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Old 06-13-2021, 06:13 PM   #1
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Diagnosing a dying battery

Last summer, starting my generator was problematic, until I removed, cleaned and re-installed the battery end of the connections. I greased them after cleaning and sanding. Problem solved.
Recently, within the last month, I have had several tough starts on my starboard engine. The starter would engage, turn the engine one rev or less, then disengage and spin just the starter. After several tries the engine would start.
I checked the connections. Those are the same connections I had cleaned, sanded and greased last summer. All were good. I checked at the starter (+) and the block (-). Those were clean and tight.
The Port engine starts within 1 revolution. Both + and - cables to the port engine come only from the starboard engine, so I was thinking the connections are not the problem.
Voltage on the start battery was the same as on the house batteries, 13.4v with the charger turned off.
I suspected that a weak start battery should have as much trouble with the port engine as with starboard.
After some head scratching and discussions with some more electrically charged than me, I decided I would replace the start battery. This battery is younger than any I have replaced before on this boat, at only 6 years. I log those sort of things, so know that age for sure.
The new battery, going in, was only reading 12.7v and needed some water in all 6 cells. I tried it right away, and it was able to start the starboard engine on the second try. On the first try the starter engaged and spun the engine maybe one revolution, then disengaged. That was just like before.
I filled the cells with distilled water and left it on the charger for 2 days. Today, I turned the key and it started on the first revolution, just like the port engine.
Conclusions:
Measuring voltage of a dying battery needs disconnection and leaving for a while, or it will be a total waste of time.
Some engines need more oomph than others, even identical engines.
Some batteries last longer than others.
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Old 06-13-2021, 06:52 PM   #2
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Electrickery

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Old 06-13-2021, 07:37 PM   #3
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Try doing a load test on the battery. Battery should have a CCA rating. If the battery fails the load test at its CCA rating you have a bad battery. While bad batteries can stil start engines they are letting you know that some day they won’t be up to the job.
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Old 06-14-2021, 05:43 AM   #4
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Your starter has a device that allows the starter to disconnect from the ring gear after the engine is started , usually called a Bendex.

If the engine starts to start , reducing the load on the Bendex it can disconnect and let the engine go as you describe.

If the starter is easy to pull, swap with the other engine and see if the fault follows the starter.
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Old 06-14-2021, 07:45 AM   #5
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It might be worth doing a voltage drop test on the starter and cables. I did and found a bad cable from the battery.
There are several u tube videos that explain how to do this properly.
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Old 06-14-2021, 08:47 AM   #6
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posts 4&5 are both possibilities as the battery is now new and fully charged.
A temp battery + cable to starter would rule out existing cable or point to the starter.
Another is to parallel more than one battery to rule out battery, even the new one.
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Old 06-14-2021, 09:10 AM   #7
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Now I'm not an expert however this is what I've found. Temperature is key to early diagnosis of problems.

First I turn on the battery charger with everything hooked up/ all interconnected. Now I wait a couple hours.

Next I use my infrared thermometer and shoot each of the battery caps. If there is an outlier that battery is investigated thoroughly. I utilize 12v deep cycle lead acid batteries from Walmart, the group 27s if memory serves me.

You'll note I shoot the caps not the studs!!! Studs don't show the problem as early. Of course you know that if your positive post is green, that indicates overcharging...

I usually will see a 10 degree temp differential IF a battery is going bad. That battery top will be hotter than the rest.

As a matter of course, I shoot my Batts the first of each month. Every three months I separate and do all the proper testing. This is my stop-gap way of accessing my battery banks. I do run my boat on "All" incidentally.
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Old 06-14-2021, 09:18 AM   #8
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This is new info I had not heard before, must try.
10* difference between battery caps and does that point to issue at lower or higher temp cap? I suspect lower as that cell is not accepting full charge
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Old 06-14-2021, 09:27 AM   #9
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Given the symptoms described, I think you might have battery cables with cable ends that are failing. Itís at least worth a check. As you have noted, with the same battery starting both engines, the battery doesnít explain the difference between starting the two engines. The crimped cable ends are a corrosion point, sooner or later.

