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Smartgauge Questions


rupertbear

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7 minutes ago, Mike the Boilerman said:

In which Gibbo is demonstrably wrong. I can show him two smartgauges, one of which is reading wrong in my opinion.

I think this because both gauges are connected to the same battery and give different readings. In my humble opinion one of them is wrong, and I Challenge Gibbo to prove its me that's wrong and not a gauge!

As I pointed out earlier, Gibbo didn’t make your Smartgauges. 

Edited by WotEver
Carnt spel
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On 06/02/2018 at 18:05, nicknorman said:

The SG is reading correctly. It is warning you that you are not properly charging your batteries fully. You can see that the voltage is dropping to float and then storage way too soon. When charing with a generator, these modes are useless and don't really charge the batteries significantly despite the genny churning away! I think the starting point would be to check the setting called "adaptive charging" and turn it off (it is on by default). Changing settings via a laptop and the correct lead is quite easy, but you have to have the correct lead which is not particularly cheap. You can also change the settings by means of the DIP switches inside the case, but this requires careful reading of the manual (which is not well written IMO!).

One thing you could try as an interim measure whilst you are getting to grips with the manual, is to try switching off the Combi as soon as the voltage drops to 13.8v, then back on again after a few seconds (genny still running). Hopefully this will put it back into absorb mode for another 45 minutes but this is by no means an ideal solution, and changing the settings is the way to go!

But don't delay too much, you are damaging your new batteries by not charging them properly.

I’ve read and re-read the manual so I’m now confident enough to change the settings. However I’m slightly unsure of which absorption voltage to set it to. Basically there are 2 options suitable for Victron deep cycle AGM 14.4v or 14.7v.  I’m inclined to set it to 14.7v giving a faster charge given that I’m off grid and using a generator. Am I correct in my thoughts?

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2 hours ago, nicknorman said:

OK I'll have to give you that one. Tuning or perhaps learning. I feel hard done by though, someone else used the word "calibrating" and now I've got a row for just repeating it!

No problem, Nick!

 

1 hour ago, rusty69 said:

Oh, do you have to? I have lined the popcorn up for at least a 1/2 hour argument.

Stirrer:giggles:

Muppets rule!

Edited by Dr Bob
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10 hours ago, Cloudinspector said:

I’ve read and re-read the manual so I’m now confident enough to change the settings. However I’m slightly unsure of which absorption voltage to set it to. Basically there are 2 options suitable for Victron deep cycle AGM 14.4v or 14.7v.  I’m inclined to set it to 14.7v giving a faster charge given that I’m off grid and using a generator. Am I correct in my thoughts?

Yes I think 14.7 is a good idea. Looking at the battery spec I’d have gone for 14.6 but that perhaps can only be set with a PC, and what’s 0.1v between friends!

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On 6 February 2018 at 09:53, Tony Brooks said:

As lead acid batteries have a cell voltage of 2.2 volts when fully charged I would suggest that a float of 13.2 is rather low.

If the above is true, why is 12.7v usually quoted as the fully charged voltage of a 6 cell 12v battery? Indeed, why is 13.2v often referred to as surface charge?

Not being funny, just trying to understand.

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7 minutes ago, Col_T said:

If the above is true, why is 12.7v usually quoted as the fully charged voltage of a 6 cell 12v battery? Indeed, why is 13.2v often referred to as surface charge?

Not being funny, just trying to understand.

To a degree it depends upon what source you look at. Automobile Electrical Equipment by Young & Griffiths (1958) states "On open circuit the cell voltage drops almost immediately to 2.2 volts and for the initial period of discharge rapidly falls to 2.0V." Battery universe quotes 2.1 volts and other sources quote 2.05 volts for some lead acid batteries.

I take the 2.2 volts to have been worked out from the chemical processes when at being charged rather than measured because you can't measure the underlying cell voltage when being charged.

Whether we call it surface charge or something different it does not matter because if the battery is trying to push out 13.2 volts then a charging voltage will have to be higher to get charge into the battery. My point was that 13.2 volts seems too low to me the keep up with self discharge and that’s what float charging is all about.  If we accept that some battery types do have lower underlying  cell voltage when on charge then in some cases 13.2 volts will be enough to keep them charged but in other cases it seems to me that it will not. 

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26 minutes ago, Col_T said:

If the above is true, why is 12.7v usually quoted as the fully charged voltage of a 6 cell 12v battery? Indeed, why is 13.2v often referred to as surface charge?

Not being funny, just trying to understand.

