Link-series Charging Algorithms -- The "Gotcha" Factor!

[Stu Jackson]

Link Algorithm Operation

In discussions over the course of a few years, and since I finally installed my Link 2000 last year, I have been investigating the operation of the Link algorithm and how it affects the indication of "complete" recharging.

Last year I was involved in a detailed discussion over on co.com about how they work, related to another issue altogether.

Rich Stidger with his Hunter 40.5 from Rhode Island, and Donalex from the U.K., helped me to understand this.  In a post today, Rich summed it up pretty well, as follows:

The Link 20 has an "gotcha" that isn't real obvious. When charging, the Link 20 considers the battery to be fully charged when two conditions are met. First the charging voltage must be at or above the entered parameter and the charging current must be below the percentage of the bank capacity that is also an entered parameter. In my case those parameters were 13.2V and 2%. 2% is about 9.2A for my bank of 460Ah. When these two parameters are met, the Link 20 blinks the top green LED indicating full charge, resets the AH used to zero, and recalculates and stores the charge efficiency factor for future charging. This can happen even if the used AH are not counted down to zero.

Without realizing this was happening, my golf carts were being cheated of 10-20Ah at various recharge cycles during the month. Thus I thought my batteries were being fully recharged but actually they were reported to be full but were short. Over the month I calculated that they were about 140Ah down out of the 460Ah capacity. Thus I had a chronic undercharge.

This undercharge showed itself as a low terminal voltage in the morning, sometimes as low as 11.9V when the voltage was 12.4-12.5 or so when retiring for the night.

The scenario for the Link 20 gotcha is this: The charging current has tapered down to about 13A with 20Ah still to go with the charging voltage at 14.4V. Now one of the refrigeration units turns on drawing 5A. This causes the battery charge current to drop below the 2% threshold and after 6 minutes the Link 20 thinks the batteries are fully charged because the charge voltage is over 13.2V, the charge current is below 2% or 9.2A, and these conditions have been met for 6 minutes. Then to make matters worse, the recharge efficiency factor is recalculated to a higher value (ex. 0.97 vs 0.95) so the at the next charge cycle the Link 20 thinks that the batteries require fewer input AH for the used AH. This is not true of course, but it makes the under-charge condition worse.

The fix for this gotcha is to set the Link 20 parameters to 15v and 1%. These parameters are not ever going to be met, so that means that the Link 20 will never think the batteries are fully charged until the AH used are fully counted down to zero. Also set the recharge efficiency factor to manual of 0.94 instead of the automatic setting of 0.95. This will stop the automatic recalculation and fix the recharge efficiency to be 0.94.

This "feature" is clearly documented in the instruction manuals, but not specifically noted to end up with this result.  I had mentioned it somewhere before here on the MB but haven't put my hands on it yet (oh, no!).  It's another one of these "do-the-math" things because when the bank is close to charged and the fridge kicks in this happens all the time.  I tried it and tested it and it works.  I haven't changed the parameters on my unit yet, but have these kind of notes in my on board Link manual and in my Electrical system notebook.

[Added July 14, 2009] I have changed these parameters on our Link and the results have been fantastic and exactly as Rich described.  Before, our Freedom 15 Inverter/charger combo, after a daysail, would go from bulk to absorption to float within ten minutes of being plugged in.  After the change to the parameters, the charger stays on absorption for a much longer time.  Ron Hill's comment, below, is also another way to check if you do the charger controls manually.  Since our Link controls the charger, it is necessary for our use.

Rich is on a mooring and uses generator power and his alternator for charging and is rarely plugged in for extended periods of time.  That "gotcha" got him, and, while you think this may NOT get those of you who have access to plug-ins on a regular basis, you're wrong!  This is because the Link will be incorrectly reporting full banks when they are NOT full.  This is very important.  You need to trust your instruments.  Knowing how they work will help you.  Rich was was simply trying to minimize his carbon footprint and learned about this "the hard way."

As far as I know, this "gotcha" is true for all Link units, because they use the same algorithms.  Check your owner's manual for your own particular units.  Connected Link "X000" series units with Freedom inverter chargers are particularly susceptible to this issue because the Link 2000 controls the Freedom charger!  "Smaller" independent Link units with separate chargers are done "manually" by the skippers by seeing the Link reporting full and operating their chargers accordingly.

