sintesis avatar image
sintesis asked

My MPPT regulator does not fully load the batteries

I have a Bluesolar MPPT 150/60 that was first used in 12 V system. Before starting to use it in another 48 V system I first changed the internal battery voltage setting. Now it goes into float mode before the batteries are fully loaded (according to the BMV they are only 65 % loaded). During daytime the system tension goes up to around 57 V but during nighttime it goes below 51 V. Is there some other setting I need to change to get the batteries fully loaded.

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It might help with the answers below if you could post some screenshots or export file of the history page in VictronConnect.

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JohnC avatar image
JohnC answered ·

Hi S. If those are Pb batts, then you're surviving the night in very good shape. Just by V.

What you may be suffering from here is unwarranted faith in a calculated SOC that really requires tuning to give a realistic figure. Yes, I'm saying it's probably wrong, and may be even accumulating the error as the days pass by. So you've gotta give it some tender loving care. The manual:

Look especially at the Peukert and Round Trip Eff settings. And Synchronizing it at the end of a good charge day for a 'fresh start'.

The mppt doesn't need tuning, and I suspect your batts are getting correctly charged.

Check it out and see how you go.. or ignore it..

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sintesis avatar image sintesis commented ·

Thanks JohnC! I may however have failed to express myself clearly. During the day the charger is only taking around 100 W (around 2 A) from the panels as it has decided the batteries are fully charged already. As soon as the sun sets the value drops directly and I presume I get the real reading from the BMV? Or is the reading on the BMV of about 50.7 V incorrect, is that what you are saying? A fully charged Rb battery would give a reading of about 52 V, would it not?

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JohnC avatar image JohnC ♦ sintesis commented ·

I'm little confused with what you're saying, sorry. If you mean 50.7V is the 'standing V' of your batts after quite a few hours (say overnight), then that's about as good as you'll ever see from Pb's. If it's just after sundown, then it likely has further to drop. I'm happy to see 50.0V after a few hours.

Your 100W, without knowing your batt size, is possibly/probably quite normal. If it's showing ~55V 'float' level at the same time (can vary with temp comp), then yes, the mppt has done it's job and your batts are effectively awfully close to full. You could leave it to do that as late as you can before sundown, then sync your BMV to 100% SOC.

Ensuing days may see your SOC 'drift', so then you start tuning the BMV so it gives you a better indication over time.

Hope this makes sense. :)

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sintesis avatar image sintesis JohnC ♦ commented ·

What I am trying to say is that the higher voltage (~57 V) is of course the float voltage value and not a real battery reading. The lower value (50.7 V) is not what is left after a nights energy consumption, but what the BMV shows immediately after sunset. Perhaps that measurement is not exact? On the BMV that value is interpreted as a 65% SOC. I probably need to fine-tune settings, and will add some screenshots, as soon as I get back to this installation, which still has to be setup for remote access.

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