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rupertbear

Smartgauge Questions

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I don't think that there has been a topic under this title for a record breaking length of time, so I thought that I would revive it!

Two questions:

Some months ago there was discussion around the suggestion that some Smartgauges may have been sold with poor voltage calibration. What was the outcome of this?

I think I am right in saying that, according to Gibbo and several users of this forum, the Smartgauge is inaccurate during battery charging but functions well under discharge. Does this mean that it is fairly useless in a system with solar charging?

My apologies if either of these has already been answered, I have missed quite a lot of recent times.

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1 minute ago, rupertbear said:

Some months ago there was discussion around the suggestion that some Smartgauges may have been sold with poor voltage calibration. What was the outcome of this?

MtB reports possessing two. Another boater had one which was returned to Merlin and he never reported back with the outcome. Merlin state that they're unaware of it being an issue. Considering the thousands that are out there the reported instances of slight inaccuracy are a tiny percentage but there again how many owners have checked theirs? So the upshot is that as far as we are aware it's a non-issue. 

5 minutes ago, rupertbear said:

I think I am right in saying that, according to Gibbo and several users of this forum, the Smartgauge is inaccurate during battery charging but functions well under discharge. Does this mean that it is fairly useless in a system with solar charging?

Nope, that's incorrect. During charging the SmartGauge can be up to 10% inaccurate but so what? If you're charging then until you get close to 100% SoC the actual charge state is irrelevant. Once you're discharging (for instance in the evening) then SmartGauge will sync itself again and that's when you need to know how badly you're hammering your batteries. 

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On 23/08/2017 at 10:11, WotEver said:

 

Nope, that's incorrect. During charging the SmartGauge can be up to 10% inaccurate 

 

Well I have two SmartGauges connected to one battery and the difference in their readings during charging is usually far more than 10%.

I suppose one could be reading 10% over and the other 10% under, but then the difference is sometimes higher than 20% even. 

But they virtually never agree with each other, not even close. Neither when charging nor discharging.

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28 minutes ago, Mike the Boilerman said:

 

Well I have two SmartGauges connected to one battery and the difference in their readings during charging is usually far more than 10%.

I suppose one could be reading 10% over and the other 10% under, but then the difference is sometimes higher than 20% even. 

But they virtually never agree with each other, not even close. Neither when charging nor discharging.

Quite apart from the fact that we know your two require calibration, as I said in my earlier post, "so what?"  The Current being pulled by the batteries is of much more relevance when charging and once you stop charging the SmartGauge resynchs automatically. 

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My Smartgauge, which is correctly calibrated, is normally within a few % of my correctly set up AH - counting SoC indicator during discharge. They are further apart during charge, as per the spec.

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I had a conversation with Chris about accuracy using solar this is an excerpt

This is a question that comes up time after time. The answer is a lot simpler than you’d think. If the solar panel is fully charging the batteries, SmartGauge is accurate throughout any period using them. It  only appears to be inaccurate for the first 10% to 15% of the following discharge cycle. After that, all is good. If the solar panel is not fully charging the batteries (the usual situation in the UK) then it is accurate throughout any period using them. it’s just that a human’s idea of state of charge during intermittent solar charging doesn’t map well with reality. It’s the human that is wrong!

I just check my % when its dark, normally when I get up in the morning. I will add that even with 400w of solar and an MPPT controller there have been quite a few days in the last month when I have put the charger on. Conditions for this is if I get two or three consecutive days when SOC at 0430 is below 70% and lower than previous day. So my conclusion is that a week or so of dull days will see batteries below 50%.

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Mine required calibration. I contacted Merlin, who initially were very helpful until I told them it was an older unit. They said they would come back to me. They never did. 

I recallibrated it myself in the end. 

1 hour ago, Mike the Boilerman said:

Well I have two SmartGauges connected to one battery and the difference in their readings during charging is usually far more than 10%.

I'll give you a tenner for both! 

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23 minutes ago, rusty69 said:

I'll give you a tenner for both! 

