Which Battery Monitor ?

[Mark Johnson]

Once again... since you have no rational argument with the point that I am trying to make, which admittedly doesn't apply to you at all, you decide to nit pick about other things, as if they somehow had some remote bearing on the point. It always baffles me when people do that. During the 21 years that I spent building my three boats, I have read tens of thousands of books, magazines, and articles on these subjects, and am relying solely on my memory over the last 40 years, not sitting there with a reference book or looking up my "NON POINT" comments on the internet. (Some of my information may be dated as well).

I see typos, mistakes, misspellings, bad punctuation, points I disagree with etc. in other people's posts all the time, but if they are making a valid point, I never point out the irrelevant aspects of their posts, it's being "petty" in my book. They probably know it already, after a good re-read of their post. What you're doing seems less like genuinely trying to help each other out in solving our boat problems, and more like tearing someone down to be the "most right". I guess we just have different values about this sort of thing.

Let me say once again... This point was not meant for you! It is a valid point for folks with a very different sort of electrical system and different approach to cruising entirely. For them alone, I said:


"For many folks who want to get their batteries to really last, their equipment to run better on the higher voltage, and have maximum reliability of the system, for these folks and these only... If you start with a large reliable house bank that can power you at least a couple of days, equip your boat as energy efficiently as possible, cycle your batteries fairly shallow, and top them off every day or AT LEAST once a week, (the top 20% of the charge is best done with alternate energy) THEN, one of the smart monitors like the "link 10" will reliably tell you your batteries state of charge, with extreme accuracy!" (end quote)

My system is 15 years old, and I was full time liveaboard for 12, mostly on the hook. I have an autopilot, windlass, refrigeration, watermaker, SSB, RADAR, watch movies listening through the sterio, etc. and my batteries have never even approached the 50% down point, or left me stranded. (This is while 99% of the time, we charged on my solar panels alone!) It was also using homemade or self installed systems, on a homemade plywood boat, while living on about $10,000 per year, and burning almost no diesel... Different strokes for different folks!

I was simply telling those interested, how this level of comfort AND hassle free reliability is done.

For folks in the other categories, I apologize if you thought that my advice applied to you. It certainly does not.

Mark

[Extemporaneous]

"What you're doing seems less like genuinely trying to help each other out in solving our boat problems, and more like tearing someone down to be the "most right". I guess we just have different values about this sort of thing."

Mark... PLEASE relax. I don't think that what you're saying above is at all true.
None of us knows what the other knows, regardless of reading a few of their Posts!

If you know it, Great, teach another!
Some people are Very literal and technical. Personally I'm for the most part literal and would Love to always be technical, but...... I can't, I'm not smart enough!!

Cheers,
Extemp.

[Maine Sail]

Originally Posted by Mark Johnson

Once again... since you have no rational argument with the point that I am trying to make, which admittedly doesn't apply to you at all, you decide to nit pick about other things, as if they somehow had some remote bearing on the point. It always baffles me when people do that.

Wow. Sorry you took t that way I was only trying to help as everyone else here does. You tested brand new batteries and only got 90% of the rating and went so far as to call Trojan tech support over it. I was only trying to help you get a better reference point rather than accepting that brand new batteries are only producing 90% of their rating.

It's great that you are getting satisfactory life out of your banks. I have many customers who call me that don't so am used to helping them understand their charging systems including the battery monitor. My posts were not about who's "right" but rather trying to help you get the most out of your system.

[SvenG]

It is easy to forget that the point of the forum is not to win arguments but to share information, help and get helped.

With that in mind It might be good for everyone to slow down a bit.



-Sven

[4wsilver]

Mark,
You seem to know quite a bit about batteries but you should listen to some of the others like Dave and Extem. I also have quite a bit of knowledge, although I admit that I have not worried much about my boat power, it was always adequate. I have more experience in motorhomes and campers dry camping for extended periods. Most of my experience is as a field engineer with General Electric, dealing with 125 and 250 DC battery banks for paper mills, steel mills, utilities, generating plants (including nuclear) I have worked on up to 1 million amp-hour battery banks one which was installed in 1926 that is still going strong with the original batteries. We built out own battery monitors, but they would be real overkill in a boat. It may sound like I'M bragging, but that is not the intent. The point is that everyone on this thread has something to contribute. Learn from others as I am attempting to do. Don't keep repeating the same erroneous "facts". I think that this is a great thread, it exercises the mind and get the thought processes going.

