I really want to find a way to extend the charging cable so I can keep the charger safe and dry while charging the battery onboard the bike.
An extension cable doesn’t seem to exist sadly, but I have found one end of it here
https://www.outdoordreams.eu/Super-Soco-plug-with-30cm-cable.html
If I can find the female end I can make up an extension cable which will solve my problem, and if I can’t I guess the only option is to cut the existing charger cable and insert more cable with waterproof connectors. I’m a little nervous about cutting the cable though. What do you think?
I think it's the most easy and cheapest way to just cut the cable and add a more waterproof cable to it.
I would insert an extention cable (same gauge wiring) with waterproof connectors like you suggested. That way you can remove it when you don't need the length. Keep us posted with what you do. Photos too if you have!
I took the plunge and did it!
I saw this video on YouTube where a guy had split the cable but in his case it was to use a high power charger, so,that gave me confidence.
I bought some 2 core flexible cable and some connectors and just did it. It was remarkably easy. The 2 core cable on the charger had sheaths of brown and blue and the connectors were labelled L and N so matching everything up was very simple.
Now I can use it in short form (I still have to carry it to work until my 2nd battery arrives) and at home I can just insert the extension and charge up with the battery onboard. It all works beautifully.
Just make sure you put the female connector ends where there is any possibility of it being live, just in case, although I always use an RCD and make sure the power is off when unplugging and replugging.