Some of this information is relevant to the "Acceptance" thread I began a while ago.  http://c34.org/bbs/index.php/topic,4787.0.html

[Stu Jackson]

I received email correspondence from one of our C34 IA members about this topic.

He wrote: "I am curious about setting up my Link Lite based on this algorithm message board topic.  Normal weekend is: hook up electric when I arrive Friday night, charge overnight.  Disconnect, sail for the day.  80% of the time anchor overnight.  Return by mid afternoon on Sunday, hook up to shore power.  50% of the time it is on over night, the other half it is charged 3-4 hours while I pack up.  The fridge is first on, last off DC appliance.   It will be interesting to now be able to monitor what is really going on.   Anyway, based on this how should I set up the Link Lite?  Data and questions are
on the attached Link Lite Set up Instructions."

This reply includes the Link Lite instructions from the manual, with specific questions and responses on a few of the Function settings that control these important measurements for the Link to measure battery bank "refills."  Please note that some of this covers differences between the Link 2000 model and the Link Lite.  They both use the same algorithm but the Link 2000 has a third feature, the ability to manually change the recharge efficiency factor, which it appears the Link Lite does not.  This is NOT a concern for changing the other two parameters (float voltage and % of current) to avoid the "gotcha" issue.          

F01 Battery capacity. Your Main battery's capacity in Amphours (Ah). Default: 200Ah Range: 20 – 999Ah Step size: 1Ah

4 Sam's golf cart total of 420 amp hours @12V.  Should I set F01 to 420 or 400 to give some cushion on 50% discharge?

The is NO need for any cushion.  Why confuse things?  The Link is doing all the work in the calculations and should be set up with your actual bank size.  The step size is in 1 ah increments, so you should use what you actually have installed:  420 in your case, mine is 360.  Our Link 2000 goes in 20 ah increments, so 400 and 420 are available, but use the right figure for each of your banks.  Since the ah capacity is used in the "full" measurement in the algorithm (the default 2% of battery capacity) using the right number is the right thing to do, even if you do change the % default value as recommended.

F02 Charger's float voltage (Auto-sync parameter). This value must be equal to your battery charger's float voltage. which is the last stage of the charging process. In this stage the battery is considered full. Default: 13.2V Range: 8.0V – 33.0V Step size: 0.1V

According to the TrueCharge 20 face plate this should be 13.5v for flooded, warm setting.  Are you saying this should be 15v?

Yes, that is correct.  The Link Lite float voltage setting is ONE of the TWO parameters that are used to calculate "FULL" and Rich recommends that BOTH should be changed and that this float voltage default should be RAISED significantly to avoid the "gotcha" issue.  The TrueCharge 20 panel says the wet cell float voltage for "warm" is 13.5V, and the float voltage is higher and lower for "cold" and "hot" conditions.  Regardless of this small difference in float voltage settings for the charger, if you do NOT change the Link float voltage setting that is used for calculating the "FULL" bank, the "gotcha" starts interfering with the "real full" bank.  The algorithm uses this float voltage and the "default" 2% current of house bank capacity to calculate "full" which is the "gotcha" issue that shows a "full" bank when it really is NOT.  The Link will say "full" only when BOTH of the TWO parameters (float voltage AND percentage of charge) are met for the specified time period, at the SAME TIME and not simply when it goes to float on the charger.

Also, this particular statement in the manual is plainly INCORRECT: "In this stage the battery is considered full."  [Ed.-] Float is NOT necessarily completely full, it's just the last stage of charging.  The statement may be somewhat  misleading to skippers who are new to electrical system issues, but most of you know that already...  Once the charger kicks into float, there may be many hours left to fully recharge the bank, covered in the acceptance topic on this Message Board (a hyperlink to that thread is provided below).

[Added July 14, 2009]  Another reason why I say "float is NOT full" is because of this Gotcha itself.  In the first post on this topic above, I noted that since our Link 2000 controls our Freedom I/C the charger would go into float almost immediately after only a daysail.  So, while it looked like the bank was full, it certainly wasn't.  So, unless you UNDERSTAND the way the Link algorithms work, you'll be being fooled that the batteries are charged when either the Link says FULL and you manually turn off your charger, or your Link 2000 is controlling your charger on your Freedom and it switches to float.  For those of us who don't leave our boats plugged in all the time, this can be very misleading, since if the Link says full or the charger goes to float, the bank must be full, right?  Wrong!  The reason?  Simple, if you follow the logic of the algorithm's switch to FLOAT: there's STILL that pesky 2% left to top up the replaced amps.  Right?

