Keeping an unused lead battery good condition for a long period of time?

vyv_cox said:
Not my experience. See post #3.
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Post three states you returned to find 12.4 v.

That is just below half full is it not (12.5 considered half full or half flat).

So your batteries did not become flat before you ‘got’ to them.

I used to read that allowing lead acids to become flat (less than 12.4v) for a period was very detrimental.
 
I was going to suggest to the OP buying a Ctek charger because they are supposedly intelligent fit and forget and go through about 8 cycles of ‘ intelligence’ but Refueller has posted the charger is not good.

I must admit to having one for my car that worked superbly, but a classic motor bike one (6v iirc) failed.

Unlike refueller, I opened it and found the inside full of very complicated components compared to an Aldi purchase that I also opened when it failed; the two were very dis-similar in comparison, but both failed (Aldi one was for 12V and failed with a month or so. Could not return as Covid lockdown was in place so it went into the we bin (I kept cut off and kept the crocodile clips; perhaps that is why I have accumulated so much ‘stuff’ over the years).
 
I don’t think Ctek are the be all and end all but, that said, my one is ten years old and working fine. There’s a YouTube clip where someone opens one up and if memory serves he was of the opinion that they’re ok, but not amazing in terms of components and design.
 
ylop said:
Is it better to leave them charging 24/7 on a suitable charger or just pop them on for an overnight charge every 3-6 months? I note that my local motor factors don't charge every battery on their shelf but have a cycle through their stock (I think charging a different battery each day), but the chandlery don't seem to charge them at all and probably have a lower stock turnover...
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Of course periodic top-up charging is likely the best - but being human - we can forget and end up with a damaged battery.

Having in the past when I lived in UK - had both Caravans and Boats - looking after batterys was a 'chore' and I admit I failed a few times ... denting the wallet !
Along comes battery maintainers ... not full chargers .. but sufficient to maintain a reasonable level of charge. My last caravan had an expensive sophisticated Carver system ... but still it was recc'd to winter store on a maintainer or periodic top-up charge and not on the Carver.
 
Cerebus said:
Post three states you returned to find 12.4 v.

That is just below half full is it not (12.5 considered half full or half flat).

So your batteries did not become flat before you ‘got’ to them.

I used to read that allowing lead acids to become flat (less than 12.4v) for a period was very detrimental.
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I think your figures are pessimistic. After an overnight with my fridge running I usually see about 12.3 - 12.4V. A couple of hours of solar charging restores them to over 12.7V.

The fact remains that my batteries were fine after 3 years of no charge and went on for another couple of years, by which time they were 6 or 7 years old. This is an excellent life for a half year live aboard boat
 
Cerebus said:
Post three states you returned to find 12.4 v.

That is just below half full is it not (12.5 considered half full or half flat).

So your batteries did not become flat before you ‘got’ to them.

I used to read that allowing lead acids to become flat (less than 12.4v) for a period was very detrimental.
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12.5V is 80%, not 50%, which is 12.1V
 
ylop said:
Is it better to leave them charging 24/7 on a suitable charger or just pop them on for an overnight charge every 3-6 months? I note that my local motor factors don't charge every battery on their shelf but have a cycle through their stock (I think charging a different battery each day), but the chandlery don't seem to charge them at all and probably have a lower stock turnover...
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A smart charger with different stages of charging connected all the time is fine. After the "float" phase, mine shuts down until the voltage drops - usually a month or longer (automatic bilge pump/conventional stern gland).
 
When we go sailing for an extended period, we put the car batteries on 4A smart chargers. They are set to come on via a timeclock once a week for 3 hours. Both cars did a two year stint with batteries on charge like this. When we came back and reattached the batteries, both cars started first time and now a year later, the batteries are still going strong. I have no idea how old the batteries are but two years stored in this way seems to have had no detrimental impact
 
Thanks all. Think I’ll swap out the batteries and be done with it. Frustratingly I just brought it home on Sunday when I was giving the boat a good clear out ahead of our upcoming summer cruise. Tenders and lead batteries are a fun workout!
 
vyv_cox said:
I think your figures are pessimistic. After an overnight with my fridge running I usually see about 12.3 - 12.4V. A couple of hours of solar charging restores them to over 12.7V.

The fact remains that my batteries were fine after 3 years of no charge and went on for another couple of years, by which time they were 6 or 7 years old. This is an excellent life for a half year live aboard boat
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Yes my figures were wrong.

After three years your batteries did really well.

Any particular brand or make?

Sealed lead acid or different?
 
The thing about 12v adapters made for powering devices is in the design. Modern design uses switch mode technology to produce an accurate 12v supply. No good for battery charging at all. Old adapters used a transformer to produce 12v under load. They often will deliver 13+ volts no load. So yes they will hold a battery up to that no load voltage over time, the current will be low but ok for maintenance. The point is you need to measure the no load voltage before assessing it's suitability. A clue is that the one with transformer will be much heavier than the switch mode style. As said of course a box made for battery charging and maintenance will be much better.
 
William_H said:
The thing about 12v adapters made for powering devices is in the design. Modern design uses switch mode technology to produce an accurate 12v supply. No good for battery charging at all. Old adapters used a transformer to produce 12v under load. They often will deliver 13+ volts no load. So yes they will hold a battery up to that no load voltage over time, the current will be low but ok for maintenance. The point is you need to measure the no load voltage before assessing it's suitability. A clue is that the one with transformer will be much heavier than the switch mode style. As said of course a box made for battery charging and maintenance will be much better.
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The maintainers I linked to show only about 0.1 .. 0.2v when no load .... typical of switch mode ..... but once connected to a battery show over 13v ... I have not used a Wattmeter on one - much better test than paper based theory !!

I also have a couple of Solar trickle maintainers ... they show over 13v no-load but reduce to high 12v when connected ..

A setup I used for years - and shows similar to Will H comment about transformer chargers :

I used a Maplins solid state splitter (this has virtually zero loss unlike diodes) (KEMO)... it would send charge to whichever battery was lowest charge state ... once both batterys near full - it would have reduced as charge level rose to low maintenance amp rate. But such splitters cannot work with modern day smart chargers. You need a plain dumb charger that just pumps out charge ... its rate reducing by virtue of the batterys increasing resistance.
I have a couple of the later higher amp rated versions still unopened .... not from Maplins of course - but direct from KEMO ....
 
vyv_cox said:
They were Winner Solar, 110Ah. Open cell. The sales blurb claims they will withstand 1.5 times the recycling that others will. The company has a good worldwide reputation.
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Thank you.

They sound like good batteries to have only dropped to 12.4V after three years.
 
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