can I charge Numax sealed batts 14.9V?

[jakub]

...or will the electrolite evaporate and I will not be able to top them up?

I have the the 55A alternator with the diode mod which seems to give me that kind of voltage.

Thanks.

[blackrose]

...or will the electrolite evaporate and I will not be able to top them up?

I have the the 55A alternator with the diode mod which seems to give me that kind of voltage.

Thanks.

 

I might be mistaken, but as far as I am aware most sealed batteries should not be charged at more than about 14.4v.

 

I don't know about the diode modification to your alternator, but couldn't you just remove it?

 

I'm sure someone will be along shortly to give some better advice.

Edited March 11, 2012 by blackrose

[by'eck]

...or will the electrolite evaporate and I will not be able to top them up?

I have the the 55A alternator with the diode mod which seems to give me that kind of voltage.

Thanks.

 

Some lead calcium batteries can be charged at up to 15.1 volts safely but for other generic types max charge volts as follows:

 

Flooded/open lead acid 14.8v

Sealed lead acid 14.4v

AGM 14.35v

GEL as little as 14.0v

[jakub]

Thank you. Ok it seems I need to change the diode...

[by'eck]

Before you do that I would try measuring battery voltage at the battery terminals. If the 14.9v you are seeing is at the alternator output terminal it will be a little less at the battery, but by how much I can't say.

 

Certainly the higher the voltage the better within the limits of the battery type. The Numax Leisure range are sealed but vented flooded cell batteries so I doubt any harm will be done with your present alternator arrangement.

[smileypete]

...or will the electrolite evaporate and I will not be able to top them up?

I have the the 55A alternator with the diode mod which seems to give me that kind of voltage.

Depends how much current a fully charged batt takes at 14.9V. If it's next to no current then there's little or no gassing going on.

 

Bear in mind this will rise at the batts get warmer and the gassing voltage drops.

 

cheers,

Pete.

[bottle]

Some lead calcium batteries can be charged at up to 15.1 volts safely but for other generic types max charge volts as follows:

 

Flooded/open lead acid 14.8v

Sealed lead acid 14.4v

AGM 14.35v

GEL as little as 14.0v

 

A good guide but not totally correct, advice to OP is check with battery manufacturer.

 

ps. My AGM can be charged at 14.8v but the recommendation is not to go higher than 14.6v (It says so on the battery)

 

 

 

Before you do that I would try measuring battery voltage at the battery terminals. If the 14.9v you are seeing is at the alternator output terminal it will be a little less at the battery, but by how much I can't say.

 

Certainly the higher the voltage the better within the limits of the battery type. Agreed

 

The Numax Leisure range are sealed but vented flooded cell batteries The venting is to allow them to release pressure, if the batteries are gassing, when batteries gas they lose water, this cannot be replaced in 'sealed' batteries.

 

so I doubt any harm will be done with your present alternator arrangement. Yet you indicate that charging at 14.9 is to high for and should be 14.4

[Nickhlx]

Do the electrics in alternators have temperature compensation ?

 

i.e. does the regulated voltage at say freezing temps remain the same when its the height of summer in a hot engine bay after a hard working day ?

 

Nick

[jakub]

Ok. It seems sensible to have a bypass switch with different diode. Or no diode at all...the voltage measured is at battery terminals. Amps delivered around 3-4 at 15.0 V, that is when I assume batts are fully charged.

From what I see I have been overcharging these batteries a bit, and certainly to replace water is going to be a bit tricky (impossible even? Hmmm) .

Thanks for all advice.

[Arthur Brown]

Unless you have a figure from the manufacturer's data sheet, then 14.4v is a fair upper voltage limit for a lead acid of any type. With all types gassing at high voltages is a problem, if it's an accessible wet battery then losses from gassing can be made up by addition of distilled or de-ionised water, BUT will they get topped up? Sealed valve regulated ans maintenance free batteries cannot be topped so gassing means lost electrolyte and lost life. Gel batteries can form gas bubbles in the gel which permanently removes that electrode surface from use.

