Battery discharge

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Jayayecee

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Normally when the boat is on the berth we leave the fridge switched on and the battery charger plugged in. However, this time the mains supply failed and the fridge was left running on the domestic battery for two weeks. The terminal voltage had fallen to 6.5V. My question is will the domestic batteries be permanently damaged or will they recover when recharged? This is the only time something like this has happened normally the batteries are kept fully topped up.
 
Every deep discharge is 'wear and tear' on the batteries.
The battery may recover and still be usable, it may continue to do its job for years, or it may have reduced capacity and not meet your needs any more.
Charge it up and see how it goes.
 
Jayayecee said:
Normally when the boat is on the berth we leave the fridge switched on and the battery charger plugged in. However, this time the mains supply failed and the fridge was left running on the domestic battery for two weeks. The terminal voltage had fallen to 6.5V. My question is will the domestic batteries be permanently damaged or will they recover when recharged? This is the only time something like this has happened normally the batteries are kept fully topped up.
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What type of batteries are they?
 
B27 said:
Every deep discharge is 'wear and tear' on the batteries.
The battery may recover and still be usable, it may continue to do its job for years, or it may have reduced capacity and not meet your needs any more.
Charge it up and see how it goes.
Click to expand...
Absolutely. I ran my domestic battery down to 2 volts once, due to an alternator fault. It recovered and served me faithfully for a few more years, though very possibly at a slightly reduced capacity.

Why run the fridge when you aren't aboard? Surely it's just wasting electricity?
 
My deepest condolences. I hope whatever was in the fridge did not stink the place out.

Whatever do people keep in the fridge when not on the boat?

Would a solar panel keep up with the fridge's power demands.
 
Sandy said:
My deepest condolences. I hope whatever was in the fridge did not stink the place out.

Whatever do people keep in the fridge when not on the boat?

Would a solar panel keep up with the fridge's power demands.
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Yes in Portugal:cool:. In Gosport ?????? ☹️ But global warning may change that. One day.
 
greeny said:
Yes in Portugal:cool:. In Gosport ?????? ☹️ But global warning may change that. One day.
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During the summer, my 200w of solar keep up with our fridge and having a stereo going much of the time. Not sure it would now, especially if it's cloudy, but they still stretch the capacity of the batteries and get them full by the next time we come down.
 
"Does it damage a car battery if it goes flat?

"The single most important thing to understand about your battery is that you need to keep it charged up. If you let the charge drop too low, your battery can become irreparably damaged. So, how low are we talking? A typical 12-volt auto battery will have around 12.6 volts when fully charged. It only needs to drop down to 10.5V to be considered fully discharged. If it drops down below that the battery will become permanently damaged due to excessive sulfation."

https://www.batteriesplus.com/blog/power/car-battery-care
 
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coopec said:
"Does it damage a car battery if it goes flat?

"The single most important thing to understand about your battery is that you need to keep it charged up. If you let the charge drop too low, your battery can become irreparably damaged. So, how low are we talking? A typical 12-volt auto battery will have around 12.6 volts when fully charged. It only needs to drop down to 10.5V to be considered fully discharged. If it drops down below that the battery will become permanently damaged due to excessive sulfation."

https://www.batteriesplus.com/blog/power/car-battery-care
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Are there not methods to de-sulfate a battery?

Pulse charging at high volts or something.

I used to look after my batteries very carefully, but **** happens and knowing a method to revive a battery is useful knowledge (that I have now forgotten or not been correct about in the first place)
 
Gsailor said:
Are there not methods to de-sulfate a battery?

Pulse charging at high volts or something.

I used to look after my batteries very carefully, but **** happens and knowing a method to revive a battery is useful knowledge (that I have now forgotten or not been correct about in the first place)
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Swift answer is no.
Various snake oil tablets etc. appear year after year, believe, none work.
 
Boater Sam said:
Swift answer is no.
Various snake oil tablets etc. appear year after year, believe, none work.
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Is the Ctek charger no longer considered a decent product?

I used to have one and it had (according to manual) a de-sulfation phase.

IIRC it was to do with pulse charging at high voltages - no tablets or chemicals involved (which I agree sounded like snake oil).
 
Gsailor said:
Are there not methods to de-sulfate a battery?

Pulse charging at high volts or something.

I used to look after my batteries very carefully, but **** happens and knowing a method to revive a battery is useful knowledge (that I have now forgotten or not been correct about in the first place)
Click to expand...

De-sulfate only works with very lightly sulfated plates ..... but if battery is already suffering - then its doubtful.

I have de-sulfators and I can 'stretch' a batterys life out a bit - but to be honest ... its waste of time.
 
It wasn't really a problem, I just had to turn the fridge off and run the relevant engine for an hour to put a bit of juice in, but the port/domestic batteries were low enough that the engine was reluctant to start until I put the stb battery in parallel.
 
I left my car on a trickle charge for three months but a power cut caused the charge to default to 6v. Nevertheless, after recharging the battery it continued to serve, including auto-stop, for seven or eight years. It may be OK but the only way to find out is to try. My boat batteries have been recorded as knackered after nine years but, pending replacement, are still holding their charge at 12.8. I have been advised not to leave the, on charge but have run the engine for as little as ten minutes from time to time with up to two weeks gap.
 
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