GHA
Well-Known Member
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..
Basic volts question for battery use
- Thread starter steve yates
- Start date
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..
PaulRainbow
Well-Known Member
There are more myths, fanciful theories and just plain nonsense on these forums about batteries, charging and solar power than anything else, anchors included. 
lw395
Well-Known Member
If you read the whole thread.....
Very few cars plug into shore power or solar, which is changing the way boat systems are used. At least for some people.
It's becoming common for boats to be charging their batteries by some means or other for a lot more hours than a typical car.
PaulRainbow
Well-Known Member
It's true that boat batteries are often on charge for long periods, either shore power 24/7 or solar all day. My own batteries are charged by solar. However, that is irrelevant to your argument that using a VSR or similar will overcharge the engine battery, unless someone is stupid enough to connect a massive solar array to the engine battery.
My solar controller is connected to my domestic bank, the alternator to the engine battery and the dual sensing VSR is connected between the two banks. When i'm using solar the VSR will allow the solar output to keep the engine battery topped up, but it doesn't over charge it, for reasons already explained.
When the engine is running and the engine battery reaches a predetermined voltage the VSR will close and allow the charge to go to the domestic bank. Again, there is no way that this will overcharge the engine battery.
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.
lw395
Well-Known Member
Your VSR is stupid enough to connect a massive solar array to the engine battery. It's what it's there for!
It's probably not an issue if the house battery bank is in float rather than bulk charge a lot of the time.
skipmac
Well-Known Member
There are more myths, fanciful theories and just plain nonsense on these forums about batteries, charging and solar power than anything else, anchors included.
Go onto one of the American forums and guns on boats will give all these a run for the money, especially in the area of nonsense. :disgust:
PS. You forgot to mention monohulls vs cats
skipmac
Well-Known Member
There are more myths, fanciful theories and just plain nonsense on these forums about batteries, charging and solar power than anything else, anchors included.
Go onto one of the American forums and guns on boats will give all these a run for the money, especially in the area of nonsense. :disgust:
PS. You forgot to mention monohulls vs cats
PaulRainbow
Well-Known Member
I don't have a massive solar array, who does have a massive one on a boat ?
lw395
Well-Known Member
Plenty of people have hundreds of watts these days.
I wonder what caused the smouldering battery in the other thread?
dom
Well-Known Member
FWIW I asked Varta about something similar. Like many many yachts I have triple source charging from alt, solar & shore-power. S/p runs through a smart-charger sensing both domestic and start batts, but the solar senses only the domestic. The machine sensed alternator is set at 14.5V.
Both banks are on float upon arrival at the boat. I start the engine from the domestic bank which immediately sees 14.5V. I might anchor somewhere for the night, the domestic bank is discharged somewhat and the solar goes straight to 14.4V when light conditions allow. Start the engine and my domestics see 14.5V. The start battery is isolated unless switched into circuit.
Varta suggested that extended motoring at 14.5V on a fully charged battery is not optimal because overcharging a sealed lead acid battery can result in gassing to the point that hydrogen and oxygen cannot recombine as normal. Excess gasses are then released from the pressure release valve and electrolyte is lost. There is also the danger of damaging the internal grid. They advisd that overvoltage conditions could exist from 14.2V at 30C.
I don't motor much so not that worried.
Much more sophisticated systems exist (esp on mobos) although a crude VSR -- which allows the starter battery to see 14.5V every time the engine is running and/or the solar is on bulk/absorption -- carries an obvious danger to the safety-critical start battery.
It would be interesting to hear what our forum battery guru Plevier thinks about this.
Both banks are on float upon arrival at the boat. I start the engine from the domestic bank which immediately sees 14.5V. I might anchor somewhere for the night, the domestic bank is discharged somewhat and the solar goes straight to 14.4V when light conditions allow. Start the engine and my domestics see 14.5V. The start battery is isolated unless switched into circuit.
