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battery life

i am a liveaboard boater and my batteries are 4 yrs old.previously charging batteries for 1 to 2 hrs every day.when charged they used to read over 13 amps.recently after the the bowlsame amount of time charging they now only read 12.66.also my bath drain pump has not been as effective.the pump hasnt kept up with the discharge of water from my bath into the bowl which is xcontrolled by a float switch.if i start the engine the pump then works fine.do you think that because of the length of time i have had the batteries that the amps in the batteries are greatly reduced and could need replacing.i have no amp metre so can only test voltage.i have a 100amp alternator charging 4 100amp batteries for domestic use and the alternator is reading over 14.5 volts when charging.

Asked by: christopher smith  | 10.00am, Thursday 18 April


WW says:

If the system works as it used to when the engine is running, it does suggest that the batteries are starting to fail. This is because the alternator is supplying the power and taking the strain off the batteries.
Fully charged batteries might read 13 volts for a short while after charging but, even with new batteries, this soon drops to a steady 12.5 or 12.6 volts.
It is a good idea to fit a circuit monitor that reads amps in and out as this will give you a better idea of what is going on in the system. It will enable you to spot faults more quickly and, possibly, adjust your use to avoid them. I have used monitors made by Adverc and Sterling and found them very useful.
If you live aboard and, maybe, have an electric fridge and an inverter, four 100 amp/hr batteries will have been working quite hard, particularly if they are 'economy' models. They will suffer even more if you discharge them to a low level - 12-volts or less - before recharging them. Also, make sure they are regularly topped up with distilled water.
So, from what you say, you may have to think about replacing the batteries before too long.

Graham Booth  | 11.21AM, Thursday 18 April

It might be worth noting that your charging routine might not be the most effective for charging the batteries- you are probably only cycling between 50 and 80% of charge- this can lead to shortening the life of batteries, by causing the plates to build up with sulphate.
It might be worth considering a charge controller to fit between the alternator and the battery bank, if you are unable to use a mains (230V) charger at times to avoid sulphating. Either that, or longer charging times whilst cruising might ensure that the batteries are better charged.

Mark Langley  | 10.28PM, Friday 19 April


Readers say:

thanks for the quick responce i supose i have done ok for them to last over 4 years

christopher smith  | 12.50PM, Thursday 18 April

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