How to truly determine start battery condition. False sense of security

[Simi 60]

Just wondering how to truly determine start battery condition.

Our starts (2x 1000cca 12v @ 24v) are only for the engine and anchor windlass and have never given any hint of trouble in the 2.5 years we have had the boat but, about 18 mths ago I decided to run the "trickle charger" wire from our victron inverter/charger to these batteries so they are always 100% good to go...........or are they?

Is that trickle charger giving us a false sense of security?

The reason I ask this is our 12v genset battery has the little window with green circle and red centre indicating battery is OK.
Voltage indicator reads 12.6 and as low as 12.4 after sitting for several days yet when I put a battery condition tester on it (do they even work?) on it reads as battery OK but low charge.
Pre heating glow plug saps power out so not enough grunt to pull the fuel solenoid in yet there is still plenty of grunt for cranking.
A few minutes on a 4amp battery charger and all is good again quick easy start and voltage reads 13+v shortly after.
I could put a trickle charger on the genset battery as well and for less money and drama than getting a new battery and all we appear to be good but is that really the solution?

So, back to the title of the post "How to truly determine start battery condition?"

[smac999]

load test them. you need a load tester.

12.4 is a low charged battery. they should be 12.8v after sitting for hours after charging.

[Scott Berg]

We use both conductance testers by Midtronics and a Snap On carbon pile load tester. At a cost of over $800 each I don't expect a cruiser to have them in their kit, but every decent electrician will have similar tools and can do the test for either free (hoping to sell a battery) or very little. It takes me less than 15 minutes to test a two battery bank and that includes disconnecting and reconnecting the batteries.

As noted, a fully charged 12v FLA or AGM battery should show a no load resting voltage of about 12.7v

As an aside I replace our starting bank every 4 years just because (we get 7-8 out of our house bank).

Disclosure: I do this for a living but am not asking to do yours...

[Simi 60]

Thanks for the replies.
So it sounds like the genset one is on its way out if it slowly loses charge over a few days.

We only pull into a fuel berth for an hour twice a year so a near impossible task to get them checked until we come out of the water in a years time.

As a quick boost with a charger gets it up enough to start is their anything wrong with leaving a battery charger connected and plugged into a timer set to come on for 30 minutes at around 7am ready for a 7:30 start if required?

[ranger58sb]

Originally Posted by Simi 60

The reason I ask this is our 12v genset battery has the little window with green circle and red centre indicating battery is OK.
Voltage indicator reads 12.6 and as low as 12.4 after sitting for several days yet when I put a battery condition tester on it (do they even work?) on it reads as battery OK but low charge.

How old is your genset battery? Does the generator charge it's own battery? How long do you typically run the genset during a normal session?

Are your measurements at the genset battery, and after a rest period? Or a voltage meter somewhere else on the boat (with some potential voltage drop along the way)? Do you mean 12.6V immediately after charging? Or later, sometime? How many is "several days" when you're seeing 12.4V? Are there any other minor loads on your genset battery?

-Chris

[a64pilot]

A starter battery you can load test, not so much a house bank.
A load tester looks like and is a heater, just hold it until the heater element turns red and see if voltage drops much, if it doesn’t then it’s good.

[ottow]

A load tester to check high-current loads, like this one: https://www.harborfreight.com/100-am...ter-61747.html


And a AH meter and a timer/cutoff circuit to check actual capacity.
Here's a DYI variant that I've used myself:

https://www.youtube.com/watch?v=W-g6SGEXEfY

Set cutoff voltage according to your battery chemistry. I used 10.5V for my FLA which worked out nicely to about 50% capacity.

[hellosailor]

Simi-
When you mention a green and red circles, that sounds like the old Delco Magic Eye that was on the first "maintenance free" sealed wet acid batteries. That type of battery always has been junk. Because it is sealed, there's no way to restore electrolyte after overcharging. Because it is wet acid, that's routine maintenance you can't do. So you wind up buying replacements faster.

https://smile.amazon.com/OTC-3180-Ba...%2C173&sr=8-10

That's an old fashioned carbon pile battery load tester on Amazon. You can find plenty of the new electronic kinds (and plenty of debate about how accurate they might be) from $45-200 online as well. Load testing is the only way to really tell the condition of a battery, although you can come close with a *calibrated* digital voltmeter if you know when and how to use it.

12.6 volts can be perfectly good. Depending on the battery chemistry, 12.6-12.7 is actually as full as it gets, and 12.4 should be perfectly useable, the problem being that every 1/10th of a volt matters, and most voltmeters have more error in them than that. Don't mistake the use of lots of numbers, for the degree of accuracy. Plenty of older online threads going into that.

[Simi 60]

Has to be battery.
Battery is a yuasa, fluids are full, it was on the boat when we got her so every day of 2.5 years but could be 25 years or all I know.

Swapped leads to one of the 12v starts for the big motor, gave it a full 10 seconds of glowplug, turned the key, pressed the button, hear solenoid click and started instantly.

Put it back to old battery registering 12.6v and couldn't get solenoid to click.
Connect charger for a few minutes, volts at 13.1 and solenoid clicks and genset starts.