F03 Charger's float current (Auto-sync parameter). When the charge current is below this percentage of the battery capacity (see Function F01), the battery will be considered as fully charged. Make sure this Function value is always greater than the minimum current at which the charger maintains the battery or stops charging. Default: 2.0% Range: 0.5 – 10.0% Step size: 0.1%

Default is 2.0%, should this be set to 1.0%?

Yes, this is what Rich & Donalex both recommended and is the SECOND of the TWO parameters that are used to calculate "FULL".   It appears that your Link Lite does not have a feature that my Link 2000 has (and Rich's Link 20), which is the ability to ALSO reset yet a THIRD feature which is changing the  "recharge efficiency factor TO manual of 0.94 instead of the automatic setting of 0.95. This will stop the automatic recalculation and fix the recharge efficiency to be 0.94." If you don't have that the ability to manually change the recharge efficiency factor on your Link Lite, you obviously can't make the change.  Check the rest of the manual to see if it does or not.  If it doesn't, it should be no problem since, first , you simply can't change it, and second, at least you now know how the Link Lite works to calculate "full" with the first TWO of the parameters.  

What I found is that once you start using the Link you'll get more comfortable with it.  It's a matter of "trust & understanding," so what you're changing are the two parameters you do have on your unit for the "full" calc, and it's either always using what's built in (recharge efficiency factor), or it's changing/recalculating it like described in the first Message Board thread on this topic.  That doesn't matter if you change the two parameters that you can change because the Link won't be incorrectly reporting full anymore.  

Your experience with the way you charge, as you've described, is a GREAT application for the Link, since you'll be able to see what the effects of how your operation and timing of being plugged in will get you.  The first post on the acceptance topic  [http://c34.org/bbs/index.php/topic,4787.0.html] will be exactly what you'll see when you get home and plug back in.  

Please let us know what you learn from your new Link.  I think you'll find out much more now that you have your Link as to what you're really able to put back into your house bank in your charging scenario of "50% of the time it is on over night, the other half it is charged 3-4 hours while I pack up." What you might want to consider is turning off your fridge first, because it's gonna stay cold for hours anyway and then its cycling on and off will eliminate its impact on the recalculation of the Link after you plug in when you return.  It shouldn't matter if you reset the parameters as discussed here.  

Your sailing experiences are much like ours and others, and will exhibit house bank discharge in the range of 20 AH for a daysail and 80-100 AH  when a night on the hook is involved.  By the time you get back to your dock, your house bank is either in the 80% discharge area or below that in the 50% - 80% range (the simple daysails compared to anchoring makes the difference; these percentages are based on a nominal 400 AH bank; with a smaller bank the %s will be different and higher), however, in all cases that last 20% takes a lot to put back.  There was a thread where I discussed this, see reply #4 in the excessive alternator heat post [http://c34.org/bbs/index.php/topic,4454.0.html] as well as the acceptance topic noted above.

It's when you're trying to minimize charging time, like with generators or the engine alternator ONLY, like Rich uses on his mooring, that this really becomes a really critical  issue.  It is also similar to your "limited" recharging time because you unplug when you leave the boat.   It's also pretty much what each of us faces when we return from a daysail or a night out at anchor and we do not want to leave the boat plugged in all the time.  For those of you who do leave the boat plugged in, the "gotcha" issue is also important, because you want to be able to depend on the validity of the Link to really tell you the bank is full.  That's why I posted this topic in the first place.  Without these changes, eventually the Link will be fooling you sooner or later that the bank is full when it's not.  This will require recalibration or reset of the unit unless you make these recommended changes to the default settings.

The approach is to recognize that the issue is not necessarily only how you use your boat in terms of how and to what level you end up discharging your house bank.  It is, rather, more important to recognize what condition the batteries are in after a discharge when you do have an opportunity to recharge, and that knowing and trusting that "full" on the Link meter is actually representing a "full" bank.  "How the Link Algorithm Works" is the purpose of this discussion topic.  

SUMMARY

The "GOTCHA" Fix: "The fix for this is to reset these two of the Link 20 parameters to 15v and 1%."  What does the 15v represent?"

