Turnigy wattmeter problem and solution

I was playing around with the $23 HK Turnigy watt meter and found that on a 14s2p lipo pack charged to 58.2 volts the watt meter would randomly go into a strange mode where the lcd would flash on and off with block pixels in place of characters. This only seemed to happen a certain time period after the output of the wattmeter was plugged into a load (the ebike kit controller and 9C hub motor). Unplugging the power and plugging it back in would reset the wattmeter to normal operation, but after a few seconds or minutes it would go wonky again. I knew that it was supposed to work at 60V so I assume there is some short spike coming from the controller (regen is not activated) although I did not try and measure this with the peak detection on my Fluke 289 (hmmm, now that would have been a good idea).

Instead, I went under the assumption that this was what was happening, so I measured the current draw of the Turnigy watt meter and found it to be under 1.6 mA. Since I wanted to mount it on the handle bar of the upright bike I built (my tadpole trike is getting the CA), I decided to just run a fat 8 gauge ground wire to and from the Turnigy, along with a thin single power wire (about 22 gauge). At the controller I created a simple RC low pass filter using a 10 ohm 1/4 watt resistor and a 80V 33uF cap (all I had on hand that was greater than 50V rating). I figured this would act as a reasonable filter for any voltage spikes coming from the controller/motor and the 10 ohm resistor would have less than 20mV of drop across it when powering the wattmeter...this would mean the wattmeter would still generate a reasonable measurement of the battery pack voltage. The red load wire of the wattmeter was left unconnected.

Works perfectly. I ran it for several hours with no weird issues, so I am thinking my initial guess of noise spikes was correct. They must have changed the software on the wattmeter recently to cause it to go wonky as a warning if it ever detects input voltage greater than 60V (or some amount around there).

If anyone is running something similar (14s or 15s) and is having the same issues I can explain in more detail how to hook up the RC filter. The Turnigy wattmeter makes a nice cheap fuel gauge...not as nice as a CA of course, but if you are on a tight budget...

I have a new Turnigy Watt Meter --- one week old --- that does the exact same thing. Once it hits 58V, it goes into a flashing fault mode. Like you, I was hoping that it had some tolerance to a slight over voltage, but apparently not. I was using mine to charge my pack. I switched chargers to see if my other charger ended in the same result and it does. Advice on remedying this situation is much appreciated.

DervAtl said:

I have a new Turnigy Watt Meter --- one week old --- that does the exact same thing. Once it hits 58V, it goes into a flashing fault mode. Like you, I was hoping that it had some tolerance to a slight over voltage, but apparently not. I was using mine to charge my pack. I switched chargers to see if my other charger ended in the same result and it does. Advice on remedying this situation is much appreciated.

Click to expand...

Ok, cool, nice to know it is a *feature* now and not just a defect in my Turnigy Watt meter.

How much above 58V do you need to go? My situation was I wanted to be able to read a full 14s pack charged to 4.15V per cell but the inductive spikes or whatever were pushing the voltage to the point where it enters the flashing fault mode. My RC low pass filter seems to have fixed this in my situation, but if you are trying to read a steady voltage while charging of say, 64 volts or something, you may have a problem. There are things you could do, some simple some complicated, to get around the voltage limit.

What upper voltage do you want?

Remember that all of these have a voltage limit (obviously) and the resistive divider used to measure this voltage is specced (along with the software) to measure within this range - it wont measure voltages like the CA for the simple reason it isn't designed (or capable) of it. The rail-to-rail opamps will only go as high as their power supply - and not much higher.

Simple solution - get a CA if you want to measure higher voltages.

heathyoung said:

Remember that all of these have a voltage limit (obviously) and the resistive divider used to measure this voltage is specced (along with the software) to measure within this range - it wont measure voltages like the CA for the simple reason it isn't designed (or capable) of it. The rail-to-rail opamps will only go as high as their power supply - and not much higher.

Simple solution - get a CA if you want to measure higher voltages.

Click to expand...

It *is* designed to measure battery packs up to 60V according to the product description on HK. My 14s pack hot off the charger is 58.2 volts.

anyway, I did buy a CA...it arrived from ebikes.CA non-working...hopefully they are sending me a replacment. (edit: I just got an email they already shipped the replacement...I have to say the service there seems to be very good!)