So last month I bought my first EV (Škoda Superb iV PHEV) and it comes with single-phase charging. I immediately noticed that the provided home charger will only draw 8A from my 16A fused phase supply (the main fuses are 20A).

OK, I can understand that: somehow the logic finds that full 16A would load the fuse a bit too much or that the phase as a whole is incapable of delivering so much current and thus reduces charge current to the only lower available setting, which is 8A.

But I have run into many situations where having the battery charged in 3 hours instead would give me more electric range. e.g. you come home from work, but have to go shopping later in the afternoon. Naturally this makes me want to have an option of charging the vehicle faster, but I also have a condition of future-proofing my purchase since wallbox prices hover around 1000€.

So I see my options as thus:

  1. Buy a charger that will be more adaptable to grid conditions and will charge at e.g. 14A if full 16 is deemed too much - should be relatively cheap.
  2. Increase main house fuses and the particular socket fuse so that the charger will recognise it as 16A capable - this one comes with added monthly costs because of increased capacity, even if the actual consumption is ultimately the same.
  3. Buy a wallbox that can fuse three-phases into a single phase.

I find option 1 a bit ridiculous: I already have a home charger and replacing it with a different one that would be a bit more adaptable seems somewhat funny.

Option 2 is risky and expensive long term. Risky because I have no idea what makes my home charger choose 8A over 16A. 25A main fuse & 20A socket fuse might not cut it.

So option 3 seems the best, especially if I want to future proof my investment (next car will probably be a BEV and will thus require a good wallbox). But I just can't seem to find a wallbox that would match my requirements. I found this one, but AFAIU, it's not future-proof as it ONLY does 3 phase to one phase conversion. It can't become a 11kW three phase power supply for my next BEV.

Do I expect too much of my would-be wallbox? Or has someone run into the same issue as me and built a true adaptable three phase wallbox that can, when needed, also merge the phases to a single one? Alternatively, build my own with the help of my better electrically educated friends?

Edit: clarification on the limitations I'm facing:

Currently my house is connected to the grid via 3x20A main fuses. This costs 15€ per month just to be connected + actual power usage. Increasing main house fuses to 3x25A would increase the connection cost to 20€ monthly + actual power usage (not to mention the change itself which would be a few hundred €).

The wiring I'm using is fully under my control, and currently I'm using 2.5mm2 wires that should be able to carry 16A. Can replace easily if needed.

The general idea with option 3 is to actually lower the current demands on the phases: if I only need 16A (max charging current of my PHEV), that means a bit over 5A per phase... I do realise that even future proofing the wallbox with a 3-phase-capable one would introduce the same issue with a true BEV with 3-phase charging capacity.

  • $\begingroup$ Check your vehicle if there is a setting that you need to activate that allows for higher charging. For my 2017 Chevy Volt PHEV using a lvl 1 EVSE and I plug it into a regular wall socket, it will default to 8 amps. However I can hit a setting that will allow it to draw up to 12 amps. It also comes with a warning to ensure the socket and wiring is able to handle a 12 amp sustained load. This setting has no effect on lvl 2 EVSE. $\endgroup$
    – Forward Ed
    Mar 10, 2022 at 21:38

1 Answer 1


I think it's important to note the difference between a charger (typically integrated with the vehicle) and an EVSE (electric vehicle service equipment) station. Today's EVs will have a charger installed that provides the EVSE with a maximum charge rate "request" or limitation.

A review of your vehicle indicates that one can get a 2.5 hour charge from a 7kW EVSE, but the review does not indicate the maximum charge rate that the vehicle will accept.

As an example, our EVs will accept up to a 10kW EVSE and charge more rapidly than from a public EVSE at 3kW and certainly more rapidly than from an ordinary house outlet EVSE device. Part of the US code requires that the 40A power draw from the EVSE be connected to a 50A circuit, meeting the eighty percent restriction.

Your example of an 8A vs 16A circuit would indicate that the EVSE will not provide more power than it is currently providing. Increasing the breaker limits may be in violation of local code and is dangerous as well. The wiring is likely to be matched to the breaker rating. Increased current will cause heating and related damage/risk to under-rated components.

Increase main house fuses and the particular socket fuse so that the charger will recognise it as 16A capable - this one comes with added monthly costs because of increased capacity, even if the actual consumption is ultimately the same.

I'm not sure how you can associate increased capacity as accruing increased monthly costs, as the charger on board the vehicle will not accept more power than is available, up to the designed-in limit. Having an outlet (socket) with greater capacity does not automatically mean more power will pass through it. I'm unfamiliar with utility regulations in your country and would be surprised if your rates are increased simply due to a greater capacity for an individual outlet.

Consider to determine the maximum rate of charge in kW that your vehicle can accept and match your EVSE to that figure. If you wish to future-proof your investment in the EVSE, increase the selected power level for that EVSE. That is to say, if your current vehicle will accept 5kW but you may want a Tesla in the future, install a circuit capable of providing 20kW and an EVSE to match, although I'm sure the expense will be substantial.

  • $\begingroup$ Updated question with clarification on stuff you found lacking $\endgroup$
    – velis
    Oct 16, 2020 at 17:58

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