Battery doubts

[westhinder]

I am having doubts about my service batteries. They were charged all day sunday and today they showed just 12.48 volts. Does that mean they are approaching the end of their lifespan? Age of batteries is unknown.
Any expert opinions?

 

[richardabeattie]

Charged with a smart charger to give them a proper fright?

 

[LionsDen]

Hi Johan

Have you run any electrical items from the batteries since fully charging them up - if they are left switched on then they will discharge a bit
I would try a batter load tester - btw how long have you had the boat for as this may assist in determining there age - can you also find any build dates on the batteries as these should be date stamped.

How many batteries and size have you on board!!!

Cheap batteries may only last 2 years for domestic use and more expensive ones a bit longer

 

[westhinder]

Hi Johan

Have you run any electrical items from the batteries since fully charging them up - if they are left switched on then they will discharge a bit
I would try a batter load tester - btw how long have you had the boat for as this may assist in determining there age - can you also find any build dates on the batteries as these should be date stamped.

How many batteries and size have you on board!!!

Cheap batteries may only last 2 years for domestic use and more expensive ones a bit longer

2 x 110 ah, charged by a Mastervolt smart charger when on mains, by a Sterling when the engine is running. I have had the boat for one and a half year, have not been able to check production date of the batteries. Apart from the volt meter no load was put on the battery after charging.

 

[VicS]

2 x 110 ah, charged by a Mastervolt smart charger when on mains, by a Sterling when the engine is running. I have had the boat for one and a half year, have not been able to check production date of the batteries. Apart from the volt meter no load was put on the battery after charging.

If fully charged and left standing with no charge or discharge for 12 hours a good battery should read at least 12.7 volts. It should take several weeks for the volts.
to fall below 12.5 if there is no load at all.

Worth charging and checking them individually perhaps . One might be good while the other duff.

A battery supplier should be able to test them using more sophisticated equipment than a "drop tester"

 

[William_H]

I would suggest that as said the batteries be isolated one from the other. Then put a discharge on each battery. An old car headlamp or 2 will discharge at about 4 to 8 amps. The wattage will indicate roughly the discharge current. 110AH batteries should give about 50 AH out to a load ie 10hrs at 5 amps before the voltage drops below about 11.0v.
Or just use each battery in service and see how they go. Using the above estimation method. A battery that won't give you the service you need is no good to you so replace. If its performance is still useful keep it.
I don't believe that the voltage after charge check will realistically tell you if it or they need replacing.
Another vital check is to ensure that each battery will start your engine. They are no good to you in an emergency if they won't.
good luck olewill

 

[VicS]

I would suggest that as said the batteries be isolated one from the other. Then put a discharge on each battery. An old car headlamp or 2 will discharge at about 4 to 8 amps. The wattage will indicate roughly the discharge current. 110AH batteries should give about 50 AH out to a load ie 10hrs at 5 amps before the voltage drops below about 11.0v.
Or just use each battery in service and see how they go. Using the above estimation method. A battery that won't give you the service you need is no good to you so replace. If its performance is still useful keep it.
I don't believe that the voltage after charge check will realistically tell you if it or they need replacing.
Another vital check is to ensure that each battery will start your engine. They are no good to you in an emergency if they won't.
good luck olewill

Checking the rested volts is a useful and easy first thing to check. If you cannot get them up to the sort of reading I suggest or if they loose the charge too quickly they are not likely to be much good.

 

[Tony Cross]

If they're not completely sealed your best bet is to buy a cheap hydrometer and check the specific gravity of each cell. That's the only sure-fire way of checking SOC.

 

[Plevier]

Doesn't sound very good but your only real check is a discharge at moderate rate as suggested by olewill.
High rate discharge testers don't really validate service batteries.
Open cct voltage and specific gravity will tell you the state of charge of a healthy battery, but can be very misleading on a battery that isn't healthy! Neither really tells you anything about available capacity.

 

[sailinglegend420]

....check the specific gravity of each cell. That's the only sure-fire way of checking SOC.

This is another controversial subject in the “electrickery game”, so care needs to be taken when using SG to measure SOC.

The SG of each cell at a 100% SOC should be about 1.265 with an open circuit voltage of – conveniently – about 12.65 volts! If the cells in the battery are not equal then an average of all cells has to be made. If individual cells are lower it means their Ah capacity is reduced due to sulfation from undercharging; temperature compensation also has to be applied to all readings. A value of 30 points lower indicates that the battery should be equalized.

For accurate results the SG must only be taken when the cells have been topped up with distilled water and then only after the batteries have been charged, this stirs up the electrolyte to give a true SG reading for each cell. Another major problem is the SG reading must only be taken when the charged battery has been allowed to rest with no charge or discharge for several hours. This is not very practical on a typical cruising boat, so the potential for errors can give poor results.

If the battery is known to be fully charged because it has been on shorepower for a couple of days then these SG readings will represent 100% charged. If these are all lower than the readings when the batteries were new that indicates they have lost some of their Ah capacity. Every time the battery is discharged and charged again these SG values will reduce very slightly.

So a lower SG reading than normal doesn’t only suggest that the battery is not fully charged, but it could also indicate that the condition of the battery is very poor - if the state of charge is known to be at 100%.

I use a BEP Battery Monitor and a SmartGuage.