Can Valen batteries be used in cars, motorbikes or caravans?

Which gives a supply reason rather than a technical one: No, and the reason is duty rather than availability. Automotive starting requires a very high current for a few seconds, which demands thin plates and high surface area, the opposite of the thick-plate construction that gives a deep cycle or standby battery its life. A starting battery in a cyclic application fails quickly; a deep cycle battery in a starting application will not deliver the cranking current. For caravan and RV house-battery duty, the requirement is a genuine cycling product, which is a different specification again from a telecom or UPS standby battery.