Answer:  The reset to the 15V represents ONE of the two factors that the unit uses for measuring full, the other being the % of current.  If the Link default of 13.2 V and your charger are BOTH almost exactly the same float voltage, when your charger goes into float AND the 2% calc are also met at the same time for the specified period, the Link will say "I'M FULL!!!" even when the banks are not.  The way this happens was explained in the first post on this topic.  

We are simply suggesting changing BOTH parameters so "it won't get fooled again."  Resetting the Link float from the default 13.2 V will work because it's higher than your actual charger float voltage. The charger float current percentage of the battery capacity  is changeable in  0.1% increments so changing from 2.0% to 1.0% is easy.  Mathematically and "algorithmically" you could theoretically change only one of the two parameters and it would/should/could suffice, since the combination of the two parameters would never be met anyway.  I recommend that you change both.

Remember, if these modifications are not performed, the Link units will incorrectly report full batteries and you will be in an undercharged condition which is bad for the life of your expensive batteries.

Please also note that for those of you who have Freedom-series combination inverter chargers AND Link 1000 or 2000 units, this "full" charge Link measurement also kicks the charger function to float, because the Link is controlling the charger.  The Link and the charger are connected by a telephone cable.  It then becomes a very critical issue for "timely" charging, 'cuz if the Link kicks the charger into float too soon it'll take a long time to recharge your bank.  

Those of you with "separate" Links and chargers where the Link does not control the charger function, simply do this visually by looking at the Link and controlling your chargers manually.

There are three very important issues with boat electrical systems:

1.  A good design and installation
2.  A healthy charging system with alternator(s), shorepower and other means
3.  A battery monitor that you understand, and that you know how it works.

For years, this and other message boards have been suggesting that one of the FIRST and BEST things you can and should do is buy and install a battery monitor.

My personal experience was the opposite, and I now regret not installing my Link when I first bought it way back in 1998!  

Buy a battery monitor, and understand how it works and you will avoid undercharging your batteries, extend their life, and enjoy your cruising more by having a working, capable and trustworthy electrical system to support all of your electrical "appliances."

[Ken Juul]

This is the rest of the Link Lite manual that wasn't posted above.

Synchronisation
In order to keep your LinkLITE battery monitor delivering accurate status information about your battery, it is important to regularly synchronize your battery monitor with your battery. As explained in the quick start guide, a synchronisation step is also needed before you can actually use your battery monitor. During operation, the battery monitor automatically indicates when a synchronisation is required, by displaying the message SYNCHRONIZE. A synchronisation step means nothing more than performing a complete charge cycle on your battery. A charge cycle will be considered complete when both
Auto-sync parameters F02 and F03 are met during at least 4 minutes. This typically means : when the battery charger switches to float mode. By meeting these conditions, the battery is considered full, which will be indicated by a flashing FULL message on the display. Besides this, the State-of-charge readout
will be set to 100% and the Amphour readout reset to 0Ah. The FULL message will disappear when a key is pressed, or automatically, when the battery starts discharging again. Performing synchronisations regularly is also important to keep your battery healthy and to increase it's lifetime. You will notice that if you are often performing full charge cycles yourselves, the battery monitor will most likely not
display the SYNCHRONIZE message, since the battery is already kept in good sync with the battery monitor. Besides automatic synchronisations based on meeting the Auto-Sync Functions, you can also manually synchronize the battery monitor with your battery when you are sure your battery is fully charged. This can be accomplished by pressing both < and > keys simultaneously for three seconds. After these three seconds, the flashing FULL message appears on the the display just like when it is
automatically synchronize.

There is no mention of the "recharge efficiency factor"  perhaps this Synchronization step was added because Xantrex realized the "gotcha".

The LinkLite is just a monitor, not a controller in my case. The LinkLite will register full when both F02 and F03 are met for 4 minutes.  I understand setting F03 to 1%.  If F02 is set to 15v, which it will never see, the monitor should never register full.  Does it matter that I will never see full?  I feel like I'm missing something.

[Stu Jackson]

No, Ken, you're not missing anything.  It WILL eventually register full because the way it works is that it does count the AH down by using the kWHr function internally.  The "trick" here is ONLY to prevent it showing full prematurely with the "default" 13.2 V and 2% "calculators," and not never ever showing "full."  It will show full when the kWHrs counts to zero, and WON'T do it PREMATURELY with the float voltage and percentage of charge "method."

