Basic volts question for battery use

[skipmac]

My response re the 100A was really just in relation to the question as to how a 100A current could happen. BTW you comment above:

"....there will not be a continuous 100 amp current flowing through the VSR. Maybe a very brief inrush current but that will not over heat anything or cause a fire."​

Nice selective quote you just did there. Manage to leave out all the qualifiers I mentioned like "properly sized for your charging system" and "unless there is some kind of problem with the start battery there will not be a continuous 100 amp current flowing through the VSR"


So I had a quick google and almost immediately came upon this link from Sterling:

"...we do not want to drain the starter battery or burn out the 80 amp relay or even worse set fire to the cables as the cables would be rated to take 80+ amps and you are now trying to pa 200 amps plus down these cables (a fire in the making). "
http://sterling-power.eu/products-proconnect-info.htm​

Note my comment above referring to the charging system. A system includes all the components including any breakers, fuses, relays AND wire. All wire in a system needs to be properly sized to handle max current it might encounter in normal operation (short circuits are not normal and dealt with by proper fusing or breaker). By the way, by their design, alternators are current limited so a 100 amp alternator cannot send a 200 amp surge down a cable.

Aside from that I agree that marine electricians regularly spec VSRs and well specced they're fantastic additions to many many marine applications. FWIW I also think Nigel Calder is a very knowledgeable chap though never met him.

Notwithstanding this, all I'm saying is that a suitable application for VSRs is not where it allows the safety-critical start battery to be endlessly exposed to a voltage, explicitly contraindicated by the battery OEMs.

Well as I've noted several times in this and other threads, Nigel Calder and numerous other experts that have probably forgotten more about marine electric than I have ever known, don't agree. The point is, unless you have a defective charging system or a smart regulator that is programmed incorrectly the voltage that worries you so much is NOT TOO HIGH and will not cause immediate and imminent death of the start battery.[COLOR]

In other words, a quiick few hour motor and the odd few days anchoring with solar running at 14.4V will probably do no harm to a fully-charged start battery combined via a VSR. More than that one needs to be careful and I doubt Calder would disagree with that?

Edit: as an aside many marine systems are designed where the start batteries are not left exposed to unregulated alternator output Unregulated alternator output??? Maybe you mean something else. Unregulated alternator output is AC and 100V or more. (Balmar, Adverc, Sterling, etc). Others use high-end Mastervolt kit, and many others design a simple switching system to keep the start battery safely isolated.

In the end most people sort out their charging needs in a cost-effective and successful manner

 

[dom]

Skipmac, your comment re unregulated output; okay fair enough, what I meant was the ubiquitous indiscriminate machine-sensed circa 14.5V alternator output. I have personally never seen a 100V a/c alternator and doubt one exists for a 12v system, but if it does, apologies.

I nevertheless stand by everything else I have said and can see no harm in referring to the OEM's own own safety-critical advice for the equipment they produce. That is surely worth knowing about? Anyone reading this thread will consider their own system in detail, perhaps call the manufacturers themselves, perhaps ask someone for advice, and finally decide what's best for them.

This freedom must be one of the biggest attractions of going to sea and hopefully we can all agree on that.

 

[pvb]

So I had a quick google and almost immediately came upon this link from Sterling:

"...we do not want to drain the starter battery or burn out the 80 amp relay or even worse set fire to the cables as the cables would be rated to take 80+ amps and you are now trying to pa 200 amps plus down these cables (a fire in the making). "
http://sterling-power.eu/products-proconnect-info.htm​

Don't take anything Mr Sterling writes at face value; in this case, he's trying to promote his much more expensive current-limiting VSR.

 

[dom]

Don't take anything Mr Sterling writes at face value; in this case, he's trying to promote his much more expensive current-limiting VSR.

I'm sure you're right, he seems to like revving things up a bit; no doubt why he Googles ever so well!
That said, I guess his products are fine for those who just want a solution and don't mind paying a few $$$s over the odds.

 

[skipmac]

Skipmac, your comment re unregulated output; okay fair enough, what I meant was the ubiquitous indiscriminate machine-sensed circa 14.5V alternator output. I have personally never seen a 100V a/c alternator and doubt one exists for a 12v system, but if it does, apologies.

Not that it is really moot to this discussion, but all auto and marine alternators produce high voltage alternating current. 100 V or more is very typical. The alternating current is rectified by a diode bridge to pulsating direct current and the voltage is "regulated" to a level compatible with charging a 12V battery.

