Chargehq and Fronius Wattpilot

I’m new to Chargehq and working through the various set-up activities.

My charging system is a Fronius - Home 22J - 22KW - EV Charger with Fronius Smart Meter. I manage it via the Fronius Wattpilot app.

Once I have set up the Chargehq app on my phone, will the Fronius Wattpilot app (which I presently use to manage my charging) still work? Assuming that the Chargehq app works fine it’ll no doubt become my principal management app, but until then I want to know that I can revert to the Solar.wattpilot app if I need to.

Thanks …

Peter - absolutely, it’s purely a change in the configuration settings on the charger. You can reverse the changes made in the configuration guide, or do a factory reset on the charger.

If you have 3-phase power, you may still find it useful to use the Fronius app to switch between single and 3-phase charging at times.

Yes, the CHQ app and the Fronius app both work in concert - the charger will take commands from whichever changes last - so CHQ might tell the charger to start charging from excess solar, and if you then hit the STOP button in the Fronius app it will stop. There are messages in the Fronius app display that identify if the charger is doing something due to CHQ control, and vice versa.

If you’re using the Fronius Smartmeter to have the charger do auto-follow-excess-solar though you may need to play with the settings to stop each one trying to modulate the charging rate so they don’t fight each other. Set so only one system, or the other, controls charging rate and not both.
I have the Wattpilot, but no Fronius Smartmeter, so I have the CHQ app controlling the follow-excess-solar rate, and end up just using the Fronius app for fine-grained visibility to monitor variations in each phase’s voltage and current draw. And I pull in the comprehensive charging stats and statuses from the Wattpilot into Home Assistant for charting and automations, as CHQ doesn’t have a Home Assistant integration.

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Thanks @andrew and @paul,

A follow-up question if I may please …

I now have the ChargeHQ all set up and working, but the Fronius app (Watt Pilot) seems to take priority. Watt Pilot doesn’t have the functionality (at least, I cannot find it) to ensure that the vehicle is charging only from solar - it always defaults to taking additional power from the grid.

I believe that I can set the ChargeHQ to take only solar power, and I think that I have set it up correctly. But Watt Pilot appears to be overriding it, and so I’m still dragging power form the grid.

Any clues/guidance on how I ensure that the Charge HQ is the principal controller? Indeed, is that possible? (I’ve looked through the various support articles, and the answer may well be there, but if so I can’t find it.)

Thanks …

@Peter I’ve had a look at your account, you had a scheduled charge configured from 9am to 3pm. Scheduled charging periods overide most other controls including solar tracking. I’ve disabled it now and can see solar tracking working correctly.

It’s a little confusing as solar tracking becomes a default charging mode once solar is connected to the app, so it doesn’t require any explicit schedule or instruction to start charging.

Thanks @andrew, much appreciated.

So if I want to stop charging at 3pm to take advantage of a higher feed-in tariff, can I set a block-out period from 3pm onwards, and will that override the solar charging setting in the same way as the “scheduled charge” does?

I appreciate your help/guidance as I get this all set up.

Yes, a blockout schedule will work well for that.


Hi @andrew - I wonder if you could assist me further please, as I must still have a setting wrong somewhere.

The attached image shows power of 1.79kw being being generated, and 3.42 kw being consumed (mainly by the car), resulting in a 1.63kw download from the grid.

I’ve tried to set it up so that the car only draws excess generated power, so that I don’t have grid downloads. I’m wondering whether somehow the Fronius app is still overriding the Charge HQ app?

Not sure what my next steps are. Sorry to keep bothering you …

Peter - not a problem, happy to help. Can you tell me what day the screenshot was taken? Then I can have a look at our logs to see what was happening.

Thanks. It was a few days back - 24th May, 12:59pm WA time (may be registered as 14:59 in your logs).

Logs from the 24th, in WA time. Looks like it was a day with intermittent sunshine / cloud cover which is always hard for solar tracking.

