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Old 22-11-2007, 22:34   #1
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Calibration Procedure for Xantrex Link 20

Would anyone have a calibration procedure for Xantrex Link 20? I've recently installed one and have been getting erroneous readings of -0.2 A on both battery banks even when the positive posts of the batteries are disconnected. It's not much, but it does add up to about false -35 Ah every week.
Many thanks.
Dan
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Old 23-11-2007, 05:50   #2
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Dan,

I've had a Link, think it's a 2000, for three years now. For the first year I fretted over the fact that when charging it'll reset to 0 amps used when you stop charging when a second ago it showed -30 or -40. I have read the manual over and over and if I recall right I started a thread on this here a couple of years ago. I think some electronics experts tried to explain it to me but I still don't understand it. In the end I use the "amps used" as a rough guide only. One question, how do you power the Link with the batteries disconnected?
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Old 23-11-2007, 05:59   #3
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Xantrex Link 20 - Owner’s Manual:
http://www.xantrex.com/web/id/76/docserve.asp

Battery synchronization & set-up starts on page 9.
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Old 23-11-2007, 08:15   #4
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Originally Posted by DanB444 View Post
Would anyone have a calibration procedure for Xantrex Link 20? I've recently installed one and have been getting erroneous readings of -0.2 A on both battery banks even when the positive posts of the batteries are disconnected. It's not much, but it does add up to about false -35 Ah every week.
Many thanks.
Dan
Dan,

Are you disconnecting all positive connections to the battery terminals *except* the link 20 when you get that -0.2A reading?

If so, I may have the answer. The Link 20 (or 10 that I have) will draw a current that fluctuates between -0.1A and -0.2A with the unit operating with all LEDs lit and running. This could be your "phantom load." In the case that it is the Link 20's power consumption, you are not getting a false reading.

In fact, I'd say no matter what your problem... the Link 20 is giving an accurate reading. It is indeed seeing a -0.2A draw that it is accounting for. The instrument is extremely accurate.

The only real calibration it needs (assuming you have a standard setup and have installed with twisted pair wires, etc...) is that of a full charge so you can set the Ah capacity up to the proper "zero" and the setting of your battery bank capacity.

If you want to post up some more details, please do... I'd be happy to help.
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Old 23-11-2007, 11:20   #5
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"and have installed with twisted pair wires, "
I recall a similar comment from a similar question some time ago, where it turned out the installation didn't use twisted pair wiring--and that's all it took to create significant errors from induction getting into the wires. Small but important installation issue.
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Old 26-11-2007, 20:37   #6
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I've just been through a lot of frustration with my Link 20 having the above described slightly inaccurate current readings, but in the end I've succeeded in calibrating it properly. Let me share the solution with those who have the same problem and wish to correct it.

Problem Background:
Since day one my Link 20 had an error in current measurement of -0.2A on both battery banks. My starting battery reading was -0.2A even when the starting battery positive was isolated. On the house bank, with everything switched off (including the main electrical distribution board), the reading was fluctuating between -0.2A and -0.3A, because the Link itself was using a bit of power.

-0.2A does not sound like much of an error, I can hear you say, but in just one week this adds to -0.2 x 24 x 7 = -33.6Ah of false discharge readings. In my case (just got new AGM batteries), no amount of charging would get the Ah reading back up to zero, because the charging current would eventually drop to 0.0A - 0.1A and the only way to "start over" was to manually reset the Ah to zero.

Needless to say, I double and triple checked the wiring. During the installation, I'd used the original Xantrex supplied cable packing 4 twisted pairs, the length of the wiring was not excessive (23 feet) and the wire did not run along any AC cables or similar sources of interference. It was obviously a calibration error, or more precisely a "zero offset instrument error".

How to fix it:
Before you go any further, you'll need a stable and precise source of 40.0V DC. That seems to be the safety Xantrex built into the unit to prevent accidental calibration. I found an electrician who agreed to lend me a variable DC power source from his shop. You may know someone at a computer shop, electronics lab, university, etc. You'll also need an accurate digital voltmeter to confirm that you're supplying exactly 40.0V DC to the unit during calibration, but these days it shouldn't be a problem - any reasonable digital voltmeter will do.

Important Notes:
1. This procedure has not been obtained directly from Xantrex, but it worked for me exactly as described. I hope it works for you too, but you're doing it at your own risk.
2. Any temporary wiring connections you make during the calibration setup should be firm and the electrical terminals clean.
3. This procedure will completely reset your Link 20, so you'll need to re-program any user defined parameters (e.g. battery bank capacity & type, Peukert's exponent, etc.) back into it. You will also lose the history from the unit.

