Buying a Smartgauge

[Kenomac]

Originally Posted by john61ct

But even one of those foldup backpackers solar chargers would be enough to save at least 3-4 hours of running the genny per time.

Side benefit of doing it much more often.

You're forgetting about something rather significant. During the day, the refrigeration system continues to operate and drain the bank, so where can you find a "foldup backpackers solar charger" that can handle the refrigeration system along with adding the extra juice required to top things off?

I'd hate to be toting something that large around in my backpack.

[ErikFinn]

At 120 USD it is not that expensive anymore.

[Dockhead]

Originally Posted by Exile

. .. We already know that the only reliable way of determining 100% SOC is by measuring amps going in (while charging source is in absorption mode). . .

I forgot specific gravity -- does no one take SG of their batteries anymore? I always used this to check whatever method I was using. And I used to log it along with adjustments to absorption time, although that's fallen by the wayside a bit.

Here is what Rolls say about it:

[I]"The most accurate and direct way to test the state of charge of a battery cell is to determine the specific gravity of the battery electrolyte. The higher the specific gravity of the electrolyte the higher the state of charge. The best way to truly monitor your system over it lifetime is to regularly take and record specific gravity readings."

"t is recommended that a specific gravity reading of one pilot cell is measured and recorded on a regular basis when it is thought that the bank is fully charged. The measurement should be compared to previous readings. If the measurement is lower than the previous reading a longer absorption time and higher voltage setting should be used. . . . Note: the specific gravity should rise as the cells use water. Look for trends in the specific gravity over a period of time and make very small adjustments as necessary."

http://support.rollsbattery.com/supp...n-instructions


Ever since I started out in this sport, that was always the way I determined whether the battery charger was doing its job correctly or not. And note well -- you can't sit on your laurels, because your batteries change over time. The absorption time needs to be in correct adjustment -- too much and you can boil the batteries out or corrode the cathode plates (or is it anodes -- I forget); too little and they never get full and sulphate.

And obviously the absorption voltage needs to be right -- voltage AT THE BATTERY, not at the charger output, and CORRECTED FOR TEMPERATURE. But once you get this right, you don't usually need to fiddle with it much more.


In my opinion, once you have good charging equipment, well set up, and kept in adjustment, then it's not necessary to carefully monitor SOC. You should try not to get below 50% too often (and voltage reading or SG is fine for this) and you should be sure to get a really good full charge on a regular basis, and equalize as needed, and that's all there is to it. In my humble etc.

[conachair]

Originally Posted by Dockhead

I forgot specific gravity -- does no one take SG of their batteries anymore?

On the monthly to do list, though not really practical on a day to day basis but once a month useful to see if the SG is drifting between cells.

I reckon amps in at absorption is best way which is actually going to work day to day. Temperature changes things a bit though so if you do end up on shore power it's probably a good idea to force the charger to stay at absorption for a while and make a note of the current when it settles at a minimum. Right now my 2 x trojans are taking 1.3A at 14.85V. Living up a ladder in a boatyard for the foreseeable so I should reset the voltages a bit lower than the "genny in the anchorage" high settings. And with the charger back in absorption the boatyard power has obviously tripped when I popped out for a swift beer

[john61ct]

Originally Posted by Kenomac

You're forgetting about something rather significant. During the day, the refrigeration system continues to operate and drain the bank, so where can you find a "foldup backpackers solar charger" that can handle the refrigeration system along with adding the extra juice required to top things off?

I'd hate to be toting something that large around in my backpack.

You might be surprised. The 80W ones fit in a coat pocket, if your setup is efficient a couple of those should be fine.

Personally I have no problem shutting my freezer/fridge down for a few hours.

My next one will be a eutectic holding plate unit, not just higher efficiency but really for much greater flexibility.

In any case the larger question is, why not put in some solar?

[john61ct]

Originally Posted by Dockhead

I forgot specific gravity -- does no one take SG of their batteries anymore?

Just like voltage, needs a resting period (thanks MaineSail)

And many used sealed chemistries these days.

But yes, a useful addition to the tool kit.

But for precise determination of 100%, nothing's as good as endAmps.

[Paul L]

Originally Posted by a64pilot

......

I believe if given several hours in discharge the SG gets its act back together, reason I believe it’s accurate late at night and early in the morning......

I have a broken analog watch that is spot on accurate twice day too Turns out not very useful.

[sailorboy1]

Checking SG, that seems excessive 😬 I only do it if I’ve done something like an equalization charge. I’m getting lazier and lazier about the batteries and they seem to be the same as always.

[john61ct]

Probably best to leave SG meaning SmartGauge for this thread, even though the other meaning is a defacto standard TLA

[Kenomac]

Originally Posted by john61ct

You might be surprised. The 80W ones fit in a coat pocket, if your setup is efficient a couple of those should be fine.

Personally I have no problem shutting my freezer/fridge down for a few hours.

My next one will be a eutectic holding plate unit, not just higher efficiency but really for much greater flexibility.

In any case the larger question is, why not put in some solar?

