Electric General Discussion General Discussion forum about rc electric related aircraft, accessories, flight, tips, etc.

Ask your electric FAQs HERE!

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Old 05-17-2004, 08:31 AM
  #1  
Matt Kirsch
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Default Ask your electric FAQs HERE!

I think it's high time that the electric flight area of RCU had an Electric FAQ. It's always discouraging to have to send people over to the competition when they just need to know the basics. While I suppose we could simply plagiarize their FAQ, that's just not a nice thing to do, so let's create one from scratch.

What I need from you is your help. Anybody with basic questions, post them. Experts, please take a few minutes and post an answer or two.

Please refrain from asking about specific applications or specific products, or answering a question using a specific product if possible (e.g. Astro Whattmeter is okay because it's pretty much the only product of its kind on the market).

For now, we'll run it as a "Living FAQ," but I do intend to compile the answers into a single document, perhaps something we can post somewhere on the website.
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Old 05-18-2004, 09:27 PM
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hbruhn
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Default RE: Ask your electric questions HERE!

There is an other wattmeter on the market, better but also more expensive.
It is made by Graupner and looks and works like the one electrician use,
Clamps around a wire and that is it, no connecting to wires .
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Old 05-20-2004, 01:02 AM
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Time Pilot
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Default RE: Ask your electric questions HERE!

I've asked this question today, but how to properly do a water break-in on a brushed motor.

I've read about it in a magazine, but it wasn't clear enough. How much of the motor needs to go in the water? How long does it need to dry out (should one use WD-40 to disperse the water)? Where exactly does the oil go after the motor is dry? How much oil? What kind of oil?

Pictures would be very helpful. For someone who doesn't know what names of the parts are, a description of what to do is not always that helpful.
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Old 05-21-2004, 06:33 AM
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Matt Kirsch
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Default RE: Ask your electric questions HERE!

Well, this idea isn't going nearly as well as I thought it would...

Come on, guys! It takes but a second to post a simple electric question.

Thanks for your submissions so far, both of you.
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Old 05-21-2004, 02:15 PM
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Greg Covey
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Default RE: Ask your electric questions HERE!

Why should I fly electric? It seems more complicated and costly than glow-powered setups.
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Old 05-21-2004, 02:30 PM
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Default RE: Ask your electric questions HERE!

what is the best 1500 batteries pack for racing cars
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Old 05-21-2004, 06:22 PM
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Jim Finn
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Default RE: Ask your electric questions HERE!

Some of the advantages of flying electrics are: You can build as small or as large as you like............Quietness allows you to fly most anywhere...................No mess to clean up..................Planes stay looking new because of no fuel mess.................Quieter.............More challanging to fly ...............Quieter..............Smoother running...................Quieter................. .no fuel smell on everything including your car.....no fuel purchase required..............Quieter.......Multi engines are a dream (no one motor qutiing)..........You can test your powerplant in your living room....and did i mention that it is quiteter?
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Old 05-21-2004, 06:27 PM
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Default RE: Ask your electric questions HERE!

How about these:

How and why (or why not) one would put a fuse on the electrical system?

How big of an ESC should you get for different motors?

How should you manage batteries to get maximum life out of them?

What is a rough guide to gearing, propping, and powering different kinds of planes (sometimes you want to convert a direct drive plane to a geared system, or upgrade from the manufacturers recommendations....)?
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Old 05-21-2004, 06:34 PM
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Jim Finn
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Default RE: Ask your electric questions HERE!

A rough guide to sizing planes to motors to props to cells is a computer program called "Electricalc" $40. Fuses are a source of failure and add weight. Many manufactures recommend them and few flyers use them.
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Old 05-23-2004, 03:58 PM
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Default RE: Ask your electric questions HERE!

OK I'll bite!

I really could use some help understanding where my lippos should be as far as Max and Min charge.. I understand running them too low will do damage.