If a float charger held the voltage at 12.7, the battery would slowly self-discharge and sulphation would ensue. This is just down to the chemistry of the batteries. A voltage of 13.2v will pretty much keep self-discharge and sulphation at bay. A higher voltage say 13.6v will eliminate self-discharge and sulphation, but there will be slight positive plate corrosion which could shorten the life of a battery kept primarily on float. So there is a trade-off (compromise) between a float voltage that eliminates sulphation, and one that doesn’t cause excessive plate corrosion. It’s not back and white! And it will depend a bit on the specific battery chemistry (additives to the lead such as antimony or calcium, acid strength). So the best thing to do is to look at the battery manufacturer’s recommendation.

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1 minute ago, Tony Brooks said:

I also noticed no source I looked at specified the temperature so as chemical reactions seem to go faster as temperature rises this will also have a bearing on the cell voltage at an given time.

Can you expand/clarify that point please? I think I disagree with it but don’t want to rip it to shreads if I’ve misunderstood it!

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Just now, nicknorman said:

Can you expand/clarify that point please? I think I disagree with it but don’t want to rip it to shreads if I’ve misunderstood it!

You may well be correct but from my experience chemical reactions do go faster with heat. For example the setting of polyester or epoxied resins. Cold batteries requiring a higher charging voltage etc. Please substitute whatever word you think more appropriate for "faster".

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15 minutes ago, Tony Brooks said:

You may well be correct but from my experience chemical reactions do go faster with heat. For example the setting of polyester or epoxied resins. Cold batteries requiring a higher charging voltage etc. Please substitute whatever word you think more appropriate for "faster".

The issue is not that chemical reactions go faster when hotter, it is about the effect on battery voltage.

If you are saying that a battery’s rested open circuit voltage is higher when hot, this isn’t correct to any noticeable extent. Yes a chemical reaction normally goes faster when hot, but in an open-circuit battery the chemical reaction is stopped when the cell voltage matches the electrochemical potential of the reaction. (dr Bob will be along shortly to correct my chemistry terminolog!) with the latter varying mostly according to the electrolyte acid strength and barely if at all according to the temperature.

Where the effects of temperature are noticeable is when the reaction is taking place. So a cold battery under heavy discharge will have a lower voltage than the same battery at the same SoC but hotter. But once the discharges stop and adequate recovery time is given (longer for the cold battery) their rested open circuit voltages will be the same.

Edited by nicknorman
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56 minutes ago, Tony Brooks said:

You may well be correct but from my experience chemical reactions do go faster with heat. For example the setting of polyester or epoxied resins. Cold batteries requiring a higher charging voltage etc. Please substitute whatever word you think more appropriate for "faster".

Yes, Tony you are correct. As a rule of thumb, a chemical reaction will double in speed for each 10°C rise in temp so your epoxy/polyester curing comment is spot on. There is more than just a chemical reaction going on in a battery, ie transport of ions to the surface etc so although the battery chemistry is affected by temperature, you cannot use the 'double' rule of thumb ...so Nicks description is right.

46 minutes ago, nicknorman said:

The issue is not that chemical reactions go faster when hotter, it is about the effect on battery voltage.

If you are saying that a battery’s rested open circuit voltage is higher when hot, this isn’t correct to any noticeable extent. Yes a chemical reaction normally goes faster when hot, but in an open-circuit battery the chemical reaction is stopped when the cell voltage matches the electrochemical potential of the reaction. (dr Bob will be along shortly to correct my chemistry terminolog!) with the latter varying mostly according to the electrolyte acid strength and barely if at all according to the temperature.

Where the effects of temperature are noticeable is when the reaction is taking place. So a cold battery under heavy discharge will have a lower voltage than the same battery at the same SoC but hotter. But once the discharges stop and adequate recovery time is given (longer for the cold battery) their rested open circuit voltages will be the same.

Quite so. :)

 

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13 minutes ago, Dr Bob said:

Yes, Tony you are correct. As a rule of thumb, a chemical reaction will double in speed for each 10°C rise in temp so your epoxy/polyester curing comment is spot on. There is more than just a chemical reaction going on in a battery, ie transport of ions to the surface etc so although the battery chemistry is affected by temperature, you cannot use the 'double' rule of thumb ...so Nicks description is right.

Quite so. :)

 

Polyester Resin works better in low Temps. if more catalyst is added to the Mix.Epoxy must have a decent Ambient Temp to Cure at all and it's resin /Catalyst may not be altered to compensate for low Temperature.

 

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12 minutes ago, cereal tiller said:

Polyester Resin works better in low Temps. if more catalyst is added to the Mix.Epoxy must have a decent Ambient Temp to Cure at all and it's resin /Catalyst may not be altered to compensate for low Temperature.

 

No. Polyesters dont cure well below 15°C. You can force them with more cobalt accelerator and peroxide catalyst but the cross linking is compromised. I wouldnt do it.

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12 minutes ago, cereal tiller said:

Polyester Resin works better in low Temps. if more catalyst is added to the Mix.Epoxy must have a decent Ambient Temp to Cure at all and it's resin /Catalyst may not be altered to compensate for low Temperature.

