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Old May 05, 2010, 08:21 AM
ancora imparo
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Melbourne, Australia
Joined Jul 2005
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Mini-Review
Two attractive Wattmeters?

Some comments on the “AEO-RC P1 Wattmeter” and the “Battery Balancer and Wattmeter”. This is not intended as a detailed review of product features and there are other threads on both meters.

I recently bought two different Wattmeters because of their apparent attractive properties. One was a straightforward Wattmeter that was particularly compact and simple to use – see picture P1Normal, the other a combined Wattmeter/Cell-voltmeter/Balancer which promises to combine all the necessary features in one handy package– see picture BBWM4.
The first is from AEO-RC which seems to be a small innovative Chinese company with some very interesting unusual products. Their co-axial motors are worth a look but I have been impressed by their concentration on uniquely useful items. In particular, their “Dr Servo” which measures servo response speed and their kV Meter for rapidly measuring motor kV are out of the usual run of things. I’ve reviewed both on the forums and have been impressed. This P1 Wattmeter is uniquely small for a self contained meter and has a Hold function for airborne logging of Max and Min values. Additionally it is dead easy to use. One button and it does only two things – my kind of user interface.

Web site is www.aeorc.cn


The second appears under different names and in variations of packaging from different sources. It combines two Deans female power connectors and a 6 cell balance connector in a nice sized rugged case with a two line LCD display. Comes with a balance adapter and a male-to-male Deans lead. See BBWM and it’s particularly popular with low price eBay vendors. The manufacturers of mine (which I got from RC Timer) are so proud of it they don’t put their name or any identification on the package but with a bit of careful Internet sleuthing (including comparing some slightly odd spellings on the case) I am pretty sure it comes from Maytech whose web site is at

http://www.maytech.cn/eng/default.asp.

Maytech appear to be a “generic” manufacturer – they have 328 different Brushless Motors listed on the site alone and many of their ESC’s and motors will be familiar to HobbyKing and Turnigy buyers. I have seen a number of very similar wattmeters, sometimes in different plastic cases. See GT Power Meter, Tenergy Wattmeter-Balancer and Trakker pictures. Whether one is an original and others clones, or they are all the same insides in different wrapping I don’t know. This review is about mine which is just called the “Battery Balancer and Wattmeter”.


Both of these meters have been reviewed before but as far as I can tell only in a descriptive way, which is “this is how it works”. To the best of my knowledge no one has published any proper test data but be happy to include it here if there is any. One of my pet hates is meters that lie to you, particularly gear that is aimed at the non-technical modeller with no way of knowing whether the numbers they are getting are reasonable or not. So I gave both meters a bit of a wring out and here are my conclusions.

Firstly, they serve different purposes.

The Battery Balance and Wattmeter (BBW from now on) is an all in one field meter aimed at the modeller who doesn’t already have any measuring gear. It’s the Swiss Army Knife with pack voltage, current, watts, cell voltage, alarms and balancing. Easy enough to use. Just plug it in between the battery and ESC using the supplied Deans male-to-male adapter, plug the balance lead into the adapter board and choose the function you want from the fairly obvious menus.

Pros: Comprehensive information all in the one box, easy to read display, (although not all that good at a quick glance since everything is the same size), built in beep alarm for low voltage which can be turned off, tough case (unlike some PC board and shrink wrap efforts). Menu system is relatively obvious and easy to use but has several layers of selection and choice. You need to actually select a function before it starts working.
Cons: Uses two female Deans connectors as a part of the meter. They are pretty low grade knock-offs and cannot be replaced if you want to do so. The use of two females seems daft to me as beginners could easily wire this thing up in reverse and it needs an extra, easy to lose, adapter wire which adds another bit of connector resistance. Guess it’s cheaper than assembling a male plug in the case. There are no normal user adjustments if the thing is inaccurate except an undocumented zeroing function. A user called Arkom on the forums discovered that the balancer can be zeroed by plugging a fully charged (and balanced) 6 cell pack into the balance port and power source plug, then hold ESC and SELECT together. This is not a calibration function however and the real minus with this thing is its performance (see later).

The P1 Wattmeter is also a meter aimed at the modeller who doesn’t already have any measuring gear or wants something as simple as possible for field use to compliment an Emeter or Eagletree. It’s a one-trick pony that does what it does as simply and straightforwardly as possible. Even easier to use than the BBW. Just plug it in between the battery and ESC using the Deans male and female plugs and read the voltage, current and Watts. This meter doesn’t measure cell voltages.

