I have a Multi II, Cerbo GX, smart shunt and a 250/100 Smart MPPT.
Charging with the MPPT is flawless and beautiful - so many options and all do take effect. I rarely need the Multi and for low EMF reasons it stays OFF most of the time.
One of the cases I need however is during the dark days, then I need its charger. Charging with Multi is a pain, because:
It does not “listen” to controller’s charging settings nor its own. I set the same Absorption and Float voltages in both devices. And when I start the Multi, It just rises the battery’s voltage to the Float setting and stays there and the status in Cerbo immediately goes to “Float” without being to anything else before that/
I tried to stop the previously enabled “Battery monitor” option of the Multy, hoping that it could have been bothered by the shunt’s SoC percentages but nothing changed.
Multi has no setting for tail current. And once in a while when it decides to really rise its voltage to the set Absorption levels, it doesn’t stop even after the current drops below 1% of batteries’a AH, which is devastating for the batteries.
I’d be quite thankful if someone can explain how can I use the “Tail current” option in the shunt’s config to tell the Multi to stop charging when reaching it and to go through the Absorption phase every time instead of immediately going to Float in the first place.
@Vanko I am not sure how the system is set up but I would suggest using the smartshunt as “battery monitor” in the CerboGX and enable DVCC in the CerboGX so the CerboGX controls all charging parameters.
When the batteries need charging the CerboGX will determine the needs of the batteries and control the charging sources accordingly.
Hi Ivan.
Your Multi’s charge settings aren’t dealing with sun power that’s rising every morning, then slowly rising to a peak. It’s dealing with your whims, so you need to set the base rules.
If you might want it to reattempt an Absorption daily, then set Repeated Absorption Interval to 0.5 Days. Then it will reset itself sometime during the night and be ready for a fresh start the next day.
The Tail setting in the Shunt is used to sync itself to 100% SOC. Not to pass across to a nonexistent function in the Multi. Forget it. Set a fixed Absorption Time in the Multi that won’t ‘devastate’ your batteries. Whatever they are, you don’t say - does your Multi know?
Yes, Trevor, DVCC is enabled already but there I can set only limits, not actual voltages. I switched back on Battery monitor and there is no change.
It refuses to do anything other than “Floating” the batteries, and now it refuses even to set them at the float voltage.
Sure, I’ve missed to tell about the batteries.
They are Lead-acid Rolls 5000 with ANAM (carbon based) 337Ah , 2 12V pcs in series, resulting in 24V.
Yes, the batteries are set that way in the Multi.
That was precious clue you gave me, that the Multi can’t possibly know what I know - that the batteries need a “new cycle” and that I want it to rise their voltage to the Absorption voltage right away upon switching on the Multi.
I wouldn’t like to rely on randomly occurring intervals based on the “repeated Absorption” as I want to keep the Multi off most of the time (almost all of the time).
But if I understand you correctly there is no way to tell (or to configure it so) the Multi to start charging whenever it’s switched on and the voltage is below the float ( set in Multi and controller to 27.00V in my case)?
Had I got you right?
Okay, that would be better than noting (than no “stop condition”) but far than reliable. I’m using it in my other location’s solar installation (another house) where I have a cheaper controller brand without the tail current option and I’ve seen how inaccurate it may be in terms of proper charging. It either undercharges or overcharges the batteries there, as they are differently discharged throughout the different days.
That’s why I was happy I have the Tail current option in the MPPT and now I realize, it’s no longer “available” when I put the Multi in the game (for 4 years I’ve used the system without an inverter, utilizing just DC loads).