FAQ

Does OpenDTU-OnBattery work without a battery?

Yes, OpenDTU-OnBattery always worked in systems without battery.

In addition, you can activate the "solar panels only" option in the DPL (Dynamic Power Limiter) in order to achieve zero feed throttle (Nulleinspeisung) even if you do not use a battery.

Is it possible to have 2 solar panels directly on the HOYMILES and connect the other 2 inputs to the 48v battery system?

No, this is not supported. (we talk about a 4 input, two MPPT version, eg HM-1500) The HOYMILES in this setup will only "coincidentally" cover your household consumption exactly when the solar panels can provide enough power. At night this will not work **because only about 50% of the power limit can be reached (two inputs out of four are used). **

The set limit to the HOYMILES applies to the sum of all MPPTs (i.e. all inputs). This means is, on a four input system with two MPPTs, any given limit will be split equally among two MPPTs.
e.g. a limit of 400W set, HOYMILES HM-1200/1500 will expect 200W from each of the two MPTTs. So, at night when only one MPPT (two inputs) is connected to the battery, 400W/2=200W is delivered although the set limit is 400W.

The limit is then probably adjust itself and gradually/possibly(?) might still somehow get there, but honestly, we would strongly advise against it.

Keep in mind, above applies when you connect the two panels to one MPPT, and the battery to the other MPTT (HM-1500 has two MPTTs each handling two inputs).

Actually, OpenDTU-OnBattery has an embeded algorithm trying to estimate the number of active inputs and "scale" the commands given to the inverter. "Scaling" works only for inverters which have one MPTT pro Input (e.g. HM-800 and HMS-1600 models). Inverters whose MPPTs control more than one Input (e.g. HM-1500 with two MPPTs for four Inputs) cannot be scaled for the time being:

• Prerequisite #1: The total power of the inverter is higher than the number of Inputs times 10. e.g. HM-800 (two MPPTs/two Inputs) 2x10=20W, HMS-1600 (four MPPTs/four Inputs) 4x10=40W
• Prerequisite #2: Only the Inputs that deliver more than 2W will be taken into account.

Based on the above conditions, OpenDTU-OnBattery will scale the limit appropriately.

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Can OpenDTU-OnBattery handle the information of multiple Victron MPPTs?

It is not necessary to connect every Victron MPPT individually with the OpenDTU-OnBattery : If you are using (highly recommended) Victron MPPT SmartSolar models, The Victrons will be connected among them with Bluetooth. In this case, you need to connect only one Victron with the OpenDTU-OnBattery.

As of Firmware 2024.03.23, OpenDTU-OnBattery supports up to two Victron MPPT charge controllers using the VE.Direct interface.

As of Firmware 2024.06.03, OpenDTU-OnBattery supports up to three Victron MPPT charge controllers on ESP32-S3-USB boards (this fiddles with the available hardware UARTs to make it possible to use a third Victron MPPT. If three MPPTs are defined int the pin mapping, you will not be able to use the SmartShunt and JK BMS battery interfaces).

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Do I need separate Victron MPPTs if I place my Solar Panels in different directions? (the infamous East/West Question)

You do not need to have separate Victron MPPTs for each direction.

For more information: https://github.com/helgeerbe/OpenDTU-OnBattery/wiki/Victron-MPPT-battery-charger#east--west--panels-with-only-one-victron

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Huawei AC charger RG4850 with CMT2300A radio board (for HMT- HMS- Series Inverters)

Using the Huawei AC charger in combination with the CMT2300A radio board (for HMT- HMS- Inverters) is supported as of the latest Firmware (stand: Sep.2024)
Please Note: Due to the fact that the ESP32 has only two SPI available, ONLY TWO OF THREE (NRF24, CMT23000, MC2515) modules can run simultanously.
The OpenDTU-OnBattery checks presence of the modules and allocates SPI to them in fixed sequence:

1. NRF24
   
2. CMT2300
   
3. HuaweiCAN (MC2515)
   

If the OpenDTU-OnBattery finds a PIN definition in the config, it assigns one of the two available SPI.
If all three modules are present, the OpenDTU-OnBattery will allocate the first two with an SPI and the third will be denied, without hanging up. If you have all three modules "present" on your PCB board, you need to disable one of them: Change your Pin-Out configuration and define with -1 the pins of the module you want to have disabled.

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Can OpenDTU-OnBattery Dynamic Power Limiter control more than one Inverter?

Yes!
As of Release 2024.11.20 OpenDTU-OnBattery can dynamically adjust the power output of many inverters
(Releases before 2024.11.20 can dynamically adjust the power output of only one inverter).

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