Batteries not holding charge

[WJM]

 

By taking them down to 10.2 volts regularly you will by now almost certainly have knackered them. Note that even 11.8 volts is considered a zero state of charge.

 

I have no great expertise in this area but this statement seems nonsense to me. I often drain my batteries down to very low figures like 10.2v and they charge back up perfectly. I have done this for years with different sets of batteries and never experienced any problems.

[Phil Ambrose]

Bet the capacity of the Batteries is greatly reduced.

Phil

[Tony Brooks]

I have no great expertise in this area but this statement seems nonsense to me. I often drain my batteries down to very low figures like 10.2v and they charge back up perfectly. I have done this for years with different sets of batteries and never experienced any problems.

 

Depends upon battery design. I expect with TRUE deep cycle batteries you could get away with it any number of times. However all batteries have a cyclic life and the deeper you discharge them the more of this life you use up. In fact my Exides give a cyclic life of 300 cycles to 40%. The need to maximise the cyclic life is where the so called 50% discharge rule comes from. Its not a rule, just a guide to optimising typical battery life.

 

Also going to such a depth of discharge will require very long recharge times so unless you are on shoreline or have lost of solar charging you stand a good chance of increasing the rate of sulphation and reduction in capacity. Unless you are able to accurately monitor the capacity I fear you can not substantiate your statement.

 

Such deep discharges once or twice in a batteries life may well not make a noticeable difference to the life, repeating it is very likely to.

 

Notice I have use words like "may well" rather than "will". This is because there is nothing written in stone about batteries, we are always "playing the odds" to try to optimise our battery life.

[WJM]

 

Depends upon battery design....

Thanks Tony, It is probably worthwhile me elaborating on my usage so that observers can develop a better picture.

 

My deep discharges always happen when I am away from shore-line. Typically they occur from heavy overnight usage and are always followed by a long day of cruising, eight hours or more of continuous engine running. Outside of this usage pattern the boat spends a lot of time on shore-line with an inverter/charger permanently feeding the batteries. I get three to four years from a set of batteries which to me seems acceptable.

Edited October 17, 2013 by WJM

[Justme]

I have no great expertise in this area but this statement seems nonsense to me. I often drain my batteries down to very low figures like 10.2v and they charge back up perfectly. I have done this for years with different sets of batteries and never experienced any problems.

 

 

Is that voltage reading taken under load or at rest?

[Naughty Cal]

Thanks Tony, It is probably worthwhile me elaborating on my usage so that observers can develop a better picture.

 

My deep discharges always happen when I am away from shore-line. Typically they occur from heavy overnight usage and are always followed by a long day of cruising, eight hours or more of continuous engine running. Outside of this usage pattern the boat spends a lot of time on shore-line with an inverter/charger permanently feeding the batteries. I get three to four years from a set of batteries which to me seems acceptable.

You would probably get a deal longer than that if you didnt let them get so low in the first instance.

[WJM]

 

 

Is that voltage reading taken under load or at rest?

Readings only taken 'at rest' ie: no charging input present.

 

For clarity, a voltage reading taken while the engine is running, solar panels are connected or attached to shore-power will be the voltage of the charging source, not that of the batteries.

 

Also, readings taken with a consistent minimal load, fridge and nothing else.

Edited October 17, 2013 by WJM

[Naughty Cal]

Readings only taken 'at rest' ie: no charging input present.

 

For clarity, a voltage reading taken while the engine is running, solar panels are connected or attached to shore-power will be the voltage of the charging source, not that of the batteries.

 

Also, readings taken with a consistent minimal load, fridge and nothing else.

It wont be a true reading with a draw from the batteries either though!!

[smileypete]

I have no great expertise in this area but this statement seems nonsense to me. I often drain my batteries down to very low figures like 10.2v and they charge back up perfectly. I have done this for years with different sets of batteries and never experienced any problems.

 

Looks like the tables are turned and your statement is nonsense; your usage pattern is as about as different from the OP is it possibly can be.

 

For off grid use the OP would probably be better off with non sealed batts as well as better charging and monitoring of them.

 

The proper semi traction ones like Trojan T105 and US Battery US2200 should almost certainly give better value for money in the long term if looked after reasonably well, including periodic equalisation charging.

 

cheers, Pete.

~smpt~

Edited October 17, 2013 by smileypete

[ditchcrawler]

Thanks Tony, It is probably worthwhile me elaborating on my usage so that observers can develop a better picture.

 

My deep discharges always happen when I am away from shore-line. Typically they occur from heavy overnight usage and are always followed by a long day of cruising, eight hours or more of continuous engine running. Outside of this usage pattern the boat spends a lot of time on shore-line with an inverter/charger permanently feeding the batteries. I get three to four years from a set of batteries which to me seems acceptable.

But out of those 4 years how much time is spent of the land line.

I knew a chap swore by Ecosols but we openly joked he never went further than his curly land line would reach from Braunston Marina. If he did 4 weeks a year that was it, so in 6 years his batteries only worked for 6 months and he thought that was a good life.

[Naughty Cal]

But out of those 4 years how much time is spent of the land line.

I knew a chap swore by Ecosols but we openly joked he never went further than his curly land line would reach from Braunston Marina. If he did 4 weeks a year that was it, so in 6 years his batteries only worked for 6 months and he thought that was a good life.