[4wsilver]

Ok, sorry about that, it just came out. I want to point out that most manufacturers of lead acid batteries recommend limiting discharge to 50 percent of rated AH unless you want to shorten the life of the battery. Some of the comments in the thread seem to indicate that many are going below that value. I won't say I haven't done that myself, especially in my Electric Car but I think it is worth mentioning.

[goboatingnow]

"For many folks who want to get their batteries to really last, their equipment to run better on the higher voltage, and have maximum reliability of the system, for these folks and these only... If you start with a large reliable house bank that can power you at least a couple of days, equip your boat as energy efficiently as possible, cycle your batteries fairly shallow, and top them off every day or AT LEAST once a week, (the top 20% of the charge is best done with alternate energy) THEN, one of the smart monitors like the "link 10" will reliably tell you your batteries state of charge, with extreme accuracy!" (end quote)

Its really hard to impart information SvenG, when people constantly put up black and white arguments

Mike, your statement is simply not true and be validated by compariing accurate hydrometer reading with a battery monitor, Most are very poor at estimating state of charge.( due to the need to change the exponent as discharge rates move with age and usage patterns) The Link 10 unit for example is easily fooled as to when it considers teh battery bank full, then it resets the Ah counter, then it attempts using Peukerts exponent to compute SoC, ( ie the Leds). It gets this wrong regulary in my experience. Even when it announces a fully charged battery it can lie ( and lie bad). Then simply monitor Ah counting is in itself misleading as it conveys no idea of remaining capacity, ie both you and the monitor are essentially "guessing"

PS, I see no validity in saying the last 20% should be put in by alternate power, with a proper IUI charger it can be put in by any charging source.

In your case youre not using a battery monitor, merely a "battery full" meter, and that can easily and more accurately determined by an amp meter.

Im not against Battery Monitors, thery're all we have and certainly better then voltameters, but like all indirect measuring devices, they have to be treated with caution.

Now back to the science

Originally Posted by goboatingnow
Hold your horses there, Wh are a measure of energy used. Ah is a measure of electric charge. Watts is a measure of power.
Dave
Okay, so you're saying they're different?
Quote:
Originally Posted by goboatingnow
At a fixed voltage watt hours and amp hours are measuring the same thing
Dave

Okay, so you're saying they're the same?
Actually "at a fixed voltage" they equate but are still not the same.
Also, that is kind of the point, as your batteries loose capacity, it is not "fixed voltage".

Extem, please look up the definitions, Wh are a measure of energy , AH is a measure of electric charge, both at a fixed voltage are measurements of energy. ( or available energy) ( effectively)

Ah x V = Wh ( for the same V). They are for a given voltage the same ( not equivalent ) the same. The advantage of Wh meters, is that they integrate change in voltage over time of the measurement, whereas Ah, assumes a fixed voltage ( as in 20ah at 12v). But in practice Wh is also stated for consumers and batteries at a fixed system voltage

Quote:
Originally Posted by goboatingnow
Peukerts law applies to the fall in capacity against increase in discharge current. It's has nothing to do with Wh or Ah. A lead acid battery specified in Wh will have it's Wh rating derated in exactly the same way
Dave

I was thinking Ohm's Law more than Peukert's Law. Sorry.
And it makes sense you're right regarding a battery being de-rated but my point was more of monitoring equipment and which unit of measure is more meaningful.

NO, a lead acid battery exhibvits by the nature of its chemistry a reverse relationship between rate of discharge and capacity. In an attempt to model that Peukert developed his inverse law. Battery monitors use it to model the discharge curve. its got nothing to do with Ohms law. ( the effective battery resistance is changing all the time of course according to ohms law).

PLease explain how Wh is any more accurate or useful to the discussion here, I can easy state my battery capacity in Wh, its not more accurate. I really feel you have the wrong end of the stick.


I was involved in battery monitors some years ago, Lead acid is one of the more difficult chemistries to profile from curent flow and terminal voltage, Lithiums are the easiest., with Nimh and Nicd next.

Dave

[Mark Johnson]

The reason I suggested that you use alternate energy systems to put in the last 15% while topping off your batteries, is that when they are say, 50% down, that big 150a alternator will really be charging you up fast. ONLY TO A POINT! It might bring you up to 80% full in less than an hour. The last 15% however, might take several hours to accomplish the "top off" because near the top of their charge, batteries will only accept a small charge, no matter how powerful the alternator. It might take 3 or 4 more hours of running your engine... This is why the standard practice for years has been to cycle your batteries down to as much as 50%, and only bring them back to about 80% or 85%. This is what can be done quickly and easily with an alternator, and what is practical with that technology.