The Link algorithm has TWO ways of showing full:  1)  the 13.2V and 2% method; and 2) counting the amp hours (really kWhrs) down to zero.  It's the first of these that can make it say FULL prematurely.  The idea is to avoid the first and ONLY use the second, which is when the algorithm actually counts the input amperage back to zero, meaning "I'm really full!"

What we need to do is to think of it in two different ways:

1.  Your concern:  "My Link will never show it is full."
vs.
2. Rich's concern:  That the Link will show it IS full BEFORE IT REALLY IS, and therefore, if operated either manually or in my case automatically, will undercharge the banks.

These are two very important and different things.  It's kinda like thinking of going up stairs or down stairs.

Rich wrote: "These parameters are not ever going to be met, so that means that the Link 20 will never think the batteries are fully charged until the AH used are fully counted down to zero."

He's NOT saying it never will say full, he's saying that it will NOT show a "full" display PREMATURELY based on the recognition of the 2% and 132.V"matching" for 4 minutes (regardless of what the amp hour/kWhr  counter is doing) and will not say full until the ah are counted down to zero.

This means there are two ways for the Link to say full:  1) the 13.2V and 2% of ah capacity over 4 minutes (which we've shown can mathematically happen when your fridge kicks on after a daysail) ; and 2) when the ah counter gets to zero.  Item 1) is the "premature" real world possibility unless you make the changes suggested here.  Item 2) is what you WANT to actually happen all the time.

What's happening inside the Link it that it is using kWHr to do the actual measurements and converting them to AHs for the display.

The Link WILL eventually count the AH down to zero, but simply will NOT BE FOOLED into prematurely declaring FULL too soon (manually) or tripping into float (when connected to a Freedom inverter/charger) when the example Rich used, which I have seen myself, happens.  It will ONLY use the amp hour countdown as the method of saying FULL.  And that's all you need or want it to do.

This is when "one of the refrigeration units turns on drawing 5A" when the charger is in float and the current going into the bank is 2% of your 420 AH bank, or 8.4 amps.  This WILL occur, say, when you've done a ONLY a four or six hour out and back to the dock daysail.  

Condition:  Your bank is only down 20 AH and you pull back into your slip and keep your fridge on and plug back in.  Because of the battery acceptance (see that thread again) only a small amount of current, regardless of how big your charger is, is ever going to be "allowed" to flow back into the bank.  My experience is that the charging current could easily and quickly reach that low of 8.4 amps (your case, or in my case 7.2 A =  360 X 2%).  

What happens in real life is that the charger almost immediately kicks from bulk to absorption right into the float mode of 13.2 or 13.4 V because of the low acceptance of the batteries. And then the fridge kicks in drawing 5 A.  Even without your Link, take a full bank after being charged overnight.  You could drain your bank by running the fridge for an hour, and the first hour the fridge runs almost continually, so let's say it takes out that 20 ah.  Turn on the charger.  It'll go B-A-and right into float almost immediately.  That happens all the time when the banks are within that last 15% of being charged.

At the time this occurs and after the next 4 or 5 or 6 minutes (the "specified" time period) of this condition, the Link says it is full.  That's because the default 13.2 or 13.4 V is reached (you're in float mode right away) AND the 2% charge is being met because of low current acceptance exacerbated by the fridge making the current reading even LESS than the % (8.4 A less 5 A).

That's because the Link is always measuring the NET current flow, not only what the charger is producing.  Flow from the charger (8 A) LESS the instantaneous current draw of the fridge (5A) = 3 amps, which is what the Link is seeing.  Turn on some more lights or other DC appliances and it'll be even less, right?  

Again, based on that acceptance thread, the batteries are NOT full. You've only been plugged in for 10 minutes, and your fridge is running, but the Link says full - NOT!  This is a very real situation.  

Some people also mistakenly think that a charger will increase its amperage when the fridge kicks in.  This is NOT the case, because chargers simply aren't that smart - they produce a rising voltage until the set point, and the battery acceptance limits and reduces the current as the bank gets full.

