andybierlair avatar image
andybierlair asked

ESS overriding MPPT RS 450 charge parameters?

Under the ESS documentation (Section 4.2.) you can read that MPPT charge parameters are being ignored when ESS is enabled on your Multiplus/Quattro configuration.

Does this also apply to the newer MPPT RS 450 models?

I have been finetuning the Float/Absorb settings in my MPPT RS devices today and I had the feeling that they were taken into consideration by the system even though I'm running in ESS mode with slightly different batterty settings in my ESS assistant.

Can anyone shed some light on this?

ESSmppt rs
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

2 Answers
Alexandra avatar image
Alexandra answered ·


The mppt will charge to the voltages set unless you override them with dvcc to cap the voltage.

It is important that the Absorption and float voltages are eet to the same values on all charge sources (including the inverter).

In ESS assistant it is cut off voltages that are set for the system under load, these values are unrelated to charge. (They are discharge values.)

The MPPT will be controlled by the GX, it will be told to produce when a load needs to be supported and/or the batteries need to be charged.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

andybierlair avatar image andybierlair commented ·

Got it, but then what does this paragraph in the ESS documentation mean?


Note that, for systems with the ESS Assistant installed, the MPPT Solar Chargers will follow the charge curve as set in VEConfigure. The charge parameters configured in the MPPT Solar Chargers are ignored in an ESS setup."

0 Likes 0 ·
Alexandra avatar image Alexandra ♦ andybierlair commented ·

So it means that the mppt will continue to produce power for loads even if the battery is charged.

Otherwise what will happen is the batteries would have to drop back down under float to the rebulk offset before production begins again.

This scenario is really is not a desired thing. Cycling up and down alot during the day would happen.

With ESS, your battery can be in float (0W in or out) but the mppt will be bulk producing (for loads). If you look around on the forum, there are many who will ask "why is my mppt in bulk but my inverter is in absorption" ANS -well because ESS.

And the point of having solar is to run your loads off the sun, not the battery or grid.

0 Likes 0 ·
andybierlair avatar image andybierlair Alexandra ♦ commented ·

Hmm, the way I read this it means that if for instance you set your absobtion voltage in VEConfigure to 54.0V and in your MPPT to 55.2V, the MPPT would not follow its own set value, but follow the 54.0V from VEConfigure instead.

Of course it does not make sense having different values in multiple chargers, but I'm still tweaking on my end, so I would like to know if there is a single source of truth in the system in case there is ESS involved.

0 Likes 0 ·
Alexandra avatar image Alexandra ♦ andybierlair commented ·


No it means from grid the battery will not charge to the same value as the mppt. (And in troubleshooting systems have I have found this is actually a common error on the part of an installer)

In theory the inverter will stop charging before the mppt does. And you would see errors appear on the GX as an example.

The other one is to not stick to the manufacturer recommendations for voltages.

0 Likes 0 ·
offgridvoltage avatar image
offgridvoltage answered ·

Hi @andybierlair Did you end up with a clear solution to your issue ? I have been searching for a similar situation, where I have learned that Yes, the MPPT Charge parameters (bulk/abs/float) are ignored when using ESS environments as set in VE-Config. This will be indicated by the 'Ext-Control' label on VRM. (Paragraph 4.2.5 ESS Design and Installation manual)

The best true values will be from a managed BMS of course, and will overide both MPPT values and Ve-Config Charge Tab voltages. Under these circumstances one single voltage will apply for charging as sent from BMS to Cerbo. This voltage can still be governed by DVCC max charge voltage limits however.

Also note: there is an MPPT +0.4v (fixed solar offset) that is applied to the charging voltage when ESS = ‘Optimized’ with “Feed-in excess” enabled (or) when ESS = “Keep Battery’s Charged”

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.