Batteries - 12.5v fully charged?

Tim Good

Tim Good

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Ok so since removing my solar panels which tends to keep the batteries 100% all the time and maybe masking the voltage they would normally settle at, I now get 12.4v -12.5v if I charge the batteries one evening and then come back the following day.

Would 12.4 or 12.5v be acceptable for a bank of 4 batteries after a charge the previous day with no load inbetween.

If no do I need to disconnect them all and test each separately?

I recon the batteries were replaced in 2012 with relatively minor use.
 
12.4 - 12.5 volts 24 hours after resting from full charge is a little too low I suggest, especially for new fairly new batteries.

I would test each one separately to see if one is dragging the others down.

12.6 - 12.7 is the minimum you should see and I have seen 12.8 - 12.9 under similar circumstances.

Also worth checking your voltmeter against a known voltage (a new dry cell perhaps) or trying another voltmeter just to be sure.

Richard
 
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12.4\5 is knackered in battery terms, load test them as ludd says check electrolyte if they are jiggered buy your new ones here cos they are cheaper than elsewhere suggest T105s cos the work hard longest

John
 
I don't disagree with previous responses, and I have no expertise, BUT my batteries give similar numbers to yours, have done for years, and yet they always start the engine first crank, and were load tested recently and found to be fine. (The load testing was done professionally, and the sparky would have sold me new batteries if they had failed - ie it was not in his interests to falsely pass them.)
I have checked my voltage readings with other voltmeters - giving same result (12.4v after 24 hour rest).
I know batteries can fail suddenly sometimes, but I am happy to do nothing for now (as per local sparky advice).
...not expressing opinion - just reporting my experience.
 
northcave said:
Ok so since removing my solar panels which tends to keep the batteries 100% all the time and maybe masking the voltage they would normally settle at, I now get 12.4v -12.5v if I charge the batteries one evening and then come back the following day.

Would 12.4 or 12.5v be acceptable for a bank of 4 batteries after a charge the previous day with no load inbetween.

If no do I need to disconnect them all and test each separately?

I recon the batteries were replaced in 2012 with relatively minor use.
Click to expand...

You cannot assume the solar panels charged to 100%, it could be 60 / 70% which your voltage is reasonable for. It then depends what charge you gave last night, again your voltage could be okay, equally they could be duff.

You need to get a proper multi stage charge into them, then check rested voltage, a more reasonable comment could then be possible.

Brian
 
More questions: Not sure if they were answered in previous threads.

When you are using your battery charger, to what voltage do they rise under charging? You should see at least 14.4V - below 14V is pretty useless.

How are you checking the voltage? Digital multimeter ? or older original equipment analogue dial?

Do you have a battery monitor so that you can see how much charge is actually going in to the batteries?
 
halcyon said:
You cannot assume the solar panels charged to 100%, it could be 60 / 70% which your voltage is reasonable for. It then depends what charge you gave last night, again your voltage could be okay, equally they could be duff.

You need to get a proper multi stage charge into them, then check rested voltage, a more reasonable comment could then be possible.
Click to expand...

It is charged with a genuine multistage via a Heart system. The solar panels are not on the boat at the moment hence why the batteries get a proper rest after I charge them with the multistage charger.
 
Chris_Robb said:
When you are using your battery charger, to what voltage do they rise under charging? You should see at least 14.4V - below 14V is pretty useless.

How are you checking the voltage? Digital multimeter ? or older original equipment analogue dial?

Do you have a battery monitor so that you can see how much charge is actually going in to the batteries?
Click to expand...

- Yes they get over 14.4 when charging and then settle down after they go to float.
- Voltage from my Heart Interface
- Yes via the interface I can see a range of data.

I think maybe I will charge them all up and disconnect them and see what they all settle to independently.
 
northcave said:
Ok so since removing my solar panels which tends to keep the batteries 100% all the time...
Click to expand...

