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Battery Question (yes, another one)


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I started to notice that our batteries were producing significantly less power than they should.  I keep them topped up fairly regularly and checked them today. Of the four batteries, three of them took hardly any water, but the fourth took a LOT more.  It was warm to the touch (on charge through shore power) and when I took the first plug out there was an audible inrush/outrush of air (?).

I am rubbish with electrics. I presume that the drop in overall power is due to the fourth battery not doing its stuff as well as the other three.

What I don't understand is why one out of three has 'broken'.

4 x 12v 135Ah deep cycle leisure batteries the same age, all connected to a bus bar using exactly the same cables (length and thickness).  The batteries are now 2.5 years old and have been well looked after, always on charge with shore power when not out and about and have never dropped below 60% (as far as I know) as a bank.  I am pretty sure the casing isn't cracked, there are no signs of a leak. I think I screwed the plugs in properly when I filled them last. 

I only have a mid range multimeter, but I have no idea what I would be testing for, I told you I was rubbish with electrics.

Do I have to buy a new battery, or can I recondition this one, or will it sort itself out??

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The hot one is likely to have a shorted cell.

Disconnect it and leave it for a couple of hours. Check the voltage. If it is below 12,2 volts, possibly down to 10.2 volts, its dead. Don't reconnect it, it will pull the others down. New one required.

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A rough guide to battery health is to compare the voltage of the suspect battery ,against a "good" one,if it's 10% less it's on its way out.I stress this is a very basic test ,which is what you asked for ??

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I had a 'hot battery', it actually set off the Co alarm in the middle of the night.

It was so hot it was untouchable - fortunately I managed to isolate it before it exploded (as they can)

 

Disconnect it from the bank (but leave it in place to stop the other sliding about) and replace it - it almost certainly has an internal short and it will not 'get better' - replace it.

 

An internal short happens when the sulphate builds up in the bottom of the battery, until it get to the bottom of the plates and 'shorts them out' producing high current and a lot of heat.

 

Lead drop is another cause of short in which chunks of lead break loose from the welded bars connecting the plates. Unlike a soft short that develops with wear and tear, a lead drop often occurs early in battery life due to a manufacturing defect. This can lead to a serious electrical short with a permanent voltage drop that could result in thermal runaway.

The most radical and serious form of short is a mechanical failure in which the suspended plates become loose and touch each other. This results in a sudden high discharge current that can lead to excessive heat build up and thermal runaway. Sloppy manufacturing as well as excessive shock and vibration are the most common contributors to this failure.
 

 

https://batteryuniversity.com/index.php/learn/article/corrosion_shedding_and_internal_short

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Thanks guys - I think I can test the voltage easily enough with my limited knowledge and multimeter and should be able to compare with the other three.

 

But it looks like I need to get along to Bardens and pick up a replacement.

 

What would have caused it to fail?  Is it something I have done, or was it faulty? There isn't any warranty left, but I might have a go and see if I can get some money off the replacement.

 

ETA  -  posted before I read Alan's really helpful response 

Edited by lockedout
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Things you may have done to help it on its way:

 

Over discharged so it reduced cyclic life.

Never fully recharged or recharged too rarely so it sulphated.

 

Alan did not say the lead sulphate takes up more room than fully charged lead oxide so it can push against the plate separators until it punches through so can short. You will often see older batteries bulging at the ends through sulphation.

 

Best practice is to replace whole sets rather than one battery because if one fails another of similar age is likely to fail soon and if it shorts while you are not around it will discharge the rest and may ruin them However as long a you accept the risk and keep a careful eye on the others so you change one the instant a cell starts to lose  electrolyte faster than the rest, a battery gets hot or starts to smell you will probably be OK.

 

 

 

 

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Thanks Tony - Every day is a school day.

 

The bank has never gone below 60% (to my knowledge) and when not on alternator, the boat is plugged in via the electric mooring line and the charger is a decent one.

 

I really don't want to replace all 4 batteries, they are only about 30 months old and the other three seem to be ok (I have my fingers crossed!).

 

I will follow your advice and replace the duff one and keep a really close eye on them.  I am going to take the duff one back to Bardens and get their opinion, if they are prepared to give one!

 

Thanks again everyone...

