Buying a Smartgauge

[sailinglegend]

Originally Posted by rgleason

....It appears that our purchase of a 15 watt PV and controller has been a perfect and simple way to keep our two T105 in series charged......

I hate to tell you but a 15W PV panel will not be anywhere large enough to keep your batteries charged whilst you are using the boat. OK over winter.

For summer cruising you need about 400W depending on your Ah daily usage and your cruising area and many other factors!!!!!!! For spring and autumn add at least another 200W.

Even so most cruisers NEVER get their batteries to 100% regularly at anchor, even though a little light comes on saying full, or your BM or Smartgauge says 100%.

Dropping to FLOAT mode does not mean 100% full!

[john61ct]

Originally Posted by sailinglegend

Dropping to FLOAT mode does not mean 100% full!

It **should** mean that.

AFAIC it's my job to adjust the charge sources so they don't drop to Float early.
If a source is not that adjustable, IMO it likely needs replacing with a better unit that is.

Originally Posted by sailinglegend

Even so most cruisers NEVER get their batteries to 100% regularly at anchor

That is not IMO a situation to simply accept.

As long as there's some solar input, a strategic use of dino juice in the morning, maybe just 30min, maybe all the way to 80 or 85%, should help.

A known-good SoC reading helps you get familiar with how long is necessary for a given set of conditions.

Finally, note that a LFP bank makes this whole issue go away, and Firefly Oasis 90% so.

[john61ct]

Originally Posted by Paul L

I see this statement made about full time cruisers on CF often. I think the most part of this is just not accurate.

See?

> Even so most cruisers NEVER get their batteries to 100% regularly at anchor, even though a little light comes on saying full, or your BM or Smartgauge says 100%.

I think it is in fact true, most people have no way to get accurate SoC, are not tracking endAmps, and don't calibrate their charge regulators.

Likely most just leave settings at factory defaults.

[Dockhead]

Originally Posted by a64pilot

You need a battery monitor for the same reason you need a fuel gauge.
You need a monitor cause very, very few people actually get to fully recharge to 100% every day, so they start walking down in charge, and without a good way to know what their SOC is, how would they know when it’s time to get up early in the morning and let the generators give then bank a good kick of bulk charging to let Solar finish off?
You need a monitor cause this year it only take three days of walking down before you end up at 50% where last year it was two due to lost capacity.
You need a monitor because it’s been a little cloudy for the last several days, and your average Solar production is down, or you made more ice than normal, or watched more TV than normal etc, etc. . . .

But you can see all of that, with perfectly adequate accuracy, just by watching voltage. If you see 24.2v with no charging going on, and only light loads on, just charge. 24.2v (or 12.1v for you 12v guys) is in the very worst case 50%. Really cannot be 49%. Could be 55% or so, depending on the size of the load as %C, but unlikely to be 60%. That's plenty, plenty close enough. And closer than an amp-counting under even above-average management.

Originally Posted by a64pilot

Now admittedly a person who watches their bank closely as to voltage and understands what they are seeing can to some extent replace a monitor, but an SG is truly a set and forget thing, you don’t have to keep resetting it etc.

You don't actually have to watch the bank so closely, to understand what's happening, nor do you have to reset anything, using the voltage method.

But the Smart Gauge is definitely a convenience. It remembers, it averages, and it will always give you some kind of opinion. You don't have to look up anything in a table. I'm glad to have mine.

Like all other battery monitors, the Smart Gauge has the fault of giving a false impression of accuracy which it doesn't have (under certain circumstances). But nor do you need such accuracy. Accurate measurement of SOC is not required to fulfill the main goals of lead acid battery management -- avoid systematic undercharging, avoid systematically discharging too deeply, be sure to get a really full charge regularly.

[john61ct]

Voltage varies so much without resting the bank, depending on so many variables.

Sure you can make the case for "good enough" but not for me.

And I see in this thread people saying 5/10% for SG, while I recall MaineSail's numbers as 4/8%.

NBD but curious if I missed a revision?

[Dockhead]

Originally Posted by john61ct

Voltage varies so much without resting the bank, depending on so many variables.

Sure you can make the case for "good enough" but not for me.

And I see in this thread people saying 5/10% for SG, while I recall MaineSail's numbers as 4/8%.

NBD but curious if I missed a revision?

It depends on the size of the currents relative to the size of the bank, but with a decent sized bank, voltage is very stable.

And let's think about what voltage DOES --

1. it's artificially high only when a surface charge is on

2. both charging and loads present, and it can be anything

3. if the surface charge is off, and no charging, take off loads, and voltage will gradually rise to open circuit voltage.

4. with no surface charge and small loads, the voltage will be very close to open circuit voltage, and ALWAYS slightly less.

5. Put a big load on, and voltage will sag, then gradually come back up when the load is off.


In Condition 4, you can make a very accurate, more accurate than you need, picture of SOC by reading voltage. On my boat, voltage read against the Trojan OC voltage vs SOC chart EXACTLY corresponds to what my SmartGauge tells me -- always. And these readings have been extensively checked against specific gravity, proving the high reliability and accuracy of Smart Gauge in Condition 4. With smaller banks, YMMV. If you have solar, so you are often in Condition 2, in my opinion neither voltage nor Smart Gauge is much good. I would probably go for an amp counting meter in that case, but try to figure out a practical and reasonable way to manage it. I have decades of experience with Link and Victron amp-counting gauges, and was never able to rely on them, despite trying hard to calibrate them and keep them calibrated. I started checking against specific gravity and my hair stood on end when I realized how wildly off they were.

