Min / Max charge speeds, Non Tesla EV support & home battery integration

Dear Andrew,

We have received our EV and we have immediately created a ChargeHQ account.

I’ve still some questions, because a friend of mine as also subscribed to ChargeHQ but he as already installed the charger.

We have a Tesla Y and PV with SolarEdge of 11kw. For the moment we use the original EV charger, so the charge is limited to 2.4kw. We would like to maximise the charge with our electricity, so for me the problem will be more during the winter than in summer. During winter we have sold as extra production ~300kW, and the months before/after more than 700kW.

I’ve read your FAQ that are already full of interesting information. But I’ve still some questions…

So in details my questions are :

  • With our EV the minimum charge it doesn’t depend on the charger, but only on the ChargeHQ minimum, so it’s :
    • If with single phase minimum is 5A = 0.24 kW. And then improve 1 amps until the max of 32a = 0.24*32=7.68 kW
    • If with 3 phase minimum is 6a = 0.7Kw. And then improve each time 3 amps until the max of max 48amps = .24*48=11.52 kW
    • Are the minimum, increasing and maximum eventually different depending on charger properties?
  • We also would like that our charger could charge a non-Tesla EV (and this is the configuration of my friend). In this case the minimum charge will be the one of the charger. So, this is where I don’t understand:
    • In this case the minimum depends on the charger or it’s the same for all chargers? For example, for chargers (available in Switzerland) Pulsar Plus or Max, Zappi or ABB Terra AC Wallbox and installed with 3phase connection at which lower charge speed will they start to charge? Because our electrician told us that the minimum with the SolarEdge charger is 4.6 kW and with Zappi of 1.4 kW in single phase (without talking of ChargeHQ service because he didn’t know about it)
    • In your FAQ it’s written:
      • Some 3 phase smart chargers support both manual and automatic and switching to single phase charging to allow slower charging speeds. Charge HQ currently does not support switching smart chargers between single phase and 3 phase. (What is the minimum speed I can charge at?)
      • Charge HQ currently does not support switching smart chargers between single phase and 3 phase.
        • It is possible doing it manual (switch)?
        • Or only possible with inhouse system, and not using ChargeHQ?
      • Which charger supported by ChargeHQ manage manual or automatic switching from single phase to 3 (to allow slower charging speeds in winter period)?
      • What about Zappi (it’s the only one I understood could manage 1 to 3 phase switch when wired with 3 phase)?
  • Finally, we don’t have a home battery, but if in future we would ‘like to add one at our home system?

Thank you for your help in choosing the solution fitting with our needs!



Great questions, the answers are a little detailed but here goes!

Are the minimum, increasing and maximum eventually different depending on charger properties?

It’s a combination of both the EV and wall charger.

The minimum charge speed - for a Tesla EV, is governed by our app. 5A for single phase and 6A for 3 phase (2A per phase). For a non-Tesla EV, the minimum with Charge HQ (and other chargers to my knowledge) is always 6A per phase.

The increments - are the same for all chargers, and work per: Single vs 3 phase when EV charging from Solar, being 1A increments on single phase and 3A increments on 3 phase - see notes below re phase switching…

The max charge speed - is the lower of the maximum supported by the car, and the maximum supported by your wall charger.

Re single vs 3 phase chargers, with phase switching

For some makes of charger, the same charger can be wired either to one phase or to 3 phases. This is the case for the Telsa Gen 3 wall charger for example. For others, the single-phase version is a physically different charger to the 3 phase version (e.g. Wallbox chargers).

Some makes of chargers can do phase switching, i.e., they can be wired to 3 phase (with a maximum charger rate of 3 x 16A), but the charger can automatically switch to single phase (allowing a minimum charge rate of 1 x 6A) if you want to charge slowly from solar.

Currently - Charge HQ cannot tell a charger which is capable of phase switching to switch between 1 phase and 3 phase (or vice versa). It might be possible to add this feature in future but we won’t know until we attempt to develop it. There’s no timeframe for this work currently.

The only charger I’m aware of that we’re compatible with that can phase switch is the Fronius Wattpilot, but I don’t know if it’s possible to manually set it to single or 3 phase. This charger can only do solar charging when used with a Fronius inverter, or if used with Charge HQ. I believe the Wattpilot is based on the Go-e charger which works with other inverters and may be worth a look. I’m not familiar with the Zappi capabilities.

Regarding adding a home battery in future

Provided you add a supported battery, or connect it to a supported hybrid solar inverter it will work with any supported charging arrangement.

When used with a supported battery we can do some cool things like [Charge Priority Limit] (Home Battery Priority Charge Limit configuration) setting which is not possible using a hardware based solar EV charger.

I think you’ll end up with some form of compromise - a charger that works best now with your Tesla EV, or one that is more future-proof for supporting a different EV later.

As a user of the Fronius WattPilot with ChargeHQ on 3-phase power - with a BMW non-Tesla car, allow me to fill in some gaps:

  1. with the Wattpilot app I can switch the charger between 1-phase mode and 3-phase mode. I do this sometimes when I want to charge quickly and access the maximum 11kW rate my car can charge at (16A on 3-phase), but usually when I’m solar-aware charging I leave it in 1-phase mode so that there are smaller increments between amp-steps and it follows the solar curve more closely (each 1A step is 0.23 kW or so) - which maxes out at 32A = 7.3 kW charge rate.

  2. Minimum charge rate with the Wattpilot is 6A - on 1-phase this is 1.3kW, on 3-phase its 3x this = 3.9kW.
    Max is 32A - on 1-phase this is 7.3kW, on 3-phase this is 22kW, but most cars limit to 11kW anyway (including mine), and the difference between 7.3kW and 11kW isn’t significant if I’m charging overnight anyway, so I usually just leave it in 1-phase mode.

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Thanks you Andrew and Paul for your answers: very helpful.
To resume: the charger Fronius WattPilot allow switch via the app from 1 to 3 phase, and works with any VE and compatible with ChargeHQ.

@Andrew: what about the go-e Charger Gemini and compatibility with ChargeHQ? It’s not listed in the page of the supported, unsupported or incompatibles chargers EV Charger Support Register
Furthermore, you mentioned that fronius is based on the go-e : that means that go-e is also supported? This always needed with other VE than Tesla with which ChargeHQ communicate and works.
Thank you for your help.

@martino.bilello Re the Go-e, sometimes even though the hardware is the same, the software can be different. This is quite possible with the Fronius Wattpilot.

The Go-e charger is not available in Australia so we’ve not tested it. Some chargers will work automatically, but most will require some changes by us after testing.

@paul thanks for the details on the Watt Pilot - super helpful and great to know.