You don't say where you are from, or any details about your chair.
The electrical infrastructure in Spain is 220-240 volts 50 Hertz. Make sure your wheelchair charger can handle that with nothing more than a plug adapter... (I'm in the USA and our systems are 120 volts 60 Hz and my Camino will be next year... I'm going to have to purchase a few new items before I go).
Another point... I looked up the chair name that was visible in the photo - Forcemech Navigator.
The info I found says it uses a pair of 6.6 amp-hour batteries. It does not say if the batteries can be field-swapped, or if a extra charger is available. Might be worth calling the company. Maybe they use a field-swappable battery pack?
If - and that's a big "if" - the chair battery is field-swappable then it might be worth carrying a second battery then swapping them when the first gets low. Then at night the chair charger can recharge the battery in the chair, and a second charger could simultaneously charge the battery that is not in the chair. This setup could double your daily range (or triple it with a third pack).
If the chair battery pack is not field swappable now then maybe the chair could be modified to make it so? There are a lot of e-bike battery packs that plug in, and your two 6.6 amp-hour batteries are smaller than a number of e-bike field-swappable packs.
History: over a decade ago I did a similar modification for a friend that was chair-bound due to an auto accident and spinal damage. His chair did everything he needed but his church was too far away - the chair battery got him there but died on his way home. There was room under the seat for a second battery, so I added one (the design of his chair made field swapping impossible). The added weight of the second battery limited his acceleration and speed but added 35-40% more range, which is what he needed. The technology back then was lead-acid, your chair uses lithium, and those are MUCH lighter and shouldn't have that problem.
Sorry to run on like this, but I'm a retired engineer, and in engineering details matter...
Buen Camino!
Mike