Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.

mtdocmtdoc Solar Expert Posts: 600 ✭✭
My Wattsun AZ 125 tracker has worked flawlessly for the past year - that is until last week when it stopped tracking.

The tracker controller cannot take greater than 50V so with a 48V nominal battery bank Array Technologies sells what they call a "linear voltage pre-regulator" for use with their Wattsun trackers to step down voltage from 48 to 24 Volts nominal. Details of this can be found HERE .

I was relieved to find that this small piece of electronic was the culprit in my tracker not working. Test with a multimeter showed that with 55 Volt input it was only putting out 17 volts when unconnected to the tracker. When connected to the tracker controller - even when off - the voltage output dropped to 4.5V. With 24 volts directly supplied to my tracker I could move my tracker with the manual control and set it facing South. When doing this it draws about 0.4 amps as measured by a Fluke clamp on meter.

I called Array technologies and they agreed to repair or replace the regulator. I've mailed it to them - but given past experience when I first ordered my tracker - I don't expect a speedy repair or replacement.

So - on ebay I found and purchased one of THESE 48 to 24 Volt step down regulators. The specs appeared close enough to me that I thought for $21 I'd take a chance and see if it would work while I was waiting for my replacement from AT.

But it doesn't work. When connected to my 48V bank it does indeed put out about 25V. But when hooked to the controller - no go. And heres the other thing I don't understand - when hooked to the controller which is in the off position, the output drops to about 4.5 V -the same thing that happens with the dysfunctional AT regulator.

Any ideas on what it going on here? My understanding of electronics is pretty minimal- so I'm at a loss why it wouldn't work based on the specs and don't understand why the voltage output drops when connected to the tracker in the off position.:confused:

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.

    The question everyone will want to ask: how did you supply the 24 Volts to get it to work manually?
    Another question: can you measure current being drawn by the tracker when connected to the DC-to-DC converter?

    It actually sounds like something may have shorted in the tracker control that is drawing the Voltage low. This circuitry may not be involved if powering the tracking motor manually, so no short is detected.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.

    Thanks for the help.
    The question everyone will want to ask: how did you supply the 24 Volts to get it to work manually?
    2 12 volt batteries carried to the base of the tracker.
    Another question: can you measure current being drawn by the tracker when connected to the DC-to-DC converter?
    Zero (at least none picked up on my Fluke clamp on meter).
    It actually sounds like something may have shorted in the tracker control that is drawing the Voltage low. This circuitry may not be involved if powering the tracking motor manually, so no short is detected.
    But the manual control does not work when either the AT Voltage converter or the ebay special is hooked up to my 48V bank to power it.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.

    This is curious indeed.
    You're saying if you supply power from two batteries it works, but if you use either DC-to-DC converter it sucks the Voltage down to 4.5? With no current being drawn? But with it disconnected either converter will show 24 +/- Volts?
    It isn't actually possible to create such a V-drop without some (quite a bit of) current going somewhere. Another possibility is that some small current draw is causing trouble on the 48 Volt side due to a problem with wiring on the supply side.

    Two things to check: Voltage drop on the 48 Volt side at the converter with changes in load at that point (you may have to rig up some strings of 12 Volt bulbs to load it), then the same on the output (without the tracker connected).
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.
    This is curious indeed.
    You're saying if you supply power from two batteries it works, but if you use either DC-to-DC converter it sucks the Voltage down to 4.5? With no current being drawn? But with it disconnected either converter will show 24 +/- Volts?
    Yup, that's what I thought too.
    It isn't actually possible to create such a V-drop without some (quite a bit of) current going somewhere. Another possibility is that some small current draw is causing trouble on the 48 Volt side due to a problem with wiring on the supply side.

    Two things to check: Voltage drop on the 48 Volt side at the converter with changes in load at that point (you may have to rig up some strings of 12 Volt bulbs to load it), then the same on the output (without the tracker connected).

    Yes- good thought. I'll look into that possibility. I can say that with either regulator hooked up to the array (and output dropping to 4.5V) there is no drop in voltage at my battery bank. I can see this by looking at my logged data. But maybe something between my epanel and the array? The 48V from my batteries are supplied to the tracker base by 120 feet of 10AWG wire running underground in it's own conduit.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.

    That wiring should be good for up to 6 Amps before the Voltage drop becomes an issue.
    Now if this is powered from your 48 Volt battery bank there should be no issue with PV wiring; it would have to be in the 48 Volt wiring from the battery bank to the tracker base. It may even be a case of water in the conduit. Under the right (or should we say wrong?) conditions, the DC current flow can cause the water to migrate through the insulation and cause conductivity between the wires. The open circuit current flow would be near to zero and so not cause the problem.

