January 2001: The Acid Horror

On the morning of January 23, 2001, I looked down at my garage floor as I backed the Lectra out to go to work and saw the unmistakable sign that something had been very slowly dripping from the left front corner of its faring.

What could this be? Or rather, was there any possible way that it could be anything but battery acid?

I ran back into the house and grabbed some baking powder, which I sprinkled on the very slightly wet stain. Fizz. Proof positive. This pretty much ruined my day. I had not been planning on replacing the battery pack for another couple of years. I did not want to see what I was sure was inside the faring. I was imagining hairline cracks in the battery case, requiring me not only to immediately buy a new battery but also giving me a brainteaser in terms of transporting a leaky battery.

So finally, tonight, I rolled up my sleeves to face the horror within. Below, for your amusement, is a picture of what a Lectra looks like with the faring and seat removed:

By the way, that is not the side that the acid was dripping from. The first piece of good news was that the dripping was not coming from a crack in the side or bottom of the case, but was seething out of (in the picture above) the far electrode of the rear battery on the top of the battery pack. If you look closely you can see the little brown stain. Below is a detail of that stain:

So, not a tremendous amount, but one that caused me some worry. It implied that what might be malfunctioning was the charger, possibly overcharging the battery. Putting my hands on all sides of all four batteries increased this suspicion: the leaking battery was definitely the warmest.

I went inside to have some supper and put the kids to bed while my subconscious pondered the various possible causes of this problem. A memory returned: when I was taking off the protective caps from the top two batteries in the battery pack, what seemed to be a loose wire fell out and dangled. I was alarmed at first until I saw that the wire was not broken, but was actually terminated intentionally in a small black flange. The other end of the wire led into the charger (which is under the seat).

Of course! The wire must be a thermocouple! It must provide feedback to the charger to warn it when the battery pack is getting too warm. Except that the wire must have worked its way into a slightly cooler region and so was telling the charger that the batteries were cooler than they were, making it dump more voltage into the batteries, eventually making the electrolyte in the battery above seethe and spill over.

Confirming this hypothesis was my memory that over the last month or so, the charger had seemed noisier than usual, even when in the garage. What causes this extra noise is an extra fan that kicks in to keep the charger cool when it gets too hot charging the batteries. The normal cause of this is when the bike has been run long enough that the batteries are almost depleted and the charger has to fill them up quick.

Yet I was hearing this extra self-cooling noise after a long quiet night in the garage. I had dismissed it as the work of the charger keeping the electrolyte warm and liquid during our recent cold snaps (a couple of Pacific storms had drifted in). Now I suspect that the charger was simply overcharging the batteries, heating itself up with the effort, and making one of my batteries boil.

So, to solve the problem, I decided to fasten the thermocouple to the hottest part of the battery pack, which by manual inspection appeared to be the top of the leaking battery, on the “high side” (opposite of the leaky side, which was on the side of the kickstand). I did this with a couple of pieces of inexorable duct tape:

Having done this, I cleaned up the battery, the inside of the faring, and the floor with baking soda and water. Plugged the Lectra back in again and put a paper towel under the “leak point” so that in the morning I can check to see if it worked. Some babysitting of the Lectra satisfied me that the charger was not spending time cooling itself, that all I can hear is the very quiet noise of a trickle charge. Time will tell if this was the actual solution to the actual problem.

In the meantime, I have some lingering questions about the batteries:

You can see what the answers to these to questions were, in the next entry…