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Now I have two Smartgauges...


MtB

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Well this morning I finally got around to installing my spare Smartgauge.

Whilst doing it I ran the genny for a couple of hours during which time the original Smartgauge brought the SoC of the (now dying fast) bank from a displayed 62% up to 100%.  

After configuring the new, second Smartgauge display the same as the old one (i.e. permanently ON, and at min brightness) I compared the voltage reading on the two gauges. Results are all over the place as the sun keeps going in and out but during the cloudy bits, the new Smartgauge seems to read between 0.5v and 0.6v lower than the old.

And between 0.2v and 0.3v higher than the the BMV702. The BMV seems to be roughly half way between the voltage readings on the two Smartgauges, so either one or both of my Smartgauges seems badly calibrated out of the box.

I'll get a better idea tonight when it gets dark.

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A continuing theme in my battery threads is how my Smartgauge voltage seems to read consistently high and SoC is consequently over-reported. 

As fitting a Smargauge is simple and I bought one for the other boat but never fitted it, I've fitted it in this boat to assess the accuracy of the existing Smartgauge. Or inaccuracy, it would seem...

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22 hours ago, Naughty Cal said:

Or even three of you count the BMV!

I think someone has gone monitoring mad :blink:

 

When your brand new Trojanoids die in less than six months, you'd be looking for the reason too I suspect.

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As I've said before, due to the design requirement of very high resolution, the technique chosen to measure voltage is inherently not particularly accurate. The voltage accuracy of SG is quoted as +-0.5% which at say 27v (batts under a gentle charge) is of course +- 0.135v. The dithering if the SG display means that should equate to 0.1 or 0.2v max error. So if the BMV is dead accurate then the second SG is slightly out of cal. But the BMV quotes accuracy of +-0.3% which equates to .081v so if that is high, the new SG could feasibly be within limits, but we can't know unless a calibrated reference is used.

Anyway, the most interesting thing will be to see how the two SG's report SoC (once the second one has had a few cycles to settle down). Please keep us updated.

Just now, Victor Vectis said:

Doesn't the Smartgauge blurb say something about needing a few charge/discharge cycles to tune into the SoC?

Yes, but not the voltage reading.

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Just now, Robbo said:

Someone with a decent multimeter like a Fluke will be able to confirm what the voltage is with good accuracy.

I have a voltage calibrator and so can check Mikes multimeter, there just hasn't been a beer drinking meeting in the last couple of weeks.

Buying a cheap Chinese calibrator off eBay is much cheaper than renting a calibrated multimeter and as long as the calibrator uses a proper reference chip rather than a Chinese copy the accuracy should be fine.

Just now, Robbo said:

Someone with a decent multimeter like a Fluke will be able to confirm hat the voltage is with good accuracy.

My mouse is going dodgy and sometimes turns a single click into a slow double click so it keeps repeating myself.

................Dave

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Now I`m worried. I had intended- as a result of this forum -installing a SmartGauge on my sailaway. This topic causes me concern both as to proof of accuracy on a new item and whether it needs an annual re-calibration anyway!! 

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11 minutes ago, dmr said:

I have a voltage calibrator and so can check Mikes multimeter, there just hasn't been a beer drinking meeting in the last couple of weeks.

Buying a cheap Chinese calibrator off eBay is much cheaper than renting a calibrated multimeter and as long as the calibrator uses a proper reference chip rather than a Chinese copy the accuracy should be fine.

My mouse is going dodgy and sometimes turns a single click into a slow double click so it keeps repeating myself.

................Dave

Problem with buying a calibrator of unknown provenance is that you still don't know if your meter is accurate or not, unless you can compare it with a meter of known calibration afterwards.

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Just now, jddevel said:

Now I`m worried. I had intended- as a result of this forum -installing a SmartGauge on my sailaway. This topic causes me concern both as to proof of accuracy on a new item and whether it needs an annual re-calibration anyway!! 

It is a SoC meter, the voltmeter function is just an add-on. If you want to know voltage to better than 0.5% then you'll need to get a more accurate device - but why would you? The calibration doesn't seem to drift, but some SGs seem to come out of the factory having not been properly calibrated in the first place. If I were going to buy another one I'd check the voltage reading against a good reference and if not within the spec (+-0.5%) I'd send it back and ask for one properly calibrated. Yes it is annoying that they can't be trusted to calibrate it properly, but once you get one that is properly calibrated it is a good product.

We currently have some batteries in good condition with their full capacity still remaining. We have been out on the boat this week and every morning I have a glanced at the Smartgauge, which measures SoC just by looking at voltage profile, and the Mastershunt which is an AH-counting gauge set to 450AH capacity (the badged capacity of the batteries). On a couple of days they have had identical readings (typically around 75% SoC) but all days they have been within a few % of each other, probably no more than 5% difference. Which I think is a pretty good considering these two gauges use completely different concepts to measure SoC. The difference is that once the batteries start to lose capacity, the Mastershunt will lie whilst the SG will tell the truth!

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