Buying a Smartgauge

[sailinglegend]

Originally Posted by sailorboy1

5% seems a lot when you consider the 1,000s of thread pages aguring wheather batteries are fully charged or only 98% charged

The point about all these arguments is simple to understand WHY it is important to get to a true 100% regularly. Most people find that hard to accept and impossible to achieve which is why their batteries die prematurely.

[sailorboy1]

Whether they die “permaturely” or just lived a full life gets questionable.

But my statement holds true. What good is a “smart” gauge if you are interested in being 100% charged and not just 97% if the gauge is only accurate within 5% or more? Sounds like another battery toy to mess with your head. And this comes from a guy who worries too much about his batteries already.

[sailinglegend]

Originally Posted by sailorboy1

....But my statement holds true. What good is a “smart” gauge if you are interested in being 100% charged and not just 97% ....

A SmartGauge will not accurately tell you when a bank is 100% charged nor will a shunt based battery monitor.

A Smartgauge will be more accurate than a BM when the battery bank has aged - you need to understand why this is a true statement.

The only accurate way to tell when your bank is 100% is with a charge current of about 0.5% of Ah capacity at 14.4v or higher. This needs to be repeated so many times for readers to understand - they also need to understand that you will never see this condition in normal life because your charger will have dropped down to a float voltage much earlier. You have to turn off the charge source and then on again to force it back into charging at 14.4v. The charge current at 14.4v can be 4-5 times higher than at a float voltage of 13.4v.

[sailorboy1]

Like I said what good is a smart gauge. I can easily see on my BM when the batteries are accepting only 0.5% at 14.8V (for mine)

[Dockhead]

Originally Posted by CatNewBee

I consider the SmartGauge useless.

It simply cannot work accurately without a shunt - especially if you have a solar panel, that constantly adds charging voltage during the day. If you cannot measure the current and the direction it flows, you cannot guess the state of charge sole based on voltage measurements - no matter how often and how precise they may be taken, because the battery is never alone during the day.

Also the voltage drops on adding a load related to the batteries resistance. There is no way the SmartGauge can tell if the measured voltage results of the SOC of an idle battery or an battery under heavy load.

It simply cannot work.

This conclusion is based on theory? Have you tested it yourself?

The actual tests (and I did a large series of my own, using SG measurements) show that it is much more accurate than other types of meters -- at least during discharge. Read MaineSail's extensive lab tests. My tests show that it is more or less useless during charging; but others got somewhat different results. But during discharge it is superb --and there's not any serious controversy about this as far as I know.

[Dockhead]

Originally Posted by sailinglegend

The point about all these arguments is simple to understand WHY it is important to get to a true 100% regularly. Most people find that hard to accept and impossible to achieve which is why their batteries die prematurely.

You're right -- but most cruisers do this by being plugged in overnight or going for a long motor with a well regulated alternator. Crude. But effective!

Even if you could know (easily), what good would it do you? Killing your batteries is cheaper than killing your generator.

[sailinglegend]

Originally Posted by Dockhead

... most cruisers do this by being plugged in overnight or going for a long motor with a well regulated alternator....

Beware - charging on shorepower overnight might not get a heavily depleted bank back to 100%. Come into a marina at 2000hrs and leave at 0800hrs - that's just 12 hours - may not get you fully charged.

It all depends on the size of your charger and when it drops to float mode. If its 95% or higher you might get back to 100%, if its as low as 85% like my Victron I never make it by 0800hrs and I'm still putting in 15 amps in float mode. Before it dropped to float I was putting in 65 amps at absorption voltage. That's why an accurate SOC meter and an amp counter is important.

[a64pilot]

The value of a SG is in knowing SOC, that’s it.
That becomes more and more important when a bank ages.
Your 400 AH bank starts out maybe as a 400 AH bank, but what is it in a couple of years? How do you know when it’s approaching 50% discharged with just an AH counter?
You can’t, however with a SG you know that when it is approaching 50% that you need to get it into charge or stop taking power out of it. As your bank ages, that may be only 125 AH or so, maybe more, maybe less.
But if you keep pulling 200 AH out of it, your going lower and lower than 50% and it’s rate of decline accelerates.
A SG is not useless with Solar, look at in before you go to bed if you stay up late, or in the morning when you get up. If your like me you can’t make it through the night without visiting the head, look at it then, but look at it before it’s been charging on Solar for hours.
And if your primarily on Solar, don’t let your controller trip to float unless your a very unusual boat, cause it’s unlikely your actually at full charge when it trips to float.

[john61ct]

Originally Posted by CatNewBee

I consider the SmartGauge useless.

It simply cannot work accurately without a shunt
...
There is no way the SmartGauge can tell if the measured voltage results of the SOC of an idle battery or an battery under heavy load.

It simply cannot work.

This simply reflects your lack of knowledge compared to

Gibbo the inventor

Merlin the company that bought him out, freeing him to work for

The military contractors that adapted his tech and put it into widespread use in the field

MaineSail as linked to above

Thousands of satisfied customers

Yes, very few people on the planet actually know *how* it works

certainly nothing to do with just "reading voltage" as you seem to think

but it does work - at least better than anything else practical for SoC readings within our use case, and within clearly stated limitations.