I have two battery packs One a 3 cell hacker 11.1V 3x700 mAh
the other a ThunderPower 860 mAh 7.4v 2 cell

I have a Radio Shack Multi meter.

Thanks guys!

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Old 05-24-2004, 08:17 PM
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Default RE: Ask your electric questions HERE!

Well that worked out well!
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Old 05-24-2004, 08:30 PM
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Jim Finn
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Default RE: Ask your electric questions HERE!

I do not know enough about Lipos to comment. I use nicads. I do know that a wattmeter is what is needed to know what is going on with any battery pack. A multi meter does not tell you much about a batteries state of charge.
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Old 05-24-2004, 09:57 PM
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Default RE: Ask your electric questions HERE!

It was recommended that when I build up a wing that I not use a single conversion Rx. What is the difference between single and multi conversion Rx's, and what would be the advantage of one over the other? Would having a multi conversion Rx require a different Tx?
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Old 05-26-2004, 01:11 AM
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Default RE: Ask your electric questions HERE!

It depends on the Rx. I use a Berg Stamp 4 which is a full range, single conversion, Rx that can be used in glow models.

The advice to stay away from the cheaper single conversion Rx's was likely because they are more prone to interference from other radios. How much I don't know because I've not used one but didn't get one because of what I read here at RCU. I choose to spend the extra $20 than take the chance of crashing because of a glitch.

As long as the Rx is on the same frequency as your Tx, and the Rx is compatible with your Tx, it doesn't matter whether your Rx is single or double conversion.
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Old 05-26-2004, 06:37 AM
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Matt Kirsch
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Default RE: Ask your electric questions HERE!

ORIGINAL: Walt1
I really could use some help understanding where my lippos should be as far as Max and Min charge.. I understand running them too low will do damage.
Such information should be provided with the battery packs themselves, as overcharging seems to be the main cause of LiPoly fires.

For our purposes, LiPolys have a MAXIMUM voltage of 4.2 Volts per cell. You do not want the charge voltage to exceed that.

It is generally recommended that you also do not go below a MINIMUM voltage of 3.0 Volts per cell. Something on the order of 95% of the pack's capacity is in between 4.2V and 3.0V, so running it any lower doesn't really gain you much.

What does this mean for packs? To get the maximum and minimum voltages for a pack, you multiply the maximum and minimum cell voltages by the number of SERIES cells in the pack. An 11.1V pack has three cells connected in series. 3 times 4.2 Volts gives you a maximum voltage of 12.6 Volts. 3 times 3 Volts gives you a minimum of 9 Volts.
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Old 05-26-2004, 09:04 AM
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Default RE: Ask your electric questions HERE!

Thanks Matt!

walt,
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Old 05-26-2004, 10:38 PM
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Default A question on LiPo cell packs.

Here is one for you.
I am building an electric powered Hangar 9 Aresti. I am using an AXI 4120/18, Jetti controller and 3 X 5S 1500Mah Kokam LiPo cells.
I built up the 5S packs myself from individual cells and was going to put shrink tube around them to hold the packs together like
the packs you get from vendors. My question is, should I place some kind of spacer between each cell in the packs to allow air to
circulate between them to cool them? If so, any suggestions what material to use and what thickness?
Thanks for your help.
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Old 05-27-2004, 01:00 PM
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Matt Kirsch
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Default RE: Ask your electric questions HERE!

Guys,

Keep 'em coming, but please try to keep the questions basic. Think back to when you were starting out with electrics and how clueless you were. I'm looking to compile questions and answers for things like basic battery care, terminology (e.g. What do the motor numbers mean?), differences between types of motors, etc.. Stuff like that. Specific application questions should go in their own threads in their own appropriate forums!

We'll get it, slowly but surely.
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Old 05-27-2004, 01:20 PM
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Matt Kirsch
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Default RE: Ask your electric questions HERE!

