Li Po batteries, C ratings?

* Ratings: 8C / 82% * Outputs: 11.1 V Nominal, 1500 mAh * Weight: 113.0 g (3.99 oz) * Dimensions: 78 x 40 x 18 mm * Applications: Supports up to 12.0A continuous discharge

Sorry to keep coming back with more questions. The above are the specs for a Kokam battery. If the "Applications: Supports up to 12.0 A continuous discharge", for one pack. Then if I connected 2 packs in parallel, would they support about 24 A continuous discharge?

Wan

Yes.... Many e flyers are using them in 3P and 4P for .40 and up size gas to electic conversions. Kokam has some nice little PC Boards with the Ultra Deans connecters already attached to let you put up to 5 packs in either series or parallel very easily. Look at

| How much is the fee to join the Super Saver club at GP?

Well, it's at Tower Hobbies, actually. Tower Hobbies and Great Planes are basically one in the same.

It's $15/year. It pays for itself in shipping if you make two orders over $150 each year.

But it also doubles the warranty for `Tower Hobbies Brand' items -- so your 0.46 Tower Hobbies ABC engine will get double the warranty. But the Triton is Great Planes or Electrifly branded -- I don't think it's covered. But that would be nice if it was!

You also get a 3 issue subscription to one of a few magazines.

The `Bonus Buys' aren't very good, and the Coupon book isn't either. The Scratch and Dent stuff is usually best avoided -- they'll lose a full half of a wing kit, then discount it 25%! Wow! What a bargain!

But for the shipping discount alone, it's a good deal.

Oh, they say it costs $30/year, but I've never paid that. You just wait until it's time to check out, and it'll offer to sell it to you for $15. I've done that for the last few years.

I just looked at the box for my Triton and the proof of purchase label says Greatplanes Triton Electrify on it. I bought mine locally. Too bad yours is not covered by warranty.

I used to get the catalogue from Tower Hobbies and you're right. The scratch and dent "bargains" were usually something that no one wants.

I clicked onto that web site. It seems to be a sales pitch for magazines, albeit they're about modeling of one type or another. How long are they for free? I got some free subscriptions, supposedly for a short trial, but the billings kept coming.

You actually never paid the fee?

I clicked onto the web site you provided. The airplane and accessories sections were very good. It was fine until I wanted to browse for Li Poly batteries.

Seems to me they were overly cautious about the hazards of handling these batteries. With each battery presented, a disclaimer. Before I entered the Li Po section there was already a lengthy warning statement I must accept. The warnings with each battery was so overwhelming that I forget to look at the specs.

We should all be CAREFUL, but am I being too sensitive? Take a look for yourself.

Wan

Most all retail sellers of Li-Poly batteries have gone to some type of disclaimer page that you have to agree to prior to viewing thier selection page. They seem to think it protects them from idiots that abuse thier equipment. PITA if you ask me, but you didn't. :-)

remove my-wife to reply :-)

No.

Irates are large and thin - more surface area per unit volume and shorter path for the electrons through the electrodes maybe. These thin flat cells are a pain to fit in a fuselage, but seem to offer better lower) internal resistnace and better heat dissipation - especially in you leave airgaps between cells.

I have 2 of those Kokam packs reserved at the LHS. Maybe I should

Kokam 1500 are slightly beter than Etech, slightly worse than Irate IMHO, and similar to Thunderpower.

With LIPO its best unless you have a critical application, to rate them conservatively and simply parallel up. Having surplus capacity menas never falltenning them, which is very good, and running them cool, which is equaly good.

AND being able to charge them quicker - since they never flatten. I.e. you can charge a half flat pack in 1/2 hour etc...

Yes.

| >

| | I clicked onto that web site. It seems to be a sales pitch for | magazines,

Read the text rather than just looking at the pictures :)

| albeit they're about modeling of one type or another. How | long are they for free? I got some free subscriptions, supposedly for | a short trial, but the billings kept coming.

Three issues.

| > Oh, they say it costs $30/year, but I've never paid that. You just | > wait until it's time to check out, and it'll offer to sell it to you | > for $15. I've done that for the last few years. | | You actually never paid the fee?

No, I paid it. Only I paid $15, not $30.

In any event, my GP Triton is off in the mail to GP. We'll see what/if they charge me ...

After reading these postings, I'm excited and bought 2 of those Kokam batteries packs (KOK 1500 HC-3S-DNS, 8C). They will be my third Li Poly battery packs.

Since they are much lighter than the original NiMH batteries, I have to move the batteries all the way forward in my E3D for balance. The other plane is much too tail heavy, I thought about extending the nose section, but with the lighter batteries I will add weight instead for balance. This has not been done yet. Have any better ideas?

I strongly believe electric power is the wave of the near future. My

2¢ worth. Your assessments of the future of RC in the future may differ.

