True Deep Cycle....great article link

[Frank]

"Heave Too" over on the Compac board posted this link.
Long read.....but very good!

http://www.pbase.com/mainecruising/deep_cycle_battery

[Norman]

Maine Sail is the best!  I worked for an Electric Utility.  The controls of our power plants and substations were battery powered.  This was absolutely essential, as the controls must keep working, no matter what the AC world does.

Our Excide batteries were 2 volt, 200 amp hour cells in SMALL stations, 800 to 1000 amp hour in large stations.

Cases were clear, and the space at the bottom to accumulate falling lead debris was large, space at the top relatively smaller, but still more than the deep cycle batteries that he cut open.  Putting the empty space at the bottom prevents cell shorts.  Space at the top keeps the cells submerged.  On boats with deep cycle batteries it is critical to keep the electrolyte at the proper level.  The more space at the top, the more water can be lost without damage.

At work, even with a large electrolyte space above the lead, the operator checked the specific gravity, and then added any water necessary to get to the mark, EVERY WEEK!

The first inspection each month was by a maintainance man, and also required a voltage check of every cell.

These checks were recorded in the station battery log, along with comments, such as a cell which is using more water than others, indicating a developing internal failure.

We also keep our cells spotlessly clean.

On a boat with "real deep cycle batteries" we should regularly check the water and add as required, otherwise, the top of the plates will sulphate and become useless.  If your batteries do not have convenient caps, they are not deep cycle.  Many 12 volt batteries have plastic covers that can be pried off sets of 3 cells to add water.  Do not over fill!  If yours are this type, it is very important to clean every trace of water or acid off the top of the battery before replacing the top.  At home, I wash and rinse the caps thoroughly, then dry them, before replacing them. We do not want an acid bridge between cells discharging a cell!

If you have not read it at M.S., the cells should be terminals to port and starboard, to reduce exposure of plates when heeled.

The batteries at work are true deep cycle, and maintained as we do, last 12 to 15 years.  We test them annually for remaining AH and replace them at 50% of nameplate rating.  At that point, the battery can supply all the controls of the station for 24 hours, giving adequate time to get a generator in to keep the battery charged.

I say it again, Maine Sail has all his facts straight, best advice around on boat related topics.

[Norman]

PS!  Those batteries were a total of 129 volts!  60 cells each battery!

One power plant had a total of 6 batteries, with a total of more than 5000 AHs at 129 volts!

They also have 2  15 million watt fast start generators to supply power to keep the plant supplied until conditions return to normal.  The plant itself had two 750 million watt generators.