 

However all these are battery terminal volts and at serious current then there will be serious volts dropped across the cables so alternator at 15v may mean batteries charging at 14.2v.

[smileypete]

Ok. It seems sensible to have a bypass switch with different diode. Or no diode at all...the voltage measured is at battery terminals. Amps delivered around 3-4 at 15.0 V, that is when I assume batts are fully charged.

From what I see I have been overcharging these batteries a bit, and certainly to replace water is going to be a bit tricky (impossible even? Hmmm) .

Thanks for all advice.

15V is a bit high at the very least. A power schottky diode (loads on Ebay) has a lower voltage drop, 0.2V to 0.4V, so might be worth a try. Probably best put in parallel with the existing diode so there's some sort of backup if it goes phut.

 

Ideal way to check for gassing would be charge for 24h at 14.4V with shoreline charger, then try a higher voltage and see how much the charge current increases.

 

cheers,

Pete.

[by'eck]

I think smileypete's suggestion of trying them on a charger at increasing voltages may be worthwhile.

 

IF the Numax leisure range use calcium in their construction which seems likely, then they can probably take 14.9 volts.

 

My experience is with AC Delco sealed leisure batteries of lead calcium construction in a 420 Ah bank of four.

 

I set my Victron to charge them at 14.9 volts as measured at the battery, being the manufacturer's upper limit.

 

They were then used without any issues for over five years, including a one month period during an Atlantic crossing when the generator powered charger (only power source used) was never run for more than three hours a day.

 

When fully charged the current draw dropped to little more than an amp. Consequently they didn't gas through the pressure release valve and were only replaced when a Walmart offer I couldn't refuse came my way.

 

Their capacity had reduced by then but they still retained the sharp cut-off of current draw when fully charged & the indicators still worked, which require electrolyte to float in.

[jakub]

Thanks, for the replies. I don't have shoreline connection..so I cannot test my batteries. They are numax marine type (CXV Leisure).Not expensive. I will try to find spec which is not going to be easy, because I have tried already, but I do not think they have got Calcium technology.

I looked at various diodes and I could not decide which to go for. What current rating should I be looking at? Schottky sounds good, but I couldn't find them and I wasn't sure what was I looking for. Any advice? Thanks.

Edited March 13, 2012 by jakub

[by'eck]

Have checked and found that Numax CXV-X sealed leisure batteries are of lead calcium construction. The suppliers who gave me this info suggested 14.4v as a max charge voltage but I wonder if they are being a tad overcautious.

[Canalwatcher]

...

Edited March 16, 2012 by zodiak

[Keeping Up]

The comment I got from my supplier of the Numax CXV's was "The introduction of Calcium Technology was to prevent 'gassing', but this had no effect on the charging voltage" - and they recommended 14.4v

I must say I am a trifle disappointed that after just 6 weeks of careful use they were down to 83% of their nominal capacity (as tested by the supplier after I returned them under guarantee) which I was told is above their 80% threshold for replacement under guarantee. However they did tell me that the guarantee is for 2 years and to contact them if they lost any more capacity.

[by'eck]

The comment I got from my supplier of the Numax CXV's was "The introduction of Calcium Technology was to prevent 'gassing', but this had no effect on the charging voltage" - and they recommended 14.4v

 

I must say I am a trifle disappointed that after just 6 weeks of careful use they were down to 83% of their nominal capacity (as tested by the supplier after I returned them under guarantee) which I was told is above their 80% threshold for replacement under guarantee. However they did tell me that the guarantee is for 2 years and to contact them if they lost any more capacity.

 

As a follow on from the info you received from your supplier, here is some generic info on sealed lead calcium battery construction:

 

Lead acid batteries with electrodes modified by the addition of Calcium providing the following advantages:

More resistant to corrosion, overcharging, gassing, water usage, and self-discharge, all of which shorten battery life.