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37 minutes ago, lockedout said:

 

 

The bank has never gone below 60% (to my knowledge) and when not on alternator, the boat is plugged in via the electric mooring line and the charger is a decent one.

 

It is impossible to advise why the battery has failed in 2.5years without more info.

You say you are rubbish at electrics and only have a multimeter. How are you measuring that 60%? If the battery has failed via sulphation, it is likely that you have not had it up to 100% enough when you are off the grid or you have been hammering it with high loads. Not enough info in your posts to be able to advise. What voltage readings are you taking - how often and what time of day? How are you determining when the batteries are up to 100%? How many days a year (approx) are you off shore power and what are you typical lengths of time off shore power? I assume you have a decent charger that has a low float voltage and doesnt keep it up near 14V.

Once you have disconnected the duff battery, you should be able to estimate the state of the remaining 3 batteries with a decent voltmeter and preferably an ameter.

Have you any solar?

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2 hours ago, lockedout said:

 

I really don't want to replace all 4 batteries, they are only about 30 months old and the other three seem to be ok (I have my fingers crossed!).

 

I will follow your advice and replace the duff one and keep a really close eye on them. 

Why not just live with 3 batteries until these fail, then buy 4 new ones?

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20 hours ago, David Mack said:

Why not just live with 3 batteries until these fail, then buy 4 new ones?

 

Hmmmmm...  Now that's not a bad idea. we have just had two weeks working on 3 and we got on fine. Certainly worth thinking about.

 

Thanks

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21 hours ago, Dr Bob said:

It is impossible to advise why the battery has failed in 2.5years without more info.

You say you are rubbish at electrics and only have a multimeter. How are you measuring that 60%? If the battery has failed via sulphation, it is likely that you have not had it up to 100% enough when you are off the grid or you have been hammering it with high loads. Not enough info in your posts to be able to advise. What voltage readings are you taking - how often and what time of day? How are you determining when the batteries are up to 100%? How many days a year (approx) are you off shore power and what are you typical lengths of time off shore power? I assume you have a decent charger that has a low float voltage and doesnt keep it up near 14V.

Once you have disconnected the duff battery, you should be able to estimate the state of the remaining 3 batteries with a decent voltmeter and preferably an ameter.

Have you any solar?

So, trying to answer some of the points raised:

 

My method of measuring the state of the bank as a whole is Smartguage/Smartbank . We certainly don't hammer the batteries when we are off grid, as I say, we have never been below 60% since the batteries were new and we always drive enough during a day to get it up to 100% at the end of the day.  We don't have solar (yet). The boat spends most of it's time on shore power, we are holiday boaters with weeks, long weekends and days here and there but we use it year round.  I can't remember the name of the charger, maybe I should look at getting something better, I think I have the space for a Vectron combined unit.

 

Thanks for taking the time to respond!

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39 minutes ago, lockedout said:

My method of measuring the state of the bank as a whole is Smartguage

Well that's the problem / question resolved.

Widely also known as the 'battery killer'

 

MTB (@Mike the Boilerman) will be along shortly to give you chapter and verse on his experiences with two (or is it now three ?) of them

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Whilst the Smartguage may be inaccurate while charging so what you think is 100% charged may only be about 90 to 95% charg4ed long periods on the shore power charger should minimise any sulphation unless you cruise for months at a time. However many multi-stage chargers go into float too soon and that won't help getting to a true 100% charged. When you visit the boat for a day turn the charger off and on again to force it to start its cycle again.

 

I suspect you may have been unlucky and got a bad battery BUT how are the leads connected to the battery bank? If all pos and neg leads are on the same end of the bank then that will not help maximise battery life. Especially if the battery interlinks are a bit thin.

 

If you have a multi-stage charger I can't see buying a Victron unit will be cost effective apart from the fact you MIGHT be able to mess with its settings so you can do an equalisation charge once in a while.

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3 minutes ago, Tony Brooks said:

Whilst the Smartguage may be inaccurate while charging so what you think is 100% charged may only be about 90 to 95% charg4ed long periods on the shore power charger should minimise any sulphation unless you cruise for months at a time. However many multi-stage chargers go into float too soon and that won't help getting to a true 100% charged. When you visit the boat for a day turn the charger off and on again to force it to start its cycle again.

 

I suspect you may have been unlucky and got a bad battery BUT how are the leads connected to the battery bank? If all pos and neg leads are on the same end of the bank then that will not help maximise battery life. Especially if the battery interlinks are a bit thin.

