The Ctek D250sa is a 'battery to battery' (B2B) charger. Basically it does what other types of 'split-charge relay' do - it permits your alternator to charge your leisure battery when the engine is running, then isolates the starter battery from the leisure battery when the engine is off, so you don't run down the starter battery as well.
Connection is easy - at least it was for the B2B charger I bought - connect +ve starter battery and +leisure battery to the B2B unit (with correct inline fuses), plus an earth - that's it.
A B2B charger does an awful lot more than any other types of split-charge relay though. To start with they are compatible with variable output 'smart alternators' like the ones used on Mk8 Transits. Secondly, they 'trick' the alternator into delivering full output if needed, meaning they will charge your leisure battery about 5 times as fast as any other split charge system (and more fully). Thirdly, they deliver charge to you leisure battery in a correct stepped charge protocol, just like a mains charger, for maximum health and long life of your leisure battery
They are well worth the cost if you can afford them.
I note that the D250sa integrates with a solar panel as well, which is a bonus if you also want solar charging. Personally, I found that the B2B charger works so efficiently that even with a small amount of driving each day I don't need solar. If you plan to park and drive very little for several days, solar might be useful though.
I bought this one:
https://www.12voltplanet.co.uk/sterling ... v-30a.html They also do a'kit' where they supply it with all the correct rated cables and fuses. Easy!
https://www.12voltplanet.co.uk/split-ch ... asure.htmlIt's also worth having a mains leisure battery charger (to charge your battery when you are hooked up to mains on site, or when at home just to keep it topped up and in premium health. You might not need one though if you have solar - not sure.
Mains is straightforward in your van if you have a basic knowledge of household mains electricity. You just need a consumer unit (e.g. a 2 gang garage unit), then run a couple of mains sockets (and maybe a mains leisure battery charger) from that. You'll need a blue three pin camping socket built into your van somewhere, and some 16 amp cable to connect it to the consumer unit,