SmartGauge -- Real Life Experience

[a64pilot]

I'm not Mainesail, but I have been assured that even in the Caribbean, in the Summer, you can't get to 100% with Solar alone.
It's not the size of the Solar, it's the number of hours of solar available vs number of hours to charge to 100%.
So what a person to do? Well my plan is to run the generator early in the morning when I can push a lot of amps into the batteries and make water or whatever with power left over, then when there is enough sun so that the panels will power the boat and make all the power the batteries will accept secure the generator.
Other than running the engine, I know of no other way, unless there is a lot of wind and you have a large wind generator. I don't, short of shore power I will be burning Diesel to get to 100%, I have just accepted that, but I'm planning on two watermaker runs a week, wash clothes etc., so I should be able to get to 100% twice a week, just means early mornings.
You could of course run it late in the day after the panels sign off, but that's when the battery acceptance rate is real low, so I'd be using my generator to push 10 amps into the bank or so.


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[hellosailor]

"Zen and the Art of Motorcycle Maintenance" comes to mind. Sounds like you have rediscovered and validated the old fashioned, archaic, obsolete, and downright simple old system of two battery banks and one voltmeter. Run on "1", when the lights get dim or the voltmeter says "Help" you switch over to "2" and put the chargers on "1". Yes, that will consume battery lifecycles faster. Then again, it will also "double" the power of your chargers, so you might hit a 100% charge that much sooner. Sometimes the obsolete, inefficient, dog simple old ways of doing things still have a purpose.

[Sandero]

Originally Posted by chris95040

A voltmeter doesn't measure amps, it measures volts.

And measuring amps is presently done in a very inaccurate manner, at least in the hardware I've seen.



Unless you happen to be using them. I'm generally not all that interested in my batteries' state of charge when I'm not using them.

Sorry... I meant meter... as in Link... which does measure volts and amps..

[chris95040]

Originally Posted by Sandero

Sorry... I meant meter... as in Link... which does measure volts and amps..

Gotcha.

The way the Link measures amps is by inserting a very low resistance shunt in the path of the juice, and then a twisted pair wire brings the very low voltage across that shunt to the Link unit itself. This is not a very accurate measurement technique, and I'm theorizing it's one of several reasons why charge-counting is so error prone.

[Dockhead]

Originally Posted by chris95040

Gotcha.

The way the Link measures amps is by inserting a very low resistance shunt in the path of the juice, and then a twisted pair wire brings the very low voltage across that shunt to the Link unit itself. This is not a very accurate measurement technique, and I'm theorizing it's one of several reasons why charge-counting is so error prone.

I think you are confusing these with some other technology. Current measuring shunts are the most accurate mass produced current measuring devices, with typical accuracy better than 0.25%.

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[Maine Sail]

Originally Posted by chris95040

Gotcha.

The way the Link measures amps is by inserting a very low resistance shunt in the path of the juice, and then a twisted pair wire brings the very low voltage across that shunt to the Link unit itself. This is not a very accurate measurement technique, and I'm theorizing it's one of several reasons why charge-counting is so error prone.

These shunts are actually very accurate but some do lack the ability to catch super low mA loads. The shunt is the least of the worries, in terms of accuracy, when counting Ah's.. Improper set up, incorrect programmed battery capacity, Coulombic efficiency, Peukert, battery temp, battery health, false resets, PSOC use etc. throw far more hooks into an Ah counter than does the shunt..

[redsky49]

So who publishes an "under load" voltage/state of charge chart? I admit I have only ever seen "resting" voltages published.

Is there such a thing for flooded batteries, from a manufacturer?

How would they determine the "load"?

[chris95040]

Originally Posted by Dockhead

I think you are confusing these with some other technology. Current measuring shunts are the most accurate mass produced current measuring devices, with typical accuracy better than 0.25%.

At the shunt itself, maybe. So its dead simple, right, V=IR, and we know R (that's probably what we know to within 0.25%), so we solve for I.

But the problem is V is very, very, low, because R (by necessity) is very, very low, and then you clumsily send that teeny weeny voltage across a long run of wire to your measuring device. My Link-10's measurement of current was certainly no where NEAR 0.25% accurate. And I spent a lot of time trying to improve it with different wiring strategies, changing where I stuck the shunt so it was closer to the link10, etc.

Certainly there are other huge problems with charge counting, too, as MaineSail suggests. The actual capacity removed from a battery is a function of charge used by the load, sure, but also age, chemistry, past cycles, temperature, state of charge at the time the load was used...They are baffling little devices, batteries.

I've been thinking the current measurement was some low hanging fruit in all this mess, but maybe it doesn't matter.

[conachair]

Originally Posted by a64pilot

I'm not Mainesail, but I have been assured that even in the Caribbean, in the Summer, you can't get to 100% with Solar alone.
It's not the size of the Solar, it's the number of hours of solar available vs number of hours to charge to 100%.
So what a person to do? Well my plan is to run the generator early in the morning when I can push a lot of amps into the batteries and make water or whatever with power left over, then when there is enough sun so that the panels will power the boat and make all the power the batteries will accept secure the generator.
Other than running the engine, I know of no other way, unless there is a lot of wind and you have a large wind generator. I don't, short of shore power I will be burning Diesel to get to 100%, I have just accepted that, but I'm planning on two watermaker runs a week, wash clothes etc., so I should be able to get to 100% twice a week, just means early mornings.
You could of course run it late in the day after the panels sign off, but that's when the battery acceptance rate is real low, so I'd be using my generator to push 10 amps into the bank or so.

