PaulRainbow
Well-Known Member
How does your post at #11 answer my question to Richard at post #10 ?
Alternator and Solar living in perfect harmony!
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How does your post at #11 answer my question to Richard at post #10 ?
PaulRainbow
Well-Known Member
That was the point of my question at #10, it tells you nothing of use if there are two charging sources connected to the battery. You would need some additional data from elsewhere, or adopt a different method of measuring.
rogerthebodger
Well-Known Member
Paul
GHA , Richard and Neolex are all correct.
My domestic bank have 3 separate solar panel regulators and a 120 Amp alternator. I do also have a wind generator and when all are charging the battery voltage will be the same depending on the state of charge and the current available from the various charging sources.
When my batteries start to become fully charges and the voltage rises the various charging sources do turn odd depending on their cut off voltage.
I have both on/off regulators and PWM regulators which all work together.
Consider what happens when you jump a car with a discharges battery with one that is fully charges. Current will flow fro the charges to the discharges and the internal resistance of the batteries will cause the resultant voltage to equalise.
Its basic electrical theory.
RichardS
N/A
Surely that would tell me that the Victron would only be putting out 14.4V if the batteries were almost fully charged since it would be in it's bulk phase if the batteries were low. If the batteries are not fully charged then the 14.4V is the result of the alternator putting charge into the batteries which is what the OP wants?
Richard
PaulRainbow
Well-Known Member
What about the second source ?
GHA
Well-Known Member
Really confused now, Want to know the voltage across battery terminals then measure it. What's so difficult about measuring voltage with more than one power source connected?
RichardS
N/A
I don't understand. I thought there was a paralleled set of batteries and two charging sources, solar and alternator?
Richard
noelex
Well-Known Member
Precisely. The information is of no value (unless the adsorption voltage is at or below 14.4v) therefore a voltage reading like this does not play a role in the charging algorithm of the alternator or solar regulator (with rare and minor exceptions)
A typical charging algorithm will raise the voltage to the absorption set point (say 14.6v ) for the absorption time (usually around 1.5 hours) it then deems the batteries charged and will drop down to float.
It does not matter if the absorption voltage was reached primary with the alternator output, the solar panel output, or a mix. The battery is indeed fully charged.
PaulRainbow
Well-Known Member
There is a big difference between measuring battery voltage and measuring voltage at the battery.
It is a well known fact that multiple charging sources can be difficult to manage, Google it if you don't believe me.
As i sit here my battery monitor is showing 12.7v The batteries are 95% charged and the solar controller is putting out 2.5a, that give me an overall deficit of of -1.6a
Let's see what happens if i turn the mains charger on.........................
Five minutes later, the battery monitor shows 14.3v, the mains charger is at 20a giving a net gain of 17.3a The solar controller almost instantly went into absorption (from bulk) and the output has dropped to a fraction of an amp
This proves that measuring the voltage at the batteries has little to do with actual battery voltage, when there are loads or charging sources. It also proves that one charging source will influence another.
Let's try turning the mains charger off again..........
Surprise surprise, the solar controller has gone back into bulk mode, the voltage has dropped back to 12.9 and the output from the solar controller has risen to its former 2.5a
If there was more Sunshine the output differences of the solar controller would have been even more noticeable. If i turn the mains charger on while the solar controller is asleep it will not start again, as it sense the voltage from the mains charger.
It is a well known fact that multiple charging sources can be difficult to manage, Google it if you don't believe me.
As i sit here my battery monitor is showing 12.7v The batteries are 95% charged and the solar controller is putting out 2.5a, that give me an overall deficit of of -1.6a
Let's see what happens if i turn the mains charger on.........................
Five minutes later, the battery monitor shows 14.3v, the mains charger is at 20a giving a net gain of 17.3a The solar controller almost instantly went into absorption (from bulk) and the output has dropped to a fraction of an amp
This proves that measuring the voltage at the batteries has little to do with actual battery voltage, when there are loads or charging sources. It also proves that one charging source will influence another.
Let's try turning the mains charger off again..........
Surprise surprise, the solar controller has gone back into bulk mode, the voltage has dropped back to 12.9 and the output from the solar controller has risen to its former 2.5a
If there was more Sunshine the output differences of the solar controller would have been even more noticeable. If i turn the mains charger on while the solar controller is asleep it will not start again, as it sense the voltage from the mains charger.
