Voltage meter on House batts? necessary?

sailinglegend420 said:
It doesn't matter what size the cup is, what you want to know is when you must charge your batteries as they should never get below 50% State of Charge or their life cycle will be reduced.

If you want to keep a watch on your batteries then all you need is a digital current meter for about £40 and a digital voltmeter for about £5. Use some brain cells and you can get an idea of when you need to charge your batteries.

It would seem you and ghostlymoron don't really understand why this is important. If you don't spend much time cruising away from shorepower then none of this really matters - I'm going back to the Liveaboard Forum.
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I agree with that, but where I disagree is whether there is any product that can tell you that to anything like the accuracy figures you have quoted, and even if it could, there is absolutely no way for the user or to know whether the value it is showing is anywhere near correct - a marketeer's dream product.
 
sailinglegend420 said:
It doesn't matter what size the cup is, what you want to know is when you must charge your batteries as they should never get below 50% State of Charge or their life cycle will be reduced.

If you want to keep a watch on your batteries then all you need is a digital current meter for about £40 and a digital voltmeter for about £5. Use some brain cells and you can get an idea of when you need to charge your batteries.

It would seem you and ghostlymoron don't really understand why this is important. If you don't spend much time cruising away from shorepower then none of this really matters - I'm going back to the Liveaboard Forum.
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If all you want to know is when to charge your batteries, a voltmeter will do that. Re-charge when you're down to 12.2v or am I being to simplistic?
 
sailinglegend420 said:
It doesn't matter what size the cup is, what you want to know is when you must charge your batteries as they should never get below 50% State of Charge or their life cycle will be reduced.

If you want to keep a watch on your batteries then all you need is a digital current meter for about £40 and a digital voltmeter for about £5. Use some brain cells and you can get an idea of when you need to charge your batteries.

It would seem you and ghostlymoron don't really understand why this is important. If you don't spend much time cruising away from shorepower then none of this really matters - I'm going back to the Liveaboard Forum.
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I understand very well just how important battery maintenance is having spent many years living onboard well off the beaten track. Which is why keeping a close eye on battery capacity is very important. Also something very difficult if not impossible to do with a simple clamp meter and volt meter. It might be easy to get replacement batteries never venturing beyond the med, in lot of the planet getting decent batteries can be very difficult and you really need to keep a very close eye on them to be able to plan ahead.
It matters very much knowing what size the cup is.
 
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ghostlymoron said:
If all you want to know is when to charge your batteries, a voltmeter will do that. Re-charge when you're down to 12.2v or am I being to simplistic?
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Simplistic is sometimes OK. At 12.2v you could be well below 50% - because it depends on the current too, that is why I would recommend a Digital Voltmeter and a Digital Amp meter side by side.

At 12.2 volts and 10 amps discharge you could still be at 70% SoC - depending on your battery capacity. At 12.2v with 10 amps charging into the battery you could be well below 50% SoC. To use voltage to measure SoC you need to let the batteries rest with Zero discharge and Zero charge for at least an hour or six and see what the voltage comes back to. Very difficult to do on a boat - so you can just disconnect one battery for 6 hours and see what that recovers too.

So get to know your boat and be aware that at a discharge current of 10 amps the batteries may go down to 12.05v but will recover to 12.2v when open circuit.

GHA said:
...It matters very much knowing what size the cup is.....
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"Know your Boat"

You know what the cup size was - so keep an eye on how quickly it changes over time. So if you were always 75% full at lunchtime and six months later - everything else being equal - you are always at 50% by lunchtime then you have lost a lot of capacity. There is no cheap kit to tell you what size the cup is.
 
sailinglegend420 said:
"Know your Boat"

You know what the cup size was - so keep an eye on how quickly it changes over time. So if you were always 75% full at lunchtime and six months later - everything else being equal - you are always at 50% by lunchtime then you have lost a lot of capacity. There is no cheap kit to tell you what size the cup is.
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At last we're converging :) the key phrase above being "being equal", it won't be in my experience, which is where recording amps used can be a godsend in getting some decent data to help keeping an eye on things.
As for no cheap kit testing kit....
Hope and strongly suspect you are wrong there :) , for less than the cost of a meal for 2...

http://www.ybw.com/forums/showthread.php?387493-Arduino-as-battery-capacity-tester
 
sailinglegend420 said:
OK - my mistake for quoting it.

