Forum bmwbike.com

My 1953 R25 is having some charging problems.. I have a fairly new battery, regulator, points and wiring. I suspect the charge isn't correct during normal opperation and the battery is creating a mess (white powder everywhere). What is the process for checking the charging rates?

Thanks.

how much is the output voltage of the electronic regulator? is 7volts sufficient?

The white residue is dried salts of the sufluric acid electrolyte, and it indicates that the top of your battery is leaking.

I wonder if you have one of those black tar-top batteries? They tend to leak where the terminal posts penetrate the tar. They have hurt many bikes over the years.

Hi Allan,

I have a "Blitz"battery. I think I ordered it from Bob's. I suspected it leaks ( which it seems to always do) to either over charging (boiling?) or because it was overfilled? Is this common? My frame, muffler and battery holder are paying the price.

Batteries can leak if overfilled so there is not enough room for the electrolyte to slosh around. They can also leak if they are charged too heavily, by a powerful battery charger or perhaps by the generator with a malfunctioning voltage regulator, which makes the liquid bubble so that acid droplets can escape through the venting caps.

If your battery is black, with a soft material forming the top, with or without a hard plastic cover, then you have the most common cause of acid damage. You cannot see the liquid level in those batteries, so they are easy to overfill. And the tar does not seal perfectly around the terminal posts, allowing liquid to come out around the posts.

I prefer the modern clear plastic batteries by Yuasa. They show the liquid level, have plenty of air space above the liquid, have good vent caps that stop any droplets of acid from escaping, and do not leak around their terminals.