Link 10 Battery Monitor

[Rick]

The Link 10 (E-Meter) will automatically establish a "full" once a charge cyle is complete. A completed charge cycle is defined when the "Charged Parameters" have been met. Consult your manual to understand these parameters and just how you can change them, if necessary, to suit particular needs.

Once the Charged Parameters have been met the accumulated net Amp-hour reading along with the true energy reading (kilo-Watt-hours) is set to zero and the right-hand green LED comprising the "fuel-tank-level" bar-graph will blink indicating a "full" battery. If positive zero Amps is measured or higher this flashing will continue. The first time that a negative zero (or greater) occurs the green LED will stop flashing indicating a discharge, no matter how slight, has occured. This can happen if you have a dc load that your charger cannot react to fast enough to provide all current from the charger in the "converter" mode.

What is precise about the meter readings are: voltage, current, Amp-hours, kilo-Watt-hours. Now what can never be precise is the indicated level of the capacity. This is because one can never know just what is that level, even if one completes a BCI standard discharge test completely discharging the battery. Once a complete discharge has been made one cannot know just what capacity recovery has occured. This is unknowable for lead-acid batteries but we can make reasonably good guesses. Reasonably good means that if (and only if) proper charging methods are used capacity recovery can be fairly guaranteed. If not, state of charge can be guaranteed but what good is it to have a 100% state of charge for a battery that has failed to recover its capacity to an optimum amount? In other words, what good is a full stat of charge yielding 1 Amp-hour when it should have been recovered to 100 Amp-hours? Such is the difference between state of charge and state of capacity.

Most people believe overly optimistically advertised battery Amp-hour ratings. Most batteries that I have tested fail to meet the advertised spec. Full River and some Trojan batteries have tested as advertised. I am not saying that others do not meet specs, merely to view those specs with skepticism. Be a skeptic on the safe side. For example, de-rate the advertised value by 10% (or more if you are very skeptical). You might also de-rate them 5% or more for the first year and then take 5% (or more) of the remaining value the next year, etc.

Algorithms have been developed to do such things automatically yet they were not realized before (or after to my knowledge) Xantrex bought out the product line.

By applying skeptical initial Amp-hour values to enter for your battery one has a good chance of realizing the 50% DOD rule with good battery bank cyclical performance.

[Therapy]

Originally Posted by Rick

The Link 10 (E-Meter) will automatically establish a "full" once a charge cyle is complete. A completed charge cycle is defined when the "Charged Parameters" have been met. Consult your manual to understand these parameters and just how you can change them, if necessary, to suit particular needs.

Once the Charged Parameters have been met the accumulated net Amp-hour reading along with the true energy reading (kilo-Watt-hours) is set to zero and the right-hand green LED comprising the "fuel-tank-level" bar-graph will blink indicating a "full" battery. If positive zero Amps is measured or higher this flashing will continue. The first time that a negative zero (or greater) occurs the green LED will stop flashing indicating a discharge, no matter how slight, has occured. This can happen if you have a dc load that your charger cannot react to fast enough to provide all current from the charger in the "converter" mode.

What is precise about the meter readings are: voltage, current, Amp-hours, kilo-Watt-hours. Now what can never be precise is the indicated level of the capacity. This is because one can never know just what is that level, even if one completes a BCI standard discharge test completely discharging the battery. Once a complete discharge has been made one cannot know just what capacity recovery has occured. This is unknowable for lead-acid batteries but we can make reasonably good guesses. Reasonably good means that if (and only if) proper charging methods are used capacity recovery can be fairly guaranteed. If not, state of charge can be guaranteed but what good is it to have a 100% state of charge for a battery that has failed to recover its capacity to an optimum amount? In other words, what good is a full stat of charge yielding 1 Amp-hour when it should have been recovered to 100 Amp-hours? Such is the difference between state of charge and state of capacity.

Most people believe overly optimistically advertised battery Amp-hour ratings. Most batteries that I have tested fail to meet the advertised spec. Full River and some Trojan batteries have tested as advertised. I am not saying that others do not meet specs, merely to view those specs with skepticism. Be a skeptic on the safe side. For example, de-rate the advertised value by 10% (or more if you are very skeptical). You might also de-rate them 5% or more for the first year and then take 5% (or more) of the remaining value the next year, etc.

Algorithms have been developed to do such things automatically yet they were not realized before (or after to my knowledge) Xantrex bought out the product line.

