The Charge of a Lifetime
The Charge of a Lifetime
Shortly after I arrived at my first boat it went into the shipyard for a few weeks to get a new battery. When the battery was installed, each of the 504 cells had a random amount of charge in it. Each cell required a different amount of charging current run through it to bring it up to full charge.
But the battery was now all connected together, and there was no way to charge one cell individually. So we simply charged the whole battery until the lowest cell was fully charged. This required us to charge the battery at 1,200 Amps for twenty hours beyond the point where a "normal" charge would have been completed.
The battery was divided into four banks of 126 cells each, connected in series. These banks of cells were referred to as Battery #1 through Battery #4. Batteries 1 and 2 were connected in parallel to form the Forward Battery. Batteries 3 and 4 were connected in parallel to form the After Battery. The Forward and After Batteries were connected in parallel to form The Battery.
Several hours into the initial charge, we noticed that the After Battery was no long accepting any current, and all the charge was going into the Forward Battery. We discussed this at some length with the sales rep from the battery manufacturer, and with the battery expert from the shipyard. After several hours of this situation, the Engineer (our boat's Engineering Officer) decided that the After Battery needed more charge to catch up with the Forward Battery. We ordered the Electrician's Mate to trip out Batteries 1 and 2, and we proceeded to charge just the After Battery for six hours.
At that point the cumulative charge given to the Forward and After Batteries was the same, as measured in Ampere-hours. We switched the Forward Battery back into parallel with the After Battery.
The needles on every Ammeter in the panel swung over and hit the peg, unable to measure just how much current was actually flowing in the battery bus. All we knew was that energy was flowing from the After Battery to the Forward Battery at a rate significantly exceeding six megawatts, or more than 8,000 horsepower. It never occurred to the designers of our Maneuvering Room that we would need to measure more than 12,000 amps of discharge or 4,000 amps of charge on each of our four batteries. We panicked.
The only escape route was the single door, 28 inches high by 18 inches wide, that led to the After Torpedo Room. We all glanced quickly around the Maneuvering Room, and two of the eight of us headed for the door. After five seconds of eternity, the needles on the Ammeters began to swing slowly back off the pegs, toward the normal range.
We should never have tripped out those batteries. The cells knew, better than any of the experts did, just how much charge to accept. When certain cells were fully charged, they simply quit accepting further charging current.
After only one month aboard, I had learned an important lesson about listening to the "experts".