BusyBear

Do I need a Watt Meter? [sm=confused.gif]

I am brand new to electrics, still trying to sort thru all the confusion... trying figure all this electric stuff out...[sm=spinnyeyes.gif]
I do have Nitro experience, and am fling a second hand electric Bird-E-dog... working on a couple others

It seem to be that there are so many variables that you can't go very far in electrics without a watt meter. (such as the Astro Flight or Watt's up meter)

I'm leaning toward the watt's up meter...

I figure if it saves me from burning up one brushless motor or one battery pack... Its pretty much paid for itself.

Any advice or thoughts????

Thanks in advance!

BMKDesigns

I would never argue against getting one, better safe than sorry.

michpittsman

My Feedback: (11)

I went down the same road a few months ago; personally, I love my Wattsup meter. It gives instantaneous readings of amp draw and watts of power, and will also check your charger's performance. If your plane will carry 2.3 oz payload you can put it in your airplane and check the in-flight numbers when you land.

If you have the continuous amp-draw numbers for your motor, you could buy a battery pack and ESC that would supply the right amount of amps, and just go up in prop size until the motor temp starts to get up into the hot range. That will get you in the ballpark, but it is comforting to know EXACTLY what is going through the wires....Jim

PS I don't have any specs, but the new Eflite watt meter from Horizon is significantly less expensive than some others. JB

Time Pilot

I'd say it depends on the type of person you are. You can always get recommended setups here at RC Groups. But if you like to extract every single watt out of your system, it might be a good idea.

If you're new, you might want to spend the money on Lipos or a brushless system first.

jooNorway

If you have an amperemeter it is enough for check of setups. Also, as mentioned you can get a lot of flying just by following the recommandations given by the motor-manufactors, on forums and read tests done properly.
As an addict gadgetman I have the E-Meter from Hyperion... Built in RPM-counter and the ability to put in prop-constants to get thrustreading is a hit

exeter_acres

My Feedback: (2)

I use the Watts up.... one of the more used items in my workshop

Matt Kirsch

My Feedback: (21)

Having the meter is only useful if you learn how to make use of it, though.

The meter is useful for checking that you aren't exceeding the ratings of ANY piece in the system. That means battery, ESC, and motor. Knowing that your system is drawing 37.6 Amps does you no good if you don't realize that the battery is only rated for 25 Amps peak, or the ESC is only good for 30 Amps...

The meter is also useful for finding problems. In a 30 second run, you can watch to see what the voltage does. If you see it dropping dramatically, you know that there's a problem. Either the battery has been damaged, or you're exceeding its rated capacity.

BusyBear

Very Good Point Matt...

I understand the concept of what you are saying... The ratings on ESC seem pretty simple most come with a stated limit 10, 25 ect.
But what about batteries...how do you figure out the limit on the batteries?

I am currently using a 8 cell 1100mah Nicad battery to fly my bird-E-dog...has been working okay...not what I'd call anywhere near overpowered.. won't ROG...strictly handlaunch getting 5- 8 minute flights or so... but the battery is pretty hot when I'm done.

I just ordered a GP Electrfly 8 cell 9.6 volt 1100mah nimh pack...I'm assuming this pack will work also? First thing I noticed is the wire are a whole lot thinner? Is this really going to work? How do I know if I'm okay? [sm=drowning.gif] (I mean before I see smoke and flames????)

As someone suggested I could spend the money on Lipos and brushless motors rather than a meter...can't figure out what ones to get.
I would hope to be able to such eqipment in other airplanes too... but I get the impression that as soon as you change one variable...prop, gearbox, motor or battery.. everyting changes[sm=spinnyeyes.gif]

Matt Kirsch

My Feedback: (21)

Every LiPoly is rated with a C rating, which is marked right on the battery's label, but if you're using NiCds/NiMHs, things are unfortunately a little murky... Because NiCd/NiMH cells are not manufactured for R/C use, the manufacturers rate them based on industrial/commercial applications where they need to be dependable and last for years. If we stuck with the manufacturers' recommendations on current for NiCd/NiMH, we'd still be in an electric "stone age."

