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alan_fincher

Solar Overcharging Normal Lead Acid Battery Bank - Asking for a friend...

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5 hours ago, Tony Brooks said:

 . Just in case the controller thinks its on a 24 volts bank.

That has been known of a few occasions 

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If that is a possibility, are there any configuration options that allow you to override it deciding what voltage bank it is connected to, and to tell it is 12 volts, and never to switch to 24 volts?

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1 hour ago, alan_fincher said:

If that is a possibility, are there any configuration options that allow you to override it deciding what voltage bank it is connected to, and to tell it is 12 volts, and never to switch to 24 volts?

I assume that you are discounting the possibility that it is performing an equalisation charge then.

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1 hour ago, alan_fincher said:

If that is a possibility, are there any configuration options that allow you to override it deciding what voltage bank it is connected to, and to tell it is 12 volts, and never to switch to 24 volts?

If had 'switched' to the default 24v, why / how would it be putting out ONLY 15v - 16v instead of 26-28v ?

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4 minutes ago, Alan de Enfield said:

If had 'switched' to the default 24v, why / how would it be putting out ONLY 15v - 16v instead of 26-28v ?

I have never tried but I doubt you would ever get a 12 volt battery bank up to 26 volts unless you had lots of power and a cooling system for the batteries

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1 hour ago, ditchcrawler said:

I have never tried but I doubt you would ever get a 12 volt battery bank up to 26 volts unless you had lots of power and a cooling system for the batteries

 

I would imagine charged 12 volt wet cell batteries would gas very profusely if you put 24 volts across them for any time. They certainly do with 16 volts across them when equalising them.

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2 hours ago, Alan de Enfield said:

If had 'switched' to the default 24v, why / how would it be putting out ONLY 15v - 16v instead of 26-28v ?

Maybe because the batteries are themselves preventing the voltage rising anything like that high???

I'm not expert enough to know what would happen, but I'm not convinced if you put 28V of solar across a 12 volt battery bank that you would measure anything that was around 28 volts.  Would you?



 

2 hours ago, Phil. said:

I assume that you are discounting the possibility that it is performing an equalisation charge then.

I'm not discounting anything.  This isn't my boat, and I'm not familiar with the controller in use.

If it is though, it would appear to be doing it more of less permanently.  Is that something that could happen by some accidental changing of a setting on the controller.

How easy is it for the owner to check that there are no inappropriate settings in the controller?

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Does your friend not have a manual they can read through to check for any setting? Is it possible that  the batteries have got wired up incorrectly seeing as how two of them have been changed recently? Just asking.

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2 hours ago, alan_fincher said:

Maybe because the batteries are themselves preventing the voltage rising anything like that high???

I'm not expert enough to know what would happen, but I'm not convinced if you put 28V of solar across a 12 volt battery bank that you would measure anything that was around 28 volts.  Would you?



 

I'm not discounting anything.  This isn't my boat, and I'm not familiar with the controller in use.

If it is though, it would appear to be doing it more of less permanently.  Is that something that could happen by some accidental changing of a setting on the controller.

How easy is it for the owner to check that there are no inappropriate settings in the controller?

Yes it can happen more or less permanently, if the setting to equalise has inadvertently been set to occur daily. I don’t have this particular controller, but with the manual and sitting in front of it, it would be fairly straightforward to check and then resolve.

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On my MT50 controller you can manually select the equalisation voltage (up to 17v) and the duration from 0-3hours.

 

Maybe the OP's friend could do a 'factory reset' which may sort out any buttons that have been randomly pressed without understanding the implications.

 

 

 

 

 

Screenshot (134).png

Edited by Alan de Enfield

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2 hours ago, Phil. said:

Yes it can happen more or less permanently, if the setting to equalise has inadvertently been set to occur daily. I don’t have this particular controller, but with the manual and sitting in front of it, it would be fairly straightforward to check and then resolve.

Yes,

I have now downloaded what I think is the right manual, and whilst automatic equalisation should be "off" by default, when it is enabled, it can be set to as frequently as "daily".  Default voltage would be 16.2V though - greater than any value he has so far reported seeing.

I'm not clear if my friend can currently access these settings.  He has apparently now ordered up a Bluetooth dongle that will allow him to see more information.

I have asked him if the equalisation stuff is something he can currently check, or whether he can only do so with the dongle, once he has it.

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Just now, alan_fincher said:

Yes,

I have now downloaded what I think is the right manual, and whilst automatic equalisation should be "off" by default, when it is enabled, it can be set to as frequently as "daily".  Default voltage would be 16.2V though - greater than any value he has so far reported seeing.

I'm not clear if my friend can currently access these settings.  He has apparently now ordered up a Bluetooth dongle that will allow him to see more information.

I have asked him if the equalisation stuff is something he can currently check, or whether he can only do so with the dongle, once he has it.

Just on the default voltage, during equalisation this is the maximum voltage that will be delivered during the process, but it can take a long time to get there, as the charge voltage generally commences around the absorbtion rate, and then gradually climbs to either the maximum, or until the allotted time limit is reached. This process can be even slower when being done by solar, as occasional cloud cover can reduce the voltage level.

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He tells me he needs the dongle before he can check current settings.  I will report back, but currently he is "manually controlling" it by part covering a panel with a rug when the sun is strongest!

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10 hours ago, Alan de Enfield said:

If had 'switched' to the default 24v, why / how would it be putting out ONLY 15v - 16v instead of 26-28v ?

