand with it.

BTW, there is a difference between ME deciding YOU and your friends can die in some buildings and not telling you; and you and your countrymen deciding that my type of communications (crashing airplanes) are not to be allowed, encouraged, or tolerated.. Your CBA is in error because it assumes the terrorists were right in their initial actions. Is that really the position of folks in Europe, or just the pseudo intellectuals?

You suggest by implication that we should all bow down to terrorism whenever and where ever it raises it's ugly head. Please limit your surrender to yourself and your immediate family since the majority of the world is not in agreement with your assessment, values, or goals.

For an exercise in proving your value to the world, try showing exactly what the CBA was to the US in bailing Europe out from under Nazi rule? Be rigorous in your proof because holes in that type of thing are the marks of liberal liars and hypocrites.

They are no worse than any other folk.

Never said that. Don't put words in my mouth.

No, I dopn't. Thats your shoulder chip showing.

I am merely examining the cost benefit of one response vis a vis another.

Please confine your arguments to what was said, not what you in your apparently infinite prejudice, take to be the only other possible view.

Try a google search on the 'doctrine of the excluded middle' - and by the way.. "when did you stop beating your wife?"

Just because I happen to thnk that attacking what has proved to be - as predicted - a relatively defenseless country, that never had ANY connection with Al Qaeda, beyond being somewhat near Saudi, where most AlQaeda is funded from - at HUGE expense in cash, fairly high expense in collateral damage and loss of public support for the USA, and not a few US casualties as well, was an incredibly stupid waste of money and lives, does NOT mean I have ANY sympathy for Al Qaeda whatsoever.

However Dubtya has declared that 'if you ain't part of the solution, you are part of the problem' so I guess that makes me a ricin toting terrorist don't it?

I mean, Dubya can't be a stupid prat, can he? It is inconceivable that a politically inept baboon can not only be elected, but actually pretend to RUN the USA ?

One thinks of Nixon, one thinks of Carter, one even thinks of Clinton. Flawed men all.

What pray is the CBA?

I pondered for a long time and hesitate to ask. How did we ever get off into a tangent? Please lets get back on topic, shall we?

Wan

Fine with me. I was just using terms D.H. brought up.

OK, I have learned much from this thread. Though this is not about storing batteries, but......

I have read and have been told that the wires in the electrical system, if too thin or too long would cause resistance to and from our batteries, ESCs, Y-harnesses, servos, and motor.

And article, written in an e-flight magazine where the author told about how he replaced wires with heavier gauge, shortened them where he can, and even replaced small connectors with heavy duty ones, resulting in an increase in power and duration as much as about 20%. That's a lot for the effort.

My concern is that my Kokam batteries have leads that are 10' long. Should I shorten them by about 5"?

Any input would be appreciated, Wan

How much can you save by increasing the size or shorting the wire is easily computed using a few simple formuli.

power losses due to the wire is equal to I^2*R

The voltage to the motor will decreased as well and can be calculated by determining the voltage drop across the wire E=I*R and subtracting the answer from the source voltage.

Where I is the current going through the wire in amps and R is the resistance in ohms.

You can find a wire table at

Short, fat wire is the best, and watch the connectors as well. Lets take a foot of 16 guage hookup wire, it has a resistance of 0.00402 ohm per foot where as a foot of 12 guage has a resistance about 1/4 of the 16 guage.

If you don't want to fool with the math, a calculator that will let you enter ohms and amps can be found at

Hope that was some help. Sorry I had to get so long winded.

No, this is a useful length for strangling people with.

"Momma! Look, no guns!" :-)

Never sully politics with reason or common sense, and particularly not reasoned scientific analysis.

Neither the politicians, or the voters, are educated to a standard high enough to understand.

Please excusse my ignorance. I wasn't paying attention while in school. But if the voltage to the motor is decreased, would it not produce less power? Oh, you're talking about the loss of current to the motor due to resistance, no?

According to your wire table, household wire has the least resistance, but it would be too stiff for our purposes. I bought some 12 gauge wire with 400 very thin strands and silicon encased, making it very flexible. Should I use this to replace the thin wires?

I don't think I would want to buy a special calculator. I believe I could use the calculating table you provided. That's if I know how to book mark it.

Not long winded, comparatively speaking. Your wire table is of great help. I probably would not go to the library to find it. I like to build and fly but too lazy to deal with academics. I will make a print of it. Thanks.

I made an error on the above sentence. It should've been 10" long.

Current is the same in a series circuit, the voltage across a component is related E=I*R. If I is the same in a series circuit, reducing the resistance reduces the voltage drop across the wire leaving more for the motor. tough enough getting all the watts we need without wasting it in wire..

You are correct in that leaves more voltage for the motor. If the current is the same and the voltage increases, the power increases.

as losses go up as the square of the current, the resistance of the wire becomes significant once you get out of the park flier stuff.

The place to start is to measure the current your motor draws and determine what wire guage will give you resonable losses.

The way *I* learned about electron flows (better known by some as electrictiy) was that it was on the outside of the conductor. That means that a multistranded wire will carry more EMF because there are more 'outsides' AND Ohm's law. Work it out just for Ohm's law and the result becomes obvious.

The above web site provided by W4JLE is really informative. I''ve book marked it for future reference. So many equations and definitions.

So much to learn. Is there a tutorial site available for this?

Wan

Then you didn't go to the same school I did. Low frequency currents which include DC travel all through the wire. RF has what is called the skin effect and that is where it travels on the surface (Skin) of the wire. I can't prove either.

Dan Thompson (AMA 32873, EAA 60974, WB4GUK, GROL) remove POST in address for email