Smartgauge w/ 3 batterys

[Exile]

Originally Posted by john61ct

Diversity of opinion is a good thing, disagreement can help everyone learn, and off the wall ideas can advance best practices eventually.

Just takes some long familiarity with the various posters to figure out whose opinions to pay more or less attention to.

So indulge a relative noob when it comes to figuring out how to reliably monitor boat electrics. Taking one of RamblinRod's examples, what is wrong with the conclusion that "all's well" (i.e. SOC is at least 50%) when seeing 12.2v on the meter first thing in the morn before solar or any other charging sources have had a chance to kick in? If there's been no charging going on all night, and assuming some ongoing overnight discharge from say a anchor light, bilge pump and/or CO detector, then wouldn't 12.2v (on most LA batts.) indicate that SOC has not gone below 50% and is likely a bit higher? And this can always be cross-checked with an amp counter, no? I understand why a full capacity test provides the most reliable answers, but this is not practical or desirable for many.

And what about the problem pointed out by sailcrazy below? It seems like most cruising boats these days have some amount of solar and other charging sources that are often continuous.

Originally Posted by sailcrazy

And, based on comments made on this thread I'm leaning away from using a Smart Gauge as we have solar and wind installed(continuous charging).

I'm not knocking the Smartgauge in the least, and for less than $300 it's likely a useful tool & may wind up buying one myself. I just want to be clear on what type of monitoring it can & cannot do. After all, knowledgeable cruisers got along quite well monitoring their batts. for a long time without it.

[john61ct]

Originally Posted by Exile

Taking one of RamblinRod's examples, what is wrong with the conclusion that "all's well" (i.e. SOC is at least 50%) when seeing 12.2v on the meter first thing in the morn before solar or any other charging sources have had a chance to kick in?

To start, RR is not interested in SoC accuracy, and apparently deals mostly with inexpensive banks, where just replacing more frequently is NBD.

Regarding using voltage for SoC, to start with, different chemistries have different SoC correspondences to **resting** voltages, and that changes as their capacity walks down over time.

Second, banks in cycling use don't show their true resting voltage for days, 24 hours is certainly not enough.

[john61ct]

Originally Posted by Exile

And this can always be cross-checked with an amp counter, no? I understand why a full capacity test provides the most reliable answers, but this is not practical or desirable for many

When traveling far from shore, I don't want any surprises, but I also don't want to pay thousands for a new bank if it isn't needed.

IMO the protocol for an initial benchmark load test is so close to what you should be doing at install time anyway to break in the bank, silly not to do it.

And if you're coddling a top quality bank, the next ones don't need to be done any more frequently than once a year, even 18 months for the first one.

More frequently only if I notice the bank is getting suspect, or before a long sea journey.

In the later stages, the coulomb counter is just guessing without an accurate capacity number.

If you want to cross-reference it, then a SmartGauge is the tool, not a voltmeter.

[john61ct]

Originally Posted by Exile

most cruising boats these days have some amount of solar and other charging sources that are often continuous

A use both types, keep the AH counter in sync with the SG, and cross-reference while charging, or

B switch off the charge source for 5-10 minutes to get a more accurate reading, or

C use the SG to judge the bottom end only, after dark, ensuring your top-notch charge sources go to float only after 100% full, ideally based on tail amps, which defines that better than anything else anyway

Originally Posted by Exile

knowledgeable cruisers got along quite well monitoring their batts. for a long time without it.

They also got along with nothing but maps, compass and sextant. The modern use of electrical mod cons is far beyond what anyone but the very wealthy even imagined twenty years ago.

[Exile]

Originally Posted by john61ct

To start, RR is not interested in SoC accuracy, and apparently deals mostly with inexpensive banks, where just replacing more frequently is NBD.

Maybe so, or perhaps with customers who don't take extended cruises and are more likely to be plugged back in with more regularity than cruisers doing long passages & living on the hook. But the specific issue is whether you can safely rely on 12.2v as shown on a voltmeter to not be below 50% SOC.

Regarding using voltage for SoC, to start with, different chemistries have different SoC correspondences to **resting** voltages, and that changes as their capacity walks down over time.

I am only familiar with Lifeline AGM's whose manual states that a 12.2v "resting" voltage corresponds to 50% SOC. (12.5v = 75%). I thought that many if not most FLA's were similar. What I did not know is this can change as capacity diminishes over time. Any idea by how much?

Second, banks in cycling use don't show their true resting voltage for days, 24 hours is certainly not enough.

I don't doubt this is correct, but wouldn't it also mean that true resting voltage would necessarily be higher as the impact of any loads dissipates over this period of time?

