Flymick

Hi folks,

I have recently got into electric flight. It is a magic challenge and something new at the same time.

I am looking for two things;

1. A meter / measuring device that I can connect in line between the controller and the motor for bench testing. I would like to know what amps are being drawn at given voltages with different battery, motor and prop combinations. Nigel Hawes writes a column for RCM & E and refers to a Wattsmater which does exactly that. Anyone know of anything similar ?

2. Advice on putting together a large scale plane ( Cub or similar ), maybe 1/4 scale fpr electric flight. Has this been done and what are the implications.


Would appreciate some of your suggestions.

Thank you.

Rich-RCU

Astro makes a wattmeter:

http://www.astroflight.com/Whattmeter.html


Rich

Matt Kirsch

My Feedback: (21)

1. The only thing that does what a Whattmeter does is another Whattmeter. It's the only product of its kind on the market right now, but it's not really necessary to be successful.

Instead, you can get a clamp-on DC Ammeter, or build yourself a "shunt" that will allow you to measure Amps using an ordinary DC voltmeter. One of these days I'll find the link to the plans for the shunt, but it's very simple, a piece of 12Ga solid copper wire about 12" long or something like that. You connect the voltmeter in parallel with this wire, and the volts you measure will tell you how many Amps the system is drawing. Of course, this is only a rough description. You'll have to find the exact details.


2. Sure, large scale planes have been done. The implication is that it will take a lot of homework on your part, and a lot of money! Check out the Ezone, http://www.ezonemag.com.

Tippie

As suggested by mkirsch, go to the website he shows and then click on "discussion" on the left side of the page and when you get there do a search for "sears meter" and you will see a number of threads for it. They discuss a Sears clamp-on ammeter #82062 that has digital display and will do DC volts and DC amps. Price is $49.99. Multiply the two and you have watts. The advantage is you don't have to wire it into the circuit to get a reading. One other point that was brought up is the fact that some ESC manufacturers don't like to have a long lead from the ESC to the motor when using a brushless motor and adding a wattmeter in series will lengthen the lead thus a possible voiding of any warranty on the ESC.

gwright

the wattmeter is only around $60 and one of the best purchases you'll ever make for electric flight support equipment. As for 1/4 scale,.. yes, been done quite a lot actually. I have a funtana which is basically a "funscale" Katana at 26%. Short video is at www.rccraze.com/funtana1.mpg . 30 cells, prototype hacker motor, although it would fly on a LOT less, just not the way I would want to fly it There have actually been some 50% (1/2 scale) electrics also. If you research a bit on the Ezone, there are links to a Klemm that's 1/2 size and electric powered.

crashcraft

Check out Maxx Products MX 8100 amp meter. It measures volts or amps for $45 from my local hobby shop. It will not show watts or amp hours like the super whattmeter, but for $15 I can multiply.

SoarNeck

You didn't mention your power choice, but be VERY careful using a Whattmeter with brushless systems. The maximum length of the lead from a battery pack to a brushless controller shoul be 6-8", with some controllers being more tolerant of this than others.

There are a lot of threads on Ezone about people wrecking speed controllers with Whattmeters (by itself adding more than 6" of wire).

I have a friend who recently came across a solid-state chip that should do the trick in measuring these systems up to about 100A. I don't know much about the specs yet, but it won't add more than 1" of extra wire.