Sounds like this is to be my medium term solution

. As a quick boost with a charger gets it up enough to start is their anything wrong with leaving a battery charger connected and plugged into a timer set to come on for 30 minutes at around 7am ready for a 7:30 start if required?

I have 2 of the original 220ah agms from the mostly dead battery bank when we got her 2.5 years ago that tested OK when load tested then
I'll link them back up as 24v and get out the spare 60amp victron charger and see if they come back for a possible new lease of life as spare starts.

[hellosailor]

"but could be 25 years or all I know."
EVERY battery has a manufacturing date code on it. The vast majority of them use a code, as opposed to a plain date, and it is usually an inch or so down from the top, intentionally covered by the side label.
The code HAS TO be there so they can access it for warranty confirmation. But they hide and obfuscate it to prevent the customer from being bothered with these things. Or, from seeing the "new" battery they are buying has been sitting around for nine months. (Or longer, it happens.)
So if you get really curious, get a good light, check the top, then start to peel back labels and see if a code shows up. Usually heat stamped into the plastic, sometimes printed. It may be something like "2814" meaning the 28th week of 2014 but with some companies, you have to call them up and say "WTF does this date code mean?" and if the battery is old enough...then it doesn't pay to worry much, it may just be time to replace it. Likewise if the battery is newish, then it pays to look at testing.

[gmakhs]

If the starter battery fails I have the hand crank so not really bother with them , currently my service batteries are failing .

[Simi 60]

Originally Posted by hellosailor

"but could be 25 years or all I know."
EVERY battery has a manufacturing date code on it. The vast majority of them use a code, as opposed to a plain date, and it is usually an inch or so down from the top, intentionally covered by the side label.
The code HAS TO be there so they can access it for warranty confirmation. But they hide and obfuscate it to prevent the customer from being bothered with these things. Or, from seeing the "new" battery they are buying has been sitting around for nine months. (Or longer, it happens.)
So if you get really curious, get a good light, check the top, then start to peel back labels and see if a code shows up. Usually heat stamped into the plastic, sometimes printed. It may be something like "2814" meaning the 28th week of 2014 but with some companies, you have to call them up and say "WTF does this date code mean?" and if the battery is old enough...then it doesn't pay to worry much, it may just be time to replace it. Likewise if the battery is newish, then it pays to look at testing.

Checked them and engraved codes as follow.

Yuasa genset battery has D17LJ and D115c on it.
No idea whatsoever what that could mean and nothing found online.

Century main engine starts have Bat 1) KA2H13. Bat 2) KA2I19 (looks a lot more a 9 than a 3) but assuming both bought together guessing at a 2013 build

Yuasa spares for main still reading 12.6v are KA5E12 so guessing at a 2012 build.
These were the batteries being used when we got the boat and changed them over for the century's 12 mths ago for no real reason but to give them a run.

Seems the big batteries are past their use by date and i should replace when next on the hard.
They are still going strong and I have working spares.

[chasfgr]

Manufacture date probably May 2011.


https://www.yuasabatteries.com/wp-co...ode.x78244.pdf


Hope this helps

[Suliwar]

We use the following simple method to monitor our batteries: When leaving the boat unattended at the mooring, we always open all battery switches (positive-pole only) so that each individual battery remains electrically disconnected from the system and FROM EACH OTHER (making it thereby impossible for an eventually bad battery to damage the others during our absence). Upon returning to the boat, and BEFORE switching-on the battery switches, we first measure the open-circuit voltage of each individual battery.

Usually, if all batteries are fine, after a week (or more) at the mooring, we find voltage values between 12,7-12,9V. If all batteries show a lower value, we suspect we mistakenly left them partially discharged the last time we left the boat at the mooring.

Instead if only one of the batteries shows a lower voltage value, while the other batteries are fine, we suspect this to be a first sign of possible ageing of the battery showing the lower value. If same battery continues over time (months) to show lower open-circuit voltage each time we return to use the boat, sooner or later it will start showing also first signs of reduced capacity (such as the starter battery will show difficulty to crank the engine). Once this stage is reached, we usually replace the battery with a new one.

This simple battery management method allows us to replace house-bank batteries (deep-cycle type) every 9-10years, and the starter battery (commercial type) every 7-8 years.

[BlackHeron]

A load tester is the best and easiest way to determine a starter battery's health.

But before you freak out make sure your electrical connections are good. Check them at the batteries, the starter solenoid, and especially at the engine block ground. And by check I don't mean just look at them and say, "yeah it's connected and I don't see much surface corrosion."

You need to do a good wiggle to see if the crimps are loose and there is corrosion in there inside the crimped lug. You need to remove the bolts and clean the lugs to be sure they are not corroded. Sand the block where the ground lug connects with some emory paper or fine sandpaper. Put everything back together with dialectric, or better yet anti-ox grease or fancy battery lug copper grease.

Your symptoms sound a little bit to me like a bad engine ground. Also, you can have your alternator checked for bad diodes. Bad diodes be will give poor charging (or no charging) and in some cases actually discharge the battery slowly.

If the battery is a little weak you can always get a small solar panel and hook it up to just serve the starter battery. That will help you limp on a little longer.

How to check an alternator: (car/boat not much difference)
https://youtu.be/xgikeXt91vM