Merlin Smartgauge specifications and accuracy

[WotEver]

Paul, the problem with any Ah counter is that the SoC figure cannot be 'counted'. It has to be calculated based on several fudge factors. This is why the BMV (for example) gives no accuracy for its SoC readout. As opposed to the SmartGauge which will be within 5% accurate on discharge.

[Graham.m]

And the really important distinction of course is that SmartGauge gives an accurate, self-correcting figure for SoC (discounting one example that we are aware of that is faulty), even in the most inexperienced hands. Whereas an Ah counter will tell lies about the SoC which compound themselves daily unless continually adjusted by an extremely competent user.

 

 

Think you will find there is more than one. AS to your second sentence I do not agree

[Paul C]

 

In fairness; at the end of the day an Ah counter is simply a glorified Ammeter with and algorithm we're expected to trust that provides SoC, of which the details are closed-source.....

 

 

Daniel

 

 

I'm not sure that's true - the algorithm used is simply that it counts the amps in or out, is programmed with the battery capacity and its SoC is one divided by the other. I'll have to look at the Victron BMV700 manual, but I think it contains the equations it uses.

 

https://www.victronenergy.com/upload/documents/Manual-BMV-700-700H-702-EN-NL-FR-DE-ES-SE-PT-IT.pdf

 

Section 5.1 has equations in it (for Peukert).

 

Yes they're likely to drift, but that occurs when the batteries aren't fully charged since it resets itself to 100% upon full charge. The default settings for tail current in the Victron are a bonkers but adjustable. Yes admittedly the battery capacity is not simple to determine but altering these 2 items should give a reasonably useful gauge. And with an ammeter, the user can know when batteries are fully charged and also if usage patterns change, can find out the actual current draw of a load and re-do their power audit.

[Graham.m]

Paul, the problem with any Ah counter is that the SoC figure cannot be 'counted'. It has to be calculated based on several fudge factors. This is why the BMV (for example) gives no accuracy for its SoC readout. As opposed to the SmartGauge which will be within 5% accurate on discharge.

 

What do you mean by "cannot be 'counted'"

[Paul C]

Paul, the problem with any Ah counter is that the SoC figure cannot be 'counted'. It has to be calculated based on several fudge factors. This is why the BMV (for example) gives no accuracy for its SoC readout. As opposed to the SmartGauge which will be within 5% accurate on discharge.

 

I know. That's the main weakness. It can be "worked around" though.

 

The Smartgauge's main weakness is that it doesn't have any way of measuring the current. This requires more money to be spent to work around - eg buying additionally, a clamp ammeter or also having an ammeter fitted.

[nicknorman]

https://www.victronenergy.com/upload/documents/Manual-BMV-700-700H-702-EN-NL-FR-DE-ES-SE-PT-IT.pdf

 

Section 5.1 has equations in it (for Peukert).

 

Yes they're likely to drift, but that occurs when the batteries aren't fully charged since it resets itself to 100% upon full charge. The default settings for tail current in the Victron are a bonkers but adjustable. Yes admittedly the battery capacity is not simple to determine but altering these 2 items should give a reasonably useful gauge. And with an ammeter, the user can know when batteries are fully charged and also if usage patterns change, can find out the actual current draw of a load and re-do their power audit.

Peukert has no place in the calculation of SoC.

 

Regarding your main para that's an awful lot if faffing and if we consider many real-world boaters who don't or rarely fully charge, the second part of your first sentence is a bit pie in the sky. Why go to all that faff when you can have a simple fuel gauge that has no settings to mess with and just works out of the box? Of some people like tinkering, I agree, but plenty don't.

[DHutch]

Whereas an Ah counter will tell lies about the SoC which compound themselves daily unless continually adjusted by an extremely competent user.

I think 'lie' is a strong word. Display incorrectly, or with a significant error, might be fair. It is doing so in ignorance after all, rather than to deliberately mislead.

 

And I have to admit, the fact that the Victron meter has no way of determining capability, and or adjusting to capacity reductions due to age, does appear to be a significant issue, as well as well as the fact it may fail to re-sync at all if you are not charging to 100% each time as the majority of off grid users will not.

 

Lets face it, for the majory of narrowboat users, if you are charging to 100% each day, either because you have access to mains or are moving the boat for long enough each day, you are highly unlikely to actually need an accurate battery monitor!

 

 

Daniel

[nicknorman]

I know. That's the main weakness. It can be "worked around" though.

 

The Smartgauge's main weakness is that it doesn't have any way of measuring the current. This requires more money to be spent to work around - eg buying additionally, a clamp ammeter or also having an ammeter fitted.

That is only an issue if you want to measure the current, and why would the average punter want to do that?

[Loafer]

Lack of current measuring isn't a 'weakness' in the Smartgauge. It was never designed to show it.