Varta suggested that extended motoring at 14.5V on a fully charged battery is not optimal because overcharging a sealed lead acid battery can result in gassing to the point that hydrogen and oxygen cannot recombine as normal. Excess gasses are then released from the pressure release valve and electrolyte is lost. There is also the danger of damaging the internal grid. They advisd that overvoltage conditions could exist from 14.2V at 30C.
I don't motor much so not that worried.
Much more sophisticated systems exist (esp on mobos) although a crude VSR -- which allows the starter battery to see 14.5V every time the engine is running and/or the solar is on bulk/absorption -- carries an obvious danger to the safety-critical start battery.
It would be interesting to hear what our forum battery guru Plevier thinks about this.
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Plevier
Well-Known Member
Ha my ears are burning!
Have not read whole thread as I know next to nothing about VSRs or solar.
I can only agree with Varta's comments. Really prolonged charging above 14V will cause water loss and possibly grid corrosion. Certainly worsened by high temperature. (The charging voltage should be temperature compensated anyway.)
The battery does get quite a lot of time at over 14V in a heavily used car but whereas on most boats the start battery has zero load when engine off, cars will provide some drain overnight for alarm systems etc.
However as I always say, overcharging is rarely as harmful than undercharging.
Have not read whole thread as I know next to nothing about VSRs or solar.
I can only agree with Varta's comments. Really prolonged charging above 14V will cause water loss and possibly grid corrosion. Certainly worsened by high temperature. (The charging voltage should be temperature compensated anyway.)
The battery does get quite a lot of time at over 14V in a heavily used car but whereas on most boats the start battery has zero load when engine off, cars will provide some drain overnight for alarm systems etc.
However as I always say, overcharging is rarely as harmful than undercharging.
PaulRainbow
Well-Known Member
You have a funny idea as to what constitutes a "massive solar array"
lw395
Well-Known Member
It's massive when you're trying to find space for it on deck.
But it only takes a few hundred unwanted milliamps to see off a battery over a season.
sailinglegend420
Well-Known Member
That is why I stopped posting on here - but on threads like this someone needs to input some new facts.There are more myths, fanciful theories and just plain nonsense on these forums about batteries, charging and solar power than anything else, anchors included.
The man from Varta got it right on dom's thread below - and so did Plevier.
The point that every one is missing is that “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.
So consider when charging only the starter battery just how long the charger would normally stay at absorption voltage before it falls to float. With only 1-2 Ah to replace it will not take very long, maybe only 15 minutes.
During the absorption phase of charging the house bank it can sit at their gassing voltage of 14.4 volts for 4 hours or more with no problems, there will be small amounts of gassing but the electrical energy from the current is charging the batteries. It is only when the batteries are fully charged, and still sitting at the gassing voltage, that this voltage will causes the batteries to gas more heavily. By reducing the charge voltage from 14.4v to a float of 13.8v or less gassing will stop. It is worth noting that gassing voltages and therefore the correct absorption charging voltage are based on battery temperature, 14.4v of 25ºC, 14.2v at 30ºC, 13.98v at 40ºC.
Next consider what happens when a VSR joins the two banks together and the starter is nearly fully charged, but the service bank is heavily depleted. There will be a large discharge of current, maybe 100 amps or more, from the starter to the service bank as the voltages equalise. In this situation the starter bank may have lost more Ah, but it will still not need 6 hours at 14.4 volts before it should be dropped to float voltage. This discharge is also an unnecessary extra load on the starter battery and another good reason why manual switches or automatic battery combiners are not the best solution to split charging.
Also consider what happens if the temperature in July has risen to 30 degrees. At 30 degrees batteries gas at 14.20 volts, so a sealed battery sitting at 14.4 volts will gas much harder. This is "overcharging" the battery which will lose water and die more quickly, especially if it is a sealed battery that can't be topped up with water.
BUT WHY DON’T CAR BATTERIES GET OVERCHARGED?
All detractors of these gassing theories always quote car batteries and simple car regulators as not being a problem. Surely a car battery is happy sitting there for hours without overcharging?