    The thing that is curious is that merely connecting the tracker control causes the Voltage drop, even though it is off. In light of that I'd also suggest checking the resistance across the tracker control power input with the control off and no power connected. It should be no conductivity or very high Ohms.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.
    The thing that is curious is that merely connecting the tracker control causes the Voltage drop, even though it is off. In light of that I'd also suggest checking the resistance across the tracker control power input with the control off and no power connected. It should be no conductivity or very high Ohms.

    OK - I'll check this tomorrow. Thanks again for the help.
  • Dave AngeliniDave Angelini Solar Expert Posts: 4,984 ✭✭✭✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.

    Fuse and wire the Wattsun off of 1/2 of your 48V bank. At 20 watt hours per day this not going to hurt your batteries. You could rotate every 6 months if it makes you feel better. The company that makes the wattsun DC converters is a big suspect. They make a product that takes an extremely reliable Wattsun system and makes it very susceptable to surges and other issues. Most of my 48 volt customers have 2 wattsuns and each is off 1/2 of the bank. BTW Wattsun is excellent with customers but orders can often take 3 months if they are doing Utility tracking systems during the time you order. I have never had a problem with them for 10 years except for one that probably skipped the very basic maintenance for years.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.
    That wiring should be good for up to 6 Amps before the Voltage drop becomes an issue.
    Now if this is powered from your 48 Volt battery bank there should be no issue with PV wiring; it would have to be in the 48 Volt wiring from the battery bank to the tracker base. It may even be a case of water in the conduit. Under the right (or should we say wrong?) conditions, the DC current flow can cause the water to migrate through the insulation and cause conductivity between the wires. The open circuit current flow would be near to zero and so not cause the problem.

    The thing that is curious is that merely connecting the tracker control causes the Voltage drop, even though it is off. In light of that I'd also suggest checking the resistance across the tracker control power input with the control off and no power connected. It should be no conductivity or very high Ohms.

    Ok - the resistance across the control leads when off is high - about 300 k ohms. That is too high to allow much current flow (0.00008 amps at 24 V if my calc is right). Still can't figure out how this would cause regulator output to drop to 4 Volts. :confused:

    As far as water in the conduit - you're saying that even though there is not continuity between leads when no current is flowing (I confirmed this with DMM) this may change when there is a load applied? Wouldn't that show up as large current spike and V drop at my battery bank when this happens?

    I don't have another 24 volt load to apply to the end of the wire run. Don't really want to buy 12 volt lights just for this. Is there any reason why reconnecting the step down regulator at the tracker and measuring the voltage at it's input would not accomplish the same thing?

    Thanks again.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.
    Fuse and wire the Wattsun off of 1/2 of your 48V bank. At 20 watt hours per day this not going to hurt your batteries. You could rotate every 6 months if it makes you feel better. The company that makes the wattsun DC converters is a big suspect. They make a product that takes an extremely reliable Wattsun system and makes it very susceptable to surges and other issues. Most of my 48 volt customers have 2 wattsuns and each is off 1/2 of the bank. BTW Wattsun is excellent with customers but orders can often take 3 months if they are doing Utility tracking systems during the time you order. I have never had a problem with them for 10 years except for one that probably skipped the very basic maintenance for years.

    Thanks Dave. I can see you've had a lot of experience with these trackers. It sounds like you've encountered failures of these voltage regulators before.

    So have you measured the 20 watt hour per day load from the trackers? It sounds about right. I've measured 0.4 amps (at 24 Volts) when the tracker is moving- which of course it only does for short bursts throughout the day.

    If it turns out that there is some issue with my tracker power wire/conduit run I was thinking that getting a couple of very small 12 V batteries and placing them at the tracker base with a small 24 volt panel to keep them charged. This would be a heck of a lot easier (and likely cheaper) that laying down another run of conduit and wire to the tracker. If so, knowing the load this would need to supply would be critical.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.

    You are right that 300k Ohms is so high that it should have no noticeable affect on the Voltage output of the converter.

    At this point the converter is an "unknown" as to how much power it will pull. You can check the input and output Voltages on the converter with the tracker disconnected then connected and see what difference it makes. But ideally you need a "known" load to apply to eliminate the possibility that the failure is this new converter rather than the tracker or wiring.

    Another way to check against the water infiltration problem is to run a separate, temporary cable of 12 or 14 AWG wire from the battery bank to the tracker and see if you get the same Voltage drop behaviour.

    Over-all the current being used by the tracker and what should be used by the converter are so small they shouldn't affect Voltage enough to cause it to stop working.

    You should also try Dave's suggestion and wire the line for 24 Volts instead of 48 to at least see if it works this way or if the V-drop is too high. Remember that the current will be about double at the lower Voltage and the V-drop on the line will be much higher than with 48 Volts.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.
    You are right that 300k Ohms is so high that it should have no noticeable affect on the Voltage output of the converter.

    At this point the converter is an "unknown" as to how much power it will pull. You can check the input and output Voltages on the converter with the tracker disconnected then connected and see what difference it makes. But ideally you need a "known" load to apply to eliminate the possibility that the failure is this new converter rather than the tracker or wiring.

