Are my batteries knackered?

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bromleybysea

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I have 2 110 AH sealed service batteries. I fully charged them with a Sterling mains charger when the boat was in the yard but on the mooring I found that the battery monitor was reading less than 30%. when the engine is started, the monitor shows a charge of 40A but this rapidly (10-15 mins)falls back to less than 5 and according to the monitor will take 70 hours to fully charge! Voltage at the battery with the engine running is shown as 14.2 and at rest 12.5 though this drops away quite rapidly. After about an hours engine running the monitor shows 50% charge. The batteries are about 8 years old and have had a lot of use in that time. Given the eye-watering price of batteries these days I want to be sure that they need replacing before psrting with bthe thick end of £250. Thanks for any advice!
 
bromleybysea said:
I have 2 110 AH sealed service batteries. I fully charged them with a Sterling mains charger when the boat was in the yard but on the mooring I found that the battery monitor was reading less than 30%. when the engine is started, the monitor shows a charge of 40A but this rapidly (10-15 mins)falls back to less than 5 and according to the monitor will take 70 hours to fully charge! Voltage at the battery with the engine running is shown as 14.2 and at rest 12.5 though this drops away quite rapidly. After about an hours engine running the monitor shows 50% charge. The batteries are about 8 years old and have had a lot of use in that time. Given the eye-watering price of batteries these days I want to be sure that they need replacing before psrting with bthe thick end of £250. Thanks for any advice!
Click to expand...

8 yrs is a reasonable innings
the alternator is putting the correct voltage
try here for reasonably priced replacements
http://www.batterymegastore.co.uk/products/group/?c=Battery&a=Boat
 
Last edited:
bromleybysea said:
I have 2 110 AH sealed service batteries. I fully charged them with a Sterling mains charger when the boat was in the yard but on the mooring I found that the battery monitor was reading less than 30%. when the engine is started, the monitor shows a charge of 40A but this rapidly (10-15 mins)falls back to less than 5 and according to the monitor will take 70 hours to fully charge! Voltage at the battery with the engine running is shown as 14.2 and at rest 12.5 though this drops away quite rapidly. After about an hours engine running the monitor shows 50% charge. The batteries are about 8 years old and have had a lot of use in that time. Given the eye-watering price of batteries these days I want to be sure that they need replacing before psrting with bthe thick end of £250. Thanks for any advice!
Click to expand...
If you're asking - you probably have. Afraid you'll have to bite the bullet. You should be able to get replacements for about £100 each. £25 per year isn't too bad.
 
You can do a capacity test.
Fully charge the batteries
Put a know load on them about 10 A, ( for C20) but it's not critical.
Measure the time till they reach a vey low voltage say 10v they will drop rapidly near the end.
Multiply the time by the current. This is the actual capacity. If its 70-80% of spec they are pretty good.

Note I think your batteries are probably dead, but the test is easy to do.
The test is very hard on the battery, charge them up immediately even so it's likely to kill them if they are almost dead now, which is likely.

As others have said, the batteries have done well. What make and brand are they?. It's nice to know which batteries work well in the real world.
 
I thought I had completely destroyed my batteries by not checking the levels for 3 years and sailing in the med. I topped them up (took a lot) and hoped for the best. They were trickle charged throughout the winter via the solar panel and now seem as good as new. Is this possible??????? Maybe it can work for you though I don't know if you can manage a 6 moth trickle charge.
 
rtchina said:
I thought I had completely destroyed my batteries by not checking the levels for 3 years and sailing in the med. I topped them up (took a lot) and hoped for the best. They were trickle charged throughout the winter via the solar panel and now seem as good as new. Is this possible??????? Maybe it can work for you though I don't know if you can manage a 6 moth trickle charge.
Click to expand...

i believe that once a plate is exposed its capacity is diminished
 
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