As others have said, there's a degree of supposition in that. The panels may well not have brought them to 100% charge (depending on panel size and sophistication of controller).
12.4 to 12.5V after resting suggests they're 70 to 80% charged.
Are the batteries open lead-acid? If so, the most reliable test is with a hydrometer. Given your plans, I'd get one.
 
northcave said:
It is charged with a genuine multistage via a Heart system. The solar panels are not on the boat at the moment hence why the batteries get a proper rest after I charge them with the multistage charger.
Click to expand...

I had similar thoughts to Halcyon and wondered how you had determined 100% charge from solar. If you are now on mains charging for long periods, say 3-4 days, the batteries should be getting to 100%.

I'd suggest monitoring the charging voltages at start and end of charge period and then disconnect all batteries from everything and each other. Test each with a good multi-meter 3-4 hours after disconnecting. Test again on your next visit.

You should spot any dud batteries by the drop in voltage. If all voltages are similar and around 12.7-12.8V then you may have a parasitic load (i.e. something you didn't know was always connected).

12.4-12.5V would be 75%-80% charged for my flooded batteries (T105s) and I'd expect them to sit around 12.8V when 100% charged. T105s will actually drop quite quickly as then have a rather high self-discharge rate. Normal leisure style should retain higher charge for longer.
 
Venus1 said:
I don't disagree with previous responses, and I have no expertise, BUT my batteries give similar numbers to yours, have done for years, and yet they always start the engine first crank, and were load tested recently and found to be fine. (The load testing was done professionally, and the sparky would have sold me new batteries if they had failed - ie it was not in his interests to falsely pass them.)
I have checked my voltage readings with other voltmeters - giving same result (12.4v after 24 hour rest).
I know batteries can fail suddenly sometimes, but I am happy to do nothing for now (as per local sparky advice).
...not expressing opinion - just reporting my experience.
Click to expand...

That is similar to my experience. I have always been used to voltages at the high end of 12.6 - 12.9 but last season replaced all (three) domestic bank with nominally sealed types that had a top-up facility. They are almost always at 12.5v or so, no loss of electrolyte. They seem to work well enough despite this.
 
northcave said:
- Yes they get over 14.4 when charging and then settle down after they go to float.
- Voltage from my Heart Interface
- Yes via the interface I can see a range of data.

I think maybe I will charge them all up and disconnect them and see what they all settle to independently.
Click to expand...

With a voltage of 14.4 you will not necessarily get 100% recharge, depends on charge wave form, a rectified transformer will give a higher charge than smooth solar panel. The other complication is 12.7 volt quoted for 100% charge varies with battery age, new batteries can be above 13.0 volt settled.

So check after a good mains recharge, around 12.7/12.8 I would not worry.

Brian
 
richardabeattie said:
Are small cheap mutimeters really accurate enough to measure these fine variations in voltage?
Click to expand...

The precision is useful when monitoring small variations.

However one must remember that precision does not equal accuracy. IIRC the specified accuracy of mine ( and they dont come much cheaper) is ±0.5% of the reading
 
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northcave said:
Ok so since removing my solar panels which tends to keep the batteries 100% all the time and maybe masking the voltage they would normally settle at, I now get 12.4v -12.5v if I charge the batteries one evening and then come back the following day.

Would 12.4 or 12.5v be acceptable for a bank of 4 batteries after a charge the previous day with no load inbetween.

If no do I need to disconnect them all and test each separately?

I recon the batteries were replaced in 2012 with relatively minor use.
Click to expand...

I always remember the rhyme given in this forum many years ago that helps the memory:-
12.7 I'm in heaven
12.5 I'm still alive
12.2 charging due
11.8 it's too late

Www.solocoastalsailing.co.uk
 
richardabeattie said:
Are small cheap mutimeters really accurate enough to measure these fine variations in voltage?
Click to expand...
An Excellent question.
I have a trade quality Mulitimeter. Cost price was 100s of pounds equivelent. It didnt matter what i did with trickle chargers and solar panels, based on measured voltage, the boat deep cycle battery seemed to be on its last legs - and yet it kept performing.
Long story short, my expensive Multimeter is nearly 1 volt under reading at 12.8 volts as compared with all other voltmeters.
I have yet to find an easy instrument test methodology such as a way to generate reference voltages so as to be able to verify or calibrate a voltmeter.
Any suggestions?
 
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