Think my loads are much less than yours but last time I was long term on the hook that's what I did with a honda genny running the mains charger, run early on for a while when the batteries would accept a decent current and at the same time plug in anything and everything which could take a charge from mains - mostly the laptop but AA rechargeable batteries, usb stuff as well. Then let solar have the rest of the day for the last slow climb to the top.
Seemed to work OK.
If it's the tropics most people wake early anyway so a nice relaxed start to the day watching videos swapped in the anchorage the night before

[sailorboy1]

Originally Posted by a64pilot

So what a person to do? Well my plan is to run the generator early in the morning when I can push a lot of amps into the batteries and make water or whatever with power left over, then when there is enough sun so that the panels will power the boat and make all the power the batteries will accept secure the generator.

My plan is pretty much the same. But the other part of my plan is to just know that batteries are consumables and if I replace my 460AH FLA bank every 5 years so be it (I expect longer). I will spent the $100-200/year this costs over the everyday obsessing about the dam things.

[zboss]

I have noticed that as the solar day starts to close (the overall amps and voltage coming in from the solar starts to wane) that the Smartgauge is tailing. By the time the solar is putting out negligible power the gauge is almost at the right % charge state.

That means that several hours before the solar day closes we have a pretty good feel as to how well the batteries charged that day. It helps that we also have an amp counter so we can do a sanity check on the solar power coming in during the day. If we woke in the morning to find we are 60% charged, and during the say we only see us putting in a portion of the power I know something is off - like poop on the panels - and can fix it. In this regard the SmartGauge is not useful.

For us, having a reliable voltage and %charge reading along with a amp counter is the best of both worlds.

[a64pilot]

Originally Posted by sailorboy1

My plan is pretty much the same. But the other part of my plan is to just know that batteries are consumables and if I replace my 460AH FLA bank every 5 years so be it (I expect longer). I will spent the $100-200/year this costs over the everyday obsessing about the dam things.

I would agree, but due to sizing constraints of my battery box I couldn't go with 6V FLA batteries, so I was faced with building a new box or going with AGM, I went with AGM that are I believe about 300% the cost of golf cart batteries, and they are way less tolerant with PSOC cycling.
Five years can be done, if your Anal with your bank, unlikely if your not, but if your 6V FLA golf cart batteries, it will hurt the kitty a lot less come replacement time.
I suspect that many if not most banks out there that are 5 yrs old have met the definition of being dead for quite some time now, just as it happens so slowly that people become accustomed with living within the reduced capacity and don't replace a bank until a cell shorts or some other catastrophic failure forces them to.

[a64pilot]

Originally Posted by zboss

I have noticed that as the solar day starts to close (the overall amps and voltage coming in from the solar starts to wane) that the Smartgauge is tailing. By the time the solar is putting out negligible power the gauge is almost at the right % charge state.

That means that several hours before the solar day closes we have a pretty good feel as to how well the batteries charged that day. It helps that we also have an amp counter so we can do a sanity check on the solar power coming in during the day. If we woke in the morning to find we are 60% charged, and during the say we only see us putting in a portion of the power I know something is off - like poop on the panels - and can fix it. In this regard the SmartGauge is not useful.

For us, having a reliable voltage and %charge reading along with a amp counter is the best of both worlds.

That I think jives with what I'm seeing with the shore power charger, I think as you get close to a full charge and sort of spend a few hours trickling in that last few percent, the Smart Gauge catches up? Cause mine reads 100% right at about the time when my charge acceptance rate drops to about .5% of banks rated capacity.

[CGirvan]

Originally Posted by Maine Sail

These shunts are actually very accurate but some do lack the ability to catch super low mA loads. The shunt is the least of the worries, in terms of accuracy, when counting Ah's.. Improper set up, incorrect programmed battery capacity, Coulombic efficiency, Peukert, battery temp, battery health, false resets, PSOC use etc. throw far more hooks into an Ah counter than does the shunt..

I was wondering if these amp counters tend to be more accurate with LiPo batteries as they seem to have less of the variables listed above. Wouldn't the SmartGauge be easier to upgrade to LiPo for the same reasons.

[Maine Sail]

Originally Posted by CGirvan

I was wondering if these amp counters tend to be more accurate with LiPo batteries as they seem to have less of the variables listed above. Wouldn't the SmartGauge be easier to upgrade to LiPo for the same reasons.

Ah counters get out of whack on LFP too. I have to manually reset mine every time I attain full or it quickly gets out of sync.. The SmartGauge utilizes database driven behavior models, by battery type, and a learning algorithm. There is no model, and none expected, for LFP. The SmartGauge does not work and does not learn LFP, I tested it for nearly six months hoping it would.