By applying skeptical initial Amp-hour values to enter for your battery one has a good chance of realizing the 50% DOD rule with good battery bank cyclical performance.

Thank you.
I am skeptical.
But I think I could (once no longer boatless) be able to figure out the actual capacity - pretty much anyway.

Lets see.
Supposed to have 100ah. (is ah correct?)
Run all the dodads for a day and link says 50 are gone.
Charge it all up.
Run all the dodads for most of a day and link says 50 are gone.
Hmmm.. not really a capacity of 100.

A few more days and a little math (simple is all I can handle) and I know I have only 92ah.

So boat rules change to 40ah.

Cool!! I will have one!!

[Sandero]

I think the amp hour deal is a bit of a scam.

It presumes that the battery cycles with out any degradation. That's bunk.

Batteries degradee as they are used so it's not a matter of using amps and then adding the amount used back in and zeroing out. It's a known unknown.. or and unknown known. Which means it's an approximation and over time you need to "make adjustments".

That's what they don't tell you. They treat the battery like a zero sum game with no entropy.

What you can get from the things is Amps, and volts... accurately.

[Rick]

I'm not sure what defjef means by "Amp-hour deal is a bit of a scam". What I am sure of is that Amp-hour measurements and ratings have ALWAYS been misleading because what we actually use and pay for are kilo-Watt-hours which is Amps times Volts times time and Amp-hour measurements are missing the Voltage factor. This becomes particularly important when measuring discharges under sagging battery terminal voltage whilst attempting to think that recharging the same number of Amp-hours using a much higher voltage (sometimes 20% higher or more) is comparable. It is not.

This is why the Link 10 measures true energy in both directions; kilo-Watt-hours. Whether or not users optionally choose to indicate those numbers is not as important as how the instrument uses that information.

What defjef does seem to imply is that a precisely measured depletion or addition of Amp-hours (and kilo-Watt-hours) can be visualized as a window within the real limits of the battery where the exact placement of the window cannot be precisely determined regarding the lowest bound or the greatest bound of the actual battery. This fact is not glossed over in the use of the instrument. The use of the instrument accurately allows one to determine just how much of an energy budget is used. Because it is generally agreed that the best economic application is to use the 50% DOD rule we have a 50% "slop factor" multiplied by a user's chosen "skeptical factor" to work within safely and fairly reliably.

In addition, the meter allows one to interpret battery charge acceptance and internal resistance to understand degradation of the battery. This was covered in a submission in the archives addressing such issues.

[ssullivan]

Thank you for the input, Rick. And again... thanks for being part of such a great product. I felt like something was amiss with my use of the meter, rather than the meter being at fault. Just like in computers - it's normally "user error."

Just by gut instinct, what would your opinion the state of charge be, given the following:

*440 AH Trojan T-105 battery bank
*Smart chargers (Iota) dropped off to 15A charging current, as read on the Link 10
*Battery temp was between 40F and 50F

Would you consider this state of charge to be "adequately" recharged for another draw down to 50% of C/20 rating? It "felt" like it was quite charged up, but the meter had me second guessing.

I will never meet any "charged parameters" that fully charge the battery up to float charge levels. Because of this, are you suggesting that maybe I have to reset the charged parameters to a lower "good enough" charge? In the case of my above charging example, I could just set the charged parameters to realize fully charged at 15 amps charging current, right?

My big concern is to do this correctly, so I don't have batteries that are chronically under charged. I know the theory is to discharge to approx 50% and recharge to approx 90% (of C/20). Would 15 amps charging current be close enough to this level for a set of 4 Trojan T-105s?

I have to laugh a little at all of these questions I'm asking. I went for 2 years without ever needing to ask them. When doing this all by "feel" with no data, I was discharging to between 75% and 85% of C/20 and charging to about 90% with *daily* genset runs. Now, the meter shows me that it takes much longer to get down to 50% than I had previously thought using inaccurate methods such as a voltmeter and listening to the load on the genset (as well as feeling the heat produced by the chargers). It's a great device, but it's one of those things... it is leaving me with more questions... ha ha

[Sandero]

Rick,

The point about the amp hours I tried to make was as follows.

The capacity of a battery is not fixed. As one uses it, it degrades. So rather than thinking of the capacity as a fixed volume of say a glass of water... amps out the glass becomes empty, amps in the glass becomes filled and can't fill more than the volume.