Pros: It doesn’t come any simpler. The Deans are on 12g wires of a good length and can be replaced. For the small size the screen design is brilliant. Has a big Watts number that’s easy to see and smaller but adequate voltage and current readouts. Just one button which you push to set the “hold” function and you can record Min and Max voltage and current plus Watts. It weighs only 2oz so you can use it to record these in flight. The voltage can be calibrated by the user. Yes! Again, comes in a well thought out custom case.

Cons: Can’t think of any, provided you understand what this thing does – it’s the simplest solution to measuring the three key parameters. See post #7 though where Jack points out it only does over 8V (So 3S and above).

I’ve got a couple of suggestions for improvement though. If there is enough room in memory, I would love to see a slight display change to best use the big numbers. I would have it display Watts on the large display at switch on, toggle to Amps with one push of the button and activate the Hold function by holding the button for 3 secs. People may often be interested in monitoring Amps rather than Watts when testing and having that on the big display would be nice. An enhancement, which would need a new model, would be to add a clock so it measures AmpHrs. Starting to lose the “beautifully simple and easy to use” feature however.

Price

Both of these are in the same price range. I hesitate to quote prices on the BBW as they are all over the place depending what package they are in and where you get them. I’ve seen a range from about $20 off eBay Chinese vendors to $50 at US on-line stores. Mine cost $30. The AEO-RC products are available from some quality stores on-line and they have prices on their web site but an email to the very helpful Tiffany is recommended as being worthwhile.
Tiffany writes good English and her email address is

ZJ Chang info@aeorc.cn

Also, I have noticed HobbyCity have items under their own brand that look strikingly similar to the AEO-RC product but I have only tested the original.

Test results are in the next Post.
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Last edited by jj604; May 06, 2010 at 05:12 PM. Reason: Updated with comment from Post #7
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Old May 05, 2010, 08:33 AM
ancora imparo
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Melbourne, Australia
Joined Jul 2005
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Performance

This is where one attractive sister turned out pretty and the other ugly. I really like the P1 for its size, simplicity and accuracy. There have been lots of folks enthusing about the BBW on various forums, particularly at the price. My considered opinion is it isn’t worth it at any price and here’s why.

Measuring voltage is fairly trivial. All these gadgets use a small microchip (generally an Atmel 8 or 16) with a built-in voltage reference. They have high impedance analog inputs and decent circuit design will minimise any errors caused by stray voltages and the like; but really it is not a difficult task. The cell voltage measurements of the BBW were accurate to within about 50mV worst case.

Measuring current IS a harder ask. There are only two common ways in use to measure high currents in a small gadget like this. The first is to pass it through a VERY low value precision resistance and measure the tiny voltage drop. This can be extremely accurate, reliable and results in a negligible voltage loss if the resistor is small. But it requires very careful design and high resolution AD conversion, a balancing act between creating a large enough signal and low enough losses and expensive high precision low temperature coefficient resistors for accuracy. The EmeterII uses just such a solution with a 0.2 milliOhm precision power shunt resistor and is the “standard” of quality for many of us. The second is to use a solid state Hall Effect sensor which delivers a substantial voltage created by the magnetic field when a current passes through it for almost zero resistance. Despite the obvious advantages, design needs to deal with some non-linearities which can be a real problem.

The P1 uses a quality Allegro ACS775 Hall Effect sensor which can measure up to 100Amps, puts out 40mV/Amp (ie 4 Volts at full current) and has a very low resistance of 100 microOHMS. It looks like a clever design and is well made. See Board1 and Board2.

The BBW uses the resistance method but it is neither precision, nor low temperature coefficient – it’s two bits of wire. See the red arrowed wires in BBWMinterior. Worse, the circuit requires an analog pot as adjustment shown by the big red circle. The construction quality is hardly Rolls Royce either. Solder joints are all dull, there appeared to be two missing components on my board (that is the solder marks showed they were positioned but never attached, not just that they weren’t required) and one resistor had been replaced by a crude pair soldered end to end as seen in the small circle. During testing, mine simply stopped measuring cell voltage properly. See BalanceFault.

I tested the BBW when I got it against my EmeterII RDU, measuring current with a precision 0.025% shunt and a 50,000 count Multimeter which I have checked and calibrated against a 6.5 digit certificated Voltmeter. The results are in the As Received graph. The BBW read 100 Amps when the true current was 70! Obviously the happy factory worker just didn’t bother to set mine up the day it was assembled.

Most purchasers wouldn’t open up one of these gadgets, but I did and used the pot to get the best possible response which is as shown in Calibrated. It is concerning that the slopes are different indicating fundamental non-linearity. Worse, when I did the P1/BBW comparison 3 weeks later it looked like Current and Watts. This is a device that cannot be relied on.