Originally Posted by john61ct

When traveling far from shore, I don't want any surprises, but I also don't want to pay thousands for a new bank if it isn't needed.

Funny you mention since a friend who's also a tech claimed I would have to replace my 7-year old bank if going on an extended passage, even though my batts. have spent a disproportionate amt. of time plugged in, and I condition them 2-3x/year. For a capacity test the Lifeline manual recommends a 25ah load until the battery is down to 10.5v. Record the time & then compare to rated capacity. Btw, where do you find 25ah of load to put on your battery all at once & maintain it for up to 20 hrs., esp. if you don't have an inverter?

IMO the protocol for an initial benchmark load test is so close to what you should be doing at install time anyway to break in the bank, silly not to do it.

Can't find anything in my manual about this type of break-in that you often mention. Lifeline says only to "boost" them upon initial installation but that's just one mfg. obviously.

And if you're coddling a top quality bank, the next ones don't need to be done any more frequently than once a year, even 18 months for the first one.

More frequently only if I notice the bank is getting suspect, or before a long sea journey.

A bit easier if you can isolate each battery I suppose, esp. if you live aboard.

In the later stages, the coulomb counter is just guessing without an accurate capacity number.

Good point worth remembering.

If you want to cross-reference it, then a SmartGauge is the tool, not a voltmeter.

Certainly for precision, yes. But if, for e.g., you routinely fire up your genset at 70-80% SOC based on voltmeter readings, and in any event no lower than 50%, then RR's point is that the voltmeter can provide a reasonable approximation that won't kill your batts. I read his comments as less of a ditz against SG & more of a pragmatic solution that, while not absolutely precise, is close enough to keep your batts. healthy. So back to his example, can his 12.2v reading first thing in the morn ever indicate a SOC under 50%?

Originally Posted by john61ct

A use both types, keep the AH counter in sync with the SG, and cross-reference while charging,

Good idea. Then, for example, if your rated 100ah batt. has only consumed 40ah when the SG reads 50% SOC, you know you are at approx. 80% capacity. or

B switch off the charge source for 5-10 minutes to get a more accurate reading,

Can you do this with solar or wind?

or

C use the SG to judge the bottom end only, after dark, ensuring your top-notch charge sources go to float only after 100% full, ideally based on tail amps, which defines that better than anything else anyway

They also got along with nothing but maps, compass and sextant. The modern use of electrical mod cons is far beyond what anyone but the very wealthy even imagined twenty years ago.

True, and I noticed that Maine Sail has lowered the price of the SG by $20. Not trying to argue with you, btw. Your frequent replies have been most helpful. Sometimes it just makes it easier for me to understand this stuff when I play devil's advocate. I've unfortunately learned the hard way over the years to be more circumspect about expenditures that go towards the addition of any new system or gizmo on the boat.

[Zil]

Hello, Stu. I'm not sure about your question. My Blue Sea switch on the negative is used when ever I work on my 12 volt house stuff, including battery maintenance. It is so much easier to turn the switch than to disconnect negative battery terminals. The voltage drop through the switch is not measurable while charging. I studied my wiring diagrams to insure no 12 volt load could sneak back to ground through thin wire. The relay in the Victron runs the exhaust fan when battery voltage is above 13.5. Before that I just let the fan run non-stop. A 1" muffin fan does not use much power but the noise can be annoying.

[john61ct]

Again, volts are not accurate unless resting, maybe 48-72hrs.

If charging they will look high, if loaded low, if both who knows. I want my meter to accurately let me know before I get too low not afterwards.

If for whatever reason you feel OK doing without that functionality, carry on, your boat your call.

For load testing a series of old school lights, rig a "dimmer" use a heater, any variable load. Or pay a pro.

[john61ct]

Commission charging:

​First step really fully charge, but no higher than ~.15C current.

Then manually follow mfg equalizing instructions.

​Then discharge at .05C or 5A per 100AH, for 20 hours. The battery voltage should then be resting around 10.5 Volts.

​Then recharge at ~.15C or below for the rest of the break-in period, say two months if regularly cycling, trying to avoid larger draw currents as well.

From then on, larger currents are best, say .4-.6C

Equalizing monthly, especially if PSOC, if getting to 100% every cycle then maybe quarterly.

I believe most of the above paraphrased from Maine Sail, didn't keep a cite.

Corrections welcome.

[john61ct]

Of course any charge source can be powered down, just check for that unit how.

Could also divert, eg, to load shed like water heater, or just another batt.

[Exile]

Thanks for all the comments John. Will re-read some of Maine Sail's stuff & cross-check with my battery mfg. manual. The eduction continues!

