Technically, like most HEV, the car has several modes, driving electric, regenerating during braking, driving and charging in various combinations (drive done by low speeds by the electric engines and petrol only charging, petrol driving wheels and charging), and finally, at higher speeds, petrol only. Basically the same a Toyota Hybrid does, though the differences are in detail: the MG uses a 3 speed torque converter automatic, whilst the Toyota system uses a planetary gearbox called eCVT, that in allows for in theory infinite combinations of ICE and electric engine, though the various gearings still mean that above a certain speed, propulsion is mostly done by the petrol engine, and the electric engine whilst being able to maintain speed and accelerate a bit, is used less than in the MG (the Toyota systems also use a smaller battery); That said, the conventional gearbox limits somewhat the combination of scenarios in the MG, even though it makes for a slightly more linear driving feel at higher speeds, as revs tend to build "as we know it", something that eCVTs have often as their weakness. It is also to be noted that the gearing of the engine to gearbox means that below (i believe approx. 40ish km/h), the MG uses exclusively the electric engine to drive, either on battery or on "generator" mode. because the maximum charging the MG can do is 45kw, it also somehow limits the max power at these speeds, meaning that once the battery is empty, the car has basically 45kw at its disposal, which naturally means that starting from a hill or launching feels very sluggish. The other thing is that 3 speeds naturally mean that there are quite considerable differences in engine RPM per gear, and the power differences in every day driving filled by the electric engine and also support the ICE, and that is when it really feels powerful, which works very well as long as the battery has some charge (and the gearing allows for electric support, thus somehow the gear box occasionally hunting for gears at European motorway speeds, particularly in combination with ACC. Another difference to many Hybrids is that the MG doesn't let you go into pure EV mode at the press of a button, just when it decides to do so. Maybe this is already an acknowledgment that running the battery too low is not ideal.
That said, the current update should in theory somehow mitigate the low battery scenarios by more often charging it, thus having maybe a tiny impact on economy, though again with a lower threshold, charging happens less frequent, but then for a longer period, as the top threshold seems untouched. The bigger impact will be on the EV only range, where the MG could claim a much longer distance than any other full hybrid. And it also means, that whilst power Loss will be less of an issue, there will still be scenarios where the system will reach its limits. Just less often.
Mind you though, every hybrid system has their limits (an Alpine road with my back then Toyota Auris Hybrid also left me with some power loss after a while and mostly screaming engine, and loss of regenative mode after a while, but it was a one time scenario in 5 years of ownership), some just are a little more polished thanks to the experience of their maker. And I will also point out, that despite living in the outskirts of the Austrian alps, thus hilly region, I had so far no power loss in my ZS, just the occasional high revs, partly I guess thanks to the ICE running a lot more in winter and thus having a similar "more charging less EV range" effect that the update is supposed to give.
www.mgevs.com