RichardS
N/A
But surely that's two smart charging systems and one might well "out-smart" the other. The OP has a smart system (Victron) and a stupid system (alternator) and he wants the stupid system to take precedence ..... which is what it will do.
Richard
GHA
Well-Known Member
ISTM there are a couple of fundamental wrong turns back at the start if anyone would like to chime in...
Sense the voltage from the solar controller? Does it have any say about the voltage at the battery terminals other than limiting the max voltage it will put out?
"reduce its output.". Is that possible? Don't alternator regulators limit voltage, not current. Again it's down to the batteries to decide how much current they will take.
"To get max power into the batteries from an alternator you need to turn off your solar" sounds very much like myth.
Sense the voltage from the solar controller? Does it have any say about the voltage at the battery terminals other than limiting the max voltage it will put out?
"reduce its output.". Is that possible? Don't alternator regulators limit voltage, not current. Again it's down to the batteries to decide how much current they will take.
"To get max power into the batteries from an alternator you need to turn off your solar" sounds very much like myth.
noelex
Well-Known Member
Sorry Paul that does not make sense to me. The battery voltage is always the battery voltage. It may measure very slightly different at different points due to the effects of resistance in the wires etc. Perhaps you mean the resting battery voltage then yes, there is often big difference between the battery voltage and the resting battery voltage.
I am not sure what concerns you about the above behaviour. If you are expecting the solar regulator to keep putting out the same current when the battery charger is turned on this is not correct, nor would it be usually be appropriate in the above situation. The solar regulator has switched to absorption mode because the voltage has risen to (or above) the bulk/absorption voltage which once again is appropiate.
The two charging sources will influence each other, once again this is exactly as should be. The net summuation of the two charge sources is what will charge the battery. If regulation voltage has been reached and one charge source suddenly produces more current the other charge source will produce less.
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PaulRainbow
Well-Known Member
Yes, i'm referring to the resting voltage.
Nothing concerns be about the above behavior, it is indeed exactly what i would expect. I mention it because some people here clearly think that two charging sources will not influence one another. The effect is particularly noticeable when the two sources are solar and shore power chargers, in my experience.
matthewriches
Well-Known Member
Interesting subject but not really for a friday night :very_drunk:. Thankfully not had to worry about it too much but I did have a weird situation on a survey dive boat, twin engine mobo with a solar charger and shore power charger.
The results with all batteries paralleled were...
500w solar on its own to act as a trickle charger if mains was ever disconnected in the marina - worked fine.
Old victron charger as ships main charger for both engine batteries and ships service (3 outputs separated) - worked fine.
Big ass pretolite alternators running on their own - worked fine.
If the charger was on with the solar, it pretty much stopped the solar.
If the engines were running with or without the charger, it pretty much stopped the solar.
If the engines were running with the charger but no solar - variable output on both alternators and charger.
If the engines were running on their own with no solar or mains charger - both alternators variable output.
The above was on marginally discharged batteries (both engines cranked a few times with the stop in to cause deliberate discharge).
There wasn't 2 smart chargers in the above situation.
But I suspect the alternator will just cause the solar to turn off unless you happen to have an Adverc or similar, so therefore ending up with 2 smart chargers which I would guess could try and guzzump each other.
I think it is one of those things that isn't worth worrying about. But as a conclusion the way to really see what is going on with the OP setup is to go around with a clip on ammeter (ensure it is DC compatible) and actually see what is coming out of what in different circumstances as I did last year with the above.
The results with all batteries paralleled were...
500w solar on its own to act as a trickle charger if mains was ever disconnected in the marina - worked fine.
Old victron charger as ships main charger for both engine batteries and ships service (3 outputs separated) - worked fine.
Big ass pretolite alternators running on their own - worked fine.
If the charger was on with the solar, it pretty much stopped the solar.
If the engines were running with or without the charger, it pretty much stopped the solar.
If the engines were running with the charger but no solar - variable output on both alternators and charger.
If the engines were running on their own with no solar or mains charger - both alternators variable output.
The above was on marginally discharged batteries (both engines cranked a few times with the stop in to cause deliberate discharge).
There wasn't 2 smart chargers in the above situation.
