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Old 07-14-20, 04:45 PM   #365
Daox
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I got the LED voltmeters today. Of course, being a cheap product from overseas I started by taking it apart. Inside there really isn't much. Its a single circuit board with one main chip (LM3914V), a resistor and two potentiometers (assuming for meter calibration). The wires are soldered right to the circuit board without any strain relief, so I'll have to fix that as the mower isn't exactly a smooth ride.







So far not too bad. Next I moved on to testing their calibration because who knows what the heck these things are set to. I ordered 5 units and tested each one with my power supply and a multimeter (for greater accuracy).





I was pleasantly surprised by this. Here is the testing results:

#1
max = 13.37V
two red = 11.10V
min = 10.43V

#2
max = 13.42V
two red = 11.24V
min = 10.65V

#3
max = 13.56V
two red = 11.20V
min = 10.56V

#4
max = 13.48V
two red = 11.38V
min = 10.76V

#5
max = 13.16V
two red = 11.22V
min = 10.65V


This is actually pretty darn close to what I want. I typically stop mowing when the voltage on the weakest cell starts hitting 11V. This can likely be achieved without any further calibration by just stopping mowing a bit after I hit the two red LED mark. With the varying load the mower sees, the voltage really jumps all over the place, so super precise measurement is not necessary at all. That being said I still really want these more balanced becuase... ocd?

The main point in having these meters is to make sure that no batteries are dropping below 10.5V, and to make sure the batteries are charging properly. For the entire life of this mower, I've just used a single multimeter to monitor what I believe to be the weakest battery. This in theory works but it doesn't cover all the bases. I've had multiple chargers (I use 4x 12V chargers) die over the years. So, I go plug the mower in after cutting the grass, and the battery just never charges. The next time I go to mow I murder the battery because I didn't notice it never got charged. This really sucks because not only do I need a new charger, but now I need a new battery we well. This solution should prevent that possibility.
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