By Adrian - Wed Nov 06, 2019 10:35 am
Here's what I came up with in the end.
I managed to find a super-dinky little battery. A ET4B-BS.
I also found you can fit a "tea caddy" air filter on either side of the bike so I've fitted one on the left instead of a battery box. The battery sits snugly inside half of it leaving the other half and the top compartment free to hide all the connectors for the regulators, coil, and rear brake switch in. Giving some weather protection and neatness. (an old type tea caddy with one "spout", I made a base for it out of alloy plate).
A little more controversially, I decided to stick with AC/DC but using a non-enfield headlamp switch. I have always found the original switch to be a bit on the shonky side, especially when it comes to going between dip and beam. Half the time I hit the wrong one (both are thumb sliders, difficult to get the right one with thick gloves/muffs) and turn the lights off instead of dipping them or the dip slider doesn't go fully home and turns the lights off. Either way, it's dark...
This is not simple but I came up with a relay system to use DC switching voltages to route the AC through. This isn't as daft as it sounds because it means the actual lighting power is going directly to the lights, not through the switch contacts which in my experience, lose a fair bit on the way through.
It uses two DPDT relays. I soldered them up and potted them into epoxy to make a "lighting unit" that fits in the headlamp shell. I can now use a nice allloy switchgear off a C90. You can even use the choke lever for the decompressor.