Osbrook: sorry for not understanding/remembering, but could you remind me about the £2700 and £3700 cost? Is £3700 the cost for a new battery and £2700 if you buy it from Renault after 10 years?
Also: today I actually spoke to a Renault mechanic that has changed a battery and he said that if you change a charger unit, then you need to re-configure it before it can work. However, if you change a battery, you do not have to re-configure, so this means that you could buy a separate bms and just connect it to whatever cells you can get your hands on (ofcourse, they need to be able to handle up to at least 4,1V/cell or down to 2,75V/cell).
If someone wants to build their own battery I can sell Leaf modules for £40-50/pc. For the same capacity as the standard Twizy battery you will ned 14 modules which will cost £560-£700. Including bms and box it will probably require an additional £1500. The benefit with leaf cells however is that YOU WILL be able to fit an additional battery string of 7 modules and still have room left for BMS etc. That will give you approx. 50% larger battery! So if you want to be able to travel 60miles (with your own battery) instead of standard (rented) 40, this could be an alternativ