This has been an ongoing saga for me, where the multiplus causes voltages spikes in the absorption cycle. I’ve boiled it down to: My batteries are damn full and and bit of extra current causes the voltage to spike.
Unfortunately I have integrated BMS with no comms.
With my mppt I can set the tail current to something like 1amp (365 amp/h bank) and I never experience voltage spikes.
Multiplus can’t do that. Nor can I reduce the absorption time less than 1h.
Here’s my question: Can adaptive charge curve reduce my absorption time below 1h?
Any other way to get the multiplus out of absorption when current drops to 0 - 1?
Yeah, I do exactly that using node red and ajust DVCC to limit the charge current when the voltage rises. Here is a flow that does that. All you need to do is inject the voltage, and the function will scale the output. This is a demo mode of the Venus OS on a 48V system. Here is a scale for the output to 1a when the voltage goes above 54V. It goes from 35A to 1A.
I run ESS with exports for DC solar. The solar current is not changed, just the internal charger. You may have your system set up differently, and the solar charge might be reduced using DVCC. But it doesn’t really matter if the battery is full. If you scale the current back too far you might not get absorbtion at all if you have a load on the system. You will need to tweak it to suit.
Flow is in the text file just download and import the JSON code.
Modify these values in the function to suit the charge voltage and current.
Fantastic! I wondered about node red. I have a bunch of other ideas for it as well. Short of an easier solution, looks like I’ll be going that route. Thanks for confirming it can be done with node red!