I'll give you a fiver. 

But only if you package them up with that scope...

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2 minutes ago, WotEver said:

I'll give you a fiver. 

But only if you package them up with that scope...

I'll do you a horoscope for a fiver if you like:)

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11 hours ago, WotEver said:

If you're charging then until you get close to 100% SoC the actual charge state is irrelevant.

When Smartguage first shows 100% when charging, your batteries are nowhere near fully charged. My batteries are generally still drawing about 20A when Smartguage reaches 100%. This is generally about 2 hours, or more, before they are drawing the 4A or less which suggest close enough to fully charged.

Anyone who relies on Smartguage to tell them that their batteries are fully charged will be destroying their batteries, (I think myself and MtB have suffered from this until realisation dawned).

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3 minutes ago, Richard10002 said:

Anyone who relies on Smartguage to tell them that their batteries are fully charged will be destroying their batteries

Firstly, anyone who does that has not read the SmartGauge manual nor the copious posts on here giving advice on how to tell charge status when charging. (Clue: don't use SmartGauge for it)  

Secondly, whether SmartGauge shows 100% before or after the batteries actually approach that SoC depends on many factors including the size of the bank, size of the charger, parasitic loads and more. Obviously in your case it reads early but do not assume that all systems will react similarly because they won't. 

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3 minutes ago, WotEver said:

Firstly, anyone who does that has not read the SmartGauge manual nor the copious posts on here giving advice on how to tell charge status when charging. (Clue: don't use SmartGauge for it)  

Secondly, whether SmartGauge shows 100% before or after the batteries actually approach that SoC depends on many factors including the size of the bank, size of the charger, parasitic loads and more. Obviously in your case it reads early but do not assume that all systems will react similarly because they won't. 

I dont disagree to any material degree. The fact is that a Smartgauge showing 100% is not an indication that your batteries are at 100% SoC, so it cannot be relied on, as you rightly state. (One could ask what is the actual point of a Smartgauge, in the absence of an additional Amp Hour counter?).

When I first started coming here, (2010 or so), whenever a new boater asked whether they should get an Amp Hour Counter type of monitor, or a Smartguage, the advice from most quarters was that a Smartguage could be used by the inexperienced as a simple fuel gauge for their batteries. I perceived this to be the case until a while after I bought one.

I actually bought an Amp Hour counter, (NASA BM2), long before I bought a Smartguage, so have been fully aware for a long time, of the need to get the Amp Hours drawn during charging down to 2% or so of capacity.

It is only very recently that the chickens have come home to roost with respect to advice given here on the Smartgauge and it's fuel gauge like properties and, IIRC, this was only truly hammered home due to some persistence by Mtb, (and myself to a degree).

It's all been said before, but it bears repeating, particularly when those new to this are reading, or the experienced boater who doesnt get electrics and charging :) 

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1 minute ago, Richard10002 said:

The fact is that a Smartgauge showing 100% is not an indication that your batteries are at 100% SoC, so it cannot be relied on, as you rightly state. (One could ask what is the actual point of a Smartgauge, in the absence of an additional Amp Hour counter?)

But it clearly states that in the manual as has been pointed out. 

I find it invaluable to know when to start charging. 

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5 minutes ago, rusty69 said:

I find it invaluable to know when to start charging

Precisely. Something at which an Ah counter fails abysmally unless regularly re-calibrated, which for most folk is an impossibility. 

Edited by WotEver

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Just now, WotEver said:

Precisely. Something which an Ah counter fails abysmally at. 

If you want the best of both worlds, fit both and understand their respective limitations. 

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Just now, rusty69 said:

If you want the best of both worlds, fit both and understand their respective limitations. 

Absolutely. 

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1 minute ago, rusty69 said:

But it clearly states that in the manual as has been pointed out. 

I find it invaluable to know when to start charging. 

