Granny charger

[Coulomb]

Found another voltage/SOC data point from a video, 389V @83%.

Ah! Thanks. That certainly seals it: it's a lower voltage battery. And presumably, these figures would be from the higher capacity battery. I suppose though that the video might be from a prototype vehicle that has a different battery configuration from the production model. But that seems unlikely. Perhaps the video was from a standard range prototype.

I wonder if the new voltage is related to the new motor it is using - it must be different motor mustn't it to be using a lower normal voltage range?

Sorry for the long winded response.

It's hard to say. A motor can be wound to any desired nominal voltage very easily: just add or subtract a few turns of copper wire, adjusting the wire diameter if necessary. So it depends on whether they are prepared to design a motor specifically for this model, or stick to what's available off the shelf. Similarly, I would think that it's easy to adjust the nominal battery voltage: just add or subtract a few cells. But batteries are in tight supply, so maybe there is less room to wiggle there.

My guess is that for this "refresh" they couldn't justify much re-design. So they wanted to stick with the 108 cell arrangement. Perhaps they have gone to LFP for both battery packs (long and standard range), or we really were seeing voltage values from the standard range model (it needed testing too, even if not released right away).

LFP nominal cell voltage is 3.2V. NMC is variously quoted as 3.6 V, 3.7 V, or 3.75 V. The latter seems familiar from something I read recently, not necessarily about a ZS though. If we roughly take the usual voltage for NMC as 350V plus 1V per percent of SOC, then 89% would be around 439 V. LFP voltage is much flatter, so a linear approximation isn't appropriate, but for the purpose of testing my theory, it will do. You'd expect the LFP 108 cell battery to be about 3.2/3.75 times the voltage, or 375V. That's not so very far off the 389 V you saw.

If we take the nominal voltage of NMC as 3.6 V (which seems to be the "non-marketing" agreed value), then it's closer: 3.2/3.6 * 439 = 390 V, almost identical to what you saw.

So that's my guess: the voltages are from an LFP battery. Now, can you also see the range remaining estimate in the videos, so we can guess whether it was a long or standard range model?

 

[Coulomb]

It appears like a step backwards to lower the voltage, I thought the future was higher battery pack voltages e.g. 800V so that they can be charged quicker on DC.

I agree. But if this was from the standard range model, it makes more sense: the standard range model is cheaper, and can make do with lower charge speeds. The battery layout and BMS electronics can stay much the same between the two models, only changing battery chemistry.

 

[Coulomb]

Just seen it: 350V at 40% battery (@ 2Amps).

That was your first new-model battery voltage data point. Using the same very crude maths: expect 40% of NMC to be 350 + 40 = 390 V. 3.2/3.6 x 390 = 347 V. It's spectacularly close again, closer than I'd expect with the crudeness of the approximations.