I returned to my boat this morning to find the house battery was dead. I left things on for five days. I ran the engine and the house battery seemed to be taking a charge. It does not have a start date on it. The engine battery is still going strong with a start date of 2012 written in Texta. When do you suggest I replace these two?

I can call in the morning and run through a few things.

Simplest first test for a typical liquid lead-acid battery I use is to fully charge it and immediately afterwards check voltage (anything from 12.6 to 13.2volt is ok).
Now let it sit overnight (unloaded) and check voltage in the morning - if it's below 12.0volt, I give up right away.
If above but not close to 12.6volt, I might try more stuff (discharge cycling, de-sulphation charger etc.).

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Karsten said..
Simplest first test for a typical liquid lead-acid battery I use is to fully charge it and immediately afterwards check voltage (anything from 12.6 to 13.2volt is ok).
Now let it sit overnight (unloaded) and check voltage in the morning - if it's below 12.0volt, I give up right away.
If above but not close to 12.6volt, I might try more stuff (discharge cycling, de-sulphation charger etc.).

Thanks for the advice.
My progress is:
I removed the AMP-TECH 12Volt 55AH from my boat and charged it overnight with a CTEC 7.0 battery charger.
It is showing full.
I then went to the bunker (underground storage) and found two ODYSSEY Extreme PC925 batteries. I charged one and around twenty minutes latter I noticed it was showing full.
The ODYSSEY Extreme batteries were removed from a helicopter at annual service. They were tested with a charge of greater than 80% up to 89% in 2017.
Because the AMP-TECH battery weighs 26 Kilos and the ODYSSEY battery weighs 11 kilos I intend to use the ODESSY battery if it has successfully charged. I expect so and will follow Karsten advice and check both tomorrow.
Do you agree with my plan?

It's not really a good thing when old batteries reach a full charge after 20 minutes with a 7 amp charger!

Nice battery .. Odyssey are my favourite non-lithium battery.

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Ramona said..
It's not really a good thing when old batteries reach a full charge after 20 minutes with a 7 amp charger!

Yep, it generally means the battery has lost capacity.
As batteries age, the available surface area of the lead plates is reduced by sulphation ('gunk') reducing the amount of energy it can hold.
From personal experience, I had a 140 Ampere Hour battery (AH) reduced to 10 AH - so it charged and discharged very quickly.

Someone once told me that if you take such batteries to a battery supplier they can put a very large power burst through the battery and "blow'' the gunk off the plates, restoring it to normal use. Is that a fact ?.

My 'smart' charger has a button for a de-sulphation option that does this, i think by pulsing a high current as part of the program. I know it works for 'wet' lead batteries, but can it be used on AGM batteries? I've never tried it for fear of damaging them.

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Azure305 said..
My 'smart' charger has a button for a de-sulphation option that does this, i think by pulsing a high current as part of the program. I know it works for 'wet' lead batteries, but can it be used on AGM batteries? I've never tried it for fear of damaging them.

De-sulphation is stage one on my charger.

Lets see if I have this right, you seem to think that an old secondhand battery, weighing half or less that the failed battery, will perform as well as the old battery did??
Lead deep cycle batteries are by their nature heavy, because they have more lead in them than start batteries, the very lead that provide the deep cycle performance.
John, surely you can't be serious??
Suggest that you have a conversation with a knowledgeable battery vendor.!!

BB, a 9 yr old start battery and a failed small house battery, save your self some pain and embarrassment,buy 2 new batteries from a recognisable manufacturer

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woko said..
BB, a 9 yr old start battery and a failed small house battery, save your self some pain and embarrassment,buy 2 new batteries from a recognisable manufacturer

i agree that it's not worth the potential pain of having one (or two) suspect batteries in a dual-battery setup. 9 years is getting up there for a start battery.

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Bundeenabuoy said..

Azure305 said..
My 'smart' charger has a button for a de-sulphation option that does this, i think by pulsing a high current as part of the program. I know it works for 'wet' lead batteries, but can it be used on AGM batteries? I've never tried it for fear of damaging them.

De-sulphation is stage one on my charger.

On mine its a separate option with a separate button, that's why I'm not sure about using it.

Generally, if a suspect battery of mine passes the overnight test (resting voltage > 12.5v in the morning), I would next be encouraged to do a simple load test to see whether it still has guts.

