Battery Woes

The suspect is in here somewhere….

We have been in Bahia Los Tortugas (Turtle Bay) for the last couple of days after a 35 hour run down from Ensenada. We have a great story in an upcoming blog post with lots of pictures, but it will have to wait until we get someplace with better data connectivty. We had great Telcel phone signal, but no data here.

This is the first time we have anchored overnight in a month (since we were in Neah Bay). Unfortunately, when I got up the first morning to make coffee, I discovered that the battery voltage was unusually low. I realize that before I continue the story, I need to do a little aside explaining our electrical system and why low battery voltage is not a good thing…

Our boat has an electrical system based on large 12V DC batteries. These batteries power the electronics, lighting, water pumps, heads, etc, that all run on 12V DC, and in combination with an Inverter, also power 120V equipment such as the refrigerator, freezer, etc. The batteries (in what we call the “house bank”) are charged by chargers which run from shore power when we are at a dock or from a generator when we are at anchor. They are also charged by the solar panels that we installed recently. The bottom line is that the house battery bank is a critical system on the boat, and we carefully monitor the “state of charge” to make sure that everything keeps working as it should. One important detail here is that the battery voltage is a (rough) indicator of how fully charged the batteries are, and a fully charged 12V battery should read not 12, but 12.8 volts. If the reading is below 12V, as it was on this morning, that means that the batteries are either deeply discharged, or a warning sign that something is amiss.

Back to the story… we ran the generator to recharge the batteries and decided to monitor and record the state of charge data over the next 24 hrs to see if we could identify the problem. During the day, our new solar panels are working well, producing enough energy to keep up with the house loads (usage by the refrigerator, freezer, etc) all day. When the sun goes down, we start drawing on the house banks, and the battery voltage got pretty low by bedtime that night. The next morning, we were down to 11.5V. Clearly something was wrong.

Because our batteries are split up into two banks (they are in two bix boxes in the lazarette), I was able to isolate the problem by turning each bank off and observing the results. When I switched off the port bank nothing happened. So I turned it back on and switched off the starboard bank… and everything on the boat shut down. Clearly there is a bad battery in the port bank – so bad that the boat can’t even run on it. My suspicion is that the bad battery is creating a load within the battery banks, therefore drawing down all the other batteries. So, I disabled the port battery bank and started the generator to charge up the starboard bank. That bank charged back up, with voltage and other parameters as expected, so we think that set of batteries is still good. Therefor we are good to go, except with half our our battery capacity. We will need to conserve electricity usage and monitor the batteries carefully, but will have no problem continuing on down the coast to San Jose Del Cabo. Once we get there, our task will be to determine which battery (or batteries) is dead and figure out how to get a warranty replacement from the manufacturer.

Today (Wednesday, Nov 5th) we are underway from Turtle Bay to Bahia Santa Maria. It is a 30 hour run, and we have the same great weather (and fishing… also the subject of another post) that we had for the ride down to Turtle Bay. We expect to arrive tomorrow (Wednesday, 11/6) around 2 PM. We have heard that there is decent cellular data there, so we will be able to do some updates on the great time we have been having so far on the CUBAR Rally, Fishing, and enjoying Mexico.

2 thoughts on “Battery Woes”

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