But many car alternators regulate at 14-14.2 volts, or less, well below the gassing voltage. Modern alternators may go as high as 14.6v, but they also have built in temperature compensation that will fairly quickly reduces the voltage below 14v - well below the gassing voltage, this makes them like very simple multi stage chargers. Modern cars with smart alternators are ECU controlled to drop the voltage down to a float level when the batteries are charged.
So the bottom line is car batteries never get overcharged, but many boats use car alternators with temperature compensators that also drop the voltage down quickly to below 14 volts. This means a service battery that needs to sit at 14.4 volts for several hours is being undercharged.
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. This is the same problem when overwintering and leaving the solar controller on for 6 months. Every day the sun shines and the controller takes the voltage up to 14.4v or higher and sits there based on a timer - maybe for 3 hours. Do this every day on a fully charged battery with all loads disconnected and the batteries with be "overcharged" and gas excessively and dry out.
It is worth noting that Odyssey Batteries say batteries charged with a high voltage multi-stage regulator must all drop to float - at a voltage of 13.5v to 13.8v - when the batteries are fully charged. If not their warranty is void.
GHA
Well-Known Member
Where are the facts?
Lots of opinion which may or may not be based in reality but without a single link to any detailed analysis or a single piece of data.
Without backup it's just more forum noise.
Unless it's from Plevier, as he's shown time and again to be probably the only poster here who really does have long term experience in the industry and really know his stuff. And never really says anything 100%definite
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PaulRainbow
Well-Known Member
Will this "someone" be arriving to post anytime soon ?
In the meantime ;
Seriously, 100 amps, just because you parallel a fully charged battery with a depleted one ? Methinks that's nonsense. In fact, i know that's pure nonsense. In my van at the moment are some brand new batteries and a couple of not so good ones. I'll bet you any amount of money you choose, at 100/1 that if i connect them in parallel and monitor any current transfer with an ammeter it isn't anything remotely like a fraction of 100a. If this were true, when jump starting a car with a flat battery, from a vehicle with a fully charged battery, you'd have 100 amps or more flowing from one to the other and the donr car would be flat in time time at all. In the real World, this does not happen.
This discharge you claim occurs does not happen, so is irrelevant. A decent solar controller will not be charging at 14.4v absorption for 6 hours or more. The solar controller will be primarily charging the domestic bank, if setup correctly, so will be regulating voltage accordingly, it won't be constantly charging at 14.4/6 volts.
When my engine is running the alternator is charging, whether or not i have a VSR or any other form of split charging makes no difference to that. So, i could argue that by having a VSR i am overcharging the engine battery less, as the domestic bank is taking some of the charge and the onboard systems are taking power from all of the batteries, engine battery included, as they are all in parallel. Just like a car, the alternator output will be running the equipment that's on and keeping the batteries topped up.
You also mention smart alternators. I doubt many of us have those on a boat. But, regardless, you cannot use a VSR with a smart alternator, it won't work.
dom
Well-Known Member
Crumbs!!
1. Sailinglegend's 100A: simple; all you need is to switch on the engine with a depleted domestic bank, while simultaneously activating a biggish load, perhaps through an inverter. The VSR connects the start batt into line and a whack of amps flows through the VSR cable ...quite possibly lots more than the maximum charge the alternator can deliver. Serious fires have started this way, which is why marine electricians will only fit VSRs with overload cutouts amongst other safety features.
2. "A decent solar controller will not be charging at 14.4v absorption for 6 hours or more": well, even Victon's popular 15/75 baby MPPT Controller does this! If it sees 11.9V in the morning (easily possible under load), then 6 hours absorption it is (P6)
https://www.victronenergy.com/uploa...er-MPPT-75-10--75-15-EN-NL-FR-DE-ES-SE-LU.pdf
3: VSR makes no difference in practice to charging the start battery: On your simple setup, no, and perhaps that's fine for you. But it would not be fine for serious sailors. Such a setup will wash the start battery with 14.5V for hours when motoring, and then the solar kit alongside any other charging gear will wash it some more at a similar voltage each day. Varta amongst other 'reputable' batt manufacturers explicitly warn about the possibility of battery damage with too high a float. Trojan are okay with 13.8V float, but Varta recommends just 13.4V for its SLAs with a slightly different chemistry:
www.varta-automotive.com/en-gb/varta-battery-support/charging/how-to-charge-a-car-battery
Why on earth would any sailor choose to disregard hard manufacturer advice, incidentally backed up by Plevier the forum's undoubted expert on batteries, in favour of hearsay which endangers a safety critical piece of gear like the start battery? Not to mention invalidating the guarantee in the process.