For a start battery - simple: how many times will it start my engine in succession?

For a house battery, I take the fully charged battery and load it with a simple resistive load and see how many hours it will drive that load without flinching.

To me, a convenient load could be a car headlight bulb (often rated 55watt) that would draw approx 4Amp. But there are many alternatives. If the battery drives this bulb at full brightness for 20 hours, the battery is good for 80 Amp-hours.

Compare that figure to the original AmpHour spec for the battery - if it comes up close to original, I'll keep using it despite age.

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UncleBob said..
Lets see if I have this right, you seem to think that an old secondhand battery, weighing half or less that the failed battery, will perform as well as the old battery did??
Lead deep cycle batteries are by their nature heavy, because they have more lead in them than start batteries, the very lead that provide the deep cycle performance.
John, surely you can't be serious??
Suggest that you have a conversation with a knowledgeable battery vendor.!!

+1

You can do all the tests recommended above but unless you have a proper battery tester you won't know.
Two weeks ago my modern car had a flat battery. The battery is only 2 years old, top of the line from NRMA. I thought a door had been left ajar or something similar causing it to discharge.
I charged the battery overnight. It tested perfectly the next day using the above methods.
It worked ok until last Wednesday, flat again. NRMA man comes out with a tester the size of a suitcase. He tests the battery and it was knackered. Usually it is a cell failure that causes this sort of problem and a cell failure is what you will pick up with the normal tests.
In this case it was another failure in the battery. Replaced under warranty.
A new 120 amp/hr battery will cost maybe $300. An old battery is a recipe for failure.

You do not want to be out on the water with a flat battery. If you're going to mess around with suspect batteries, make sure you have a generator and charger on board and/or a lithium jump starter kit as backup. You're planning on taking your boat north? Factor in waiting outside a bar for a night, masthead and nav lights on, maybe using radio or charging a phone. Are you going to run the motor all night? A reliable battery setup is non negotiable.

failing start batteries often come as a nasty surprise as a nearly dead battery might be able to get your motor to fire once even though it is nearly kaput, which often conceals the fact that the battery is getting close to failing. this is in comparison with a start battery in good condition which should be able to fire your motor many times before running out of juice.

My must have list for leeshore sailing ...
- a good battery and charging system;
- a good engine (iron or sail); and
- the ability to steer.

I had 2 batteries out of a 4 battery bank start to die. I ended up with less than a quarter of the usual Ah as the other two batteries were trying to charge the two naff units, which is an exercise in futility. I isolated the two suspect batteries to get home and got the proper 50% of Ah.
Even though it hurt the wallet, I replaced them all . No battery power has that nasty cumulative knock on effect, comms, instruments and lights. Most things you can fix , but it's really really hard to Macgyver a suspect battery to nominal working order when you're offshore.

I have a reading of 13.17 volts in the recharged battery that I took off the boat. I am getting a hand putting it onboard this afternoon. While my engine battery is fine at the moment, I plan to replace both house and engine batteries when I am next on a berth in a couple of weeks.
Thanks for your help.

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Bundeenabuoy said..
I have a reading of 13.17 volts in the recharged battery that I took off the boat. I am getting a hand putting it onboard this afternoon. While my engine battery is fine at the moment, I plan to replace both house and engine batteries when I am next on a berth in a couple of weeks.
Thanks for your help.

Good move John.

Spent (too much) time operating the tractor over the weekend and remembered a situation that might save some trouble for members. I replaced the 900cca start battery on the tractor after about 6 years of infrequent use, which is a similar situation to a boat. After about 18 months with the new battery, one day it wouldn't start so I charged the battery to 13+v and tried the next day with the same result. Went over the obvious connections with no issues identified, so attempted to jump start with my diesel ute with no result. Eventually (months later) I bit the bullet and got an auto electrician out, he tested the starter circuits and didn't find anything wrong, the battery load tested at 8 amps so that was the problem. He asked if I had tried to jump start the engine and I said yes but with no success which was strange to me. He then took the leads of the tractor battery and jump started it with his ute, if fired up straight away.

Learnings: 1. Apparently if you have a collapsed battery you probably won't get enough amps to start the engine if the battery is still in the loop. 2. If you have a problem with your battery get it checked straight away rather than wait until the warranty is expired .