L-16 "cycling" requirements? [RE-wrenches]

[Doug Pratt]

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Ok Windy, here's a battery horror story for you. And Jay, this is going to
answer your question about "fully" vs "semi" automatic watering systems.

About ten years ago the nameless large retail solar company I worked for
sold an off-grid 101 kW solar system to a commercial resort in Belize that
included a nominal 240 vdc battery pack of something in excess of 6,000
amp-hours. Yeeoowseers! Biggest battery pack I've ever seen by a wide
margin. If I recall correctly there were four parallel strings of 120 cells.
These were the largest commonly available traction batteries, probably 85-33
cells with poly cases in individual steel cans. Naturally, they had a
watering system installed. Sorry, I don't recall the brand, and wouldn't
mention it anyway because what happened wasn't their fault. The system was
nicely equipped with a series of filters, de-ionizers, and other hardware
that would take the ordinary tap water and turn out an almost endless supply
of "distilled" water that was gravity feed from a wall-mounted tank. All
very clean and professional. There was an electric switch that operated the
supply valve between the tank and the watering manifolds. The switch that
was installed to turn all this hardware on or off was a momentary contact
type. You had to hold it down to keep it turned on. Ohhhhhhh noooooooo...
guess what happened? *Nobody* is going to stand there for 10 to 15 minutes
holding down the switch, so a rubber band showed up...and within the first
year of service some one forgot to take the rubber band off. The "automatic
shut off" caps on three or four cells leaked slightly, and over several days
flooded the cells and eventually the floor. 

For the lack of a ($20) 15-minute, wind-up, no-hold switch over $2,000 worth
of batteries in a very difficult to reach country were lost, and there was
no real way to clean up all the acid under all the adjoining cells. Which
were showing the corrosion effects fairly seriously a couple years later
when I visited for service on other components. I certainly wouldn't trust
the bottoms of those steel cans to still be there in 20 years when the
batteries need replacement.

The moral of this story is don't install battery watering systems with
unlimited water supplies that can accidentally be left turned on. (All the
systems I know either have valves or plug-together bits which can be left
turned on, but they only have a 5-gallon supply tank that must be manually
refilled.)

Cheers,
Doug Pratt  



Wrenches,

Thanks for pitching with such useful information. I am lurking, and 
taking notes for the Battery Blunders article I'm working on for HP.

Keep up the conversation. Those of you who make significant comments 
will, of course, be credited in the article.

Stay positive and negative,
Windy

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