I nevertheless stand by everything else I have said and can see no harm in referring to the OEM's own own safety-critical advice for the equipment they produce. That is surely worth knowing about? Anyone reading this thread will consider their own system in detail, perhaps call the manufacturers themselves, perhaps ask someone for advice, and finally decide what's best for them.

Forget my knowledge, degree in electrical engineering, and 40 years boating. I defer to experts in the field and if you think Nigel Calder and others who are specialists and literally write the standard references on the subject are wrong then I suggest you pass your reasoning on to them. I can say no more on the subject and you can hold on to your beliefs that standard industry practices are wrong and are killing batteries.

This freedom must be one of the biggest attractions of going to sea and hopefully we can all agree on that.

Different ships, different long splices. On this we do agree. And if I ever run into you on the water somewhere I will happily buy you a pint and cheerfully tell you how misguided you are.

 

[dom]

Skipmac, your quip about alternators first producing an 'alternating' current, indeed they do!

But where is the conflict between a 'degree in electrical engineering', 40 years experience and deferring to 'experts'? If large and reputable marine battery manufacturers contraindicate circumstances which might damage their products, then I'm personally inclined to take them seriously. For example, if Yanmar advised against a certain antifreeze, I wouldn't use it. There is after all no obvious conflict of interest between the manufacturer's aspiration for a long product service life and mine to be a happy customer. BTW re Calder, have you a reference to where he argues that OEM warnings re extended overvoltage exposure should be disregarded? For that is the only substantive point of disagreement here.

Anyhow, I guess we have all made our points and that beer is 'probably' the best suggestion of this entire thread; though I'm guessing we can agree that Carlsberg is probably not.......

 

[lw395]

Some of Nigel Calders books go back to about 1990?
When serious solar power was not available.
It would be unfair to be taking his advice out of context.

 

[sailinglegend420]

....BTW re Calder, have you a reference to where he argues that OEM warnings re extended overvoltage exposure should be disregarded? For that is the only substantive point of disagreement here. ...

This was the main fact in my post that appears to have caused so much problem - let me repeat it:

“Overcharging” is not providing more current than the batteries want but holding the charging voltage for too long at or above the gassing voltage of about 14.4v.

This I thought was common knowledge but I'm asked to produce links to support the obvious.

So for those who can't be bothered to Google this here are some links which make far better reading than many of the posts on this Forum:

https://www.victronenergy.com/upload/documents/Book-Energy-Unlimited-EN.pdf

A mixture between float use and short, shallow discharges when motoring or moored.
The risk here is that a 3-step alternator regulator (when motoring) or a charger, (when connected to shore power) is frequently triggered by these shallow discharges to go into bulk and then absorption mode. The result could be that the battery is continually subjected to absorption charging and will be overcharged.

An academic paper: Book Fundaments of Photvoltaic Modules and their applications

https://books.google.co.uk/books?id...&q=battery full excess energy gassing&f=false

“A battery cannot absorb all the energy from the charging during the end of the charge….at full charge all the energy, except a small resistance loss, is consumed by the electrolysis.’

Non-believers always quote car charging as a very bad example:

What about the millions of cars & vans with alternators set mid 14v?

They'll be running an awful lot more hours than average leisure boats so maybe not as big a problem as all that..

....So, although my batteries are receiving some form of charge for several hours a day it is nothing like running an automotive alternator at 14.4/14.6v for hours on end.

I believe I addressed these issues and nobody has yet disproved it.

 

[pvb]

This was the main fact in my post that appears to have caused so much problem - let me repeat it:

“Overcharging” is not providing more current than the batteries want but holding the charging voltage for too long at or above the gassing voltage of about 14.4v.

This I thought was common knowledge but I'm asked to produce links to support the obvious.

You keep quoting this 14.4v charging voltage and saying it results in overcharging. That may have been "common knowledge" in olden times with earlier flooded batteries, but modern deep-cycle and maintenance-free batteries usually incorporate calcium in the plates, which allows a higher charge voltage without gassing. As an example, Exide suggest an absorption charge of 14.8-15.0v for 12-24 hours for a number of their calcium technology batteries. You can see their recommendations here - http://www2.exide.com/Media/files/Location Data/Battery Charging & Storage Specs 11_13_15.pdf

Over 20 years ago, I used Delco Freedom maintenance-free batteries on my boat. Delco recommended higher charge voltages for these, and they were routinely charged at 14.8v using an Adverc booster on the alternator. They lasted around 8 years, and I replaced them with Merlin Powerpack batteries which were manufactured to similar specs as the Delco Freedom. These also lasted over 8 years with the same charge voltage.

