During absorption, the app is reporting a steady 14.86 volts, but checking with a voltmeter at the battery terminals shows 14.4 - 14.5 volts. I have the charger set on high (14.7 volts). Why the difference?
asked
IP65 12/10 app-reported output voltage vs measured battery voltage
The higher voltage could be a result of ambient temperature. AFAIK the IP65 automatically compensates for temperature during the charge process. My guess is that ambient temperature of your battery is well below 25°C.
It is in my house at 22°C, but I do not see how that would matter. We are talking about voltage measurements 4 feet apart on a #10 wire, from inside the charger to the clamps.
UPDATE: The app is still showing 14.86 volts, but actual voltage at the terminals is steadily rising and now at 14.75 volts. So, where does the voltage reported by the app come from? It is obviously not a measured output voltage.
@mkc, voltage drop at an 8' round-trip distance over #10 wire at 10A current, 12v nominal is expected to be ~0.69%, and your reported value is ~1%, so you're well within spec, particularly at a lower temperature. VC is reporting internal voltage as measured before the charge current "leaves" the charger.
I just checked a voltage drop calculator and the answer was 0.08 volts, nowhere near what I reported. The initial figures I reported represent a 3% voltage drop.
@mkc, 14.86v to 14.75v is not a 3% v drop. And the voltage drop calculator you're using is either incorrect or you forgot to enter round-trip distance; a 4' distance is 8' round-trip. Expected v drop at 8', 12v nominal, 10A current, 10AWG wire is 0.63%.
The calculator I used specifically said to input one way distance.
Also the point you are missing is that the voltage reported in the app is steady at 14.86 volts while the voltage at the terminals is rising, starting at 14.4 volts and now at 14.8 volts. The 14.86 volts cannot be an actual measured voltage.
Right... that's how a charger works, though. It puts out a steady voltage, and the voltage of the battery slowly and steadily rises to meet it (until the battery is full).
Actually, they charge at various levels of constant current through bulk and absorb stages, then switch to constant voltage in float.
@mkc I suppose that depends on which charger you're talking about. In this case, since we're speaking about a Victron, the Victron is putting out a constant voltage at decreasing current until a threshold is reached - which threshold depends on how you have the unit configured.
My point regardless is that your unit is not apparently malfunctioning. Voltage at your battery posts will not match voltage put out by the charger until the battery is essentially full. Your app is reporting voltage at the charger, not the battery - variation between the app-reported voltage and measured voltage at the battery is to be expected.
