I finished version 3 of my solar system at the weekend. Or rather I finished the main bulk of the board. (330W panel, 40A EPEver MPPT, Multiplus 24/800).
I'm left to figure out the "auxiliary" stuff. The first part of the auxiliary stuff is what I like to call the "maintenance bus". This runs things like the RS485 Wifi adapter for the MPPT, the Raspberry PI for the VEnus GX interface to Victron gear, a mini Wifi travel router, the ESP32 BLE-MQTT proxy for the JK-BMS etc. etc.
Luckily, so far, that stuff all falls nicely into "Battery voltage" or "USB 5V" categories. The later can come from 2 x little 4 port USB buck converter charger things I have. That gives me 4 or 8 5V USB power sources up to 3A each.
There is however the garage lights, which run 12/24V AC/DC, garden lights screwed to the ceiling joists, they don't seem to mind 28.80VDC either.
Finally there is the main DC load output. This currently gets fused at 15A and sent up an 8 meter long 6mm^2 3-core outdoor cable to the office. It powers a 5 Amp boost/buck converter which runs a bunch of low power devices with a stable 13V. This circuit is marked for upgrade however to 240V and fed from the multiplus. So it's validity going forward makes "upgrading" it to be tidier and integrated to the new V3 board... questionable. I may remain temporary until I convince the spark to hook the office up to the multi.
Problem 1:
To have monitoring and control over this Aux DC Load circuit, it has to come from the MPPT "Load" output. Given I hate RV/caravan panels with a passion, what options are there to take the "Load" output and split it into multiple switched feeds (garage lights, maintence bus, etc.)?
I looked at dry contact relay boards with an ESP32 or ESP8266 that can run tasmota, but I don't really want another sub project and while being able to switch individual loads with the Tasmota interface would be cool, none of them seem to support switching them manually as well!
I need something in the middle. Something smaller/less bulky than an RV panel, but more of a finished product than a chinese relay board.
Problem 2:
Related to the maintenance bus. I would "like" to have a UPS for it. In the event, say, the BMS cuts discharge, I would still like the BMS MPPT proxy and Wifi to stay running so it can alert me and still report the battery voltages and allow control etc.
There lies some janky options!
1. Configure the Multiplus such that in the event the discharge cuts out, it will transfer back to grid power. Use that "protected 240V" outlet to power the maintenance bus.
2. Connect the maintenance bus directly to the battery, pre-BMS.
3. Buy a bunch of cheap 18650 based 5V UPS boards off Ali* and choose the best one.
Option 1 is undesirable as I would rather not have to run the inverter constantly. It also gives the maintenance bus and unrecoverable self shutdown button! Option 2 fixes that, but would require a voltage supervisor (mini BMS) to shut itself down, which either means it needs a full set of cell taps or I trust it remains in coms with the BMS and can switch off with it. Option 3 - unfortunately I have seen several poor reviews on those little UPS boards, so I need to find the "right" one.
On option 2. Surely there is somewhere, even the power button leads, from the JK-BMS I can find a "switched DC" for the BMS power itself. If I was to use that BMS power to hold a mosfet on to power the maintenance bus. In the event the BMS itself gives up due to low voltage that BMS power will drop out and disconnect the maintenance bus also.
I'm looking for ideas at this stage.
I'm left to figure out the "auxiliary" stuff. The first part of the auxiliary stuff is what I like to call the "maintenance bus". This runs things like the RS485 Wifi adapter for the MPPT, the Raspberry PI for the VEnus GX interface to Victron gear, a mini Wifi travel router, the ESP32 BLE-MQTT proxy for the JK-BMS etc. etc.
Luckily, so far, that stuff all falls nicely into "Battery voltage" or "USB 5V" categories. The later can come from 2 x little 4 port USB buck converter charger things I have. That gives me 4 or 8 5V USB power sources up to 3A each.
There is however the garage lights, which run 12/24V AC/DC, garden lights screwed to the ceiling joists, they don't seem to mind 28.80VDC either.
Finally there is the main DC load output. This currently gets fused at 15A and sent up an 8 meter long 6mm^2 3-core outdoor cable to the office. It powers a 5 Amp boost/buck converter which runs a bunch of low power devices with a stable 13V. This circuit is marked for upgrade however to 240V and fed from the multiplus. So it's validity going forward makes "upgrading" it to be tidier and integrated to the new V3 board... questionable. I may remain temporary until I convince the spark to hook the office up to the multi.
Problem 1:
To have monitoring and control over this Aux DC Load circuit, it has to come from the MPPT "Load" output. Given I hate RV/caravan panels with a passion, what options are there to take the "Load" output and split it into multiple switched feeds (garage lights, maintence bus, etc.)?
I looked at dry contact relay boards with an ESP32 or ESP8266 that can run tasmota, but I don't really want another sub project and while being able to switch individual loads with the Tasmota interface would be cool, none of them seem to support switching them manually as well!
I need something in the middle. Something smaller/less bulky than an RV panel, but more of a finished product than a chinese relay board.
Problem 2:
Related to the maintenance bus. I would "like" to have a UPS for it. In the event, say, the BMS cuts discharge, I would still like the BMS MPPT proxy and Wifi to stay running so it can alert me and still report the battery voltages and allow control etc.
There lies some janky options!
1. Configure the Multiplus such that in the event the discharge cuts out, it will transfer back to grid power. Use that "protected 240V" outlet to power the maintenance bus.
2. Connect the maintenance bus directly to the battery, pre-BMS.
3. Buy a bunch of cheap 18650 based 5V UPS boards off Ali* and choose the best one.
Option 1 is undesirable as I would rather not have to run the inverter constantly. It also gives the maintenance bus and unrecoverable self shutdown button! Option 2 fixes that, but would require a voltage supervisor (mini BMS) to shut itself down, which either means it needs a full set of cell taps or I trust it remains in coms with the BMS and can switch off with it. Option 3 - unfortunately I have seen several poor reviews on those little UPS boards, so I need to find the "right" one.
On option 2. Surely there is somewhere, even the power button leads, from the JK-BMS I can find a "switched DC" for the BMS power itself. If I was to use that BMS power to hold a mosfet on to power the maintenance bus. In the event the BMS itself gives up due to low voltage that BMS power will drop out and disconnect the maintenance bus also.
I'm looking for ideas at this stage.
