I have searched for the answer on this, but cannot find anything related. Apologises if I have missed the obvious. We have had the S since mid December and until have been charging it with a 3 pin plug (16 A 4 kw). It hasn't been an issue as it does a very low mileage, typically less than 50 miles a week. Last week we had a Zappi charger fitted to coincide with the commissioning of our PV system. Initially I tested the Zappi on a fast charge and it put in 7 kw / 32 A as it should do. It is also very good at charging when sun is available and cutting in and out as required, albeit always at a slow state of charge (not a lot of Sun in the South of the UK this week!). Last night, as an experiment, to prove the system works, we did a boost charge over night during the hours of cheap electricity. It did charge at the correct times, but only at half the rate I was expecting, i.e. 16A / 4 kw. At lunch time today, I set the Zappi off on a fast charge and it was straight up to 32 A / 7 kw I left it for 20 minutes to prove it could do it, then stopped it (expensive electric time). The ambient temp was around 10/12 C. just now I thought I would try another overnight charge to test the speed, but before I did so I thought I would just check it was still putting in 7 kw / 32 A. Alas, no. Before charging it said 0/32 A. Once charging started it quickly went to 16/16A before ever going any higher. I stopped the charge, waited ten minutes and tried again. Exactly the same. Ambient temp about 2 C. Is slower charging at just above freezing normal, or is there a fault with the car or the charger?
Well, yes, if you start a charge and immediately look at it. It's probably still warming up the battery and may not begin charging right away in the first few seconds or minutes. But if you check it after 15+ minutes or so, it probably will be charging and maybe at a normal rate, because it has gotten to warm up some to get to charging without hurting the battery. Charging below about freezing point is harmful to the batteries, so the car won't let it do that until it gets to warm it up some. But on the other hand, I am not at all familiar with this Zappi connector. It sounds like it has some detection and intentionally scales its power up and down based on some factors? I don't know if that is operating correctly.
Last night it charged for 7 hours, but never went above 16 A. I would have expected the battery to warm itself in that time frame? I agree it may be the Zappi, but just wanted to make sure this wasn't normal model S behaviour before telling them they had a fault.