Forum bmwbike.com

Is it practical to charge the battery on my R50/2 using the plug beneath the seat which was originally there for sidecar lighting ? Was thinking it would be pretty easy to get a plug adaptor ("jack") and wire it up to my 6V charger. Then, rather than have to remove rubber strap and battery cover to charge, I could just connect the charger "jack" into the plug on the bike and keep the battery juiced up between rides. Is there any reason not to do this ? A diode or fuse in the circuit ? My laziness meaning I'll never check the battery levels again ? Your advice welcome.

I think the sidecar socket is connected to the lights, not to the battery. The socket becomes "hot" (receives power) when the parking light or headlight are on. If the socket is only connected to the battery only when the light switch is on, then I don't see how plugging a charger into the socket can charge the battery when the lights are off.

And I don't know what would happen if you plugged the charger into the socket while the lights were on. Even if this caused no damage, even the parking and tail lights would probably draw more current out of the battery than the trickle charger was putting in. But you could rewire the socket so it is connected directly to the battery, and use it as a charging jack. But it seems easier to put a proper charging pigtail on the battery, one that is made for the charger to plug into. That is what I have done with my three old bikes.

I would initially ask why you feel you have to charge your battery so often? If the bike is run regularly and the battery and generator are in good condition then it should remain fully charged without the need of attention - apart from checking the electrolyte level at regular intervals, probably something that might be neglected if you adapt the jack plug for charging.

Trickle charging the battery on a /2 works great through the accessery socket; I've been doing it for years. However I wouldn't recommend the socket for an initial heavy charge.

I must be mistaken in saying the socket is wired to the headlight switch, with the circuit to the battery only being completed when the switch is on.

I once had a sidecar on my R60/2, and I am trying to remember what happened when I inserted the power plug into the socket on the bike. I think the sidecar lights came on, meaning that the socket was always hot.

In that case, the battery could be charged from the socket, as you say.

My socket only goes hot when the lights are on.

I wired a separate connector for charging.

My charging system works well, but I tend to take short tips on the bike and the winter season gives me many weeks in a row that I do not take the old girl out.