The "math" can also happen at the end of every charge cycle, even if you start with a 50% depleted bank and you're running your fridge.  For me, it'd kick the [Freedom combined inverter/charger] charger off PREMATURELY because the Link says the bank is full.  That was the genesis of Rich's discussion, regardless of whether it was his generator with which he tried to minimize run-time, or someone being plugged in all the time with the Link 2000 running a Freedom inverter charger.  It would also apply to anyone who is manually switching their charger off when the Link says it's full without making these changes to the default values.

If allowed to occur on a regular basis, those few "missing" ah start to add up in real life and real AHs, and chronically undercharged banks.

Rich is not saying it will never show full, he's saying that the concept is to avoid showing "full" prematurely when they are not, because the way the "guts" of the Link works, it WILL eventually and correctly show full when the ah are counted down to zero.  This is based on the kWHr calculation within the algorithm.  By simply changing the full parameters will assure that the bank is actually full, and not before then.

The "synchronization" issue you mentioned is pretty much the same for both your Link Lite and our Link 2000, and is not an issue in this concept.  It is essentially a reset to zero concept.

[Ken Juul]

That clears it up.  The Xantrex documentation about how the linklite operates is very poor.  Installation instructions were very clear though.

Thanks!

[Stu Jackson]

Ken's idea to refer to Xantrex on another thread got me to thinking about his note about the limited information provided with the Link Lite.  I looked up the Link Lite installation information and he's right - OK to install, but not much about how it works.

If you have a Link Lite or Link Pro, I suggest that you download the installation and operation manual for the Link 2000, since they use the same algorithm.  You can find it here, ["Xantrex download page"] scroll down and download it:  http://www.xantrex.com/support/web/type/3/docldoc_type.asp  This is the download page that I bookmarked since I find it hard to find this particular and important page when I start out at Xantrex.com.

Added January 20, 2011 - The link to Xantrex doesn't work anymore.  I'll try to find it again.  Xantrex is removing some very important and helpful data.  The PDF file for the Link 2000 is too large to post here.  Here's a link to the older Link 2000 manual, same concept, one different button, replies #18 and on:  http://forums.catalina.sailboatowners.com/showthread.php?t=125568  I have both the older and newer Link 2000 manuals in PDF format.  pm me with your email, or email me if you need them.

One of the other advantages of having these downloads available is that if you're thinking of buying a product, you can check out the details before you buy.  The details included in most of the Installation & Operations Manuals are way beyond the glossy catalog information, and in many cases provide a lot of technical information not found elsewhere.  An example is the discussion we had recently of charging rates for different battery types:  the Balmar MaxCharge 612 regulator manual had the complete recommended charging voltages for over seven different types of batteries:  www.balmar.net.  If you're ever thinking of "mixing" and "matching" battery types, you MUST check the charging voltage regimens for each type before you try to charge them with a single charging source.  This is one of the best comparison tables I've seen, page 9 of the MC-612 PDF file manual.  Go to www.balmar.net

[Stu Jackson]

An alternative to the Link series is this, provided by Maine Sail:

http://www.jamestowndistributors.com/userportal/show_product.do?pid=51843&familyName=Victron+BMV+600+Battery+Monitor

It is important to note that the charging efficiency and timing parameters remain the same for the Victron as discussed for the Link-series above, so the Gotcha is still in play.

Victron also makes a unit that will check the voltage (only) of a second reserve bank - look around.

[Ron Hill]

To double check on the "Got'ya Factor" I note the blinking light on my Link 10 - here's what I do.
 
To really know what's up check the amps that are charging.  If the charging amps (with nothing ON) are about .2/.3 amps; that tells me the battery bank is fully charged.   

[Stu Jackson]

Another superb Maine Sail contribution

Installing and Wiring Battery Monitors

http://forums.catalina.sailboatowners.com/showthread.php?t=125606

[Stu Jackson]

For VICTRON users, some interesting and important user features not found in the manual, from co.com:

http://forums.catalina.sailboatowners.com/showthread.php?t=128645

Thanks, Dan.

*******************************

I'll just list the fields that were reporting odd data, some of the fields are self explanatory.

H2: The depth of the last discharge. This field will be reset to zero each time the monitor determines the battery is at 100% SOC.

H3: The depth of the average discharge. This field will only average discharges that take the battery below 65% SOC and then return to more than 90% SOC. I was getting a zero in this field because I had not taken my house bank below 65% since installing the monitor.