The big problem is the dependence on ordinary wire and a calibration pot to measure resistance. Not only does it lack long term reliability, but it has woeful temperature performance. I ran about 72Amps through both the P1 and the BBW for about 2 ˝ minutes. Look at the result in Temperature Stability (the actual current falls slightly over time as my resistive – light bulb – loads heat up).

The P1 uses a more expensive solution but the result is negligible added resistance and excellent accuracy and long term stability.

Conclusions:

I would unreservedly recommend the AEO-RC P1 to anyone wanting a low cost Wattmeter that just does the job without any need to understand the Electricity Magic behind it. Plug it in, read the number – it’s that simple and it can be relied on. As a bonus it’s small enough (about the size and weight of a full size servo) to go up in the plane and come back with a record of maximum and minimum Volts and Amps and the maximum Watts during the flight. I hope AEO-RC do well. Any manufacturer who makes the effort to make the best quality product, not just the cheapest, needs encouraging these days in my view. So many seem to be disappearing.

My Battery Balancer and Wattmeter went in the bin.
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Old May 05, 2010, 10:27 PM
Registered User
Melbourne, Australia
Joined May 2006
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Excellent detailed review, thanks for sharing. I have EagleTree and DPR data loggers, both old models that are no longer available. Send me a PM if you would like to test them out of interest or for comparison.
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Old May 05, 2010, 10:38 PM
CamLight Systems
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Joined Oct 2003
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Great work John!
It's nice to see something well made and I'm really glad to see that the Allegro sensors are now being used and are accurate enough.
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Old May 05, 2010, 11:09 PM
BEC
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Thanks for this. I've been seeing the cheap wattmeters and been wondering if they are any good (but been unwilling to try and test them myself since I have a bunch of meters already).
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Old May 06, 2010, 03:46 AM
ancora imparo
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Melbourne, Australia
Joined Jul 2005
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Thanks, kgfly. I have an early (Mk2?) Eagletree myself and an original Astro Whattmeter (which I bought about early 80's from memory) and might try and find time to include them. Frankly I prob won't have the time though as there is some other interesting testing to be done soon.

John
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Originally Posted by kgfly View Post
Excellent detailed review, thanks for sharing. I have EagleTree and DPR data loggers, both old models that are no longer available. Send me a PM if you would like to test them out of interest or for comparison.
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Old May 06, 2010, 06:51 AM
Jack
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On these reviews it is most helpful if you post a link to the product's specs and a link to the product, not just the home page for the maker. When I look at the product specs here:

http://www.aeorc.cn/english/?product-278.html

I see it says that the watt meter has a working voltage range of 8-30V. That seems a little limiting as it sort of rules out using it with 2S batteries of almost any type, receiver packs, and the like.

Also, it does not have an external power input so if your tested device drops below 8V it implies that you might lose your data due to the low voltage. In comparison, my Watt's Up is good down to about 4V using the power source being tested and down to 0V with external power.

So that watt meter doesn't look like that good a choice to me and would have disappointed me if I had bought it as a newbie and then got smarter about things.

I already own a Watts' Up, the 3$ Watt Meter, and an eLogger V3 so I'm not in the market for anything newer.

Jack
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Old May 06, 2010, 07:45 AM
ancora imparo
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Thanks, Jack.

Good point about the link. I never considered using this with a 2S given it has Deans Ultras already attached and all my 2S batteries use smaller connectors but of course you are correct.

The criticisms are perfectly valid. Every one of these things has its good and bad points. What you value may not be what someone else does. This deliberately wasn't a functional comparison review and this meter is attractive I think because of it's size and ease of use. It does the basics simply and can do simple airborne logging with no fuss. Adding an external supply defeats the intention in my view but everybody has different needs and people value different features - size, simplicity, low cost, accuracy, range, external logging etc. It certainly wasn't reviewed as a "better than" product against bench or top end products and the last thing I wanted is to start yet another mine-is-better-than-yours debate.

My main point was to emphasise that you can't take meters for granted based on their functionality. How accurate they are matters too, and very seldom do you see any serious attempt to quantify that.

John
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Originally Posted by jackerbes View Post
On these reviews it is most helpful if you post a link to the product's specs and a link to the product, not just the home page for the maker. When I look at the product specs here:

http://www.aeorc.cn/english/?product-278.html

I see it says that the watt meter has a working voltage range of 8-30V. That seems a little limiting as it sort of rules out using it with 2S batteries of almost any type, receiver packs, and the like.