 

If you have a multi-stage charger I can't see buying a Victron unit will be cost effective apart from the fact you MIGHT be able to mess with its settings so you can do an equalisation charge once in a while.

 

When I rebuilt the bank, I configured the 4 batteries to connect through bus bars using brand new cables, all exactly the same size and length. I can't remember the diameter, but they are good and thick, as advised by Bardens who made them up for me.

 

Good advice about resetting the charger, I will put it on the maintenance list.

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43 minutes ago, Alan de Enfield said:

Well that's the problem / question resolved.

I doubt it. OP has the boat on shore power charging for much of its life. I suspect he’s simply been unlucky with one battery plus, as Tony B points out, his charger probably switches to float too soon; most of them do. 

45 minutes ago, Alan de Enfield said:

Widely also known as the 'battery killer'

Widely? Really? So tens of thousands of boaters around the world say this?  Or just Mike?

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1 minute ago, WotEver said:

I doubt it. OP has the boat on shore power charging for much of its life. I suspect he’s simply been unlucky with one battery plus, as Tony B points out, his charger probably switches to float too soon; most of them do. 

I know, I know, I know, but MtB is missing the chance to rattle his sabre, ride his cock-horse and deride SG's calibration for the 13,006,235th time this year.

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1 hour ago, WotEver said:

Widely? Really? So tens of thousands of boaters around the world say this?  Or just Mike?

They don’t say it because they don’t know it.

 

But I have lost count of the number of boaters who ask if their batteries are knackered, state that they look after them well, and always charge to 100%. When asked how they establish the %age, they then say they have a Smartgauge. They generally don’t have a means of monitoring tail current.

 

in this case we have a Smartgauge and a charger that probably goes into float too early... pretty much a recipe for disaster.

 

You won't agree, but Smartgauge users need to be aware of the downside.... after that, they can form their own opinions, buy some new batteries, and a NASA BM1 or 2 :) .

Edited by Richard10002
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19 minutes ago, Richard10002 said:

in this case we have a Smartgauge and a charger that probably goes into float too early... pretty much a recipe for disaster.

A recipe for disaster?  You do have a way of dramatising things, don’t you?  What happens to a battery on float for days on end, do you even know? I’ll tell you, it gets fully charged. So how is a fully charged battery disastrous?  His batteries are already 2.5 years old which is pretty good going for bog standard leisures. I don’t see any ‘disaster’ anywhere in OP’s scenario. 

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59 minutes ago, WotEver said:

What happens to a battery on float for days on end, do you even know? I’ll tell you, it gets fully charged.

Not quite, that's a classic Gibboism I'm afraid. So much that's misleading in such a short statement!

 

The leading batt mfrs will carefully detail the right way to charge their batts. If you feel entitled to ignore their wisdom, then any resulting problem isn't their fault - is it? :)

Edited by smileypete
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21 hours ago, Mike the Boilerman said:

 

Aren't they supposed to get fully charged immediately, not after several days?

They are. We’re talking about a charger that switches to float too soon, not a charger that has never been in bulk or acceptance. 

20 hours ago, smileypete said:

Not quite, that's a classic Gibboism I'm afraid. So much that's misleading in such a short statement!

See above. If you choose to take my comments out of context then I can’t really stop you. 

Edited by WotEver
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If you’d care to explain how using a charger which switches to float too soon (probably) like nearly all of them do is ‘a recipe for disaster’ then I’m sure we’d all love to know. 

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On this forum there is a lot of irrelevant rubbish talked about tail current as the way of telling batteries are fully charged.

Its only relevant if you are trying to minimise the charging/engine run time.

For anyone that is cruising a reasonable amount (4-6hrs every day) and spends the rest of the time on shore power it is irrelevant as (unless they have a faulty charging system) their batteries will be nigh on 100% every evening.

Strikes me that some people on here like to blame their monitoring equipment for shortcomings in their battery management regime.

 

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38 minutes ago, Loddon said:

For anyone that is cruising a reasonable amount (4-6hrs every day) and spends the rest of the time on shore power it is irrelevant as (unless they have a faulty charging system) their batteries will be nigh on 100% every evening.

Yup. I don’t see a “recipe for disaster” in that either. 

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