Larger electrolyte reserve area above the plates.

Higher Cold Cranking Amp ratings.

Little or No maintenance.

 

Certainly many of these traits were found in the AC Delco Voyager batteries I used/abused successfully for many years.

 

I would be tempted to try charging yours at a higher voltage in absorb mode to see if they recover any of their capacity. What have you to loose?

[Keeping Up]

Well, my initial instinct is to use them for another 6 or 8 weeks and see what happens. If they don't lose any more capacity, then I'll be happy with them (and possibly try to gee them up a bit with a higher voltage) and if I lose more than another 3% of the capacity I'll just send them back to the supplier again.

[smileypete]

The comment I got from my supplier of the Numax CXV's was "The introduction of Calcium Technology was to prevent 'gassing', but this had no effect on the charging voltage" - and they recommended 14.4v

I must say I am a trifle disappointed that after just 6 weeks of careful use they were down to 83% of their nominal capacity (as tested by the supplier after I returned them under guarantee) which I was told is above their 80% threshold for replacement under guarantee. However they did tell me that the guarantee is for 2 years and to contact them if they lost any more capacity.

What is really important to know is the manufacturers recommended maximum absorption charging voltage for deep cycle use. Ideally they should copy you the email from the manufacturer.

 

What the importer/distributor thinks or hopes it is in order to sell more batts, isn't really good enough.

 

As an aside, when charging, how do you tell when they are fully charged?

 

cheers,

Pete.

Edited March 17, 2012 by smileypete

[by'eck]

What is really important to know is the manufacturers recommended maximum absorption charging voltage for deep cycle use. Ideally they should copy you the email from the manufacturer.

 

What the importer/distributor thinks or hopes it is in order to sell more batts, isn't really good enough.

 

As an aside, when charging, how do you tell when they are fully charged?

 

cheers,

Pete.

 

I agree & strongly suspect it will be more than the cautious 14.4 volts which seems to be universally handed out by suppliers irrespective of battery type.

 

With lead calcium batteries its easy to know when they are fully charged - they just won't take any more current even when presented with close to 15 volts, assuming they have been charged within their Peukert's exponent.

[Keeping Up]

I agree & strongly suspect it will be more than the cautious 14.4 volts which seems to be universally handed out by suppliers irrespective of battery type.

 

With lead calcium batteries its easy to know when they are fully charged - they just won't take any more current even when presented with close to 15 volts, assuming they have been charged within their Peukert's exponent.

 

Yes I agree too.

 

My supplier is the main UK importer, yet they are invariably reluctant to copy anything that they have received from the manufacturer (and is the manufacturer really the manufacturer anyway).

 

One thing I have noticed is that with a good battery, the current drops away very sharply once they have reached a state of being almost fully charged; a poorer or older battery it tails away more gradually. It is particularly interesting to watch the movement-patterns of the needles on the meters (I like moving-needle meters!) when the Adverc unit cycles between its two outputs of 14.1 and 14.4 volts. When the voltage is suddenly increased there is a jump in charging current from virtually zero up to about 10 amps, for perhaps about half a second, and then a reduction back to zero over the next second or two, and when it is suddenly decreased there is actually a small discharge current shown (as the boat's electrics take power and the alternator supplies nothing) which again returns to zero after a second or two. When I see this pattern I know that my batteries really are practically full.

[by'eck]

Yes I agree too.

 

My supplier is the main UK importer, yet they are invariably reluctant to copy anything that they have received from the manufacturer (and is the manufacturer really the manufacturer anyway).