In fact, we push our NiCds/NiMHs much harder than the manufacturers would like to see, and the REAL current limitations were determined by some very ambitious and generous modelers who literally blew up packs to see how much they could take at their own expense. The limits aren't widely published; in fact, the only vendor I know of who publishes them is cheapbatterypacks.com. Most limits are "published" in a forum setting like this, and as you hang around for a while, you'll get a feel for what they are. I've got many of them committed to memory, myself.

One general rule of thumb is, the shorter and fatter the cell, the more current it can produce. I'm guessing your 1100mAh NiCds are AA size. AA cells generally don't make good R/C flight packs because they're designed for capacity, not current-delivering capability, and the fact that yours come back uncomfortably hot indicates that you're pushing them too hard. I believe AA NiCd cells are pretty much limited to 8-10 Amps.

Depending on the manufacturer of the cell, a "2/3A size" 1100mAh NiMH is good for 12-15 Amps.

BusyBear

Matt thanks again for the reply....

I feel like my electric knowledge is expanding exponentially, because of these forums....and thanks to everyone else that replied..I appreciate your advice!

Yes in fact the pack that is getting warm is a AA pack.... and the new one I just received is a 2/3A... so I'll see how it does. (Wire's are a much smaller thinner though ?????)


I think I'm going to order a meter... I guess I was just looking for reassurance that I wasn't doing something silly...


and plus this way I can tell my wife that I had to order this cool watt meter because the guys on the INTERNET told me I had to!!!

exeter_acres

My Feedback: (2)

Psssssst... we are spending our money on TOY airplanes... spending hours standing in a field watching them fly...

OF COURSE it is silly!



and second rule.... NEVER tell the wife what you order!

Flypaper 2

Wattmeter is probably the most usefull tool I have next to my tomcat

nerdc0re79

i have a eflite power meter. dont know how to fully use it yet. for right now i am using it to check my battery if its fully charged or to see which ones are used. got any good explanations of how to use this machine properly? anyone?

Bad_Daddy

Go take a look at hobbycity.com - they have 'Watts Up" meters for < $40 (plus shipping)

Tram

My Feedback: (6)

Yeh.. You do..

It's of the most essential tools you can own for flying electrics..

It can save you quite some dollars.. When I first got into electrics I didn't think I needed one.. "Ahh, who needs that.."

Well, after I puffed 3 Lipo packs because I was over amping them (at $65 a pop) I had wished I had a Wattmeter...

Buy one..

Jeff
www.CommonSenseRC.com

aeajr

My Feedback: (2)

Take a look at the chapter on wattmeters here:

Everything you want to know about electric flight
http://www.rcuniverse.com/forum/m_7100376/tm.htm

cloudancer03

My Feedback: (22)

busy ....get a watt meter its very important.I am learning how to use it effectively to get the most from my lipo batteries.plus you and determine which props are going to be best for the motor you select.at its simplest I fly a timed flight and after each flight measure the wattage to see if I stayed within acceptable limits of the battery pack.the tool pays for itself.I also found it helpful in learning how one poiwer set up was not where it should be.as you get familiar with it it will become one of the most important tools in your electric arsnal.

Fast Guy

Have a look at the Eagle Tree 3 Micro logger. It can record an entire flight for volts, amps, watts, temp, rpm, air speed, battery use in mah, and elevation at 10 samples per second and play it back in real time on the included cool software an you computer.

TallDoode

You can tell her what you ordered, just NEVER tell her the price! <grin> and never, ever send her to the LHS to get stuff for you (personal experience) cuz then she will know you have been lying the entire time you have been flying!

Seriously though, as most are saying on the thread - the Wattmeter is a good thing and for under $40.00 it will pay for itself the first time you would have drained a battery too far, or over propped a plane, drained the battery too fast and have to try a dead stick landing because your ESC shuts down the plane before it can destroy your battery (personal experience again). I was able to land, but went the next day and found out the difference between a 10x7 and a 11x7 prop was enough to take my fly time from 12 minutes to 8.

Have fun.

dave

cyclops2

Whattmeters & all the other gadgets are similar to living without a Smoke Detector.

Can you live without either one of them, with no problems ? ....Of course....Millions do everyday with no problems.

Is life less stressfull with both ? Of course.

If you want to change parts for more power, you will need more knowledge of what you have and what you will need to change for more intense flying.

Whichever you do is O K.

Rich