Wan

What about simply doubling the number of cells? You get your plane balanced again and double your flight time.

I think besides the price, the advantages of glow engines are gone. It's quite funny that nowadays, people get problems because their electric engines and batteries are not heavy enough to replace glow engines without modification.

| I think besides the price, the advantages of glow engines are gone.

Not quite. You still get more power per weight, and get it longer for the same weight if you want it. I imagine it'll be a while yet before an electric plane (not solar powered/assisted) crosses the Atlantic, for example.

And don't dismiss the price issue ... it's a huge factor, especially for anything much larger than a speed 400.

Don't count glow out quite yet :)

| It's quite funny that nowadays, people get problems because their | electric engines and batteries are not heavy enough to replace glow | engines without modification.

In the post you're referring to, the problem is that the Li-poly cells are too light compared to the *NiMH* cells he's replacing. He's not replacing a glow engine.

I'm not aware of many cases where one replaces a glow engine, fuel tank and throttle servo with an ESC, motor and battery that weighs

*less* than what they took out and yet gives them the same power and duration. Actually, I'm not aware of any cases, but I can think of a few extreme cases where this could happen.

Now, there may be some issues where somebody is replacing a heavy engine with a lighter motor, but then put the battery around the middle of the plane, causing problems with the center of gravity -- but that's not a problem with the battery+engine being too light, but instead a problem with where it's all being placed. The electric setup just gives you more flexibility.

Got to keep track of what you are doing with those cells or bad things can happen.

If you think Lipos are dangerous, I recently saw a guy fly a model plane with GAS-O-LINE!

That's a bit of a special case.

I know. But I heared from others who had that problem, and I'm suspecting that I'll be facing problems like that. My new plane (a fun flyer) was made for a glow machine, and I'm planning to use it with an electric motor with similar power. Currently, I'm using NiCad for financial reasons, but with that, the plane is about 3.1kg, compared to

2.9kg of the same plane with the glow machine, though one could use a smaller machine and further reduce it by maybe 200g or so. If I replace the NiCad with LiPo, I can reduce the weight by more than 500g, getting the weight below 2.6kg, while still almost doubling the capacity compared to NiCad. But I think the battery will be too light, and the plane will be too tail heavy, so I guess I'd have to extend the capacity even further so the batteries are heavy enough. I also saw another fun flyer at an LRK meeting, powered by LiPo, and it was amazing. Lots of power, more than you ever need, endlessly flying upward, and (as the owner reported) acrobatic flight times of 20 Minutes. Why would anyone want more? You can't concentrate enough for such a long time anyway. ;-)

I haven't actually been using glow engines at all, but I have seen some as well as electric powered planes, and the electric ones don't seem to me to have less power. I don't know about the duration of glow machines though.

Of course. I was assuming reasonable placing of the batteries.

Well, you have some heavy batteries to move around (or make even heavier) for balancing, so you don't need to add lead weights :-)

Rolf, This does sound simple. Thanks. It may make my plane look funny. Sort of like having a huge bulge in the front. Weight is not a problem as the Li Poly batteries already reduced the total weight of the plane by 14 oz., compared to the NiMH battery I'm replacing.

I was thinking maybe put a 3rd battery in parallel instead of doubling the pack count. Then I will be adding just about the right amount of weight for balancing. I'm trying to imagine how to arrange the packs around the nose section. Maybe sort of like an ammo belt around the front? Or like a saddle on a horse?

Well, I have sold just about all my gas powered planes. Two engines left and a very heavy field box. Just waiting to see what the Toledo Weak Signals' show may bring in the way of electrics.

Anyone coming to that show? I live here so I may run into you.

Wan

Li Pos are not dangerous as I've found out. Just be VERY CAREFUL. I have only three Li Poly battery packs, but after intially learned about the hazards and how to avoid them, they seemed like pussy cats to handle.

There are still quite a few flyers who fly with gasolene ignition engines at our field. Not much else could be cheaper even in today's gas prices of around $1.50 a gallon and a little bit of oil.

Still, I believe gas powered planes of any kind are much, much noisier than electric. And we may be losing flying fields because of this. What is the solution? We RCers need a place to fly safely.

Wan

Wait till you fire up a direct drive Multiplex twinjet then. Two 5" props doing 25k RPM an inch behind a foam wing - man those things are louder than most IC engines...

It definitely gives a lie to those who maintain that one blade doesn't interfere with another as the airflow is going backwards. Those blades audibly interfere with a wing that is an INCH ahead of them in the airflow. Take the same motor and prop and stick it a bit more out the back and the noise goes WAY down.

I don't fly my picojet much simply because its too noisy, and I don't want to upset the neighbours. Now and again is OK, but for regular flying I stick to quieter models.

Thanks