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bobdylan asked

BlueSolar 75/15 incorrect voltage readings


I own a BlueSolar 75/15 along with a V.E. Direct Bluetooth Dongle. My MPPT controller is consistently reading the battery voltage 0.2 volts too high. To use an example, measuring the voltage with a professional grade multimeter on the battery terminals as well as directly on the MPPT controller's battery connections reads 25.5 volt. The Victron app reads 25.7 volt.

The obvious problem with this is that my battery doesn't get fully charged. While the controller thinks we are full at 25.7 volt, the battery is only at 25.5 volt.

I went over the installation and all cables. I re-cut the battery connection cable ends and attached them well to the battery as well as the controller. Everything is snug, it's a simple installation. Still, the 75/15 is consistently reading 0.2 volts more than my multimeter.

I disabled the temperature compensation to temporarily let more volts into the battery to not discharge it too much. With temperature compensation disabled I get closer to full, but that is a hack at best and dangerous at worst.

Is this a hardware issue or something that can be calibrated by me? Are there any workarounds?

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Paul B avatar image Paul B commented ·

Make sure the unit is on the latest firmware. as you dont mention that

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bobdylan avatar image bobdylan Paul B commented ·

It is on the latest firmware. I just used a second multimeter to check the voltage at the MPPT terminals and it agrees with the MPPT. So now I have 3 devices in agreement, and 2 devices in disagreement. Perhaps I need yet another reading from a separate multimeter. If that also agrees with the MPPT I suppose my professional grade multimeter isn't so professional after all.

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1 Answer
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bobdylan answered ·

The problem was the multimeter, confirmed with 3 multimeters finally. Victron scores a mark for accuracy.

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