I agree... on both points... but I didnt RTFM before I bought my Smartgauge, I relied on what I had gleaned from here, which was that it was an excellent fuel gauge for the inexperienced, and/or the electrically challenged.

Even when I bought my Smartgauge, I only read enough of the F Manual to get it up and running, which I dont think is an unusual way of doing things, (or how would the acronym have come to be? :) ). It is a manual which is written in very small print, and perhaps goes into much more detail than many manuals, (I think Gibbo says this in the manual itself, IIRC), such that reading enough to get things going could be considered a feat in itself?

It is good that heated, and repeated, discussion takes place on this, as it makes it less likely that people deciding between a NASA BM1 type monitor, or a Smartgauge will be misled.

1 minute ago, rusty69 said:

If you want the best of both worlds, fit both and understand their respective limitations. 

Which is what I did :)

 

Amp Hour counter first, then a Smartgauge a couple of years later.

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It does depend on the charging regime and when charging starts. I find the Smartgauge reaches 100% at around 4% of capacity. This isn't fully charged - but then neither is 2% or 1% - but it is the same as a BMV "out of the box" which is set to 4% tail current and remains thus for most people.

Once you have decided on what you consider to be fully charged (4%?, 2%?, 1%? 0.5%?, 0.25%?) you can use a cheap clampmeter to decide how long after the SG reaches 100% to stop charging, eg 1 hr, 2 hrs etc. That said, it is still better to use an ammeter of some sort to decide when to stop charging.

I think the point is that the SG isn't perfect, but neither is any other type of SoC meter. The SG excels during discharge with batteries of an unknown remaining capacity, something which no other SoC meter can do.

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1 minute ago, Richard10002 said:

I agree... on both points... but I didnt RTFM before I bought my Smartgauge, I relied on what I had gleaned from here, which was that it was an excellent fuel gauge for the inexperienced, and/or the electrically challenged.

Even when I bought my Smartgauge, I only read enough of the F Manual to get it up and running, which I dont think is an unusual way of doing things, (or how would the acronym have come to be? :) ). It is a manual which is written in very small print, and perhaps goes into much more detail than many manuals, (I think Gibbo says this in the manual itself, IIRC), such that reading enough to get things going could be considered a feat in itself?

It is good that heated, and repeated, discussion takes place on this, as it makes it less likely that people deciding between a NASA BM1 type monitor, or a Smartgauge will be misled.

As you detest it so much, i'll give you a tenner for it! 

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2 minutes ago, Richard10002 said:

it makes it less likely that people deciding between a NASA BM1 type monitor, or a Smartgauge will be misled.

They shouldn't decide between them because they do different jobs. It's like deciding between a spanner and a hammer. 

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I'm sure I came back to the previous thread and said that Merlin confirmed my Smartgauge was reading 0.5v high but apologies if i forgot. They replaced it with a brand new one that had been checked by them for accuracy despite me not purchasing it through them. They also denied any knowledge of any others being out of calibration. I suspect the one on my previous boat was also wrong - I always thought it read 0.15v low but never really bothered about it. I would strongly advise that anyone purchasing a new one checks the accuracy against a digital multimeter and complains if they differ. 

As to accuracy when charging, both of mine have been remarkably good. The last one read 100% when the tail current had dropped to about 1.5% which I considered fairly fully charged with those batteries. This one reads 100% when the tail current has dropped to less than 0.5%, which is quite a sharp cut off with the cheapo sealed batteries I'm currently using. No real problems with solar other than if it's been a dull day and only low charging voltages via solar. In theses circumstances my Smartgauge tends to under read the SOC by up to 10% but better that way than over reading. 

Tom

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9 hours ago, WotEver said:

They shouldn't decide between them because they do different jobs. It's like deciding between a spanner and a hammer. 

I know that now :) and so do others who venture here and read the latest posts.

 

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10 hours ago, rusty69 said:

If you want the best of both worlds, fit both and understand their respective limitations. 

Or fit a simple volt meter and ammeter and learn how to read them.

Far cheaper and far easier to understand.

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