That would depend on how many watts your panels can generate.  If say 100w that would be a current of 6A at 15.5v so quite possible, if you had a couple of kW then I would expect boiling batteries.

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Update from my friend who now has the necessary Bluetooth equpment to allow him to check system settings.

 

He reports it was indeed thinking it was a 24 volt system, so he has now reset it to a 12 volt system.

Charging now at a much more reasonable 14.1 volts.

It is not clear how it got it wrong in the first place, and I have advised hm to keep an eye on it.

 

Thanks to all who contributed ideas.

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On 17/04/2020 at 10:57, Alan de Enfield said:

If had 'switched' to the default 24v, why / how would it be putting out ONLY 15v - 16v instead of 26-28v ?

Now we know it was set at 24 volts I will attempt to answer your question.

 

Any charge source is likely to have inductive components in it so as the current rises the induced voltage (operating against the charging voltage) also rises. this has the effect of reducing the charging voltage. The current flowing from the controller set to 24 volts into 12v batteries would be high so it depressed the charging voltage.

 

 

  • Happy 1

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7 minutes ago, Tony Brooks said:

Now we know it was set at 24 volts I will attempt to answer your question.

 

Any charge source is likely to have inductive components in it so as the current rises the induced voltage (operating against the charging voltage) also rises. this has the effect of reducing the charging voltage. The current flowing from the controller set to 24 volts into 12v batteries would be high so it depressed the charging voltage.

 

 

Thankyou.

 

So he has possibly (probably) severely damaged his12v batteries buy putting both a high current and high voltage into them - sort of a 'SUPER HOT' equalisation charge.

When I am equalising at ~ 15v the current is normally only 1A - 2A

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11 minutes ago, Alan de Enfield said:

Thankyou.

 

So he has possibly (probably) severely damaged his12v batteries buy putting both a high current and high voltage into them - sort of a 'SUPER HOT' equalisation charge.

When I am equalising at ~ 15v the current is normally only 1A - 2A

Depending upon how long it was like that I agree, at least grid corrosion and probably plenty of plate shedding but the proof will be how long they continue to do what he needs them to.

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1 hour ago, alan_fincher said:

Update from my friend who now has the necessary Bluetooth equpment to allow him to check system settings.

 

He reports it was indeed thinking it was a 24 volt system, so he has now reset it to a 12 volt system.

Charging now at a much more reasonable 14.1 volts.

It is not clear how it got it wrong in the first place, and I have advised hm to keep an eye on it.

 

Thanks to all who contributed ideas.

As I said I have read several cases of this happening lately 

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Can I suggest that the solar panels were connected to the controller before the batteries, so the wrong voltage was assumed by the controller.  Victron for example do say to connect the batteries first so the controller knows what voltage the system is, then connect the solar panels.

 

This needs checking again if work is carried out on the system including if new batteries are fitted.

 

Pete

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7 minutes ago, Pete7 said:

Can I suggest that the solar panels were connected to the controller before the batteries, so the wrong voltage was assumed by the controller.  Victron for example do say to connect the batteries first so the controller knows what voltage the system is, then connect the solar panels.

 

This needs checking again if work is carried out on the system including if new batteries are fitted.

 

Pete

A couple of the posts I read that definitely hadn't happened, it just swapped over and needed resetting 

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I wonder if a 12V  charger doing an equalisation charge could the voltage high enough for the controller to mistake it for 24 volts. I seem to remember from the past that digital system (TTL I think) considered less than 2V as zero and more than 3 V as one so maybe 15V+ could just tip the balance. Perhaps Nick Dr Bob and Jen could comment.

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52 minutes ago, Tony Brooks said:

I wonder if a 12V  charger doing an equalisation charge could the voltage high enough for the controller to mistake it for 24 volts. I seem to remember from the past that digital system (TTL I think) considered less than 2V as zero and more than 3 V as one so maybe 15V+ could just tip the balance. Perhaps Nick Dr Bob and Jen could comment.

Not according to the user manual which states

The controller will automatically adjust itself to a 12V or a 24V system one time only. If a different system voltage is required at a later stage, it must be changed manually, for example with the Bluetooth app, see section 3.8.

 

So if connected in the correct order (batteries first, then panels) it will be set at 12V and will not change unless it's either intentionally changed (difficult without the remote) or until it is disconnected and then reconnected in the wrong order.

1 hour ago, ditchcrawler said:

A couple of the posts I read that definitely hadn't happened, it just swapped over and needed resetting 

I wonder if this model has a glitch in the firmware?

6 hours ago, alan_fincher said:

It is not clear how it got it wrong in the first place, and I have advised hm to keep an eye on it.

Good advice, it appears.

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On 20/04/2020 at 15:45, Tony Brooks said:

Now we know it was set at 24 volts I will attempt to answer your question.

 

Any charge source is likely to have inductive components in it so as the current rises the induced voltage (operating against the charging voltage) also rises. this has the effect of reducing the charging voltage. The current flowing from the controller set to 24 volts into 12v batteries would be high so it depressed the charging voltage.

 

 

Inductive reactance. 2π f L. Since this is DC f=0. Work it out.

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1 minute ago, Sir Nibble said:

Inductive reactance. 2π f L. Since this is DC f=0. Work it out.

Too much for my brain SirN. I just know it happens and why. I also know confuses the hell out of peeps when making a stab at diagnosing charging/ battery faults from voltage alone. I am far from sure that an MPPT controller or even a PWM one can be considered as pure DC. Pulsed DC possibly but that will give rise to induction.

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