Date: 5 June 2018. Diagnosing a Bad
has a boat that would not start. Because the engine turned over
weakly, he believed the batteries needed charging. Fortunately shore
power is available. Thus it was a simple matter to charge the battery
banks. Nevertheless there was a problem. Here's how I diagnosed where the
The black batteries are 8
volts each. ↑ These are the dead ones.
After 24 hours
of charging, the engines still would not start.
These are two 871's, Detroit diesels, naturally aspirated. Each
engine has a 32 volt battery bank. For the curious, that means four
batteries, 8 volts each wired in series.
regarding the preceding paragraph that I am parroting what has been
told to me. Real mechanics will understand. I am not qualified to
provide more than a cursory explanation at this point.
There are two
ways to wire batteries in a boat, either in Parallel or in Series.
in Parallel means the
voltage stays the same and the amperage increases. (connect + to +,
and connect - to -)
in Series means the
amperage stays the same and the voltage increases. (connect + to -)
Larger boats generally have bigger engines. Tug boats have powerful
This is the tugboat Charles M ↑
pushing a barge off Pensacola, Florida. No doubt the Charles M has
Let's get back to the batteries...
After leaving on the charger for 24 hours we again tried to start
the engines. Neither turned over.
The first task was the verify the battery charger was working. To do
that I took a multi-meter down into the bilges. These are 8 volt
batteries wired in series. That means that the positive terminal of
one batt is connected to the ground of the next. Done four times,
and voila: a 32 volt battery bank.
I should have verified the charger was working PRIOR to leaving it
on for 24 hours.
I drew a sketch of the batteries and where the wires
test that the Charger is charging:
On a battery bank wired in
series (positive to ground, versus positive to positive) you place
one lead from the multi-meter on a positive terminal and the second
lead on any ground in that bank. This will tell you how much power the charger is
putting into the batteries. For a 32 volt system the number
should read 36 volts.
I saw. I checked both the port and starboard banks. Both showed the
full 36 volts incoming.
When the charger was shut off however
the voltage fell back. There was
not enough power even with the battery charger turned on to start
There are several methods for identifying a bad
battery. My favorite is easy. I use an infrared thermometer.
This is mine. ↑ I
use it far more than anticipated prior to purchase.
During charging your batteries heat up. To figure out which battery
has a problem point the infrared thermometer at the top of each
battery. You are looking for one area that is warmer than the others.
That one will have a problem.
One battery had a cap that was
about ten degrees warmer than the others. On careful examination
that battery had a swollen top. Then I removed the cover. The
BATTERY ACID WAS GONE. That's bad!
There should be liquid in the battery. Good
maintenance would have spotted this before the battery was ruined.
I could clearly see that the inside was damaged. Because the 8-volt
batteries were several years old, the boat's owner elected to
replace all the batts in both 32-volt banks. Eight batteries in
total would be replaced. The first damaged one I slid out of the hole and lifted up
Then I discovered that indeed I
was too old for that sort of nonsense. Of course I knew that, but
this time it was going to be different. Because I'm special. And
these are just 8-volts not the bigger 12-volt batteries I have in
To be fair the owner did say
"don't do it" but I knew better. Sometimes, like a favorite
economist of mine... Well he said it best:
"Before you take on some big job,
full of confidence because you did it before, just remember that you
were younger when you did it before." Thomas Sowell.
So, I got smarter. And the owner hired the diver Levi to haul 'em
out of the bowels of the bilges.
Levi was kind enough to take those batteries out. Thank goodness!
And thank you again Levi. I couldn't have done it without 'cha.
Levi is the newest diver. He comes
once a month to scrape boat bottoms. Although hauling batteries out
of a bilge and replacing them again later is not his normal line of
work, he did so as a favor. That was right nice of him.
Now if you're in the St. Pete
area, I can say the young man has a good reputation over here. Levi
calls, comes when he says, and does do special projects... So far
there are three of us on this canal who have hired him to keep the
bottoms of our boats clean. He's detailing a vessel nearby later
Levi's phone number is 330-689-6652. Leave a text.
Eight old batteries, in the truck and heading for
Electro Battery in St. Pete.
So, if you've wondered what I've been doing of late, now you know.
More upcoming. On installing the new bank I made mistakes. Those I
will write about soon.
This was my first time working on
a 32-volt system. It was rather fun.
I'd love to hear when you decided hauling batteries in
and out was a job for youth.
And, what battery voltage(s) do you have aboard your boat?
In the Bilges,
Voltage Meters for the Batteries ~
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