 

One thing I have noticed is that with a good battery, the current drops away very sharply once they have reached a state of being almost fully charged; a poorer or older battery it tails away more gradually. It is particularly interesting to watch the movement-patterns of the needles on the meters (I like moving-needle meters!) when the Adverc unit cycles between its two outputs of 14.1 and 14.4 volts. When the voltage is suddenly increased there is a jump in charging current from virtually zero up to about 10 amps, for perhaps about half a second, and then a reduction back to zero over the next second or two, and when it is suddenly decreased there is actually a small discharge current shown (as the boat's electrics take power and the alternator supplies nothing) which again returns to zero after a second or two. When I see this pattern I know that my batteries really are practically full.

 

Your findings are entirely consistent with mine when using lead calcium batteries.

 

The initial rise then rapid fall in current as the charge voltage is increased or charger re-cycled is caused by the initial lack of gassing/bubbles at the plate surface as explained by Gibbo.

[smileypete]

One thing I have noticed is that with a good battery, the current drops away very sharply once they have reached a state of being almost fully charged; a poorer or older battery it tails away more gradually. It is particularly interesting to watch the movement-patterns of the needles on the meters (I like moving-needle meters!) when the Adverc unit cycles between its two outputs of 14.1 and 14.4 volts. When the voltage is suddenly increased there is a jump in charging current from virtually zero up to about 10 amps, for perhaps about half a second, and then a reduction back to zero over the next second or two, and when it is suddenly decreased there is actually a small discharge current shown (as the boat's electrics take power and the alternator supplies nothing) which again returns to zero after a second or two. When I see this pattern I know that my batteries really are practically full.

Yes, but what if you increase the charge voltage to a constant 14.8V and the charge current jumps to 25A and then steadily declines towards zero?

 

It may well indicate that you have been persistently undercharging your batts all this time.

 

cheers,

Pete.

[Keeping Up]

Yes, but what if you increase the charge voltage to a constant 14.8V and the charge current jumps to 25A and then steadily declines towards zero?

 

It may well indicate that you have been persistently undercharging your batts all this time.

 

cheers,

Pete.

 

Apart from the fact that I don't have the ability to change the voltage as easily as all that (the Adverc does it all the time) I'm not sure that I agree with your conclusion. By my reckoning, if the battery takes no current at 14.1, and then if after the brief jump at 14.4 it also returns immediately to zero, I would reckon that it MUST be full. Certainly if after the initial jump the current did NOT return immediately to zero, that would be a sign that it was not yet full and is exactly the pattern always I observe while it is charging in absorption.

 

If indeed an increase to 14.8 were to cause a jump to 25A for a second followed by a return to zero over the next few seconds, as you postulate, then since no further charge was being put into the batteries I would take this as a sign that they were already full.

[Nickhlx]

Apart from the fact that I don't have the ability to change the voltage as easily as all that (the Adverc does it all the time) I'm not sure that I agree with your conclusion. By my reckoning, if the battery takes no current at 14.1, and then if after the brief jump at 14.4 it also returns immediately to zero, I would reckon that it MUST be full. Certainly if after the initial jump the current did NOT return immediately to zero, that would be a sign that it was not yet full and is exactly the pattern always I observe while it is charging in absorption.

 

If indeed an increase to 14.8 were to cause a jump to 25A for a second followed by a return to zero over the next few seconds, as you postulate, then since no further charge was being put into the batteries I would take this as a sign that they were already full.

 

With my variable (potentiometer) 40 amp regulated bench PSU, when connecting to a "fully charged" lead acid battery, if the voltage is very slowly increased from about 14.4 volts, when increasing it by say 0.1 volts, the current jumps up and settles back - if the voltage is slowly and progressively increased, the needle on the ammeter hovers around say 100mA until a certain voltage, then starts steadily increasing as the voltage is raised. The converse is true when reducing the voltage. This certain voltage at the point at which the needle starts increasing ( the knee ?) is what I take as the fully charged voltage and I suppose could be the gassing voltage for the temperature of the electrolyte at the time. Whatever, when the battery exhibits such behaviour, that is the point I take as the fully charged status of the battery, and back off the supply or disconnect.

 

Nick