How to calculate battery life with node red

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alda asked Feb 20, '22

How to calculate battery life with node red

I want calculate a battery life from actual (or average consumption after 1minute) and actual SoC.

But not sure how to calculate with data from two sources which are not sync.

Thank you for any idea and help

Node-RED

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Answer 1 · 2022-02-26T05:17:03Z

I do just that......
I take the current battery SOC and subtract the set minimum SOC and then divide that by the current power (discharging) to arrive at a time the battery is estimated to be flat.
Similarly, you can calculate an estimate for time fully charged.
There was a useful date/time formatter node to add to the pallet to calculate the times. (node-red-contrib-moment2)

Try pasting this to save you some work....
(You probably don't need global variables that I have used in some cases.)

Answer 2 · 2023-07-30T10:53:28Z

alan-falck answered · Jul 30, 2023 at 10:53 AM

Great project, following with interest, happy to help with any testing ... thanks

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Answer 3 · 2023-08-01T11:01:11Z

Was exactly one of the first things I did for the liontron batteries that do not expose this values via can bus.

At first I set the soc as a global variable out of a

Venus System - Battery State of Charge (%)

Node with a function node with code:

global.set('soc', msg.payload)
return msg;

Then I use as input the

Venus System - Battery Power (W)

Node and a function node with this inside:

soc=global.get('soc');
watts=msg.payload;
capacity=51.2*(105+104+102+104); # Nominal Power of the Liontron Multiplied by the Ah sum of Capacity of the 4 Modules gives you the capacity in Watt Hours.
remain=soc/100*capacity;
rest=capacity-remain;

if (watts !=0 ) {
    if (watts <0) {
        timetogo=remain/watts*-3600;
        left=remain;
    } else {
        timetogo=rest/watts*3600;
        left=rest;
    }
    
} else {
    timetogo=864000;
    left=rest;
}

// Hours
var Hours = ((timetogo)/3600);
Hours = Math.floor(Hours);

// Minutes
var Minutes = (timetogo-(Hours*3600))/60;
Minutes = Math.floor(Minutes);

// Concatenate
var Time = ('0' +Hours).slice(-2)+':'+('0' +Minutes).slice(-2);

global.set('timetogo', timetogo);
global.set('watts', watts);

msg.payload=Time;
msg.soc=soc;
msg.watts=watts;
msg.capacity=capacity;
msg.remain=remain;
msg.rest=rest;
msg.timetogo=timetogo;
msg.hours=Hours;
msg.minutes=Minutes;
msg.left=left;

return msg;

As output you then have a msg object that has almost all necessary inside.

If you also want to subtract the set minimum soc to keep you can pick that also up by setting it as a global var and use it then by loading it into the function.

Hopefully that helps.

Kind regards,

Dierk

Answer 4 · 2024-03-29T22:00:00Z

andy156 answered · Mar 29 at 10:00 PM

It's worth taking into account the efficiency of the inverter. I have a function that returns the 'assumed' efficiency based on the power. For my quattro 10k . At 1kW its maximum of 95% and then it linearly decays to 90% or less ( I forget the exact figures) at 8kW. Multiply the time to go by the calculated efficiency.

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