Funnily enough we know a few like that as well.

[by'eck]

I have no great expertise in this area but this statement seems nonsense to me. I often drain my batteries down to very low figures like 10.2v and they charge back up perfectly. I have done this for years with different sets of batteries and never experienced any problems.

 

Seems a rather harsh statement given your self confessed level of expertise.

 

I think you have been very lucky with your batteries given the abuse you appear to have given them. Certainly true deep cycle batteries will cope much better with this regime though. I wonder how much of their capacity you have lost over the years though

[Martin Megson]

I may have a similar problem. I have a battery bank of 4x 120a/h sealed lead acid batteries which are 2 years old. I'm running a fridge which draws 4-5 amps and runs around 20 min in each hour so is pulling around 2amp per hour on average. Other than that it's just the lights, led in heavy use areas, car radio, led tv for a couple of hours. I rely solely on the engine alternator ( charge voltage between 13.4 and 14.4) to charge them and all is well when cruising and running the engine for 6 hrs a day on average. When moored up I tend to run the engine for around 2 hrs a day which until recently seems to have kept everything running. However, recently the battery voltage has been dropping to 10.7 by morning. After running the engine for a couple of hours and leaving the batteries to settle for an hour or so the voltage is up to 12.75 which suggests they are fully charged. I doubt this is the case and am coming to the conclusion that the batteries no longer have their original capacity

 

Is it time to replace the batteries?

[Tony Brooks]

A short charge time and a short discharge time indicates a low capacity so they are probably sulphated. The other thing that could be discharging them overnight is a partial short circuit in a cell.

 

When the batteries are charging well look into the cells and see if any individual ones are bubbling. If so they probably have a short in them. Look at the battery ends, if they are swollen then they are probably sulphated. If both of those seem OK then try disconnecting 1 battery in turn and see if the charge holds up better overnight. If it does then you have found a battery with a short in it.

 

Alternatively just buy a new set.

[Martin Megson]

A short charge time and a short discharge time indicates a low capacity so they are probably sulphated. The other thing that could be discharging them overnight is a partial short circuit in a cell.

 

When the batteries are charging well look into the cells and see if any individual ones are bubbling. If so they probably have a short in them. Look at the battery ends, if they are swollen then they are probably sulphated. If both of those seem OK then try disconnecting 1 battery in turn and see if the charge holds up better overnight. If it does then you have found a battery with a short in it.

 

Alternatively just buy a new set.

 

Thanks Tony you've confirmed what I expected. There is no sign of swelling or bubbling. I'll take them off and charge them at home individually and see how they react but I think it will be a new set in spring :-(

[Naughty Cal]

 

Thanks Tony you've confirmed what I expected. There is no sign of swelling or bubbling. I'll take them off and charge them at home individually and see how they react but I think it will be a new set in spring :-(

They are consumables they won't last forever.

 

Ours are on borrowed time, they are three years old now!

[nb Innisfree]

They are consumables they won't last forever.

 

Ours are on borrowed time,

Aren't we all...

[Naughty Cal]

Aren't we all...

Indeed!

 

We expected a couple of years out of this set. We have now done three and are heading into year four so definitely borrowed time!

[ditchcrawler]

Indeed!

 

We expected a couple of years out of this set. We have now done three and are heading into year four so definitely borrowed time!

and you have the benefit of being on a shore supply when not using the boat

[Naughty Cal]

and you have the benefit of being on a shore supply when not using the boat

Yes we do but we also use the boat every weekend and holidays so the batteries can be subject to some unsympathetic use. This use pattern killed off the first battery in a couple of years. Upgrading the bank by doubling its capacity does seem to have worked wonders but we still expect them to show signs of distress before too much longer. That said they seem to be soldiering on just fine at the moment!

[MtB]

My experience is that once a battery bank gets down to 'totally knackered', they stop deteriorating.

 

My batttery bank degraded to lasting just an hour or two three years ago after a day's cruising. These days it still lasts an hour or two. Brilliant!

 

Thank God for gas lamps

 

 

MtB

[nb Innisfree]

Our AGMs were down to less than 50% capacity a few years ago and now seem back to near original due to lots of prolonged absorption charges, due in no small part to an enforced halt to ccing.

[Bobbybass]

You have to watch for 'overwatering' as well.

 

Important to get the level as per manufactureres 'spec' as overwatering completely changes the characteristics of the battery.

[Naughty Cal]

You have to watch for 'overwatering' as well.

 

Important to get the level as per manufactureres 'spec' as overwatering completely changes the characteristics of the battery.

How do you overwater a completely sealed battery?

[smileypete]

 

Thanks Tony you've confirmed what I expected. There is no sign of swelling or bubbling. I'll take them off and charge them at home individually and see how they react but I think it will be a new set in spring :-(

 

If you can get hold of a variable voltage and current bench supply, then some careful equalisation charging might recover a useful amount of capacity.

 

For a batt bank that's generally away from a shoreline the non sealed 'open' leisure batts might be a better choice than sealed ones.

 

Sealed hold a charge a lot longer but the usual leisure batt versions probably don't like deeeeep discharge at all and sometimes don't do so well on standard alt charging voltages.

 

cheers, Pete.

~smpt~

Edited November 8, 2013 by smileypete