In fact the glass's volume is changing over time and with conditions of temperature as well. The meter can only use the crudest of algorithms equivalent to the glass with a fixed unchanging volume. This is an approximation and leads to errors, not in measuring what is going out or coming in, but in the capacity to store it. This may be small but it represents errors which accumulate.

[ssullivan]

Originally Posted by defjef

Rick,

The point about the amp hours I tried to make was as follows.

The capacity of a battery is not fixed. As one uses it, it degrades. So rather than thinking of the capacity as a fixed volume of say a glass of water... amps out the glass becomes empty, amps in the glass becomes filled and can't fill more than the volume.

In fact the glass's volume is changing over time and with conditions of temperature as well. The meter can only use the crudest of algorithms equivalent to the glass with a fixed unchanging volume. This is an approximation and leads to errors, not in measuring what is going out or coming in, but in the capacity to store it. This may be small but it represents errors which accumulate.

This sounds very reasonable to me. For some reason, my errors are not what I would called in my old science days, "insignificant error."

I feel as though my Ah reading (what is in the glass) is off by close to 100 Ah today after a charge I just finished. Wish I knew what a percentage of "fullness in the glass" was at certain charging currents for a set of 4 Trojan T105's. Anyone?

[Rick]

Sean,
Please keep in mind the discussion of Amp-hours consumed under a loaded voltage versus Amp-hours replenished under a much higher voltage. With this consideration, it is easy to visualize a conditon where a discharge/charge "Charge Efficiency Factor" (CEF) can exceed 100%. I've always been a proponent of using kilo-Watt-hour CEF because that can never exceed or equal 100%. Traditionalists not wanting to change have wanted Amp-hour CEF displayed yet, again, I believe that this is an almost useless value.

Because your default CEF is probably not set sufficiently close for your battery and becuase you rarely completely recharge your battery you should change it. An alternative is to display kilo-Watt-hours and pay attention to those and not Amp-hours. The Amp-hour consumed display "unwinds" back towards zero (full) as measured Amp-hours charged are divided by the CEF. The algorithm determination of "full" is not fooled by this erroneous value, though.

I agree that if you charge your batteries until the charge current falls to 15A (with the proviso that the charge voltage is equal to or greater than an equivalent temperature-compensated 14.4V) you can terminate the charging to save generator run time. However, once an month (or more often) you should endeavor to completely recover your battery otherwise there will be a more rapid degradation of capacity than would otherwise occur. I cannot overstress how important it is to spend sufficient time at or above 14.4Volts to prevent capacity degradation with cyclical charge/discharges without coming to a complete "full".

In addition, if you do bring the batteries to full using high acceptance voltages (remember that you can always apply the Amp-hour law to observe that the charge current spends as much time as possible near or slightly above the "missing" number of Amp-hours once a "good" zero, or full, value has been reached) you can then make note of initial internal resistance values by making delta-V divided by delta I measurements using the meter when you have significant initial loads as well as "final" loads. A good note to make when you start the gen set is to turn off all dc loads (just for a short while) to make delta V, delta charge I. Later cycles can be measured and compared to these internal resistance values to show a trending of increased internal resistance and these values are determinate to indicate just when you really should fully charge the batteries and even equalize them.

Another indication is to compare the charge acceptance current at the time when your chargers just begin to leave bulk and hit an acceptance voltage. Note the Amp-hour depth of discharge (or kW-hr). That charge acceptance current will of course equal the max output of your chargers but what changes is the depth of discharge for that current. As the battery degrades you will observe a increasing (less close to full) Amp-hour missing value.

[ssullivan]

Great advice, Rick. With the manual and your posts, I have a handle on the situation. There is a bit more to it (the CEF) than I had thought.

The Link 10 will automatically computer the CEF for me if I meet charged parameters, right? My thinking is that I will lower the charged parameters to that 15amps charging current I had mentioned and let that be the new "full battery" level, doing an equalization charge once a month, as I used to before battery monitors.

I have also set my "floor" to 50% discharge to give more LED bar graph resolution to the available battery "space" I am using.

I think the main thing with the Link 10 is you have to read and fully understand the manual to get things going right.

Thanks again. It's a cool device.

[Rick]

Yes, once Charged Parameters are met a new CEF MAY be recalculated for that discharge/charge cycle. However, you MAY choose to enter a fixed value for CEF (I am a proponent of this, especially for those who use repetitive cyclical charge/discharges with moderate variation of energy consumption and generator run times).