H4: The number of charge cycles. The monitor measures a cycle as a discharge below 65% SOC and then a recharge to at least 90% SOC.

As far as set up goes, I only had to make changes to the size of my battery bank in ah and the Peukert Exponent of my batteries to get it to produce a very accurate state of charge. Nice little gizmo!

[Stu Jackson]

I have been linking this topic on many of the other boating websites that I visit.  Other folks have been discovering this issue, too.

Re: Battery Monitor vs Voltage
Quote:
Note this issue is specific to battery monitors that control chargers. However this is a rare situation now. Very few do

Dave,

Not really. If one uses the "I'm Full!!!" output of a monitor, but hasn't correctly set the parameters, one could prematurely turn off the charger. Manually. That's covered in the Gotcha link.

And many, many folks still have Link monitors controlling Freedom inverter/chargers.

Perhaps the most important thing is to recognize that, like all electronic things, there are DEFAULT parameters that need to be set by the user to reflect THEIR PARTICULAR INSTALLATION in order for the monitor to work properly. It's usually easy for new monitor owners to figure out that your battery bank may not be the default 200 ah, and make that change. Most owners stop there.

It's not much different than setting up a new computer.  Most all have DEFAULTS that are modified by owners, like the time it takes for the monitor to go into sleep mode, etc.

But, unless you DO THE MATH and recognize that if you have a fridge (5 amps) and a 400 ah house bank (2% is 8 amps) when the fridge kicks in near the end of the absorption your monitor could prematurely declare "full".

That's all that the Gotcha post was intended to present, as was well summarized by Cruisin Cat earlier in this thread:

The current threshold to recognize 100% SOC is set too low. In your case using the factory preset 4% will result in the monitor assuming 100% SOC when that is not yet reached. I suggest you go into the Setup menu and reduce the setup parameter called "It" to 0.5% or at least to 1%.

Other setup parameters that effect detection of 100% SOC are:
"Vc" - factory preset is 13.2V (on my Victron) which is way too low. I suggest you set to 14V - 14.2V (I don't remember what type of batteries you have but this setting should work for most types)

Anything over the float voltage will do just fine.

Stu

[Stu Jackson]

MANUAL RESET OF BATTERY MONITORS (Thanks to Maine Sail)

There has been much written here and elsewhere about the NEED to do manual resets and properly program the battery monitor for Peukert, CEF, when the full reset occurs and what triggers it etc. etc.. These are not set it and forget it devices and they need human assistance..

SG and voltage only work well on fully rested batteries which often takes 12-24 hours. Was there a load on the batteries when you noted the 11.8V reading? If so then there is a possibility the monitor was closer to correct than you think. With standard lead acid batteries as the SOC drops the ability to hold a voltage under load also changes.

The EASIEST way to re-set a monitor is when you "assume" the bank is full to turn ALL ship loads 100% off. This includes turning off the inverter and DC panel main breaker, solar etc., then run the charger or alternator for 10+/- minutes to get beyond the "inrush" and let it stabilize. Now check the "I" screen and see how much current is flowing into the bank. If that current is below 2% of bank capacity then you are safe to do a manual re-set. While 2% is not "chuck full" it is about as close as you'll get when off cruising and a safe point to do a manual re-set.. It is important that this is at your ABSORPTION voltage not FLOAT voltage. This is why using a battery charger that has been on a while is not a good idea unless you re-start it so it goes to 14.4V +/- when taking this reading.

Manual re-sets, as OFTEN AS POSSIBLE, prevent counting errors in the monitor. Solar especially, can trick these devices into reading "FULL" when they are not and the monitor needs to be programmed to minimize this but it don't feel it can always be 100% prevented..

Next time it reads "FULL" do the acceptance test. You can't use solar for this you need a stable charge source with plenty of current behind it for this test. If the current, with no loads on, is not below 2% of the 20 hour capacity of the bank it is not full......

Battery monitors are only as smart as they can be and external factors can trick them. You as the programmer/human need to be smarter...

So for a 900Ah bank less than 18A flowing into the bank at 14.4V +/- would be a safe re-set range. Personally, I use less than 1.5% as my reset but with solar I can do this as it gets to full every week. I manually re-set my battery monitor every week and it takes no time to do this test. While the motor is warming up I do the "acceptance" test....

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-Maine Sail / CS-36T