I was not disagreeing with the above, only saying that: "For those who wanted a higher margin of safety, (because they always had more reserve power), who wanted to double or triple their battery life, and who wanted to maintain a higher line voltage so that v. sensitive things run better... while also knowing their batteries exact state of charge, FOR THOSE PEOPLE... there is a better way".

I have already explained why it is simply not practical to bring your batteries back to 100% with a propulsion engines alternator. It is running this huge, expensive, fuel consuming device, for hours, (causing them to carbon up), only to put in a handful of a/h. near the top of a batteries charge.

I hesitate to use numbers at all now, as some don't seem to "get it" that I am talking off of the top of my head, with no references but memory regarding numbers, and it is irrelevant to my point. The "point" is a fact, and not just my opinion.

Assuming that many boat owners might like to, they just don't have the room for enough solar panels, nor do they have have as energy efficient a boat as our little tri... What they can do is...

Size your house bank to where it is no lower than about 65%, or preferably 70% full in the morning, when they are their lowest. Then, at sun up, run your engine for no longer than it takes to bring them back to say... 85% full. (this will be "accepted" by the batteries, and require a short engine run).

For the last 15% of the charge, one or two large solar panels on your bimini top, or a rack on the davits, will top off your batteries at the "long slow pace" that they require, at the top of their charge.

By doing this daily "top off", which, as I've said, is not practical (= energy efficient) with the engine, you vastly extend the batteries useful life, line v. is higher, and IF you've installed a good monitor like the "Link 10" or it's equivalent, then the devices re-zero every day, and their calculation of the batteries state of charge will be within 1% at any given time.

A single large solar panel (like shown), can give you 30 something more A/H for topping off your batteries daily. The solar panel, it's "smart three stage" charge regulator, and a good battery monitor, are a small fraction of the cost, compared to higher engine maintenance, more fuel, and more frequent battery replacements, (If compared over 10 years or more).

These are useful points, for those with an open mind, that "can believe" that there is a better way...

Mark

[goboatingnow]

Mark , I agree and disagree,

The reason most alternators do a bad job is the problem of automtive style alternators which are not designed for battery charging at all. If you replace the high capacity alternator reg with a good IUI regulator you can push teh absorbtion phase hard, ( you may need to add a watering system, but another days discussion). BUT, I dont dispute what you are saying about solar, However in my experience many solar systems are merely supplying the boats electrical needs rather then charging the batteries, Often its only when teh boat is shut down that the solar catches up. Of course there is the issue for those of us in less sunny climes!!.

However this comment

IF you've installed a good monitor like the "Link 10" or it's equivalent, then the devices re-zero every day, and their calculation of the batteries state of charge will be within 1% at any given time.

is quite frankly horses ass, you might want to follow up on the thread discussing the Links 10 issues with determining battery full conditions. In a lot of cases where during charging , the boats electrical system is live, battery monitors can regulary fail to properly determine the "FULL" situation. Equally they only model the discharge curve using Peukerts law, and this with a standard exponent, is not very accurate, particulary as the battery ages and also as the battery can enter charge and discharge cycles on a boat all the time. The monitor is nowwhere near 1% accurate,
In my tests I'd say the monitor was about 10% accurate, thats still OK, but its not a precise measurement system. ( Indirect measurement systems rarely are).

Precise remote monitoring of State of Charge of a active lead acid system, especially one that remains in circuit during charging is very difficult, at least the really good systems, with dynamic exponent recalculation, ageing allowance, dynamic charge acceptance recalculation and a good battery full algorythms are only "good " at the job not excellent.

Dave

[tartansail]

This is a very important topic to me. My new boat has a Link 2000 and a 3xGr27 house bank. Once I figure out how the monitor works, I expect it will help me assess whether I need to modify my energy use, my charging and/or the battery bank.

I'll readily acknowledge thought, that I'd never heard of this guy Puke Art and don't really know why I should be obeying his laws. I go sailing to break free of that kind of rigid conformity and all I find are more laws!! Joking aside, it is extremely helpful to appreciate the levels of knowledge that are available so as to be able to decide how deep I need to go to keep the lights and fridge running.

[goboatingnow]

The primary problem with battery monitors is that what the user wants is a "fuel gauge". That ie the State of Charge ( or Discharge). However this quantity cannot be measured directly using terminal voltage and current in lead acid chemistry. ( it can be much better done in Li and Ni chemistries). Amp Hour ( or Amps and Voltage etc) are measured directly and are accurate, but again relating them to what state the battery is in is difficult.

So a battery monitor now has to model the battery chemistry and effectively make an educated "Guess" at the SoC.

