I happen to have a Yamaha MT-07, whose battery has seen better days. As a direct consequence of this, starting the bike after a few weeks of sitting in garage is pretty challenging. Unmounting the battery is doable, but requires ~15 minutes of wrenching, which is not ideal for using the bike opportunistically (and has a very low WAF – Wife Acceptance Factor).

Luckily, there are a bunch of wires connected to the battery with a dangling connector on the side, hidden next to passenger pegs.

I also happen to own a BMW charger, which connects to my 1200 RS via a dedicated socket on the side.

After some research, the dangling connector on the Yamaha is called an SAE connector and the socket on the BMW is an ISO 4165:2001 socket, also colloqually known as hella plug

Technical considerations:

• the hella plug has positive (+12V) in the center and ground (0V) on the side. I don’t know if this is standard, but this is definitely my configuration based on a quick check with a voltmeter
• the SAE connector is symmetrical (one male plug, one female socket). On the motorbike side, the female socket is +12V.

With this new knowledge, a quick step to aliexpress gives the relevant connectors:

• Female hella plug
• SAE connectors

2 weeks of waiting, 15 minutes of soldering and proper isolation later, TADAM, the BMW charger is happily trickling and keeping the yamaha battery fresh