Solar data updates were running at 1-minute intervals across the period.

Across the day you still achieved 75% charging from solar though. That’s about what is to be expected on such a day considering also that total charging volume was low (< 5 kWH).

Thanks Andrew, yes, it was an intermittent sun/cloud day.

So back to my basic question - can I set up Charge HQ (either stand alone or in concert with Wattpilot) to only charge when there is sufficient output from the sun?

Up until I started to use Charge HQ I simply “managed” this manually, either by unplugging the car or by scaling up and down the Amps rating, both of which are sub-optimal processes.

As we approach winter it would be nice to simply keep the car plugged in, and know that when the sun was out it would charge and when it wasn’t it wouldn’t. Is that functionality available? Or on low sun days will the system somehow override whatever manual settings I might put in?

Charge HQ checks with your solar system every 1 minute to see how much excess solar is available and then sets the charging speed to match. Your excess solar can vary every second though based on changes in production (clouds) and changes to home energy use (e.g. air conditioner switching on and off).

This inevitably means there will be short periods where the EV charging uses a little more or a little less than the excess solar available, and as a result, uses grid energy. On days such as the 24th, this means that 25% of the energy comes from the grid. On sunny days and with more solar available you would expect this to be less than 10%. With 1-minute polling intervals, we can’t stop it from drawing from the grid entirely.

It’s also limited by how often you’re willing to start and stop EV charging when the excess solar falls below the minimum rate of charge (5A on Tesla). Only cloudy days with a smallish solar system this can happen frequently. We continue charging for up to 6 minutes once excess falls below the minimum. A faster data update rate can’t help here.

On balance, I think it will be better than not using solar charging.

From a cost perspective… since you’re in Perth, there are only a few energy plans to choose from. Charging from your own solar costs $0.025/kWh before 3pm and $0.10/kWh after 3pm (via forgone credits), less if you’re hitting export limits.

If you’re on the Home Plan, all other charging from the grid costs you $0.30/kWh

If you’re on the EV plan, grid charging costs $0.08 from 9am - 3pm or $0.18/kWh overnight

In both cases, you’re better off using a little bit of grid energy whilst solar charging if it avoids deliberate charging from the grid at other times to meet your driving requirements.

From a renewables perspective - if solar charging is active at all, the sun is out and chances are there will be more renewable contribution to grid energy than other times of day.

My suggestion would be to leave it as you have it set up for the next few months and look at the percentage of charging from grid vs solar over a longer period.

Many thanks @andrew. Even though I’m new to Charge HQ, we’ve had the car and the PV system for a year now, and have been monitoring as you suggest. I’m on an old legacy tariff, and am deciding whether to upgrade to one of the newer ones.

I appreciate all your help and explanations.

Peter - one of the things you can do to help it not draw from the grid is to get into the ‘advanced’ section of the solar charging settings and set the ‘Min Solar Generation’ and ‘Min Excess Solar’ higher.
How you set these will depend on the size of your solar system and your ‘normal’ house usage and your lowest car charging rate
I know my house normally draws ~ 800W to 1kW, and my car’s minimum draw is 6A = 1.3 kW.
So I set the ‘Min Solar Generation’ high enough, and the ‘Min Excess Solar’ high enough, to virtually guarantee that the car charging won’t even start unless there is more than sufficient sun power to power the house and the car at minimum charge rate. Setting the ‘Min Excess Solar’ somewhat higher than your car’s slowest charge gives CHQ some wiggle-room margin if the house load rises slowly or the solar drops to try to cut off the charging before house+car exceeds the available sunlight by too much.
You’ll never get 100% sun and no grid usage, as the sun can be blocked by clouds and the house load can rise and fall much more quickly (kettle!) than CHQ can react and adjust the car - but thats ok, its good enough to vastly reduce grid usage compared to trying to time it by hand.

And yes, I also use a ‘blackout period’ in CHQ to stop and override excess-solar charging during a known peak rate window.