[sailcrazy]

Sounds to me like there are 4 choices, not the 3 that john61ct suggested. Certainly the 3 he mentioned, and the 4th of just installing a good amp counter(Victron, Blue Sea, Xantrex, etc (and saving the extra $$) if you do have solar/windgen installed. Maybe I'm missing something here, but what is gained by installing the SG if you do have solar/wind charging in the system....besides another gauge to check that may be accurate sometime?

[Exile]

Originally Posted by sailcrazy

Sounds to me like there are 4 choices, not the 3 that john61ct suggested. Certainly the 3 he mentioned, and the 4th of just installing a good amp counter(Victron, Blue Sea, Xantrex, etc (and saving the extra $$) if you do have solar/windgen installed. Maybe I'm missing something here, but what is gained by installing the SG if you do have solar/wind charging in the system....besides another gauge to check that may be accurate sometime?

If I understand John's analysis correctly, charging sources misrepresent both VM and SG readings upwards but are quickly corrected (5-10 mins) once removed, whereas battery discharge/cycling misrepresent VM readings downward but take a long time to correct (24-48 hrs). So the SG can fill the gap by accurately showing SOC a short time after charging sources have been removed. In your case, you would either need an easy way to temporarily remove your solar & wind charging, or wait for a calm evening. In any event, it sounds like a SG has limited value if you are using it to determine when your batts. have finished recharging back to 100% as I suspect most probably do.

But again, this also means that an accurate VM reading of 12.2v or above (or whatever V your batt mfg specifies) with charging sources removed probably means a true voltage which is higher, i.e. greater than 50% (unless an aging batt's lower overall capacity influences??). So for those less concerned with precision & want to simply know when it's time to turn on their engine or genset to recharge their batts, then a VM -- along with periodic capacity tests and resetting your amp counter accordingly -- may suffice.

I'm sure John or someone else will correct if I got any of this wrong.

[john61ct]

yes, every time I re-read his stuff it gets more clear. all three articles with "battery monitor" are well worth parsing carefully.

I f you come across original text on the "breaking in" protocol let me know.

This is from Ample ​ http://www.amplepower.com/primer/break-in/index.html

[john61ct]

Volts are higher than resting after charging.

And lower than resting under load.

Takes well over 24 hours to get true resting readings.

No measurement while bank is in use shows 100% full accurately other than tailing amps at Absorb voltage, and that - regardless of any monitor - should be what is used to adjust the algorithm of all charge sources to prevent premature floatulation.

But yes SmartGauge is accurate for that use, within 10 minutes after charge is halted - once it is acclimated to the bank; SG gets **more** accurate over time without any manual adjustment.

*No* AH counter is ever accurate for long, without

A being frequently "reset full", ideally automatically triggered by tailing amps accepted,

AND B the user periodically updating the declining actual AH capacity of the bank as it ages.

To me, accurate and easier SoC is more important than detailed AH logging, so forced to choose one alone, I say SG over AH counter.

Best is both.

[ramblinrod]

Originally Posted by sailinglegend

Now you really are showing your ignorance. You should read a bit more about Smartgauge before becoming so opinionated.

Here is what the designer Chris Gibson has said:

Full post is at,

Smartbank battery management - Page 2
post number #42

Obviously I am not prepared to disclose how SmartGauge works. Anyone who asks me to do so is simply being totally unreasonable.
But to say that only voltage can be measured via 2 wires is *completely* incorrect.....
Pull a brief current pulse from the battery and measure the voltage drop, this will give an indication of internal resistance.
Present an AC voltage across the battery and measure the phase angle and amplitude of the resultant current. This will show the AC impedance of the battery.
Do the same thing with a wide variety of frequencies and analyse the results. This is know as AC impedance spectrography.

I have a signature that I very occasionally use - in this case it is relevant.

Ignorance isn't what you don't know but what you think you know that is incorrect!

Speaking of ignorance, what are the two primary variables measured in the description above?

Answer: Voltage and time.

Don't be baffled by BS and marketing hype.

I'm not saying a Smart Gauge is a bad device. If a customer of mine wanted one, I would gladly supply and install it (in such a way not to leave scars in the boat when the device fails and is removed).

My position is that it is absolutely unnecessary if one has a voltmeter (that everyone should have aboard anyway at 1/40 the cost as I have posted earlier in this thread, it is easy and anyone can do it.

Anyone can install any amount of stuff they wish, it is just important to know, that some day it will fail, (around 10 years for the average electrical device) at which time it must be removed and any scars made installing it fixed or the boat devalued.