Ideal temperature for HV2600 battery bank?

[Ched]

Thanks to both of you, great info.
I can't seem to see cell or battery temp on HA for back in the summer - no idea why but seems to only go back about 10days but generation goes back to summer!
I do remember early this year the batteries wouldn't charge properly as they where too cold.
Great chat between Will and Fox UK the other day where they produced a table showing how much current batteries would accept at different temps.
The loft is very easy access as we have a dormer bungalow with a door to the loft space.
I think I will measure up and see what insulation I can get that will fit in the car.
Thanks again.

[calum]

How are you connecting to your inverter? IIRC it only exposes some of the BMS information via RS485...

[Ched]

How are you connecting to your inverter? IIRC it only exposes some of the BMS information via RS485...

Connection is via RS485.
My data in HA is a bit weird as I can see Energy Data page going back to July (when I put new miroSd card in) but BMS Temp High and Low doesn't seem to go back more than about 10 days. I am using a RPI and the ModBus code is probably from back in June.

No idea if I have a setting wrong so it's not storing all the data or it's a limitation of the RPi and using a microsd card?

[Dave Foster]

How are you connecting to your inverter? IIRC it only exposes some of the BMS information via RS485...

Connection is via RS485.
My data in HA is a bit weird as I can see Energy Data page going back to July (when I put new miroSd card in) but BMS Temp High and Low doesn't seem to go back more than about 10 days. I am using a RPI and the ModBus code is probably from back in June.

No idea if I have a setting wrong so it's not storing all the data or it's a limitation of the RPi and using a microsd card?

10 days for sensor data is default for HA using the sqlite database, but long term statistics such as your energy dashboard retain history indefinitely.

If you switch to a reasonable size SSD you can increase the days you keep sensor data to 60 even 90 but as you have a lot of sensors reading every few seconds it will bloat the database out very quickly.

Where I need to keep longer data I create a template of the sensor i'm interested in, and either pass it through a filter to slow the update frequency

Code: Select all

  - platform: filter
    name: "Battery Cell High smooth"
    entity_id: sensor.bms_cell_temp_high
    filters:
      - filter: lowpass
        time_constant: 4
        precision: 1

which still gives you a reasonable representation of the value

or use a template with an update interval specified, this one only updates every 5 minutes which saves a lot of space in the database.

Code: Select all

  - trigger:
      - platform: time_pattern
        minutes: "/5"
    sensor:
      - name: "Inverter Temp"
        device_class: temperature
        state_class: measurement
        state: >
            {{ (states('sensor.invtemp')|round(1,0)) }}
        unit_of_measurement: '°C'

This still gives a good idea of what the sensor is doing at 5 minute intervals

Or if you really want lots of sensor data you could change the internal database to use mariadb / influxdb which are much better at handling longer term statistics and larger datasets.

[calum]

I use MariaDB with a 30d retention period, and then InfluxDB + Grafana for the longer term stuff. But my HA is a VM on a softrouter running Proxmox, so I can easily give it 100GB of disk space so I don't have to think about it. The MariaDB never gets above 4GB so ¯\_(ツ)_/¯

(Point being, low power PC hardware that can run this stuff without breaking a sweat is inexpensive and widely available, so you don't really need to care about what you do and don't record, if you don't want to)

[Ched]

Thanks @Dave Foster. I might set up cell temp sensors for once an hour over a longer period. Cheers.

Thanks @Calum. I keep meaning to buy a low powered pc but there are so many out there it's tricky to know which one to go for. I would only want it for HA and a backup file server.

[calum]

Something like this https://www.ebay.co.uk/itm/296038491368 with an additional SSD if you need more storage would do a grand job.

[Ched]

Something like this https://www.ebay.co.uk/itm/296038491368 with an additional SSD if you need more storage would do a grand job.

Thanks for that, I will probably get one soon and have a play.