But I suspect the alternator will just cause the solar to turn off unless you happen to have an Adverc or similar, so therefore ending up with 2 smart chargers which I would guess could try and guzzump each other.
I think it is one of those things that isn't worth worrying about. But as a conclusion the way to really see what is going on with the OP setup is to go around with a clip on ammeter (ensure it is DC compatible) and actually see what is coming out of what in different circumstances as I did last year with the above.
ip485
Well-Known Member
For those who think the solar will switch off this isnt my understanding or experience.
I have two intelligent mains charger - 100A and 50A, 875W solar and Balmar alternator with a BMP monitor and shunts.
With one charger on I might put 30A or 40A into the batteries, switch both on and I can see 60A input and a significant reduction in time before the chargers go into float. One charger will inevitably go to float a little before the other and both obviously back off significantly as the bank approaches 100% charge (or something close to). The alternator and solar behave in exactly the same way and I routinely run the solar and alternator together as well as the solar and mains chargers.
My understanding is that all the chargers effectively care about is the resistance to their output and so will back off the charge as the set resistance is approached.
It is a common myth often repeated that you cant run two chargers together, and I thought so for a long time. There are some older chargers that may be problematical but I dont believe this to be the case with any modern intelligent charger and many experienced crusiers use exactly this technique to reduce charge times.
Of course again it depends on the alternator, the Balmar uses an intelligent charger in much the same way as a mains charger.
The same principle operates in light aircraft as well. Typical light twins will often have alternators and intelligent chargers on both engines, lose one alternator and there will be insufficient power to maintain all the avionics and it is appropriate to load shed. Both are contributing to maintaining input to the battery(ies) and both work happily in tandem, in fact it could be said you would very much prefer they do.
I have two intelligent mains charger - 100A and 50A, 875W solar and Balmar alternator with a BMP monitor and shunts.
With one charger on I might put 30A or 40A into the batteries, switch both on and I can see 60A input and a significant reduction in time before the chargers go into float. One charger will inevitably go to float a little before the other and both obviously back off significantly as the bank approaches 100% charge (or something close to). The alternator and solar behave in exactly the same way and I routinely run the solar and alternator together as well as the solar and mains chargers.
My understanding is that all the chargers effectively care about is the resistance to their output and so will back off the charge as the set resistance is approached.
It is a common myth often repeated that you cant run two chargers together, and I thought so for a long time. There are some older chargers that may be problematical but I dont believe this to be the case with any modern intelligent charger and many experienced crusiers use exactly this technique to reduce charge times.
Of course again it depends on the alternator, the Balmar uses an intelligent charger in much the same way as a mains charger.
The same principle operates in light aircraft as well. Typical light twins will often have alternators and intelligent chargers on both engines, lose one alternator and there will be insufficient power to maintain all the avionics and it is appropriate to load shed. Both are contributing to maintaining input to the battery(ies) and both work happily in tandem, in fact it could be said you would very much prefer they do.
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Mistroma
Well-Known Member
None of the multi-source charging results are surprising as we have no idea of the individual settings for each device.
OPs post said 115A alternator and 15W panel. Presuming battery was a sensible size (e.g. 100Ah, not bank of rechargeable AAA
) then the solar will have negligible impact on battery voltage unless battery is close to full charge. Sticking 1A from any source designed for 12V system will barely alter the voltage on a 50%-80% SOC battery (for purpose of argument).
As others have said, alternator output should not be changed by presence of solar in that situation.
Surprised OP has MPPT on 15W panel, expensive for panel size. Perhaps he has an upgrade in mind.
Completely different if 300W solar via MPPT in bright sunshine, I'd expect that to very significantly reduce the output of a standard 115A alternator (i.e. no fancy regulators, A-B chargers etc.)
OPs post said 115A alternator and 15W panel. Presuming battery was a sensible size (e.g. 100Ah, not bank of rechargeable AAA
) then the solar will have negligible impact on battery voltage unless battery is close to full charge. Sticking 1A from any source designed for 12V system will barely alter the voltage on a 50%-80% SOC battery (for purpose of argument).As others have said, alternator output should not be changed by presence of solar in that situation.
Surprised OP has MPPT on 15W panel, expensive for panel size. Perhaps he has an upgrade in mind.