Connections to make:
1. Pull out the fuse on the Link 20 power supply red wire and check that the unit is off.
2. Make sure the variable DC power source is switched off.
3. Connect the negative of the DC power source to the small screw in the middle of the load side of the shunt where the Link 20 black ground wire is connected (screw them together into the shunt).
4. Disconnect the blue wire (Bat. 1 voltage sense) from the house bank positive and the violet wire (Bat. 2 voltage sense) from the starter battery positive and connect them together and to the positive of the DC power source. Leave the fuses in those two wires.

In steps 3. & 4. you have effectively rewired the Link 20 to measure the DC power source voltage instead of the voltage of your batteries.

5. Disconnect the orange wire (Bat. 1 current sense battery side) from the side of the shunt and connect it to the green wire (Bat. 1 current sense load side) on the side of the shunt (screw them together into the shunt).
6. Disconnect the yellow wire (Bat. 2 current sense battery side) from the side of the shunt and connect it to the brown wire (Bat. 2 current sense load side) on the side of the shunt (screw them together into the shunt).

In steps 5. & 6. you have effectively shorted the current sensing circuits on both battery banks, thus simulating zero amps conditions. This is necessary because you will be calibrating the instrument for zero amps.

7. DO NOT CONNECT THE RED LINK 20 POWER SUPPLY WIRE TO THE DC POWER SOURCE, leave it connected to your house bank.

8. Connect an accurate digital voltmeter to the positive and negative of the DC power source.

The calibration itself:
1. Ensure Link 20 is switched off (fuse out on the red wire).
2. Ensure the voltage control on the variable DC power source is turned down to zero or minimum.
3. Turn the DC power source on and slowly increase the voltage while observing the reading on your voltmeter - adjust the voltage to precisely 40.0V. DO NOT EXCEED 50V!
4. You may need someone to help you with this step if your Link 20 is mounted far from the batteries. Push both Sel and Set buttons on the Link 20 and replace the fuse on the power (red) wire while those buttons are still pressed, only release them when the unit powers up. In other words, power the unit up while pressing those two buttons, then release them.
5. You should now be in the "calibration mode": the "V" and "A" lights on the Link will flash alternately, the "t" light will also be illuminated and the display should be showing the voltage from the DC power source.
6. It is not possible to proceed from here no matter which buttons you press until the voltage on the display is equal to or exceeds 40.0V (40.0V - 40.4V). If necessary, further fine adjust the voltage from the DC power source to exactly 40.0V DC and when ready hit the Sel button on the Link 20. You're now done with the voltage calibration.
7. You should now be in the current calibration mode, indicated by the "A" light being illuminated on the Link 20. The display should now be showing the small current offset error.
8. Using Bat1 (offset -) and Bat2 (offset +) buttons, fine adjust the display reading to 0.00 and press the Set button when ready.
9. The previous step needs to be done 4 times: Bat. 1 low amps range, Bat. 1 high amps range, Bat. 2 low amps range and Bat. 2 high amps range - every time fine adjust the display to 0.00 using the Bat1 (offset -) and Bat2 (offset +) buttons and when ready confirm by pressing the Set button.
10. Press Set again to enter the display test. All LEDs except the two on the right for each bank should be illuminated. The display sould be showing ±188.8
1
1. Press Set again to exit the display test and the calibration mode.
12. The Link should now be in the "normal" mode, displaying the 40.0V from the DC power source. Press Sel and Bat2 to confirm that the current readings are now 0.00A for both battery banks.
13. Remove the fuse from the red power wire to turn the Link 20 off.
14. Remove all temporary connections and the DC power source and connect all voltage and current sensing wires to their proper place, as they were before. Protect them from corrosion.
15. Replace the fuse in the red power wire to turn the Link 20 on and check for proper operation.

That's it, you're done. It sounds complicated and perhaps a bit daunting, but in reality it only took me about an hour to do, including the mop up in steps 13 - 15. To repeat the calibration, you will need to repeat steps 1. to 12.

My Link 20 now works accurately, as per Xantrex's published specs. After recharging, the batteries now show a small positive Ah reading, which gets wiped off once the discharge begins.

Hope this helps someone, it certainly cost me a lot research and frustration to get there.

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Old 26-11-2007, 21:13   #7
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Quote:
Originally Posted by Vasco View Post
I've had a Link, think it's a 2000, for three years now. For the first year I fretted over the fact that when charging it'll reset to 0 amps used when you stop charging when a second ago it showed -30 or -40. I have read the manual over and over and if I recall right I started a thread on this here a couple of years ago. I think some electronics experts tried to explain it to me but I still don't understand it. In the end I use the "amps used" as a rough guide only.

Rick,
It's normal to get a small positive Ah reading towards the end of the charging process. The older the batteries, the more positive reading you will get. This is due to the (in)efficiency of batteries accepting charge, i.e. it will always take more energy to charge batteries than they will actually store. During the discharge, Link will accurately measure the energy discharged. During the charging process, Link will try to compensate for the battery inefficiency by applying a factor less than 1 to the energy charged. This factor gets recalculated after you fully charge the batteries after discharging them more than 10% of the declared battery capacity. You start off with a factory default setting of 95% efficiency, which then gets recalculated after each charging cycle. That's when the right hand LED flashes - it means the factor has been recalculated. Check this recalculated figure for your batteries, it is a very good indication of the state of your batteries.

