How to change MPPT params in VC

[Fideri (Fideri K)]

Hello everybody,

Simple question: How do I change the charge voltages of an RS MPPT with a BYD BMS enabled? Or it’s impossible?
I want to change the params to those recommended by Victron here. I am using Victron Connect (see screenshot). It appears the higher values there are set by BYD. I can’t deactivate BYD BMS briefly. I can only restart it. Even if Expert mode is toggled on, I can’t change the values.

I understand that under normal operation, my new values will simply be ignored. I want to set them only as fallback in case of an error.

Currently, the charger is in float mode, so the watt figure makes sense.

A related question just out of curiosity: Why does Victron recommend higher absorption voltage (56.5v) for the MPPT but lower absorption voltage (55.2v) for the quattro charger in the same doc? I would think they should be the same.

Fideri

[nickdb (Nick)]

@Fideri

Simple question: How do I change the charge voltages of an RS MPPT with a BYD BMS enabled?

Those settings are ignored as they are under external control.

You would typically configure “backup” settings beforehand but once under external control they are irrelevant and overruled.

You would have to disconnect comms and power cycle the charger.

Why does Victron recommend higher absorption voltage (56.5v) for the MPPT but lower absorption voltage (55.2v) for the quattro charger in the same doc?

Which doc are you referring to?

[nickdb (Nick)]

Ok, you mean the BYD config doc. Looks like an oversight. The voltages match for the off-grid use case. Can’t see why you would set it higher than the inverter charger.

[Fideri (Fideri K)]

That makes sense, thanks.

The document in question is the compatibility list. It is titled Victron & BYD. It’s here: Victron & BYD [Victron Energy]

Though I haven’t double checked, I think the charge voltages recommended for the charger tab of VE Configure are also different from DVCC.

[nickdb (Nick)]

The BYD will adjust CVL as required. The rest of the settings are all ignored and are just a backstop.

The models we have run a much higher CVL until top of charge and then drop to 56.6V.

[Fideri (Fideri K)]

That makes sense too as my model (LV5.0) is not on the list. I will adjust my backup settings to match CVL.

[nickdb (Nick)]

My charts were from LV 5’s.

[Fideri (Fideri K)]

I will chart the same in VRM later and report back.

For now, this is what I am seeing on the Cerbo as DVCC settings. I don’t remember where those figures came from but they appear correct.

[nickdb (Nick)]

There is no need to limit CVL or CCL in DVCC, it is redundant. Don’t recall that being in the doc either, unless it changed.

If your system is capable of charging quickly then it is a good idea to reduce the CCL to help battery life.

I generally try keep it to 1/4C for my lithium batteries.

[Fideri (Fideri K)]

@nickdb

I generally try keep it to 1/4C for my lithium batteries.

Good advice. I will do the same.

Here is my CVL and CCL chart from VRM. Do you spot anything concerning?