[Paul C]

That is only an issue if you want to measure the current, and why would the average punter want to do that?

 

To do a power audit?

[Graham.m]

That is only an issue if you want to measure the current, and why would the average punter want to do that?

 

Who or what is the 'average punter'?

[WotEver]

Think you will find there is more than one.

Evidence please. Otherwise don't assume.

 

AS to your second sentence I do not agree

I wouldn't expect you to.

[DHutch]

 

Lack of current measuring isn't a 'weakness' in the Smartgauge. It was never designed to show it.

It would be nice if it did however!

 

To do a power audit?

Or just to see the current rate of discharge.

 

One of things that the Victron unit does do which I really like is the 'time until' range read out.

 

 

Daniel

[nicknorman]

To do a power audit?

But most people have no idea what a power audit is. Using the car analogy again they don't need to know the mpg at each phase of a journey conducted under varying conditions, they just want to drive along and when the gauge gets a bit low, they'll stop for petrol.

 

Surely you have noticed the average ability of newbies on the forum who come on here with electrical issues and haven't a clue about the basics. The Smartgauge is the gadget for them.

[Graham.m]

Evidence please. Otherwise don't assume.

 

 

 

 

I am not

[WotEver]

What do you mean by "cannot be 'counted'"

The sentence is unambiguous, even more so when taken with the following sentence which you omitted to quote.

I am not

Evidence please

[WotEver]

Lets face it, for the majory of narrowboat users, if you are charging to 100% each day, either because you have access to mains or are moving the boat for long enough each day, you are highly unlikely to actually need an accurate battery monitor!

Absolutely.

 

And the majority of those who don't, based on observations of the battery questions on here, have little knowledge (or often even the desire for such knowledge) of battery and charging technology. Those are the boaters who will most benefit from a simple 'fuel gauge'.

[Graham.m]

The sentence is unambiguous, even more so when taken with the following sentence which you omitted to quote.

 

Evidence please

 

Are you calling me a liar?

[Paul C]

But most people have no idea what a power audit is. Using the car analogy again they don't need to know the mpg at each phase of a journey conducted under varying conditions, they just want to drive along and when the gauge gets a bit low, they'll stop for petrol.

 

Surely you have noticed the average ability of newbies on the forum who come on here with electrical issues and haven't a clue about the basics. The Smartgauge is the gadget for them.

 

....Then tell them that a power audit is going to be a good idea!!!

 

I think we will all agree, that a boater who is discharging more electrical energy than they can put back into the batteries, is going to run out of electricity. A power audit is a basic first step in "getting it" with respect to boat electrics, and the fact that unlike a house, its not connected to the national grid and is a finite and valuable resource. You can survive without knowing the precise SoC of the battery if you know that you can/do charge, as much as you take out, so a power audit could legitimately be a first step where battery monitoring can be a second step. And I'd be recommending a £5 multimeter initially, voltage alone can be useful for a rough idea of what's going on.

[DHutch]

I am hopeful that I may have more on this in due course.

Are you speaking with the suppliers about it?

 

Daniel

[WotEver]

 

Are you calling me a liar?

Why, are you lying?

 

I asked for evidence.

Are you speaking with the suppliers about it?

 

Daniel

Yes, but not directly, via Gibbo. That seemed to me to be the fastest way to get a resolution.

 

Tony

 

Edited for clarity.

Edited January 14, 2016 by WotEver

[Graham.m]

Why, are you lying?

 

I asked for evidence.

 

That is saying you disbelieve me. You yourself have said there is a batch

[WotEver]

That is saying you disbelieve me.

Until there is some evidence then yes, I do disbelieve your assertion that there are 'several'. Provide the evidence and I will then believe it.

 

You yourself have said there is a batch

I have never said that. I would have no way of knowing that. I don't know where they are manufactured, nor in what quantities, nor how often.

 

I have said that there appear to be a few recently that are out of calibration based on some of the posts on here but I have absolutely no knowledge of such a situation.

[nicknorman]

....Then tell them that a power audit is going to be a good idea!!!

 

I think we will all agree, that a boater who is discharging more electrical energy than they can put back into the batteries, is going to run out of electricity. A power audit is a basic first step in "getting it" with respect to boat electrics, and the fact that unlike a house, its not connected to the national grid and is a finite and valuable resource. You can survive without knowing the precise SoC of the battery if you know that you can/do charge, as much as you take out, so a power audit could legitimately be a first step where battery monitoring can be a second step. And I'd be recommending a £5 multimeter initially, voltage alone can be useful for a rough idea of what's going on.

OR.... Never mind all that, just use the leccy until the gauge is getting low, then recharge until the gauge is full or nearly so. Simples!

[DHutch]

Yes, but not directly, via Gibbo. That seemed to me to be the fastest way to get a resolution.

 

It will be interesting to he what if anything he says about it.

 

 

Daniel