150V 45A MPPT - roll your own


Author Message
poida

Guru

Joined: 02/02/2017
Location: Australia
Posts: 1425
Posted: 02:35am 16 Feb 2024      

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

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.

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.

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.

here is when my battery approaches absorb voltage.
See how fast it rises with nearly constant charge power (or current)
and how fast the charge power drops while maintaining absorb voltage!

Dark Blue is charge power
Light Blue is battery voltage

it seems to me that my battery (everyone else's battery will be different)
is very sensitive to charge current when near absorb voltage
and nearly anything will make BV drop.



Edited 2024-02-16 17:54 by poida