Hello everyone – I have recently acquired a Turnigy Wattmeter and I wanted to share with you its features and what it can measure. I have no connection with the company or distributor. The main reason I’m doing this is to show that a device like this is helpful when testing motors or batteries. It is helpful to you for your own information but also helpful to us as readers, so that we can see actual numbers for comparison. This is the least expensive of this type of meter, the others being WattsUp and Cycle Analyst. I assume they have more or different features. I purchased mine from HobbyKing.com for USD23.95 + 7 s&h. It was b/o for 2 weeks but arrived about a week after they shipped it. I’m sure there are other sources.
The device is 3 ¼” x 1 ¾” x 1” thick and weighs 82 grams, less than 3 ounces. There are a pair of heavy gauge wires coming from either side and a port for an auxiliary battery, which I don’t use. It is essentially a combination digital voltmeter and ammeter that calculates watts as well as other data. It can measure up to 130 amps and 60 volts. It is wired in series between the battery and controller. Because of this, there is a valid argument that there could be some power loss with a long run, say from a battery trailer to the handlebars and back to a trailer motor like BossCat. However, unless you need constant information, you can leave the WM out of sight (near the controller or battery) if necessary and just check the displayed memory info at stoplights or rest stops. In my situation I was able to mount it on the crossbar between the battery pack behind my seat and the motor/controller in the triangle. One of the features of the device is it displays much of the vital info from its memory. The memory remains until the WM is unplugged.
The screen itself displays 4 pieces of information at a time. Please refer to the uploaded images. The upper left is the current amperage (no pun intended) to 0.01A. Of course this changes constantly with throttle, wind, pedal assist, etc. The upper right is the current voltage. You can see my partially charged LiFePO4 is at 26.74V. This number tends to stay fairly constant although a heavy or sustained draw may cause voltage sag. It also drops gradually as the battery discharges. Just below this number is the current watts being used, a simple product of the amps X volts at that time. The 3 figures above appear to be refreshed several times per second. On the bottom of the screen left is the memory, probably the most interesting feature of the WM. Here it constantly cycles through a series of 5 actual and calculated numbers, at a rate of about one per second. The repeating sequence is Ah, Wh, Ap, Vm and Wp. Ah of course stands for amp-hours and is a calculation of how many ah have been used so far, sort of like a reverse gas gauge. Valuable number to know. Wh is watt-hours, another calculated figure. Ap is peak amps, the instantaneous maximum you have drawn since the unit was plugged in. It doesn’t say how many times you have hit that peak or how long it was sustained but it is still a valuable figure. Vm is minimum voltage, again since the unit was plugged in. This shows voltage sag, so it is another worthwhile figure if you are testing batteries or a battery motor combination. You can see in one of the images that my battery dropped to 26.73. The final figure before the cycle repeats is Wp, peak watts, another calculated figure whose value is self-evident. As I said, the WM constantly runs through these figures, one per second, updating as necessary.
So I would like to strongly encourage anyone doing any testing or reporting about batteries, motors, controllers to spend the $31 for this handy little instrument. You can put spade connectors on the “load” side of the WM to hook it to the “battery in” connector of the controller and connect the battery inputs to “source” side of the WM. Easy to connect, easy to use and a wealth of information for testing or just plain riding - jd
The device is 3 ¼” x 1 ¾” x 1” thick and weighs 82 grams, less than 3 ounces. There are a pair of heavy gauge wires coming from either side and a port for an auxiliary battery, which I don’t use. It is essentially a combination digital voltmeter and ammeter that calculates watts as well as other data. It can measure up to 130 amps and 60 volts. It is wired in series between the battery and controller. Because of this, there is a valid argument that there could be some power loss with a long run, say from a battery trailer to the handlebars and back to a trailer motor like BossCat. However, unless you need constant information, you can leave the WM out of sight (near the controller or battery) if necessary and just check the displayed memory info at stoplights or rest stops. In my situation I was able to mount it on the crossbar between the battery pack behind my seat and the motor/controller in the triangle. One of the features of the device is it displays much of the vital info from its memory. The memory remains until the WM is unplugged.
The screen itself displays 4 pieces of information at a time. Please refer to the uploaded images. The upper left is the current amperage (no pun intended) to 0.01A. Of course this changes constantly with throttle, wind, pedal assist, etc. The upper right is the current voltage. You can see my partially charged LiFePO4 is at 26.74V. This number tends to stay fairly constant although a heavy or sustained draw may cause voltage sag. It also drops gradually as the battery discharges. Just below this number is the current watts being used, a simple product of the amps X volts at that time. The 3 figures above appear to be refreshed several times per second. On the bottom of the screen left is the memory, probably the most interesting feature of the WM. Here it constantly cycles through a series of 5 actual and calculated numbers, at a rate of about one per second. The repeating sequence is Ah, Wh, Ap, Vm and Wp. Ah of course stands for amp-hours and is a calculation of how many ah have been used so far, sort of like a reverse gas gauge. Valuable number to know. Wh is watt-hours, another calculated figure. Ap is peak amps, the instantaneous maximum you have drawn since the unit was plugged in. It doesn’t say how many times you have hit that peak or how long it was sustained but it is still a valuable figure. Vm is minimum voltage, again since the unit was plugged in. This shows voltage sag, so it is another worthwhile figure if you are testing batteries or a battery motor combination. You can see in one of the images that my battery dropped to 26.73. The final figure before the cycle repeats is Wp, peak watts, another calculated figure whose value is self-evident. As I said, the WM constantly runs through these figures, one per second, updating as necessary.
So I would like to strongly encourage anyone doing any testing or reporting about batteries, motors, controllers to spend the $31 for this handy little instrument. You can put spade connectors on the “load” side of the WM to hook it to the “battery in” connector of the controller and connect the battery inputs to “source” side of the WM. Easy to connect, easy to use and a wealth of information for testing or just plain riding - jd
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