It will take two people, but measure the voltage across the starter terminals while cranking. It will be easier to do if you also have a way to keep the engine from starting so you can consistently crank it to get a good reading. Do it on both engines and compare the results.

Other power loss points are the solenoid contact points, and the starter brushes. Sending the starter out for a test and rebuild might be good preventative medicine. Or just replace with new, depending on costs.

The bottom line is that I donít think the new battery has fixed the problem, only masked it. Itís going to come back.
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Old 06-14-2021, 10:09 AM   #10
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Thanks everyone for your thoughtful contributions.
I too see this as a process. I think the ease of starting the port engine, which is last in the connection chain, after the difficult star of the starboard engine, eliminates the connections at the stb from being a contributor. The starter brushes, of course, can still be weak and now overcome by a stronger battery.
Shooting the battery caps is a new approach, at least to me, and I already have a temp gun aboard so that is an easy addition to my tools.
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Old 06-14-2021, 04:24 PM   #11
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Quote:
Originally Posted by Soo-Valley View Post
This is new info I had not heard before, must try.
10* difference between battery caps and does that point to issue at lower or higher temp cap? I suspect lower as that cell is not accepting full charge
Aboard Seaweed I see the outlier as hotter. That is the battery with an issue. And it is generally only one or two caps that are hotter, not all of them on a battery.

Please note that this is a rough and ready check. Every three months presuming no hot spots, I load check each batt. I also check the voltage in each cell, again seeking inconsistencies.

Here's how I do that: First I remove caps from battery, verifying levels inside are okay. Then with multimeter, I place black ground probe on negative stud of battery. Then I stick red probe in each cell. If any differ by more than .1 or .2 from the rest I pay attention to that batt. When I see the discrepancy within three months the batt will fail.

The bad cell will have a lower number.

Yes, I know you're supposed to buy all your batts at the same time. I'm on a budget and though I match size and type there can be a couple three years difference in the ages of batts in my banks.

Anyway, that's my experience. Real experts know far more than I as to the whys and hows of power. These are what I do aboard Seaweed.

I know the smart fellows use hydrometers. I don't understand them so utilize the methods described...
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Old 06-14-2021, 04:55 PM   #12
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Janice, I find your MacGyver approach to be quite acceptable using the tools at hand and showing us that it works. I have a hydrometer and an infrared. The latter will be used next opportunity to establish a benchmark.
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Old 06-14-2021, 05:01 PM   #13
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For the OP, yes more checking is needed to be sure you have the root cause, and swapping the starters could be worthwhile as part of that. The old battery being able to start one of the engines easily suggests to me it likely still had reasonable life left in it.

I think Janice is spot-on for picking a failing battery. I replaced my AGM house bank late last year after 2 of the batteries displayed elevated temps on charging, a month or so apart. Subsequent CCA testing of the bank indicated poor health of the removed batteries also. So even though those simple testers have their limitations I believe they have some value where the batteries are able to perform deep cycle as well as start duty, in my case Odyssey PC 1800FT.

On one of the batteries getting elevated temp on charging (compared to the others in the bank) the case started to bulge at the sides. It was out of there ASAP once that happened!
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Old 06-14-2021, 05:54 PM   #14
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Regrettably, the path chosen is now irrevocable.
$260 battery, $54 core charge, recovered the same day.
No load tester, nowhere to buy one here on Saltspring Island, nobody I know has one to borrow. If I already had one, I would use it. For a one time use, I am not sure I would buy one. Having looked at the U-tube videos of some of them, I don't think the cheaper ones are worth while and the expensive ones are.....expensive.
My battery going out after 6 years is really no surprise, though its immediate predecessor lasted 10 years. I doubt they were the same brand and kept no records of brand name or cost. If I have similar problems within a shorter time with this one, I will do some more to find the root cause, like swapping starters. Until I have more problems of this sort I will not do any further investigation of root cause.
Thanks all for your thoughts.
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Old 06-15-2021, 12:41 AM   #15
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Load tester for cheap: in the automotive section years ago I found a car trouble light. It came with a cigarette lighter plug. I removed that plug, split the wires, and added battery charger clips.

