I made my own extra Battery for my DS 2011.
What is great is that the voltage of these Molicells LiMn in 14s string is the exact same range of charge and discharge as the common 16s LiFFePO4 ebike battery
If you have a bit of skill + patience and courage you can make your own.. .or buy one from Ping battery. it will cost you about 1$ per Wh range
the 16s 20Ah battery from ping is about 800$ shipped and should give you about 15-20 extra km range at 50% city and 50% highway.
The zero is about 60Wh per km in that type if run ( i measured mine with accurate measuring device)
Adding a LiFePO4 battery that can hold about 40-50A continuous and have a higher internal resistance than the stock zero mattery should not be overloaded and the stock battery will take most of the load on hard acceleration . that extra battery will just give about 20% of the total power and will add like between 1/4 to 1/3 energy.
My stock 2011 DS battery that is rated " 4.4kWh" or... 3.9kWh nominal is in fact 3.0kWh measured with the calibrated cycle analyst i installed on it.
If you want max info make a search on the Endless-sphere forum or this forum with the words zero and doctorbass. you should find alot of non published and real world technical informations i measured and tested
Oh.. by the way even if you find the courage to mae your own extra battery, here is some inspiration for you
:
Myne will have 100 km range ADDED. and should have a bit more range than the ZF6 2012
http://www.endless-sphere.com/forums/viewtopic.php?f=10&t=47812&p=713926&hilit=zero+range#p713926Doc