150V 45A MPPT - roll your own


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rogerdw
Guru

Joined: 22/10/2019
Location: Australia
Posts: 877
Posted: 12:54am 18 Feb 2024      

  poida said  Yes, the absorb timer will be reset when it drops out of absorb mode.

Yes, I can see that now. Explains a lot.

  Quote  I was educated by looking at my battery as it's voltage rises
as it approaches the absorb voltage.
The voltage rises very quickly.
If I wanted to use the float charge function, I would use a large absorb tolerance.
This is to permit large voltage variations and still remain in absorb mode,
counting down the programmed time.

That graph is excellent. I need to do the same. I have a feeling at least one of my meters can log data, I'll have to have a look.

And yes, I will widen the tolerance to perhaps 5 volts, from the 3 volts at present.

What's led me to this is the fact that the battery (forklift type) spends a lot of time bubbling along  ...  and has gone through a bit of water already. I'm sure if I can give it a solid absorb time  ...  then get it on to float, it will have an easier life.

  Quote  I suppose a better way would be to time average battery voltage and then
do the BV < (absorb - absorb_tolerance) decision.
That would be nice, actually, now I think about it.

If we sample BV each second over 5 minutes (300 times)
and average this, it will permit short BV drops due to motor startup and
other things to occur without upsetting the absorb period.

That's a great idea and I even understand the concept. Of course implimenting that is not something I'm capable of but it could be very useful.

  Quote  your work shown above looks great.
the top right mppt is running at
67.9 V x 34.7 A or 2356 W input from the panels
it's about 98% conversion efficiency.
not too bad at all.

Thank you. I was just so pleased and relieved that they all worked okay  ...  so it's even better to see that sort of efficiency.

Thanks for such an excellent design and all the work you've done over the years fine tuning it  ...  and then giving the design away. Awesome work man.