With the batt being tested separated from the rest, I clip on the light. My battery will fall .6 or so... so from 12.7 to 12.1 (give or take)

A bad battery will continue to drop. When I remove the light a good battery will come back to starting point. A bad battery will not recover. It is immediately removed from my system.

Anyway, the "trouble light" is what I use as a load tester. The bulb in mine says it is 1 amp.

Anyway that's what I do.
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Old 06-15-2021, 05:09 AM   #16
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Most folks already have a volt meter , some stores even give them away as a promotion.They are far more accurate than the normal ancient volt dash meter

It is easy to wire thin wires from the engine ground point and the starter input to the dash. This would give a place to watch much of the electric system , from everyday starting to seeing how the batt set is being charged.

A SOC meter is great for the anchor out cruiser , the voltmeter would be a useful addition for even the day cruisers.
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Old 06-15-2021, 07:10 AM   #17
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Quote:
Originally Posted by koliver View Post
Thanks everyone for your thoughtful contributions.
I too see this as a process. I think the ease of starting the port engine, which is last in the connection chain, after the difficult star of the starboard engine, eliminates the connections at the stb from being a contributor. The starter brushes, of course, can still be weak and now overcome by a stronger battery.
Shooting the battery caps is a new approach, at least to me, and I already have a temp gun aboard so that is an easy addition to my tools.
Not sure what you mean by "last in the connection chain". I would think both engines are pretty much the same from battery to starter etc. with no connection from one to the other except grounding.
PS - It always amazes me how much I learn from battery discussions. Been at it over 40 years and learn something new all the time. Amazing how complicated a plus and a minus can be. Never thought of the stuff Janis142 posted, but sounds like good techniques.
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Old 06-21-2021, 10:17 AM   #18
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To reduce battery post and cable corrosion -- and increase conductivity at grounds -- I like the PermaTex product engineered as an anti-seize lubricant.
It has copper threads.
I think that offers greater conductivity compared to a non-conductive grease such as di-electric.
.
Part number -- 39772
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Old 06-22-2021, 02:31 AM   #19
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To reduce battery post and cable corrosion -- and increase conductivity at grounds -- I like the PermaTex product engineered as an anti-seize lubricant.
It has copper threads.
I think that offers greater conductivity compared to a non-conductive grease such as di-electric.
.
Part number -- 39772
Dielectric makes no sense to me when copper-impregnated anti-seize compound both PROMOTES conductivity and protects in the same manner as Dielectric grease. KoprKote is the brand I use.
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Old 06-24-2021, 09:35 AM   #20
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Update:

With a brand new battery, now only 2 weeks old, the Sb engine continued to start well, with none of the symptoms that saw me replace the start battery, until now. Once again, the starter engaged, then disengaged and spun. Trying again, the engine started right up.
What does that tell me? That the extra energy available in a new battery is enough to overcome whatever is the actual weakness in the starter system.
Now, what could be the real culprit? I suspect the starter itself, but removal and sending it out is not going to occur until after this cruising season is over, unless there is a total failure. Stay tuned.

On a similar, but different issue, two things:
1 - my handheld, that I take with me in the dinghy, comes on for testing, but doesn't stay on for long.
2 - my Raymarine Autopilot remote, that I use when driving from the flybridge, comes on adequately and stays on, but won't accept a command. When I press any button, it shuts down. That behaviour is awkward, if I want an instantaneous response.

Costco to the rescue yesterday. A new pack of AA and AAA batteries.
Testing the existing batteries in both the radio and the AP yielded similar results, over 1.5v on each individual battery, for over 9v total in the radio and over 3v in the AP, but when new batteries installed, both returned to flawless performance. The radio now tests to over 10v. The AP doesn't have any place to test the batteries "in place", just works as it should.

Now I am looking around the boat for other things using batteries that are testing within spec, but not as strong as brand new.
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