Let me give a bit more background to SmartGauge. The figure that came from Enersys of an accuracy to 0.1% was given to me personally by the MD of Merlin Equipment who bought SmartGauge and is now developing it for high end use in US and UK military applications. They have now opened US offices and Gibbo, who invented SmartGauge, is locked in a room and not allowed out anymore - but he's the kind of geek who will enjoy that.

The MD, James Hortop, told me that he never believed SmartGauge could work - until he did extensive tests. The reason you haven't seen it marketed heavily is that Merlin have given up on the yachting market to concentrate on other areas because they know it's just not worth the effort, especially with the kind of responses they were used to seeing on this kind of thread. James should be a familiar name because he used to be a Technical Editor on PBO magazine, and used to post on theses forums. He know's how difficult it is to change yachties deep-routed opinions of what's good and what's baloney.

It now appears that Balmar are now selling SmartGauge with a Balmar logo and they are now using the Enersys tests results, but they quote an accuracy to 0.3%, so they must be very confident the these results. Check out their website.
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Unfortunately I can not share the entire white paper from Enersys, not my place to do so as the employee who gave it to me asked me not to distribute it. In the summary they stated 1% not 0.1%. That was 1% when compared to the Enersys in-house testing system, the Digatron, which is an extremely expensive system used widely by battery manufacturers throughout the world..

Essentially their findings were that the Smart Gauge was nearly as accurate as their control or bench mark high dollar factory testing machine. EnerSys invented Optima batteries, (sold the technology) and now markets Odyssey TPPL AGM batteries.

To be honest if it had not been for this EnerSys analysis I would not have paid one cent for this product. Seemed in the too good to be true category. EnerSys is a very good company and their engineers are some of the best in the industry so when I was given that paper I found it to be very interesting, interesting enough to get one and begin my own testing..

From the EnerSys White Paper:

"EXECUTIVE SUMMARY

SmartGauge® is a Battery Monitoring Unit (BMU) that is intended to be fitted
within military vehicles and to provide crucial information to vehicle commanders, such as State of
Health (SoH), State of Charge (SoC) and the time remaining they have available to continue
operation until battery power runs out.

The working partnership between EnerSys and SmartGauge® has resulted in EnerSys testing
the SmartGauge® BMU whilst connected to a Thin Plate Pure Lead (TPPL) battery type within
its electrical laboratory at Newport South Wales, to evaluate the performance and accuracy its data.

The SmartGauge® BMU was tested using a 12V 100Ah TPPL battery which was subjected to a
100% depth of discharge test, followed by a full 12 hour recharge. This cycle was repeated
continuously until the battery reached 80% of its rated capacity, the SmartGauge® BMU and
EnerSys laboratory data logging equipment (Digatron) continuously monitored the voltage, current,
time and from which the State of Charge and State of Health was calculated.

The correlation of State of Charge (SoC) and State of Health (SoH) between the BMU data and
Digatron Data was excellent with insignificant variance between the two readings base upon
resolution increments of 1%."


I now have a couple of months of in-house testing of the Smart Gauge under my belt. This is very tedious and time consuming work, and other than LiFePO4 batteries, which it fails miserably at (no big surprise though), I find its performance to be pretty amazing.

It takes a few cycles to learn the batteries but so far I have been impressed, and I am not easily impressed by whiz-bang "Ginsu" like gizmos... I have spent the last week trying to fool it and even when fooled it quickly re-finds accurate SOC of the bank. I have no idea how the algorithm works just that it seems to do what it says it does, on lead acid batteries.

The thing that I like best is that it can be connected to an old battery, that has lost capacity, and after a few cycles it is giving a pretty accurate reflection of SOC...

Still, I think a Smart Gauge and a standard battery monitor will yield the best data set.. Personally I would not have just a Smart Gauge but I would use a Smart Gauge to keep my Coulomb counter as accurate as possible.

The last FLA battery I tested was about 5 years old and, according to the owner, had been known to have lost "some capacity". The battery was run through a full work up of conditioning and equalizing before testing.