Personally I recommend also using a coulomb counter like Victron' 702-BMV, as that AH in/out data can be very helpful. But if only one, get the SG.

Originally Posted by sailorboy1

Like I said what good is a smart gauge. I can easily see on my BM when the batteries are accepting only 0.5% at 14.8V (for mine)

Yes of course if your only need for SoC is determining 100% while charging, you don't need a SG.

Just like topics that are not of interest, if the value doesn't fit *your* use case, just ignore the debate.

Originally Posted by Dockhead

most cruisers do this by being plugged in overnight

People in that situation don't need an SoC gauge. Those who do are often away from shore power for days if not months at a time.

Originally Posted by Dockhead

going for a long motor with a well regulated alternator.

Getting lead to 100% just won't happen using dino juice unless you're burning it all day for other reasons anyway.

People in that situation don't need an SoC gauge.

Originally Posted by Dockhead

Even if you could know (easily), what good would it do you? Killing your batteries is cheaper than killing your generator.

Anyone that willing to allow their House bank to die an early death doesn't need an SoC gauge.

Getting to 100% nearly every cycle is easy, once you get to know just how long to use (a little) dino juice before the solar kicks in to finish off "the long tail".

SmartGauge is very valuable for that sort of situation, given an appropriate use case.

But only for those that need accurate SoC to accomplish their goals.

Or those who can afford it and just like to know.

[sailorboy1]

People willing and/or wanting to buy a boat gadget will find a way to justify it. And once purchased are likely to defender it even if it involves spinning. Doesn’t matter to me what people talk themselves into, go ahead and spin away!

[Kenomac]

I’m disappointed with the Smartgauge performance and accuracy over the past season, it’s almost useless. We’ll be switching over to a 100% Mastervolt system which includes the Master Shunt and EasyView 5 next season. I’ll then be using the two systems side by side and will post comparisons early next summer.

Here’s a recent thread on the topic: http://www.cruisersforum.com/forums/...co-192131.html

[billknny]

Originally Posted by CatNewBee

I consider the SmartGauge useless.

It simply cannot work accurately without a shunt - especially if you have a solar panel, that constantly adds charging voltage during the day. If you cannot measure the current and the direction it flows, you cannot guess the state of charge sole based on voltage measurements - no matter how often and how precise they may be taken, because the battery is never alone during the day.

Also the voltage drops on adding a load related to the batteries resistance. There is no way the SmartGauge can tell if the measured voltage results of the SOC of an idle battery or an battery under heavy load.

It simply cannot work.

Just because YOU do not understand how it works does not mean is "simply cannot work. The world is a bit more complicated than you see...

A little knowledge is a dangerous thing. You are right when you say that you cannot use voltage alone to determine state of charge. But you are totally wrong when you assume that is the only possible measurement that the Smartgauge can make. It is NOT.

You know less than you think you do.

[billknny]

Originally Posted by Kenomac

I’m disappointed with the Smartgauge performance and accuracy over the past season, it’s almost useless. We’ll be switching over to a 100% Mastervolt system which includes the Master Shunt and EasyView 5 next season. I’ll then be using the two systems side by side and will post comparisons early next summer.

Here’s a recent thread on the topic: http://www.cruisersforum.com/forums/...co-192131.html

And if they are different, how will you decide which one is correct?

[conachair]

Originally Posted by sailorboy1

People willing and/or wanting to buy a boat gadget will find a way to justify it. And once purchased are likely to defender it even if it involves spinning. Doesn’t matter to me what people talk themselves into, go ahead and spin away!

Don't have one and probably never will, but it's not difficult to see styles of boat use where people will find the info very useful, even if you (& me) don't. Not everyone uses their boat the same way you do.

[billknny]

Originally Posted by sailorboy1

Like I said what good is a smart gauge. I can easily see on my BM when the batteries are accepting only 0.5% at 14.8V (for mine)

Of course, if you can always charge you batteries to the point they are that full, then a smartgauge is of minimal value. It can give you notice that your batteries capacity is declining, but you can get that from an occasional capacity test.

The problem most full time cruisers have is that they rarely get their batteries full enough that a standard BM gauge gets to reset itself to full. You are very lucky if your charging system has enough capacity that you can fill your batteries to an acceptance rate of 0.5% every day!

Charge and discharge efficiencies are wild ass guesses at best, and change with time, temperature, and state of charge. So if you take a battery through a dozen cycles from 50 to 80% your amp hour gauge no longer has any idea how much it really in the battery. It will most certainly give you a number, and you can believe it if you want, but it is inaccurate, and gets more inaccurate every day.

This is where a smartgauge is useful. Is it precise? NO! In the real world it is +/-5% on discharge, and 10% on charge. but in the real world, that is good enough. There is no way of actually measuring lead acid battery SOC to within 1% accurately.

I use both on my boat, and they do different things well. If I do have a fully charged battery after a week at a marina, the two gauges agree very well for the first 5 to 10 cycles. After that they drift further and further apart, until I can get the batteries fully charged (really fully charged) and the amp hour meter resets. After a month away from the dock, the capacity numbers from the amp-hour meter are total nonsense. If I was making decisions based on them my batteries would have died a very long time ago.