 

[GHA]

....So, although my batteries are receiving some form of charge for several hours a day it is nothing like running an automotive alternator at 14.4/14.6v for hours on end.

I believe I addressed these issues and nobody has yet disproved it.

No you didn't, again no data whatsoever - just opinion. Where's the temperature cut of data sheet for the most common alternators? What temperature range do cars/ vans alternators run at?

Nothing to disprove until you come up with some data.

So a quick look at what google has..


http://www.embedded.com/design/real...ontroller-driven-alternator-voltage-regulator

The temperature-compensation curve is totally dependent on what is best for battery life. Figure 8 shows a typical temperature compensation curve for some cars on the road today.
Figure 8: Typical temperature compensation curve

And from my alternator which will put out just under 14.6v into fully charged batteries & runs at just under 50DegC.

This tallies up fairly well with the minimum compensation from the chart above. The sensor is attached to the body of the alt so internal temperature might well be higher. This on a diesel engine on a boat - so what temperatures do car/van alts run at around the world< unknown.

All this doesn't mean that it's a good idea to keep voltage to a battery up high all day every day but points out your inability to produce a convincing open minded argument as opposed to generic statements with no backup.

Another waste of bandwidth goes into the ignore bin

 

[dom]

...but modern deep-cycle and maintenance-free batteries usually incorporate calcium in the plates, which allows a higher charge voltage without gassing. As an example, Exide suggest an absorption charge of 14.8-15.0v for 12-24 hours for a number of their calcium technology batteries. You can see their recommendations here - http://www2.exide.com/Media/files/Location Data/Battery Charging & Storage Specs 11_13_15.pdf

I guess that's the nub of the question here: for how long can one leave a fully-charged start-battery exposed to circa 14.5V without any damage?

My concern is that it might be as low as a few hours a day, which is why I prefer to keep the start battery off-line when it's charged. Might be worth dropping a quick line to Varta and Trojan et al to see if they can provide a definitive answer.

 

[GHA]

I guess that's the nub of the question here: for how long can one leave a fully-charged start-battery exposed to circa 14.5V without any damage?

My concern is that it might be as low as a few hours a day, which is why I prefer to keep the start battery off-line when it's charged. Might be worth dropping a quick line to Varta and Trojan et al to see if they can provide a definitive answer.

A few finds from google -

bearing in mind this is more about recharging from solar, not start batteries spending their lives fully charged.


First points towards what sounds like a very comprehensive study unfortunately not online..
http://outbackpower.com/forum/viewtopic.php?f=17&t=3123#p18426

[FONT=&quot]The study has four conclusions:[/FONT]
[FONT=&quot]1. The finish voltage (sometimes called the absorption[/FONT]
[FONT=&quot]voltage) for a flooded lead-acid battery operating at[/FONT]
[FONT=&quot]12 VDC nominal should be about 15.3 volts (2.55 per[/FONT]
[FONT=&quot]cell) rather than the customary 14.4 volts.[/FONT]
[FONT=&quot]2. Finish charge time should be at least 3 hours and[/FONT]
[FONT=&quot]often longer.[/FONT]

And from here..
http://www.battcon.com/PapersFinal2016/Arioli Paper 2016.pdf

Which actually tells us nothing much really on the topic of eng batts but hints that maybe sitting at a high voltage for an afternoon might not be a nice thing to do but might not be an instant battery killer and for recharging a house bank high can be good.

From the 2nd link, if you want your battery to love you then keep it cool!

 

[dom]

And from here..
http://www.battcon.com/PapersFinal2016/Arioli Paper 2016.pdf

Which actually tells us nothing much really on the topic of eng batts but hints that maybe sitting at a high voltage for an afternoon might not be a nice thing to do but might not be an instant battery killer and for recharging a house bank high can be good.

Golly, 15.3V seems high, esp for an SLA!

Anyway, re the start battery it seems nobody disagrees that a few hours at 14.5V will do any serious harm, yet most agree that overcharging is a risk if the battery is left well above float for extended periods.

That said, not one of us is able to go definitive on time, not even you on your new floating laboratory! Great graphs mind, though pl increase the fonts a smidge as I needed a magnifying glass for the last one

I'll email a couple of manufacturers and post their responses on here.

 

[PaulRainbow]

Golly, 15.3V seems high, esp for an SLA!

Anyway, re the start battery it seems nobody disagrees that a few hours at 14.5V will do any serious harm, yet most agree that overcharging is a risk if the battery is left well above float for extended periods.