I programmed the Victron battery monitor for "as new" battery specs rather than stabbing in the dark.... I then applied a 20 hour load based on "as new" specs and let her run to 10.5V. It put up 68% of as new capacity at that load. I then recalculated the 20 hour rate based on the new Ah capacity and let her run to 10.5V again. This time it yielded 72.8%. I then once again adjusted then BM for the new size and applied the new 20 hour rate based on known capacity and discharged it to 10.5V and got 74.8% of as new capacity or in this case 93.5Ah's out of a 5 year old 125Ah rated battery (no idea how it performed as new)..... I now finally had the current Ah capacity of the battery, for its age and condition, but it took three cycles to 10.5V to figure this out, as accurately as possible. Not something you want to do on a regular basis.

I had also previously done a Peukert calculation to try and find the most accurate Peukert value and plugged that into the BM. I now finally had my Coulomb counter tracking pretty accurately next to the Smart Gauge SOC reading...

Interestingly the Smart Gauge had already been giving more accurate data by the second cycle but I did not really know this until I had completed the capacity testing via finding the current Ah capacity and the most accurate 20 hour load rate.............

For lead acid batteries I am becoming a believer of the Smart Gauge. I fully admit it seems like "Snake Oil" and this is why am am physically doing my own testing, and continuing to do so. Today on the test bench are some aged AGM batteries......

I just wish they could develop a similar product for LiFeP04....;)



My main gripe with the Smart Gauge is they simply do not respond to emails or support questions. For US customers, in my experience, they have poor customer support. No, scratch that, NO CUSTOMER SUPPORT.... I have even had the Sales Manager for their US distributor trying to get me the information I desired. He has been about as able as I was to get a response, not at all...... Arghhh......

And yes I stand by my earlier quoted statement that the vast majority of Ah counters I see are:

A) Wired incorrectly with neg loads/charge sources sneaking past the shunt (perhaps 60%)

B) Programmed incorrectly (perhaps 90%)

C) Very often tricked by solar, wind or dumb chargers with timed absorption to float algorithms (nearly every boat with solar or wind)

I actually saw a 70Ah starting battery on a boat last summer reading -575Ah's but it still had a 12.69V resting OCV...........:p


Is the Smart Gauge a panacea? Not IMHO, especially when you factor in the price, but it seems to be a good tool to tell more accurately a batteries current SOC for its current state of health... I think both an Ah counter and a Smart Gauge can help keep each other giving the best information.. It is not unknown that Ah counters can be quite inaccurate, if not properly programmed, and not kept on top of. The Smart Gauge I think will be able to help supplement this...

The best way to keep an Ah counter as accurate as possible is to properly wire it, properly program it and then do manual re-sets when your bank is "known full".. If you want to keep it as accurate as possible beyond year one a capacity test will be necessary. Great tools when used properly but they are not as plug & play as many boaters expect they are... The Smart Gauge is actually pretty much plug & play...

Course if you are good at reading your own voltage and get to "know" your bank you can do a pretty good shoot from the hip guesstimate and get by with only volts, many do..
 
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Maine Sail said:
... Course if you are good at reading your own voltage and get to "know" your bank you can do a pretty good shoot from the hip guesstimate and get by with only volts, many do..
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Thanks for the erudition some real data. As a matter of interest, does testing include lumpy discharge regimes such as you might see on a boat - 30 amps for ten mins then nothing for 6 hours then...etc. and do you think it would impact accuracy?

I have cheap and cheerful NASA battery monitors, which I really regard as a tidy and reasonably accurate way of having a volt and ammeter - they agree with measurements with external test meters pretty well. No-one would argue with the view that it is nice to know volts and amps.

I guess we all like to think we spent our money wisely, so we go in to bat for the system we have on our own boat. (I've even defended the NASA wind instrument!)
 
Maine Sail said:
......... .
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Another big thanx for sharing that.

How do you measufe/collect the data when testing and what sort of repeatable accuracy do you think it's realistic to achieve measuring Ah capacity?


Also, for the panel, i also suspect smart regulators will undercharge by getting confused with current going to other loads around the boat and not the battery. Probably not a big deal on a mains charger but on the hook might be more of an issue. And just getting a full charge in is not that easy, so what does the panel think about balancing the gains in battery life by more aggressive charging/staying at absorbtion for longer to regularly get close to full against the losses in battery life by higher voltage charging?
 
