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douglane avatar image
douglane asked

Voltage too high with MPPT + Alternator

I have a SmartSolar Charger MPPT 100/30 on a boat with an alternator that does not have an external regulator. I'm seeing an issue where, when the batteries are fully charged, the solar controller is on and in float, and the engine is on, I'm seeing voltages between 15.25 - 15.45. That is definitely too high. The solar controller reports it is in float and putting no amps into the batteries, but when I turn it off, the voltage drops to 14.8, which is closer to normal. Why is the Solar Controller increasing the voltage in this situation, and is there anything I can do other than turn it off when I'm underway?

MPPT SmartSolaralternator
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Stefanie (Victron Energy Staff) avatar image
Stefanie (Victron Energy Staff) answered ·

Hi @douglane,

since you didn't provide us with details about your installation, it's all a guess. To get you started troubleshooting yourself, you may check the MPPT settings for temperature compensation. If this is set and the MPPT is way below 25°C, this could be the cause for the higher voltage you're experiencing.

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douglane avatar image douglane commented ·

Sorry, I thought I did provide the details I believed were relevant. The solar controller is using the default configuration with a float voltage of 13.7 volts and there is no temperature compensation configured. What other details would be relevant which I'm missing that would help you avoid guessing?

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Stefanie (Victron Energy Staff) avatar image Stefanie (Victron Energy Staff) ♦♦ douglane commented ·

You did not mention the type of battery, how many batteries, starter and service battery or only one of them, how they are wired, mppt controller settings (screenshots), which other devices you have in your setup and finally how you measure the voltage.

If you have setup your controller for a lead acid battery I think temperature compensation is on by default.

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