PeuKert law, is a model of how a lead acid battery discharges, becuase in Lead acid chemistry the rate of discharge effects the effective capacity of the battery.

SO now we have a method, we start of at a known good state , a 100% charged good new battery, we then measure amps, and use that with Peukert law to "compute" the SoC, note we are computing it , not measuring it. Thats what drives teh little "fuel gauges" on these monitors.

Then when we put net charging current into teh battery, the monitor nows "knows" in theory we are charging the battery, Since we dont have a good model for the recharge curve of a battery, we just count amps, apply a standardised efficiency factor ( 90%)
and "assume" thoese amp hours are recharging the battery, we then display this on the fuel gauge (the gauge progresses towards full).

In order to get back to a known good point, ( in essence to reset the monitor algorythm to its starting point). Most battery monitors incorporate some battery "full" determining system, usually this is a voltage threshold and a charging current falling below a certain percentage of the total battery capacity, or often just a fixed 2-5% figure.

So if the monitor figures we are discharged to 60% of a (100amp hour battery) and we put in 22amp hours the monitor shows 80% , then it increases the "fuel gauge" until the "FULL" conditions are triggered.

Then it counts amps of discharge and uses Peukerts law to determine the fuel gauge on the way down.

Problems and issues,

(1) The monitor may be fooled, becuase the battery is in circuit, that it is full when it isnt or that it will not reach the full conditions, even though on inspection by a hydrometer the battery is charged.

(2) As the battery ages sulphation, surface charge effects etc will disort the "full" conditions.

(3) Peukerts exponent is often just entered as 1.26 for lead acid, the actual exponent can vary from that, due to age, discharge cycle profiles and temperature, amongst other things, This leads to inaccuracies in determining state of charge ( ie the "fuel gauge"). 10% accruate is a good monitor in my experience.

(4) Amp hour counting on recharge and the application of a fixed charge effiiciency factor can lead to gross errors on displaying the fuel gauge in recharge. We dont have a good recharge model, like we do have a discharge model, hence the simplistic approach to determining state of charge during recharge.

(5) Error compunded by asumptions by the monitor, ie battery bank size , chemistry variations, temperature, fixed Peukert exponent etc.

All these modelling factor errors compound when the battery monitor spends a lot of time not being reset into a "Full battery" state, some have manual resets etc, but a monitor thats trying to keep track of a battery typically working betwwen say 50% and 90% , will rapidly get out of sync. Ive seen errors of over 50% on some monitors after a few days at this.

Dave

[Mark Johnson]

Originally Posted by tartansail

This is a very important topic to me. My new boat has a Link 2000 and a 3xGr27 house bank. Once I figure out how the monitor works, I expect it will help me assess whether I need to modify my energy use, my charging and/or the battery bank.

I'll readily acknowledge thought, that I'd never heard of this guy Puke Art and don't really know why I should be obeying his laws. I go sailing to break free of that kind of rigid conformity and all I find are more laws!! Joking aside, it is extremely helpful to appreciate the levels of knowledge that are available so as to be able to decide how deep I need to go to keep the lights and fridge running.

If you have enough solar power to produce "twice what you need", like we do, then they will perform fine on cloudy overcast days, (ours do 98% of the time). They will just give you half as much a/h, as they would on a sunny day, and that will be good enough. You can also compensate for an upcoming cloudy day, by a slightly longer engine run in the morning, when the batteries are lowest, and can accept the most charge. If you put the panels on a tilting bracket and tilt them accordingly, they put out power until sunset! It is more pleasant than listening to the engine.

"Calibrating" the Link 10 is simply letting it know the batteries type & capacity, and doesn't have to be all that accurate, "in most cases". It mostly helps in the function of "time to go", (which we have never used). This function tells you how long you can run the boat, at that exact moments use of amps. Since a boat's power usage fluctuates all over the place, so will the "time to go". I just don't find this hypothetical TTG information useful.

If the meter hasn't accumulated a VERY long accumulated error, from months of "not" topping off the batteries, then it counts the Amps in or out with extraordinary accuracy. I can even tell the power draw of any device on the boat, by turning off all power in or out, EXCEPT that device. The Link 10 will tell me that device's power draw to the tenth of an amp, including the line loss between the batteries and the device. This has been a very useful tool at keeping our boat as energy efficient as it is. (We only use about 40 a/h per day)

The boat may be using 4 amps, while the solar panels are producing 8 amps. This is no problem whatsoever for the Link 10. It doesn't know or care. It only measures the NET amps in or out of the batteries, through the shunt in the neg. wire, right at the batteries. In the above case... 4a out and 8a in, there are a net of 4 amps going into the batteries. The meter will read 4a. If it were reversed, and 8a going out with 4a going in, it would read -4a.