Also, it does not have an external power input so if your tested device drops below 8V it implies that you might lose your data due to the low voltage. In comparison, my Watt's Up is good down to about 4V using the power source being tested and down to 0V with external power.

So that watt meter doesn't look like that good a choice to me and would have disappointed me if I had bought it as a newbie and then got smarter about things.

I already own a Watts' Up, the 3$ Watt Meter, and an eLogger V3 so I'm not in the market for anything newer.

Jack
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Old May 06, 2010, 11:50 AM
ProgressiveRC
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Thanks John, great write-up and your effort is sincerely appreciated.
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Old May 08, 2010, 01:52 AM
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Thanks John for the excellent write up. You are absolutely correct about those Wattmeters not being designed properly.
It is like they designed a good working product, . . . . and then cut the price by lowering the resolution, and lowering the accuracy, and inserting a smaller display inside.
Makes you think what just a little effort could produce. . .
Don
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Old May 08, 2010, 02:19 AM
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Don, how true. My suspicion is that the original of these probably was well made, well designed and had some attention to the accuracy and stability ... then along come the copy factories who shave off everything they can and/or simply don't understand what's important in the design and what's not. In the meantime the original guys go out of business.

That's why it's important that on the forums we give some encouragement to the Hyperions, FMA's, Assan's, Junsi's, AEO-RC's etc (just the ones I'm personally familiar with) who try and produce quality products at a reasonable price and listen to the customers and try and improve them. I love a bargain like anybody and doing something that others do expensively, but doing it cheaply and well, is very satisfying. Sometimes cheap is too cheap though.

Trouble is, if you try and do some sort of evidence-based comparison, highly opinionated folks appear out of the woodwork telling you you are an AEO-RC or Hyperion "fan" and 99% of people know better or something equally ridiculous. Opinion on the forums is great and debate vital. All I ask is that it is relevant and at least respects what the OP was trying to do. Nothing is better than to have someone like Jack below come up with an entirely reasonable criticism and some different views based on sound assumptions that are not the same as yours. Keeps you honest and on your toes!

Just my 2c worth. Don't really want to start yet another $ vs. quality value argument - the thread will go off like wildfire.

John
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Originally Posted by HeliDon View Post
Thanks John for the excellent write up. You are absolutely correct about those Wattmeters not being designed properly.
It is like they designed a good working product, . . . . and then cut the price by lowering the resolution, and lowering the accuracy, and inserting a smaller display inside.
Makes you think what just a little effort could produce. . .
Don
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Old May 08, 2010, 06:28 AM
Jack
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John,

I was a little derelict in not thanking you for your review. In particular, the accuracy graphs are very interesting and enlightening.

Either or both of these would be very useful to own and helpful in use, particularly to someone that did not have anything better or who was new to this facet of the hobby.

When I read these kinds of reviews I always compare the items to other devices I have or have used and that is why I mentioned a couple of details as to where they differ from others. It was not my intent to diminish the value of this review in any way but to maybe even add something of value to it.

It is these kind of reviews and the constructive comments they draw that let us all make better decisions when we go to buy something like this.

Thanks again,

Jack
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Old May 08, 2010, 06:41 AM
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Thanks, Jack.

Hopefully by doing stuff of this kind we can help inform people and save them some grief.

Also it's nice to see the number of manufacturers who are taking the forums seriously as a customer feedback mechanism. FMA, Hyperion, Junsi and Assan are just the ones I know of. Bit of luck AEO-RC will modify their P1 with my display suggestion.

Regards, John
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John,

I was a little derelict in not thanking you for your review. In particular, the accuracy graphs are very interesting and enlightening.

Either or both of these would be very useful to own and helpful in use, particularly to someone that did not have anything better or who was new to this facet of the hobby.

When I read these kinds of reviews I always compare the items to other devices I have or have used and that is why I mentioned a couple of details as to where they differ from others. It was not my intent to diminish the value of this review in any way but to maybe even add something of value to it.

It is these kind of reviews and the constructive comments they draw that let us all make better decisions when we go to buy something like this.

Thanks again,

Jack
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Old May 08, 2010, 12:16 PM
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John and Jack,
I think John brought enough information on these Wattmeters, to give the hobbyist a good starting point.
I would have certainly purchased both of those, and have been disappointed.

I have the Watt's up on my desk, and I am unhappy with that also. I am thinking of designing my own.
Thanks,
Don
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Old May 27, 2010, 08:00 AM
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Thanks for the review John. Did you check the balancer accuracy? I need an accurate balancer, I wonder how accurate this one is.
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