Let me get the ball rolling:

Q. What is C?

A. C is the term used to describe Charge and disCharge rates for the batteries we use, and is equal to the Capacity of the battery pack, converted to Amps. For example, a 1200mAh battery pack will have a C of 1.2 Amps. To charge a battery at 1/10 C or C/10 means to charge it at a rate equal to one-tenth its capacity. A C/10 charge for our example 1200mAh battery pack would be .12 Amps, or 120mA.
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Old 05-30-2004, 10:10 PM
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Default RE: Ask your electric questions HERE!

I have just purchsed a 49" wingspan Piper Cub which is supposed to weigh 2.5lb when complete. It is designed for a 0.15 gas engine but it occurs to me that it would be OK with an electric motor. The question is what size? I have a Great Planes ElectriFly T-400 with 1.3 Ratio gearbox would this be suitable?


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Old 05-30-2004, 10:54 PM
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Default RE: Ask your electric questions HERE!

Hey guys. I normaly fly glow engines, but I have decided to look in to electrics. Currently, I have one small electric, an Aero Crusier, that I like to fly at my local school yard. Scince then I realized there are many appealing aspects to electric flight. So I would like to learn more about it. I mean I'm pretty clueless. All I know is that you charge the battery, connect the wires to the ESC, and turn everything on. I'm trying to figure out general information such as engine information and how the power is measured and other similar information. For example standard combustion engines are measured by displacement... (.40 .60 1.2) then how about electrics? Thx guys.
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Old 05-31-2004, 12:05 AM
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Default RE: Ask your electric questions HERE!

What litium battery would be enough for a Zagi 400X?
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Old 05-31-2004, 01:14 AM
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Default RE: Ask your electric questions HERE!

Heres some that may or may not be applicable

-How do I know what propeller to use on my plane.

-What is the difference between brushless and brushed motors?

-How do I know what size speed controller to use(in terms of AMPS)

I'll probably think of a few more.
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Old 05-31-2004, 07:23 AM
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Default RE: Ask your electric questions HERE!

Mike Barker, Solcat:

Guys, this thread is for general newbie questions, not specific applications. Mike, your question deserves its own thread in Glow to Electric Conversions, and Solcat, your question belongs in its own thread in Electric Power Sources. I do appreciate the effort, though

Everyone:

PLEASE, this thread is for gathering FAQ-type questions, the ones you might have as a newbie that have more to do with "learning to fish" than simply "getting a fish" to use the analogy. Bobsean and ZimboRaider have the right idea.
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Old 05-31-2004, 07:50 AM
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Default RE: Ask your electric questions HERE!

ORIGINAL: Bobsean
I'm trying to figure out general information such as engine information and how the power is measured and other similar information. For example standard combustion engines are measured by displacement... (.40 .60 1.2) then how about electrics?
Electric power is measured in Watts. Watts is Volts times Amps, and 746 Watts is one Horsepower, the same kind of HP that's used to rate glow engines.

One major point of confusion for newbies to electric power is in trying to compare electric motors like they compare glow engines. Unlike glow engines where the chemical reaction that releases energy happens in the engine, the chemical reaction that releases energy happens in the BATTERY on an electric. The battery is usually only considered as the "fuel tank" when it's also the "displacement."

For the motors themselves, there is no "standard." Electric motors are relatively simple to design, and every manufacturer has an opinion as to what characteristics make the best motor. The only way you could make any useful motor standard is to force all manufacturers to build motors of the exact same sizes, using the same strength magnets and same gauges of wire. At that point, everyone's motors would have the same exact performance characteristics, and the manufacturer that produced the lowest-priced motor would drive everyone else out of business

You might see motor "standards" like 300, 400, 500, or 600. Many "manufacturers" sell 400 motors, for example. These motors are all made by the same manufacturer; they're all Mabuchi RS380 motors. Mabuchi makes them by the millions for all sorts of consumer products. If you have a hair dryer, it probably has a "Speed 400" motor inside it, for example. It just so happens that these motors work well for small radio control airplanes.
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