Then, push the button to a/h, and it gives you the days accumulated amp/ hours, in or out with better than 1% accuracy. As far as a battery knows, (or the meter) if their is power going in, while also going out, it is only the net result that gets measured, and recorded.

When topping off your batteries, the 4 LEDs at the bottom flash to let you know that you're "full", and as soon as you use any amps out, the a/h function starts counting down again from "0"a/h to -1a/h, -2a/h, etc.

Many of my cruising friends and clients have used these successfully, and love them. I have yet to meet someone with a Link 10 who didn't! Even those who DON'T top off their batteries but every week or so, have had no problems at all.

I have heard that they are sensitive to lightning strikes & such, but I have had one close enough to fry a number of things on my boat, and my link 10 was fine, as it still is after 15 years! I have even changed out another boat's entire system from a spike, (with a "dual function" brand),and while the battery "charge" regulator function was out, the monitor function was fine. I had to replace both. This is why I advise using single function, separate monitors, as well as inverters / chargers etc. If they are separate, then if one function takes a dump, the other function is still there. Not so with multi function electronics. This is why I prefer the Link 10... it is a single function monitor, not also a charge regulator. It is ultimately more reliable, IMO.

Anyone who has had a different result from what I am describing, either has a defective unit, something is wrong with their system, the way that they use it, or they didn't wire it right. (This is ultra critical! Even the order of fuse insertion into the sensor wires, MUST be correct, or you fry it) The instruction book is very clear about this! If you momentarily remove a battery cable, you MUST remove the Link 10s sensor wire fuses first, IN the correct order!

I haven't had any problem complying with these requirements, as they are VERY simple things to do. I did however, get out the "book" the one time that I had occasion to remove my battery cables.

As I said from the get go.: "There is a better way, and this is it" ...

Do your homework, install it right, and you'll love it! Mark

[Maine Sail]

Originally Posted by Mark Johnson

"Calibrating" the Link 10 is simply letting it know the batteries type & capacity, and doesn't have to be all that accurate, "in most cases". It mostly helps in the function of "time to go", (which we have never used). This function tells you how long you can run the boat, at that exact moments use of amps. Since a boat's power usage fluctuates all over the place, so will the "time to go". I just don't find this hypothetical TTG information useful.

If the meter hasn't accumulated a VERY long accumulated error, from months of "not" topping off the batteries, then it counts the Amps in or out with extraordinary accuracy. I can even tell the power draw of any device on the boat, by turning off all power in or out, EXCEPT that device. The Link 10 will tell me that device's power draw to the tenth of an amp, including the line loss between the batteries and the device. This has been a very useful tool at keeping our boat as energy efficient as it is. (We only use about 40 a/h per day)

Anyone who has had a different result from what I am describing, either has a defective unit, something is wrong with their system, the way that they use it, or they didn't wire it right. (This is ultra critical! Even the order of fuse insertion into the sensor wires, MUST be correct, or you fry it) The instruction book is very clear about this! If you momentarily remove a battery cable, you MUST remove the Link 10s sensor wire fuses first, IN the correct order!

I haven't had any problem complying with these requirements, as they are VERY simple things to do. I did however, get out the "book" the one time that I had occasion to remove my battery cables.

As I said from the get go.: "There is a better way, and this is it" ...

Do your homework, install it right, and you'll love it! Mark

As you said, "Do your homework" and in that respect please read post 161......

[SvenG]

Gentlemen,

Originally Posted by Mark Johnson

Do your homework, install it right, and you'll love it! Mark

Originally Posted by Maine Sail

As you said, "Do your homework"

Since we now have complete process agreement I suggest we back off on the emotions and focus on the technical issues. Either agree to disagree or bring some new technical point to the table.

This is a really important topic and I myself am looking into the same question for Senta II so I hope we can keep the thread open and constructive ?

Thanks,



-Sven

[Therapy]

Originally Posted by Mark Johnson

(This is ultra critical! Even the order of fuse insertion into the sensor wires, MUST be correct, or you fry it) The instruction book is very clear about this! If you momentarily remove a battery cable, you MUST remove the Link 10s sensor wire fuses first, IN the correct order!

OMG!

I have a link 1000.

I have removed the battery cables to replace the alternator. The fuse to the sensor wires is on the + side and is not accessible until the - side is taken away and the batteries are slid out of the "cave" they are in.

Please tell me the Link 1000 is OK.

The cave is on the right. You can just see the first of two 6V house batts. The one seen is the start batt.