So if I want a little more working time with epoxy wood filler I’ll be better off using it in the unheated shed than in the kitchen?

Or is that just a bad idea?

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1 hour ago, nicknorman said:

The issue is not that chemical reactions go faster when hotter, it is about the effect on battery voltage.

If you are saying that a battery’s rested open circuit voltage is higher when hot, this isn’t correct to any noticeable extent. Yes a chemical reaction normally goes faster when hot, but in an open-circuit battery the chemical reaction is stopped when the cell voltage matches the electrochemical potential of the reaction. (dr Bob will be along shortly to correct my chemistry terminolog!) with the latter varying mostly according to the electrolyte acid strength and barely if at all according to the temperature.

Where the effects of temperature are noticeable is when the reaction is taking place. So a cold battery under heavy discharge will have a lower voltage than the same battery at the same SoC but hotter. But once the discharges stop and adequate recovery time is given (longer for the cold battery) their rested open circuit voltages will be the same.

This is getting very esoteric and as it now has little to do with the original question its probably best if lots of people ignore it.

I think the key is in the phrase "noticeable extent". I accept that is probably true but that is different to "there is no difference". To claim that a cold cell voltage will be lower than a warmer one when under a load and then say there is "no difference" (I know that is not what you said) between rested voltages seems to imply that self discharge does not take place. Surlily self discharge is a load, be it an exceptionally small one.

I fully accept any difference will be small or exceptionally small but not that there will be no difference, maybe even unmeasurable.

It may be of interest to note that  the Fundamentals of Automobile Electronics by Hillier (1993) uses the 2.1 volt per cell as given by Battery Universe but to the best of my knowledge Hillier was more mechanical than electrical so I would not be so keen to take his word as gospel. It is probably worth also noting that between 1958 & 1993, the two published dates) test equipment and/or battery chemistry may we have altered.

 

1 minute ago, WotEver said:

So if I want a little more working time with epoxy wood filler I’ll be better off using it in the unheated shed than in the kitchen?

Or is that just a bad idea?

Yes, and also mix it in a large area try that keeps the resin layer thin so it can radiate heat more readily. As they say, don't ask how I know this!

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28 minutes ago, Dr Bob said:

No. Polyesters dont cure well below 15°C. You can force them with more cobalt accelerator and peroxide catalyst but the cross linking is compromised. I wouldnt do it.

No? 15 C is a low Temp. so one adds a little more MEKP, not Rocket Science (just Muppet Musings?):o

You should get out more ,Barb.Take the Duck for a Walk/Waddle.

Edited by cereal tiller
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4 hours ago, Tony Brooks said:

To a degree it depends upon what source you look at. Automobile Electrical Equipment by Young & Griffiths (1958) states "On open circuit the cell voltage drops almost immediately to 2.2 volts and for the initial period of discharge rapidly falls to 2.0V." Battery universe quotes 2.1 volts and other sources quote 2.05 volts for some lead acid batteries.

I take the 2.2 volts to have been worked out from the chemical processes when at being charged rather than measured because you can't measure the underlying cell voltage when being charged.

Whether we call it surface charge or something different it does not matter because if the battery is trying to push out 13.2 volts then a charging voltage will have to be higher to get charge into the battery. My point was that 13.2 volts seems too low to me the keep up with self discharge and that’s what float charging is all about.  If we accept that some battery types do have lower underlying  cell voltage when on charge then in some cases 13.2 volts will be enough to keep them charged but in other cases it seems to me that it will not. 

IIRCC when Victron is on 13.2v storage float charge it occasionally reverts to 13.6v for a while.  

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3 hours ago, cereal tiller said:

No? 15 C is a low Temp. so one adds a little more MEKP, not Rocket Science (just Muppet Musings?):o

You should get out more ,Barb.Take the Duck for a Walk/Waddle.

Right, just been to W'spoons for a bevvy or 4 so response may be incorrerent ;).  Polyesters cure at 20°C no problem. Take the temperature lower and the crosslinking reaction slows down. Ideal MEKP level it 1-2%. At less than 15°C then you start having to add 2-3% MEKP or upping the cobalt oxylate level (normally in there anyway from the manufacturer...but more can be added). This then increases the reaction rate to get the thing to go solid....but the final crosslinking is compromised. When it goes solid you have about 10% of the final strength developed but the remaining 90% is dependent on the rest of the reaction going to completion. Trying to cure at less than 15°C is a bad idea.

Epoxies can be cured at 10°C and lower by choosing alternative curing aids but again this sacrifices the ultimate strength. For any of these systems wait until April.

Trust me, I am a doctor......and the duck agrees. Abbot is a nice pint!

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