The car was a petrol model, which revved several thousand rpm, so the gearbox has rather low gearing for the electric motor, which only likes to rev 2000-3000 rpm. So when 1000 rpm equals about 35 km/h on the fifth gear, you end up with less than 90 km/h at 2500 rpm. Other factors include voltage sag, which may have an effect since I still only have single set of 60 Ah cells in, and the tires, which are now the stock 185/65R14.
I'll get more cells before long to keep the voltage as high as it can be and I also just today picked up these 15" rims. They're meant for a Peugeot 307, just like my daily driver, but should also fit the Xsara. Both vehicles are from the same parent company, PSA, anyway. I'll get 185/65R15 or 195/65R15 tires for them at some point. That should increase the top speed by some 10-15% as well.
I know, the rims have the Peugeot lion on them, instead of the Citroën logo, but as I said, they are made by the same company. Also I don't really care.
For a bigger increase in top speed I'd have to spring for a transmission from a diesel model, but changing transmissions... Well, not my cup of tea.