Voltage too high with MPPT + Alternator

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douglane asked Apr 20, '21

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 SmartSolar alternator

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Answer 1 · 2021-04-20T13:22:44Z

Stefanie (Victron Energy Staff) answered · Apr 20, 2021 at 01:22 PM

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 commented · Apr 20, 2021 at 02:53 PM

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) ♦♦ douglane commented · Apr 20, 2021 at 03:07 PM

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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douglane Stefanie (Victron Energy Staff) ♦♦ commented · Apr 20, 2021 at 04:54 PM

You are correct, the temperature compensation is on by default. I was mistaken. I do have lead acid batteries...three of them. Thanks for the tip on temperature compensation, I think that must be at play here. I'll go do some reading on that to try to understand it better.

I really do appreciate your help, but I find your manner of answering my question passive aggressive. Please do not forget that the people you are dealing with here do not have your knowledge or experience, which is why they are here. I provided all of the information I though was relevant with my admittedly inferior knowledge. If I were to describe my entire electrical system in detail, it would waste your time and mine. Thank you again for your help.

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Stefanie (Victron Energy Staff) ♦♦ douglane commented · Apr 20, 2021 at 05:37 PM

Sorry, I didn't want to sound rude or aggressive.

Please take into account that english is not my native language. I'm just trying to help people with what I know, voluntarily and without ulterior motives.

If I were to describe my entire electrical system in detail, it would waste your time and mine.

No. The more detailed, the better.

BTW, if you make use of the search feature here in the forum, there is a good chance that your question has been asked and answered before.

https://community.victronenergy.com/questions/50060/mppt-charger-voltages.html

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douglane Stefanie (Victron Energy Staff) ♦♦ commented · Apr 20, 2021 at 06:10 PM

Yes, I spent about one hour searching for an answer in previous posts. I'm not a complete idiot.

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