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skipmac
Well-Known Member
First, marine electrical experts DO recommend battery combiners. Nigel Calder in his very well regarded technical books (arguably the gold standard in marine technical books) on boat repair and maintenance.
Very notably, Rod Collins of Compass Marine in Maine who is not only a marine electrical technician but also does very detailed testing on all things marine electrical especially batteries including long term tests on all battery chemistries, how they work with various charge regimens, life span and duty cycles and works very closely with most marine battery manufacturers AND helps write electrical standards for ABYC. Rod has more money invested sophisticated battery testing equipment than many people have invested in their boats.
https://forums.sailboatowners.com/index.php?threads/1-both-2-off-switches-thoughts-musings.137615/
I previously posted the link above to Mr Collins post on the issue but many rejected it because it was too long and involved. I posted a link to Yandina Marine commenting on the same issue and that was rejected because it was to simplistic.
Very notably, Rod Collins of Compass Marine in Maine who is not only a marine electrical technician but also does very detailed testing on all things marine electrical especially batteries including long term tests on all battery chemistries, how they work with various charge regimens, life span and duty cycles and works very closely with most marine battery manufacturers AND helps write electrical standards for ABYC. Rod has more money invested sophisticated battery testing equipment than many people have invested in their boats.
https://forums.sailboatowners.com/index.php?threads/1-both-2-off-switches-thoughts-musings.137615/
I previously posted the link above to Mr Collins post on the issue but many rejected it because it was too long and involved. I posted a link to Yandina Marine commenting on the same issue and that was rejected because it was to simplistic.
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PaulRainbow
Well-Known Member
Let's at least try and stick to the facts. Your comments above do not relate in any way to what sailinglegend said. He didn't mention heavy loads or inverters, he simply said the VSR would allow the banks to equalise at 100a or more. Nonsense.
That not withstanding, my VSR and cabling are rated at 120a and fused accordingly.
I have a Victron controller, it's 6 hrs max, not 6 hrs plus. Most mine has ever spent on absorption is just over 2 hrs. One of the benefits of having a balanced system that doesn't abuse the domestic bank.
lol, what arrogance.
My setup may well indeed be simple. I have sufficient solar panels, connected to a quality controller, a quality VSR and an appropriately matched battery bank. All appropriately matched for the needs of my boat. I have monitoring systems for the solar controller, domestic bank and engine battery with low voltage alarms and relays set to turn the mains charger in the event of a low voltage situation and my being connected to shore power.
I have not had a low voltage alarm or had the need to turn the mains charger on since i installed everything in Feb this year.
That's nonsense. The alternator will be charging whether there is a VSR fitted or not. With a VSR the batteries all become one giant battery (Goggle batteries in parallel), domestic loads will be coming evenly from all batteries and the alternator output is also going to all batteries. You appear to have a strange picture in your head of the engine battery being a single entity and the charging current all "washing over" it to get to the domestic bank. Not so.
More of your funny "washing"
That's fine, my solar controller and mains charger are both set to charge at 13.4v float. My solar controller spends a significant time each day at float, with the engine battery in parallel via the VSR, nicely sitting at float voltage.
I have disregarded no advice. I have instead built a balanced system that works very well.
Could you point me to the post where Plevier says not to fit a VSR please ?
No, of course you can't.
post #62
dom
Well-Known Member
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."
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
http://sterling-power.eu/products-proconnect-info.htm
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. 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 (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
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