question

Hi @Alexander Benner

Take a look at the 'Rebulk Voltage Offset' in the mppt settings. This might be a little tricky to set up with Lithiums, but it should reapply an Absorb target once exceeded. Not to say it will give you the full Abs period once you get there, but it's a start.

You don't mention a GX device, but I would have thought that (and VRM) would pass on the time of day, but that's just my supposition.

The heavy hit would be to 'short' the panels with a time based relay. High V etc, my last resort.

Just thinking..

Hi @JohnC

thanks for your reply, all thoughts are wellcome.

I have set the Rebulk Voltage Offset to 0,6V this works fine for me and the MPPT switches from Float back to Bulk, but then also skips the Absorption phase. I thought this would start the whole cycle again, but it seems not to do so.

The whole Bulk, Absorption, Float cycle is only completed if the MPPT was in OFF state.

Regarding the GX device, Yes there is one. I have a Raspberry PI running Venus OS.

But I think the GX device don´t pass the time and date to the MPPT, I think this is just for visualisation at the VRM

Yes, I also have thougt about to "short" the East roof string during the night. This maybe also could be done by a "pull down" resistor and a relay (and maybe could be done via Node Red), because I don´t think the streetlingt is able to push any power.

But I thought I try to ask here, maybe I haven´t found the right setting or missed something.

Regards

Alexander

I've been using MPPT 100 50, and I have suffered it going into float prematurely, because it gets tricked by clouds or something, so I have set the float voltage high, so it doesn't matter.

I know you are able to charge LFP pretty high without reducing lifespan, but you could still improve the life of the battery by setting the charge lower

I have wondered how these controllers are supposed to work in the arctic circle.

Recently, they have added Tail current to the low price MPPTs, which is incompatible with aborption time. I assume nothing is being drawn overnight, or this would call the bluff of the street lights, and the voltage would drop. If the tail current option is there, it could be set low. On my application, it's not much use, because I'm running a computer and fridge all day.

Hello,

sorry for the late answer, I have spend my time with rebuilding my whole system to a complete ESS with 3 Multiplus 2 5000

I think this changes the whole situation, because the Multiplus inverters now are controling the chargecycle.

But the problem with the MPPT RS which never reaches off state is still existing.

@nesswill I think your voltage is close enough to the 48V battery voltage + drop for the Trackers / buck stage to work, and the MPPT RS is shutting off.

I think if I could lower my 80V to about 48V mine would shut off too.

@JohnC : Yes, feeding in a signal from the RPi to the MPPT RS Remote port could be an option.

@Astrayan, yes I have the option with tail current, but I would not use that, because I think an fixed absorption time is better for the balancer to do it´s work.

The MPPT draws no current from the 80V street light string, it tries but then the voltage drops and it can´t do something with that voltage, then the MPPT releases the current draw from that string and the voltage rises again (this cycle repeats all the time, measured with an multimeter at the string)

My next steps would be to try out Node Red, and see if I can do something similar with that.

The last step to force the MPPT into OFF state could be to short the string with an relay out of the RPI, but this is realy the last thing I want to do.

I will try what I can do with Node-Red (maybe shutdown the MPPT at night at a specific time and back on at another time)

Thanks for all your answers so far :)