Now all this aside, if you leave the batteries on a shore charger for a few days on the float, you will still get a small positive accumulation of Ah due to the trickle charge current. Once the Link senses that the charging has finished and a discharge cycle has begun, it will 'wipe out' the positive Ah number and start counting into negative. It will not wipe out a negative number though and this is what frustrated me when my unit was accumulating false negative Ah readings. They were also distorting the battery efficiency calculations.

One question, how do you power the Link with the batteries disconnected?
In my installation, I have connected the red (Link power) wire and the blue (Bat. 1 voltage sense) directly to the positive house bank bus bar. So obviously you can't operate the Link with the batteries disconnected, but you can take into account the amps draw of the unit, which is 90 mA with the unit on and 25 mA in the 'sleep' mode. That's why I was getting -0.2A on my starting battery (where nothing else was connected) and between -0.2A and -0.3A on the house bank where the Link current draw was superimposed onto the instrument offset error.
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Old 27-11-2007, 04:35   #8
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In my installation, I have connected the red (Link power) wire and the blue (Bat. 1 voltage sense) directly to the positive house bank bus bar. So obviously you can't operate the Link with the batteries disconnected, but you can take into account the amps draw of the unit, which is 90 mA with the unit on and 25 mA in the 'sleep' mode. That's why I was getting -0.2A on my starting battery (where nothing else was connected) and between -0.2A and -0.3A on the house bank where the Link current draw was superimposed onto the instrument offset error.
Why would you need to take the unit's current draw "into account?" It's a real load, so it should show up as a real load, right?

Also, isn't the above what I suggested?
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Old 27-11-2007, 07:29   #9
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DanB44,

You may have misunderstood what happens in my and other cruisers cases. The amps used resets to 0 when charging is stopped even if it was showing minus 30 or minus 40 amps. I know if there is a positive amps indicated it resets to 0 the minute you draw on the battery. In other words if the bank was down 200 amps and you charge and put 160 amps, the minute you stop charging it shows -40, a couple off seconds later it resets to 0 indicating you've put in 200 amps when your bank is still down 40 amps. Two boats, mine and my friend's, experience this all the time when we're on the hook in the Bahamas. I've learned to live with it and use the Link as an indication only.
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Old 27-11-2007, 07:37   #10
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Oh geez...

I don't want to add to the confusion, but my Link 10 behaves differently, Rick.

It sets the zero point for Ah at the HIGHEST point the batteries have been charged to and leaves it there.

So... the following summarizes what happens:

Charge to full: Sets to zero
Discharge to 50%: Shows -220Ah
Charge to 75%: Shows -110Ah
Discharge to 50%: Shows -220Ah
Charge to 100%: Shows very close to zero Ah

Does yours not work this way?
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Old 27-11-2007, 10:23   #11
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Charged parameters

The Link 10 automatically resets the number of Amp-hours AND kilowatt-hours consumed to zero when the Charged Parameters are met. Your manual shows those Charged Parameters and how you can manally change them to better suit your particular needs, if necessary.

In addition, you can manually reset the number of Amp-hours to zero, if desired.

Once Charged Parameters have been met and the Amp-hour reading is zeroed a net positive accumulation will occur if still charging. Once a net negative amount of current flow (load) occurs (even if a charger is on but does not support the entire dc load) then the positive accumulation is zeroed out and the flashing green LED to indicate "full" stops blinking. A new "full" will not reset the Amp-hours (or kW-hrs) until a minimum amount of energy is removed from the battery (note in the manual this amount...I think it is 5% of stated battery capacity but my mind is off at the moment)...onward and upwards!
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Old 27-11-2007, 10:37   #12
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The Link 10 automatically resets the number of Amp-hours AND kilowatt-hours consumed to zero when the Charged Parameters are met. Your manual shows those Charged Parameters and how you can manally change them to better suit your particular needs, if necessary.

In addition, you can manually reset the number of Amp-hours to zero, if desired.

Once Charged Parameters have been met and the Amp-hour reading is zeroed a net positive accumulation will occur if still charging. Once a net negative amount of current flow (load) occurs (even if a charger is on but does not support the entire dc load) then the positive accumulation is zeroed out and the flashing green LED to indicate "full" stops blinking. A new "full" will not reset the Amp-hours (or kW-hrs) until a minimum amount of energy is removed from the battery (note in the manual this amount...I think it is 5% of stated battery capacity but my mind is off at the moment)...onward and upwards!

Yup... that's how mine works, of course. When I said 100% full, I should have used the terminology from the manual "charged parameters met."
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