So..... you're saying all we need to run a 53ft sailboat and bring it's battery bank up to 100%, is a couple of 80W "foldable backpackers pocket 80W solar panels?"

Really....

You do also realize how quickly food thaws during the hot summer months and that additional energy will be required to bring the freezer back down to minus 15 C after you've "shut down your freezer/fridge for a few hours?"

[a64pilot]

Originally Posted by Exile

In other words, same as a basic voltmeter. So as Dockhead has pointed out, the SG becomes more of a convenience item, albeit a redundant one. We already know that the only reliable way of determining 100% SOC is by measuring amps going in (while charging source is in absorption mode). And we also already know that it doesn't really matter whether we re-charge at 50-55-60-70% or even below 50% on occasion. I suppose a SG might help if one desires more precision with the latter, but whether that precision results in longer battery life sounds questionable given all the variables.

No, cause you can’t confuse a voltmeter.
I assume a Smart Gauge is pretty much just a voltmeter with a very smart learning algorithm if I used the term correctly.
I believe with just a voltmeter you can tell if it’s time to start charging so you don’t take your bank too low, but I don’t believe you can tell the difference between say 65% SOC and 80%. It’s that middle ground between when you need to charge and a full bank is what I want a SG for, and you can’t interpolate that with just a voltmeter, you can get a guess, even an educated one with a volt / SOC chart, but without an extended rest interval, it’s just a guess. SG is a Smart guesser I think.
See I typically use about 15% Capacity over one night , if I know my SOC is in the 80’s then I know is going to be above 50 in the morning when the panels kick in and won’t worry about it, but with just a voltmeter you can’t get there.
I know 50 is not a hard number just as 85 isn’t either, but if you look at the expected cycle life limit you will see below 50 it is a sharper curve, it is not a straight line. So I will endeavor to never even get into the 50’s really as the shallower you cycle them, the longer they live.

On edit, I have always been taught that the true way to tell when a bank is fully charged is by specific gravity, yes that is a PIA and with my AGM bank not an option either, but the wet Cell guys maybe can use that to tell SOC more accurately than a voltmeter, although it is a PIA to do.

[a64pilot]

Originally Posted by kenbo

What you're saying is fully supported in the SG documentation. During charging the SG only "sees" the charging source. It's during the discharge cycle that thing settle down and the SG can modify it's algorithm and offer a better result.

BTW what type or regulator were you using on your engine alternator before you installed the 614 that was going to float?

I bought a Mark Grasser alt, serpentine belt kit and Marks reprogrammed regulator from Rich Boren at Cruise RO. Now for the money it’s outstanding, is three stage and does sense battery bank temp and alternator temp, but it’s not programmable like the Balmar 614 is, but at a much higher price.
I think his alternator is at least as good as Balmar’s though, I’d rather have a Mark Grasser alternator.

[Jim Cate]

I don't pretend to understand the technique used in the SG, but it is, from the posted comments by the originator, far more that a voltmeter. He says it interrogates the battery by pulsing it with a signal and looking at phase changes in the return. All pretty sophisticated. I'm not able to judge if the method works or not, but all you folks saying it is just a voltmeter are like the aboriginal mountain man, seeing a TV for the first time wondering how they get the little people into the box!

And FWIW, we've managed to keep our batteries reasonably well for decades with nothing but an accurate voltmeter and a shunt ammeter. I'm reasonably sure that with more careful husbandry we could have extended their life by some factor, but the worry and fuss might well have shortened MY life somewhat, too!

Jim

[john61ct]

Originally Posted by Kenomac

So..... you're saying all we need to run a 53ft sailboat and bring it's battery bank up to 100%, is a couple of 80W "foldable backpackers pocket 80W solar panels?"

Really....

You do also realize how quickly food thaws during the hot summer months and that additional energy will be required to bring the freezer back down to minus 15 C after you've "shut down your freezer/fridge for a few hours?"

Are you willfully trolling or just not paying attention? I thought you knew this stuff?

No, we were just talking about putting the last few AH in after running the genny enough to handle 85-95% of the input, just saving the last few hours of runtime per charge cycle, which is wasteful just to get to true 100%.

The length of the boat is not indicative of consumption.

And yes, a good freezer will hold for many hours even in hot weather without thawing, hence holding plate units, where the compressor may only run once or twice per 24 hours.

Yes for longer on cycles, but that's no problem, the goal is to get to 100% then can draw much as you like.

[a64pilot]

Only problem with pulsing the bank with AC current etc., is people like Maine Sail I believe have put O scopes on the things to try to pry the operating principle out of it, and have observed nothing.

I think voltage compared with rate of voltage change and voltage sags etc that with a sophisticated enough algorithm that SOC can be derived.
It’s sort of like many things like sophisticated fridge controllers etc that tell you how many AH you have used per day etc. you would think that they would have a shunt, but they don’t. You tel them what type the compressor is and they have in their software the average amp draw per compressor and with an algorithm determine power usage, except it’s not actual, it’s calculated.
All our cars that give you fuel consumption numbers, well that isn’t measured either, it’s calculated for instance.