May 22nd -Port McNeill - Batteries

A post with probably more information about batteries than you want to know but in case you are wondering about on our ongoing problem, here goes.

We have three sets of batteries on board.  Set one is the main engine start and bow thruster bank. They are two sealed (i.e., low maintenance) 4-D's (about 100 lbs a piece) . Set two is a small Group 27 (car size) AGM dedicated to starting our diesel AC generator (an Onan 5KW). The last set is the "house bank" which provides power for pretty much everything else on board. This is where the problem lies.

The house bank consists of four Meridian Northstar batteries (Boat Electric in Seattle which distributes them locally)  model NSB210FT. Each weighs 128 pounds, mostly lead.

Batteries are big chemistry sets. Ideally the reactions are reversible. In one direction you get electricity and the other direction you add electricity. 

The amount of electricity (i.e., power) you can extract from the battery is measured by Amp-hours (Ah).  Our batteries started with a capacity of 800 Ah (actually 840 Ah but that is more theoretical than actual).  In practice you should never extract more than half of a battery's capacity so our house bank should give us about 400 Ah.

Unfortunately, based on the voltages and battery performance, I'd guestimate that we aren't seeing much more than 200 Ah of battery capacity.  It is kind of like having the fuel tank in your car shrunk by 75%.  This reduced capacity means we have to run the generator or tie up to shore power much more frequently than we'd like or expect.

I mentioned that batteries are chemistry sets.  After talking with a service tech at Sterling Yacht Center in Seattle that installed the battery (and lots of others), he suspects that the battery may have "sulphated," a chemical reaction that doesn't reverse very easily and reduces your battery capacity. The sulphation may have resulted from insufficient use of the battery and too passive of a charging program.

Right now, we are following a protocol he recommended of a deep discharge followed by an aggressive recharge.  We hope this will restore some capacity.  In addition, we've ordered and are having air shipped from Seattle a Nanopulser (What is a Nanopulser).  Hopefully that will arrive today.