That said, not one of us is able to go definitive on time, not even you on your new floating laboratory! Great graphs mind, though pl increase the fonts a smidge as I needed a magnifying glass for the last one

I'll email a couple of manufacturers and post their responses on here.

Have a word with Yuasa, they make a few batteries.

Ask any battery manufacturer if their batteries can be fitted to a Ford, for example.

Ask Varta what would happen to one of their batteries if it was charged at 14.8v.

 

[PaulRainbow]

I guess that's the nub of the question here: for how long can one leave a fully-charged start-battery exposed to circa 14.5V without any damage?

My concern is that it might be as low as a few hours a day, which is why I prefer to keep the start battery off-line when it's charged. Might be worth dropping a quick line to Varta and Trojan et al to see if they can provide a definitive answer.

What facts do you base this concern on ?

Real World doesn't seem to share your concerns.

 

[sailinglegend420]

You keep quoting this 14.4v charging voltage and saying it results in overcharging.....

I did say in my quote "above the gassing voltage of about 14.4v" - but your point is valid for higher battery voltages - but maintaining them at that voltage when the batteries are full will still have the same consequences.

I can see where some people, who didn' t read it properly, might be confused by my post.

Let me re-edit my quote at the top with an important correction so dis-believers don't have to read the post again:

The point that every one is missing is that “Overcharging” is not providing more current than the batteries want, we know that can't happen if the charging voltage is correct - but it should be defined as "holding the charging voltage at the absorption voltage of about 14.4v (or above and temperature dependent) when the battery is fully charged. The absorption voltage is the voltage at which the batteries start to gas slightly. When the battery is fully charged the energy from the absorption voltage causes much more gassing and therefore loss of water. The absorption voltage must be reduced to a float voltage - below the gassing voltage.

That summarises my main point.

Just to add:
I used to get 100 amps charge going into my large depleted house bank from my small starter battery - observed every time on my BEP battery monitor - when the 300 amp VSR closed. So I now charged the house bank first and the current its much less.

Here's the spec of a common Yanmar/Hitachi alternator used on boats - note the temperature compensation gradient at the bottom. So at 60C the voltage will be down to 14 volts!!!!!

 

[GHA]

Golly, 15.3V seems high, esp for an SLA!

......

I'll email a couple of manufacturers and post their responses on here.

Does seem high, though from hours on google searching for that mythical report which looked to be based on a load of testing the conclusion seems to have been towards high voltage being less of a damaging factor than cycling your batteries at less than back to 100% SOC. Not really anything to do with eng batts.

Manufacturers responses would be interesting, though suspect they will err very much on the side of caution. Trojan told me drop back to float once the SG was high and stable. But then they probably wouldn't go on record with "should be OK charged sitting at 14.8v for a few hours every afternoon"


High temperature could well be a much hungrier battery eating troll than sitting at absorption for a while, dunno but might be something to be at least as concerned with as sitting high.

". It is estimated that for every increase of 10°C in temperature, thebattery life is reduced by half, and it is suggested to keep the operating temperature between 10°C and 25°C6"

 

[pvb]

Here's the spec of a common Yanmar/Hitachi alternator used on boats - note the temperature compensation gradient at the bottom. So at 60C the voltage will be down to 14 volts!!!!!

In that case, why are you so concerned about extended running causing overcharging?

Also, in post 74, you said...

Boat alternators with an external regulator will maintain the absorption voltage at 14.4 volts and therefore can "overcharge" the starter by supplying too high a voltage for too long.

But every decent external regulator will have a temperature sensor on the batteries which will reduce the charge voltage according to rising battery temperature.

 

[sailinglegend420]

In that case, why are you so concerned about extended running causing overcharging?

Also, in post 74, you said...

But every decent external regulator will have a temperature sensor on the batteries which will reduce the charge voltage according to rising battery temperature.

I think you are confused and need to read the whole thread again to understand these quotes.

The temp sensors on the battery will not stop the gassing just lower the voltage to a point where gassing is still ongoing. These sensors are designed to set the absorption voltage to the correct value during absorption, they can do nothing to stop the excess gassing if the absorption voltage is held for too long when the battery is already fully charged.

 

[pvb]

The temp sensors on the battery will not stop the gassing just lower the voltage to a point where gassing is still ongoing. These sensors are designed to set the absorption voltage to the correct value during absorption, they can do nothing to stop the excess gassing if the absorption voltage is held for too long when the battery is already fully charged.

But modern external regulators, eg Sterling Pro Reg D, limit the duration of the absorption charge and then drop to float voltage, according to Sterling's literature, with only 4-6 hours of absorption charge (which is temperature regulated anyway).