GHA said:
....Also, for the panel, i also suspect smart regulators will undercharge by getting confused with current going to other loads around the boat and not the battery. Probably not a big deal on a mains charger but on the hook might be more of an issue. And just getting a full charge in is not that easy, so what does the panel think about balancing the gains in battery life by more aggressive charging/staying at absorbtion for longer to regularly get close to full against the losses in battery life by higher voltage charging?
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Yes thanks Maine Sail for joining us "across the pond".

I think it was Maine Sail who talks about the "Charging Gotcha" - although he has a much more memorable phrase - "Premature Efloatulation.

This is all part of the charger "getting confused", but this is a complicated subject to explain in a short post. So as not to get confused all multi-stage chargers that don't or can't measure the amps going into the battery (about 99.9%) have a timed period at the "Absorption Voltage", lets call this about 14.4v, with maybe some other assessment of how long it takes to get to 14.4v. My Victron charger stays at 14.4v for X 5 the time it takes to get to 14.4v. So if the batteries are nearly charged and it takes 10 minutes to get to 14.4v then it stays there for 50 minutes. If it takes 1.5 hours to get to 14.4v it will stay there for 7.5 hours before it drops to Float. Most chargers aren't that clever and only have a FIXED time at 14.4v, say 1-3 hours. On a good charger this can be adjusted to suit the size of the House Bank. It should also be set to minimum during light boat usage.

As I said in an earlier post this is designed not to overcharge your batteries, but can also cause problems if the charger is repeatedly being turned on and off by some other external event. If the Absorption time is fixed this can cause problems with the battery sitting at 14.4v for too long. This can happen if the boat is left over winter with charging only from a large solar array that every morning may switch on and go into full charge mode for 3 hours putting 14.4v onto an already fully charged battery. This may happen because the battery voltage has dropped slightly due self discharge or to very small loads from any kit that is left on. This may include Battery Monitors, Navtex, Car Radio memory, LED lights on the instrument panel - most of these are not connected via the battery isolator switch.

When a battery is fully charged it will take no more current, but if the voltage remains at the battery gassing voltage - 14.4v - then the energy from this voltage causes the battery to gas much more vigorously. Every battery needs to reach its gassing voltage to stir up the electrolyte but any light gassing is re-absorbed, or bubbles out. Excess gassing every day for several months will cause the battery to dry out. For a sealed battery this is very bad news.

So in answer to your question, leaving the battery at absorption voltage for longer is a good idea, and any good charger will allow this time to be adjusted to suit the size of your bank so you can get it closer to 100% before Float Mode - but it shouldn't be left at 14.4v for ever. By reducing the charge voltage from 14.4v to a float of 13.8v or less gassing will stop.

So this always begs the question why don't car batteries get overcharged if there is no multi-stage regulator to drop to "Float Mode"? This is another "Book".

Boats about 15 years old may have an automotive alternator which charges at only 13.8 – 14 volts, so no gassing in the car battery, but on a boat the batteries will never get anywhere near properly charged at these voltages!

Cars with a more modern 14.2-14.4 volt alternator with a built-in regulator will have a simple temperature sensor which will soon drop the output voltage down well below the 14.4v gassing voltage - it thinks the battery is close to it in the engine compartment. This shouldn't happen on a boat - batteries should be well away from the engine compartment, so they will see a lower voltage than they need once the alternator has warmed up, so they will not gas and so may be undercharged. Automotive alternators are NOT designed to charge a deep cycle house bank, but mainly designed to provide power to the car's electrical system. A starter battery will recharge in about 10 minutes. On a boat the alternator will in fact warm up much more than the ambient engine room temperature mainly from the high current the alternator is being asked to supply for extended periods. My Balmar alternator regularly goes up to 95 degrees C delivering 90 amps for an hour. That's why "Best Practice" for a cruising sailboat with a large house bank should be to use a "hot rated" alternator with an external regulator with both battery and alternator temperature sensors - and that's another book!
 
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sailinglegend420 said:
This is all part of the charger "getting confused", but this is a complicated subject to explain in a short post. So as not to get confused all multi-stage chargers that don't or can't measure the amps going into the battery (about 99.9%) have a timed period at the "Absorption Voltage", lets call this about 14.4v, with maybe some other assessment of how long it takes to get to 14.4v.
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When I stripped 2 expensive multi-output chargers I had inherited with boats, both broken, I found they were both single output chargers feeding the different outputs through diodes. No doubt others on the market are just the same which I view as manufacturers conning us, as all banks get the same charging regime regardless of their different states of charge. For that reason, I have fitted 2 single output (switchable 3 or 4 stage) chargers, one for each domestic bank.
 