It appears that you are zeroing in on setting up your meter for your particular needs. I, for example, hate to have the display go into "hiding" after 5 mins of no button pushing and, therefore, have set mine up to be on all of the time for my convenience of kicking back and looking across the "room" to see the status of what's going on with the system.

Once you have everything set up for your needs hopefully you will not need to consult the manual for anything else unless something needs to be changed for some reason. On the hook I rarely look at the amount of energy consumed in terms of a numerical value, I merely glance at the bar graph. Understanding kilo-Watt-hours consumed under the influence of rum and beer (actually kilo-Watt-hours are not consumed with rum and beer I have consumed the rum and beer) is by definition not a sober intellectualization yet grasping the meaning of the bar graph with a "will not be driving tonight" glance is easy.

[Fishspearit]

Originally Posted by ssullivan

I have also set my "floor" to 50% discharge to give more LED bar graph resolution to the available battery "space" I am using.

I just installed a link 10 this weekend, based partially on having read this thread a while back. I'm pretty happy with it so far, I just have one question about the setup.

If we are only supposed to discharge the battery down to 50%, it seems to make more sense to set the amphour capacity setting to 50% of actual capacity. Is that what you did Sean?

Right now the time remaining is still thinking it's got 100% of the battery capacity, when we all know that I really don't. Also the meter shows green all the way down to 59% discharge, which seems odd if you only have 9% left.

[ssullivan]

Almost...

It seemed more intuitive to me to have the meter run down to flashing red when I'm at 50% of actual capacity as well.

So... I set my discharge floor at 50% of the true battery bank's AH capacity. It is the "discharge floor" you want to change, not the total capacity of the battery bank.

So... when the batteries are *really* down 50%, the meter shows me that I'm "in big battery trouble" by going red. Helps keep you from ever going below 50% to be set like that.

Look up the discharge floor function in the manual and use that to set the floor at 50%.

Originally Posted by Fishspearit

I just installed a link 10 this weekend, based partially on having read this thread a while back. I'm pretty happy with it so far, I just have one question about the setup.

If we are only supposed to discharge the battery down to 50%, it seems to make more sense to set the amphour capacity setting to 50% of actual capacity. Is that what you did Sean?

Right now the time remaining is still thinking it's got 100% of the battery capacity, when we all know that I really don't. Also the meter shows green all the way down to 59% discharge, which seems odd if you only have 9% left.

[Fishspearit]

Originally Posted by ssullivan

Look up the discharge floor function in the manual and use that to set the floor at 50%.

Thanks!

I'm not on the boat right now with the manual, but I don't remember seeing a setting for the discharge floor. I'll have to go back through the manual next weekend.

I have to confess, my eyes started to gloss over when reading the theory behind Peukeut's Equation and all that mess in the manual. It was probably buried in that section.

I must be a real nerd, because I got a lot of pleasure out of finally learning how much everything on the boat draws, rather than just guessing. LED cabin lights 1/10 of an amp. Incadescent cabin lights, 1.5 amps. My inverter draws 2 amps in standby, I wouldn't have guessed that much. Fridge draws 4.5 after starting up, then drops to about 3 amps before cycling off.

[hanschristian38]

We installed a Link 10 before we went cruising. Every night before bed I checked be be sure that we were using no more than the amount of power that the anchor light used. One night we were using 2.5 amps when we should have been using .5 amps. After checking around, I found that the fresh water pump was quite hot. It may have saved us from a big problem as there was a problem that could have caused a fire.

The Link 10 is great! I would recommend one to anyone who intends to live aboard.

I installed it with a very large negative bus bar to solve the problems with having a single negative lead from the battery.

[Pblais]

If we are only supposed to discharge the battery down to 50%, it seems to make more sense to set the amphour capacity setting to 50% of actual capacity. Is that what you did Sean?

Actually you don't want to do this. It means if you run the battery down to 30% you'll get funny numbers. The monitor uses an intergal calculation. You need to set the amp hour capacity and the exponent based on your batteries for the magic to operate properly.

You wouldn't set your fuel gage to read 1/8th of a tank low would you? I can't see you being any smarter setting the gage to read incorrectly so you'll do the right thing at zero instead of 50%. Recharging at 50% is a desired goal but it does not mean you have to do it that way even if it is in your best interest to do so. It would be better to set the reading correctly in case you go below 50% for reasons you don't fully understand at the time it happens. You'll also notice the difference in the bank should problems occur.