Toys, Watt Meter

[Sunking]

Don't get excited, not those kind of toys. But it could be STICKY

I have a few hobbies like golf and more to the point fly RC Planes. Not sure I have ever brought this up or not but in the RC world there is a great tool that can be used on just about any solar battery system. We use In-Line Watt Meters and they are fairly cheap. Accuracy is decent once you get above 10 watts. Depending on which model you use can measure up to 130 amps @ 60 volts or 7000 watts.

They tel you more than wattage. They give you voltage current, watts, and some can even be used to measure Watt Hours, Amp Hours, and measure Battery Internal resistance. They can be inserted between panels and controller, controller and battery, or battery and load. As for cost pretty reasonable from $20 to $50. Here are a few I know about

GT Power 130 Amp @ 60 Volt for $40 to $50 You can even find these on EBAY for $15
Watts Up 100 Amp @ 60 volt for $50. Again shop around for deals.
Turnigy 100 Amp @ 60 volt for $30

There are a lot more out there ranging in price from $8 to $100. Just use the search term RC Watt Meter or RC INLINE WATT METER.

They are really easy to use and most do no teven have any buttons or controls. You just have to make sure you get the Polarity correct and work out the connector issue. They work just fine on solar panels, batteries, and controllers. Grid tied need not apply. These are for the folks who like burning $100 bills as a heat source to warm their coffee. .

[SunEagle]

Don't get excited, not those kind of toys. But it could be STICKY

I have a few hobbies like golf and more to the point fly RC Planes. Not sure I have ever brought this up or not but in the RC world there is a great tool that can be used on just about any solar battery system. We use In-Line Watt Meters and they are fairly cheap. Accuracy is decent once you get above 10 watts. Depending on which model you use can measure up to 130 amps @ 60 volts or 7000 watts.

They tel you more than wattage. They give you voltage current, watts, and some can even be used to measure Watt Hours, Amp Hours, and measure Battery Internal resistance. They can be inserted between panels and controller, controller and battery, or battery and load. As for cost pretty reasonable from $20 to $50. Here are a few I know about

GT Power 130 Amp @ 60 Volt for $40 to $50 You can even find these on EBAY for $15
Watts Up 100 Amp @ 60 volt for $50. Again shop around for deals.
Turnigy 100 Amp @ 60 volt for $30

There are a lot more out there ranging in price from $8 to $100. Just use the search term RC Watt Meter or RC INLINE WATT METER.

They are really easy to use and most do no teven have any buttons or controls. You just have to make sure you get the Polarity correct and work out the connector issue. They work just fine on solar panels, batteries, and controllers. Grid tied need not apply. These are for the folks who like burning $100 bills as a heat source to warm their coffee. .

I own one of the Watts Up meters and it is very accurate for the price.

[Sunking]

Yep and I think most are the exact same Meter. All of them as far as I can tell use a 10 watt .001 Ohm resistor and 8 bit micro controller. I use mine to measure Battery Internal Resistance. Don't let the LiPo/LiLo or other lithium reference throw you off course because battery type makes no effing difference. They make the same meter for Solar, RV, and Automotive. Only difference is a different sticker and higher price tag. I use a number of 12 volt, 50 watt halogen lights with it to test batteries and my EV connections.

[azdave]

Some years back I flew 3 meter span R/C sailplanes in "climb and glide" type events. I was twice a US National Champion in Electo-Glide competition and always had my trusty Astroflight Watt Meter by my side. I quit flying years ago but I still have my Watt Meter. Handy for all kinds on projects outside of R/C soaring. I'll never sell that nor my trusty old Simpson 260.

[PNjunction]

They are really great, especially for op wondering why his batteries are dying!

Many use them just to measure discharge, but if you turn it around so the "source" is now connected to the output of your charge controller, you can see if you are actually putting in 110% charge (like you should if daily cycling) or not!

Mine is similar from Powerwerx, just know that there is no "reset" counter unless you make/brake connections. That means that for most solar charge controllers, you should reconnect the panel input LAST. Not making it past 100% charge on a daily run? Are you even making it with the "max smoke" charge model talked about in other threads? Now you'll know.

http://www.powerwerx.com/digital-meters/

Rated at 5-60v, (Zero volt - 60v with aux power connector) 130A peak, 50A continuous. I've only used mine at 12v. I'm sure others are similar, but wise to check!

Also a good place to get your dc-cabling Anderson crimp connections going.

Whatever you do with them, these types of meters, while not lab quality, will point you in the right direction fast!