SmartGauge will give an accurate reading in Condition 5, unlike voltage reading. If that's important to anyone, then that's a clear advantage.

[a64pilot]

Just like a Smart Gauge, just watching voltage is not so useful with a charge source on, need to look late at night or early in the morning.
The smart gauge and an AH counter are complimentary, they give you different information.

[conachair]

Originally Posted by john61ct

Voltage varies so much without resting the bank, depending on so many variables.

Sure you can make the case for "good enough" but not for me.

From spending extended periods on the hook I would agree with that, if 'good enough' is knowing from voltage alone if you need to run the genny/engine first thing then just maybe you could have a stab before the sun comes up after a few months experience. Once anything is going in , forget it. Then without any idea of amps going in you've no idea if your back near full again towards sunset.

[Dockhead]

Originally Posted by a64pilot

Just like a Smart Gauge, just watching voltage is not so useful with a charge source on, need to look late at night or early in the morning.
The smart gauge and an AH counter are complimentary, they give you different information.

Originally Posted by conachair

From spending extended periods on the hook I would agree with that, if 'good enough' is knowing from voltage alone if you need to run the genny/engine first thing then just maybe you could have a stab before the sun comes up after a few months experience. Once anything is going in , forget it. Then without any idea of amps going in you've no idea if your back near full again towards sunset.

Yes, I understand and agree. I think I even wrote that if you have solar, the game is different.

I would want an amp-counting gauge if I had solar. Maybe in ADDITION to a Smart Gauge, as A64 suggested, although voltage reading is probably just as complementary to what an amp-counter can do.

[Dockhead]

Originally Posted by conachair

. .. Then without any idea of amps going in you've no idea if your back near full again towards sunset.

Just one small point -- why would you care about this? It is what it is, isn't it? What are you going to do about it? If you're mostly but not quite fully charged at the end of the day, there's really nothing you can do about it, since you don't want to run your engine or even generator for the last 10% or whatever -- that's the case of killing your generator vs killing your much cheaper batteries I was referring to earlier.


. . .. Unless perhaps (answering my own question ) you've got a Honda generator on board, which isn't bothered by running at small loads (although it is inefficient used like that). When I was spending the whole year on a mooring, I did have a Honda generator on board for the specific purpose of putting a finishing charge on the batteries after I shut down the big diesel generator. For the specific purpose of getting the batteries to 100% at least a couple of times a week.

[a64pilot]

Originally Posted by Dockhead

Just one small point -- why would you care about this? It is what it is, isn't it? What are you going to do about it? If you're mostly but not quite fully charged at the end of the day, there's really nothing you can do about it, since you don't want to run your engine or even generator for the last 10% or whatever -- that's the case of killing your generator vs killing your much cheaper batteries I was referring to earlier.


. . .. Unless perhaps (answering my own question ) you've got a Honda generator on board, which isn't bothered by running at small loads (although it is inefficient used like that). When I was spending the whole year on a mooring, I did have a Honda generator on board for the specific purpose of putting a finishing charge on the batteries after I shut down the big diesel generator. For the specific purpose of getting the batteries to 100% at least a couple of times a week.

Knowing this tells you that the next generator runs need to be longer.
However in my case, I expect my generator times will be longer than needed for just battery charging, cause I’m doing other things with it.

[john61ct]

Running even a $150 generator for a finishing charge is just silly IMO.

You learn from your experience to predict with growing accuracy, so the genny run at the beginning of the day is sufficient to let solar get to 100% by late afternoon.

If you're burning dino juice for other reasons in the pm, would do so anyway, sure, but not just for charging.

[conachair]

Originally Posted by Dockhead

Just one small point -- why would you care about this? It is what it is, isn't it? What are you going to do about it?

Spoken like a true non off the hook liveaboard

I certainly care massively about this, if the batteries aren't ever getting up to full charge then they ain't gonna last too long, which means more money plus trying to actually find some in whatever country you happen to be in at at the time - no mean feat often. Cruising is in many ways learning just how to be as nice as possible to your boat so things to break at the wrong place and the wrong time. Midocean is not where you want to find out that you've trashed your batteries by never getting a full charge.

What you should do is something, whatever it takes to get to 100% often. Which is usually answered by more solar Plus maybe a genny run on cloudy days, if you don't know if you make full charge by sundown you don't know if it was running too long or not long enough.

Without a minimum of accurate battery post voltage and accurate amps in/out you've really no useful idea what's going on.

[conachair]

Originally Posted by john61ct

Running even a $150 generator for a finishing charge is just silly IMO.

You learn from your experience to predict with growing accuracy, so the genny run at the beginning of the day is sufficient to let solar get to 100% by late afternoon.

Exactly, very satisfying on an overcast day when you got the morning genny time just right

[Kenomac]

After reading this thread, I have to wonder how many of the Smartgauge admirers are actually using the thing as full time anchorage live a boards who monitor solar and generator production.

The Smartgauge works fine if one spends a couple of days per week plugged into shore power, but it's performance stinks when used by people like me who plug in once every six months. We need more accurate information from our system.