Calculate power usage daily total to grid/solar etc locally on Cerbo

DIY
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1

I have hit the rate limit against the api while developing and it doesn’t appear to be releasing. I was no where near the 200 hits per period of time. I was calling once every 15 minutes to get todays data to extract the export and solar generation.

The documentation states

> Rate limiting

](VRM API documentation)

Most endpoints are by default rate limited with a rolling window of max 200 requests, where every 0.33 seconds a request gets removed from the rolling window. (so on average maximum of 3 requests per second won’t get rate limited). There are different types of ratelimiting in VRM. If you receive a 429 with a JSON response, you can check the Retry-After response header to check the amount of seconds you have to wait until retrying

I haven’t got anywhere close to this.
Really i only need the current totals for today, but i couldn’t find an end point for that.
My current request is https://vrmapi.victronenergy.com/v2/installations/xxxxx/data-download?datatype={{{datatype}}}&format={{{format}}}&end={{{end}}}&start={{{start}}}

To get this round i’d like to calculate the daily usage locally. I have tried this a few times in the past but I haven’t been able to massage the values i get from the various nodes into any form of useful numbers. I’ve tried integrating but the numbers make no sense. Obviously this is in node-red. Has anyone had any joy? I want to calculate the solar exported today and the grid exported today as kWh.

2

Hi @Andy156

DO you want to do this exclusively on the gx device or have you got another system/pi you could use. If so you could use Victron’s influx/grafana integrations to do the heavy lifting for you.

GitHub - victronenergy/venus-grafana: Default Grafana dashboards, for docker solution and Venus OS Large

3

Hi Matt,
thanks, that is using the mqtt values which I already use and is comprised of the live data. It unfortunately doesn’t have a cumulative energy values. I’ve tried using the data and integrating it but I am usually a kWh or more out from the VRM calculations at the end of the day. I did get something workingish. I have a node subscribing to the mqtt N/xxxxxx/system/0/Ac/Grid/L1/Power. This is passed into the function below.
Cheers
Andy

// Function to check if it's midnight
function isMidnight() {
    var now = new Date();
    return now.getHours() === 0 && now.getMinutes() === 0;
}

// Retrieve stored tracking data (or initialize if not set)
var tracking = flow.get("todaysExport") ?? { total: 0.0, lastTime: 0.0 };

// Get current timestamp
var now = new Date().getTime();

// Use last recorded time, or default to now if not set
var lastTime = tracking.lastTime === 0 ? now : tracking.lastTime;

// Reset total at midnight
if (isMidnight()) {
    tracking.total = 0;
}

// Get current grid power reading
const grid = parseFloat(msg.payload.value);
if (grid>=0)
return null
// Calculate time difference in seconds
const timeDiff = (now - lastTime) / 1000.0;

// Calculate export energy (only sum negative grid power values)
if (grid < 0) {
    var newkWh = Math.abs(grid) * (timeDiff / 3600000.0);  // Convert to kWh
    tracking.total += newkWh;
}

// Store updated values
tracking.lastTime = now;
flow.set("todaysExport", tracking);

// Round total kWh to 3 decimal places and send as output
msg.payload = Math.round(tracking.total * 1000) / 1000;
return msg;