[asdex]

I bought one of these that will handle up to 100 amps. I was going to use it to monitor AH to my 24 volt 900 w hot water element. The wires got so hot on 26 amps I wasn't keen to use it for more than a few minutes. The wires are about 6 mm sq (9 SWG). Is this normal with these meters?
Thanks,

[Sunking]

I bought one of these that will handle up to 100 amps. I was going to use it to monitor AH to my 24 volt 900 w hot water element. The wires got so hot on 26 amps I wasn't keen to use it for more than a few minutes. The wires are about 6 mm sq (9 SWG). Is this normal with these meters?
Thanks,

Not made for continuous duty. Keep in mind these are made for hobbyist Their intended use is to place between the battery and Electronic Speed Controller (ESC), then run the electric motor up to full power. Basically is a static test for props and motor compatibility. To big of a prop will force the motor to use more current and power it is designed for. Another use is to measure the a battery Internal Resistance as a means to monitor Battery Health. Also a good way to test panel and battery charge currents. But only for a short period of time. That is why it is called a TEST.

They are not built for home use or continuous use. They use standards lower than Automotive. For 100 amp sin a home would require a minimum # 4 AWG copper wire using 75 degree rated insulation. The Power Meter uses #8 AWG fine stranded cable with 105 degree silicon rubber insulation called MTW (Machine Tool Wire). So yes they will run hot. FWIW 8 AWG you can run up to 40 amps for a day, but it will be warm to touch, but not hot. As an FYI running 100 amps, the wire will be too hot for you to touch and be running close to 100 C or 212 F.

It is for testing, not daily use. Now if you want daily use, buy a .001 Ohm 10 watt Shunt (RSA-100) and figure out how to use your volt meter with it. I am not going to go into that.

[PNjunction]

Speaking of props, (!) thanks go out to Doug Ingraham and Bob Boucher of EV and solar sailplane fame for getting these things made many years ago...

[asdex]

Thanks, I might try the shunt idea. Should be able to find out where to wire it in instead of the resistor.
Cheers,

[Sunking]

Thanks, I might try the shunt idea. Should be able to find out where to wire it in instead of the resistor.
Cheers,

A Shunt is a resistor, that is what is in every watt meter. Either that or a Hall Effect Transducer, but a Shunt is more accurate. Shunts are nothing more than a precision power resistor. You run current througgh a resistor and it develops a voltage drop proportional to the amount of current running through it. They are rated as either 50 mill-volt or 100 milli-volt full scale reading. Example th eone that comes in the Hobby Watt Meter is a .001 Ohm 100 mv resistor. With 100 amps flowing through it will read 100 amps x .001 Ohms = 0.1 volts or 100 milli-volts. FWIW with 100 amps flowing it burns 100 amps x 0.1 volts = 10 watts. So as you can see this shunt is nothing more than .001 Ohm 10 Watt power resistor.

You would need to have a really good calibrated volt meter to read the voltage because you are working with a range of 0.001 - to - 0.1 volts full scale. To get 1% accuracy requires the meter to be able to read down to .00001 volts +/- 1 digit resolution.

[asdex]

I have a spare 500A/50mV Deltec shunt and was wondering if that would do? I bought one for a Midnite Whizbang Jr and another for a Trimetric battery monitor and then saw n the Whizbang Jr instructions I can use one for both the Whizbang Jr and another measuring item. My maths isn't great so am not sure if 500A/50mV which will be 10A/mV will do.
Thanks,

[ILFE]

In May of 2013, Martin Lorton did a comparison to see which of these three meters were most accurate, at the time. Pretty interesting results, as I recall.

[Sunking]

I have a spare 500A/50mV Deltec shunt and was wondering if that would do? I bought one for a Midnite Whizbang Jr and another for a Trimetric battery monitor and then saw n the Whizbang Jr instructions I can use one for both the Whizbang Jr and another measuring item. My maths isn't great so am not sure if 500A/50mV which will be 10A/mV will do.
Thanks,

You math is not that bad. It will work sort of just not real accurate in the lower range where it is mostly used at 100 amps and less. Depends on the meter to read the range. Your typical meter is 1% and can only read down to XX.YYY volts. That means plus/minus .001 volts. Well .001 volts on a 500 amp 50 mv Shunt is 10 amps as you noted. Not very usefull or accurate unless you have a good Lab Quality Volt Meter made to read micro-volts.

Never understood why Midnite Solar and Trimeteric use a 500 amp 50 mv shunt. Common in commercial and industrial applications, not so much for consumer apps. Would have been much better to use either 100 or 200 amp 100 mv shunts. That gets you to 2 and 1 amp resolution. A properly designed system should never use more than 100 amps. Understand?

[Sunking]

In May of 2013, Martin Lorton did a comparison to see which of these three meters were most accurate, at the time. Pretty interesting results, as I recall.

I have seen that video. Thing is all three are the same basic meter based on a 100 amp 100 mv shunt and a 8-bit microcontroller. Would make for a good hobby circuit to make. Takes very few parts. However you could not possibly build one as cheap as you can buy one. It would cost you some $100 to $200 in parts. You can buy them for $20 to $40. Go figure...