I have had the same experience with the milage. In the first year it was OK, but the milage has since just been fallling although the Reanaut garage gauge that my battery seems OK. Strange?
Wheel alignment, Binding brakes and Low tyres pressures all affect range. However the biggest killer is weather cold and wet are very bad for range.
You say you’re getting 23 miles out of your battery if you’re lucky. What do you typically get, which I presume is much lower than this? The first thing I’d do is to test the capacity of the battery. I’m an electronics engineer, so that makes doing this a bit easier. Once you know what the battery capacity is, and whether it’s below the level that allows for replacement of it, that may shortcut finding out what’s wrong.
You say that Renault has looked at the battery and there is no fault found. What were the test results of the battery capacity from those tests? Even a perfect battery, in a brand new Twizy will hold a slightly different charge to that stated on the spec for it. So, depending on the age of your battery, it will have a reduced capacity. You need to know that figure. By testing yourself, you will have a fairly accurate answer to the question before you get Renault to give you their figures. That way, you’ll know if they’re just making up the data to protect themselves. Get this information first, then you can narrow down what’s going wrong.
There are a number of other things which could shorten the battery life while driving, and these include, motor controller issues, stiffening of the gear train in the gearbox, poor bearing condition inside the 13kW motor. Motor windings being partly shorted internally due to insulation defects, wheel bearing issues, and the list goes on. All of these issues will lead to usage of power, but not necessarily in propelling the vehicle forward.
If you can prove that the battery capacity is the fault, which in my opinion is the most likely culprit given your experiences, then you will be entitled to have it replaced. If it’s not that, and your battery capacity is within good limits, then the problem lies in the way the car is using up that stored energy. This energy has to go somewhere, if it’s not giving you good MPG, so check for a HOT gearbox, motor and wheel bearings as a start, as these will be roasting hot if you chuck several kW of power at them…
I’ve rejected new vehicles in the past, and have been given brand new ones in return, even after 6 months of use. You just need to be fully prepared with all the data that Renault will try to defend, and have a cast iron case in reply to each of their reasons for not accepting your rejection, if it comes to that. I think you’re quite a way from being at the point of rejection, and need to go back to basics to get to the crux of what’s actually wrong with your Twizy first. Hope this helps…