Completely different if 300W solar via MPPT in bright sunshine, I'd expect that to very significantly reduce the output of a standard 115A alternator (i.e. no fancy regulators, A-B chargers etc.)
ip485
Well-Known Member
All good modern chargers and controllers can be individually set and should be set to be compatible with the batteries - the easiest way to destroy a battery bank is to believe the bank is being charged to 100% because the gauge tells you it has, when in fact it hasnt.
noelex
Well-Known Member
An example which might help explain things:
Let's assume the ideal battery algorithm for a particular brand of battery requires an absorption voltage of 14.6v. There are two charge sources, solar and an alternator are both programed appropriately. Let's also assume a one particular point in the charge cycle 20 amps will be required for the battery voltage to reach 14.6v.
If the solar panels are only capable of putting out 5 amps the voltage will below 14.6v and there will be no regulation. If we start the engine we have several possibilities:
The solar panels will shut down completely and the alternator will provide 20 amps.
The solar panels will continue to deliver 5 amps and the alternator will provide 15 amps.
Some combination of the above. For example the solar panels deliver 2 amps and the alternator provides 18 amps.
As far as the battery is concerned all these possibilities are exactly the same. The battery receives its required 20 amps and the battery voltage climbs to the required 14.6v.
Which if these above combinations will occur depends on the precise voltage set points but it is of no importance. In the first scenario the owner may be concerned that when the engine is started the solar panels shut down. In the second scenario the owner may be concerned that the alternator is only putting out 15 amps when it used to put out 20 amps, or they may notice if the solar panels are turned off the alternator output climbs. However, in all cases the battery is being charged correctly and the charge sources are doing exactly what they should be doing.
This is just one example but it shows how two charge sources typically behave to charge the battery correctly.
As a general rule multiple charge sources will “play together nicely”. There are a couple of potential problems that can be a nuisance. The absorption time can end up being longer than ideal if this applied sequentially and the trailing end amps feature on some chargers can drop the charger back to float prematurely. In most cases these are very minor issues.
Let's assume the ideal battery algorithm for a particular brand of battery requires an absorption voltage of 14.6v. There are two charge sources, solar and an alternator are both programed appropriately. Let's also assume a one particular point in the charge cycle 20 amps will be required for the battery voltage to reach 14.6v.
If the solar panels are only capable of putting out 5 amps the voltage will below 14.6v and there will be no regulation. If we start the engine we have several possibilities:
The solar panels will shut down completely and the alternator will provide 20 amps.
The solar panels will continue to deliver 5 amps and the alternator will provide 15 amps.
Some combination of the above. For example the solar panels deliver 2 amps and the alternator provides 18 amps.
As far as the battery is concerned all these possibilities are exactly the same. The battery receives its required 20 amps and the battery voltage climbs to the required 14.6v.
Which if these above combinations will occur depends on the precise voltage set points but it is of no importance. In the first scenario the owner may be concerned that when the engine is started the solar panels shut down. In the second scenario the owner may be concerned that the alternator is only putting out 15 amps when it used to put out 20 amps, or they may notice if the solar panels are turned off the alternator output climbs. However, in all cases the battery is being charged correctly and the charge sources are doing exactly what they should be doing.
This is just one example but it shows how two charge sources typically behave to charge the battery correctly.
As a general rule multiple charge sources will “play together nicely”. There are a couple of potential problems that can be a nuisance. The absorption time can end up being longer than ideal if this applied sequentially and the trailing end amps feature on some chargers can drop the charger back to float prematurely. In most cases these are very minor issues.
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Mistroma
Well-Known Member
Completely agree, my original wind/solar regulator pretty much stopped charging my T105s around 85% (based on temp. corrected SG). I checked for a few days to get a baseline and tweaked the defaults to stop regulator throwing away useful sunshine. Panels weren't large enough to get to 100% at that time but huge improvement in performance after adjustment.
I was always surprised to find how many people just accepted defaults.
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GHA
Well-Known Member
So how would that work? ISTM that given that an alternator regulator can only look at the voltage set point then it will only 'very significantly reduce the output' it the solar current is sufficient to push the battery voltage up to very near whatever that set point is. The reduced alternator output is down to the batteries accepting much less charge as they are heading towards full, nothing to do with solar somehow fooling the alternator. So why care?
Same with "turn off the solar to get max from the alternator" - why bother? How will the batteries know any different?