GrahamM376 said:
When I stripped 2 expensive multi-output chargers I had inherited with boats, both broken, I found they were both single output chargers feeding the different outputs through diodes. No doubt others on the market are just the same which I view as manufacturers conning us, as all banks get the same charging regime regardless of their different states of charge. For that reason, I have fitted 2 single output (switchable 3 or 4 stage) chargers, one for each domestic bank.
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This is pretty much standard fair in "multi-output" chargers... One voltage program two or more diode isolated outputs. Usually not a huge issue when compared to the piss poor "time only" algorithms many charger manufactures use...

We have one charger maker here in the US that starts a 4 hour timer when the charger is turned on. At 4 hours, regardless of bank SOC, it drops to float voltage..... It can literally bypass absorption altogether, if the bank or system loads are large enough to keep it in bulk for 4 hours....... At 4 hours it simply goes into float leaving many boaters with chronically undercharged batteries...

Top quality smart shore chargers use "adaptive learning" algorithms and modify the duration of absorption based on time to get to X, voltage rise over X time period etc. etc.. They learn as they go and adapt to bank size. Are they "perfect", not really, but this type of algorithm is about as good as it gets for shore chargers and inverter chargers. Good ones will not drop the bank to float until it is in the 98-99% SOC range. Poorly executed chargers can drop into float as early as 85% SOC especially if time only based..

Balmar regulators are perhaps the best and smartest products out there giving you full control over every possible parameter including min or max bulk, absorb and float times, temp compensation adjustments, current limiting of the field, float transition thresholds, bulk to absorption threshold etc. etc. etc...

A good "smart" shore side battery charger should always have at least the ability to create a custom battery charging profile...

Sterling now offers a neat little product called the BCM or Battery Chemistry Module Battery Chemistry Module. The BCM allows you to set the charge voltage for the main bank voltage, say GEL at 14.1V, then if you need to boost voltage to an AGM starter it can do that and create its own "smart" program for the second bank. It is intended to be driven off an unused output on a multi-output charger....

A tad pricey for what it is but they do work quite well. I charge our LiFePO4 bank via a Sterling PCU charger to 13.8V and use the BCM to boost charge our reserve/AUX AGM battery at 14.4V..

As has been said books could be written on charging.......
 
nigelmercier said:
MRDA.
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Another pointless post of yours.

For those who don't understand what you mean this stupid internet shorthand 'MRDA' is an abbreviation for Mandy Rice-Davies Applies is Internet slang meaning "well he would say that, wouldn't he"? - Used to indicate cynicism of a statement of fact due to the obvious bias of the person stating the fact.

Why do you believe there is obvious bias from Maine Sail? He is a very we'll respected marine electrical engineer in the USA who doesn't just take people's money when their systems fail, but he tries to educate them. He has a huge website with very good information about all things to do with boats. You would do well to read it and learn!
 
nigelmercier said:
Because he sells them.

Are you "related"?
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If you read his site he only sells them to finance the site - and as he says, much to his surprise, they are not snake oil!

The MD of Merlin who bought SmartGuage felt the same before he had done exhaustive tests. It was developed because the US and UK Military were fed up with Battery Monitors becoming so inaccurate, they are now very happy.

Its worth noting that Balmar are now selling it as a Balmar SmartGuage because Merlin have dropped out of the Yachting market due to their Military work. Bamar wouldn't put their name to a duff product.
 
nigelmercier said:
Now that I do agree with. I'm not saying they are duff, just that I don't take any notice of "the man in the shop said it was a good one".
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I have a great deal of respect for Maine Sail. He has tested all sorts of nautical equipment and has no hesitation criticising the poor stuff. I don't care if he does sell stuff he finds to be good, wish more vendors would do the same.
 
I fitted a Smart Gauge to my boat on Tue, it was easy and the instructions are very clear. It was fitted at the same time as a new house battery, initially reading 75% charged which had settled down to 100% today (shore power battery charger in the interim). At first sight it appears to be a very nice bit of kit.
 
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