    Another way to check against the water infiltration problem is to run a separate, temporary cable of 12 or 14 AWG wire from the battery bank to the tracker and see if you get the same Voltage drop behaviour.

    Over-all the current being used by the tracker and what should be used by the converter are so small they shouldn't affect Voltage enough to cause it to stop working.

    You should also try Dave's suggestion and wire the line for 24 Volts instead of 48 to at least see if it works this way or if the V-drop is too high. Remember that the current will be about double at the lower Voltage and the V-drop on the line will be much higher than with 48 Volts.

    I'll have a look at this again on Tuesday and try a few of these things. Your help is much appreciated!.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.

    Ok here's what I tried today:

    Again measured voltage in and out of the ebay special 48-24 volt converter. Not connected to tracker: 55 V in 24-25 V out. Connected to tracker (off): V out drops to 4.5-4.7V - No change at V in and no measurable current in leads to tracker ???? weird.

    Conduit running to tracker had an unused wire so I tried using this as the battery negative lead - no change in result.

    I hooked up a 24V (instead of 48V) battery source at utility room to test wire run in conduit and tracker works fine connected to this.

    So the mystery continues. I really wish I understood why when connected to the tracker the V out of the step down regulator drops from 24 V to less than 5 V with nothing on and no measurable load??? And why the Array Tech one did the same thing. :confused::confused: - any other ideas? anyone?

    I guess I'll wait until Array technologies send me a new one of their step down voltage regulators and see if it works. If not, I could - as suggested pull 24 volts off of my 48V battery bank to power it directly. That does make me nervous - even if it is only a very low load. I don't want to do anything to shorten the lifespan of my $batteries$. The other option I've considered is a very small inexpensive set up at the tracker base with 2 low capacity batteries and a 20watt 24 V panel to keep them charged.
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.
    mtdoc wrote: »
    Ok here's what I tried today:

    Again measured voltage in and out of the ebay special 48-24 volt converter. Not connected to tracker: 55 V in 24-25 V out. Connected to tracker (off): V out drops to 4.5-4.7V - No change at V in and no measurable current in leads to tracker ???? weird.

    I hooked up a 24V (instead of 48V) battery source at utility room to test wire run in conduit and tracker works fine connected to this.

    So the mystery continues. I really wish I understood why when connected to the tracker the V out of the step down regulator drops from 24 V to less than 5 V with nothing on and no measurable load??? And why the Array Tech one did the same thing. :confused::confused: - any other ideas? anyone?

    I have a hypothesis:

    One way to protect the output of a DC power supply (whether AC or DC input) is to use what is called "foldback" voltage regulation. An accurate enough description for this purpose is that when the maximum output current is exceeded, the supply will reduce the output voltage. Not just enough to keep the current at maximum, since the load may try to draw more amps at the lower voltage to keep its power usage up. Motors are notorious for this behavior. So the output voltage goes to some very low value at which the output current is tolerable and stays there until the input voltage to the supply is turned off and back on.

    So I suspect that what is happening is that when you first connect the tracker unit, either the motor is driven momentarily during startup or the electronics unit itself has enough of a surge draw to trip the foldback feature of the power supply.
    When you connect directly to a 24 volt battery, the surge current does not bother the battery or trip any circuit breakers or fuses. Then it settles down to the normal current drain that you can actually measure.

    One way to test this hypothesis would be to set up a DPDT transfer switch so that you can "start" the tracker connected to the 24 volt battery and then a few seconds later flip the switch to the converter output.

    If this works, then the solution is to either devise a soft start circuit for the tracker or get a bigger convertor with better surge capability.

    The right person at Wattsun may be able to tell you just what the connection current surge of the system is.
    SMA SB 3000, old BP panels.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.

    Thank you inetdog. It does make sense - I think - at least to my limited electronics level of understanding. I'm not sure when (or if) I'll get around to setting up a DPDT switch to test this as you suggest - I have so many projects going on right now. But if I do, i will let you know what I find out.

    The biggest frustration for me is just not understanding what is going on. I know I'll have the tracker following the sun again soon (with either the new AT regulator or by doing a direct 24V supply)- I just want to know why these voltage regulators are behaving this way. I may not know much about electronics but I do understand Ohm's law (I spent years doing electrophysiology and working with Ohm's law at the milli to microvolt level). The fact that the output V is dropping without any measurable load confuses me. The idea that something is transiently triggering the regulator's circuitry to limit it's voltage output below 24V makes sense.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: Wattsun Tracker - 48 to 24 Volt step down regulator failure- ?Questions?.

    Just a follow up in case anyone else runs into the same issue on a Wattsun Tracker.

    I just now have my tracker back running of of my 48V bank using a new stepdown regulator from Wattsun.

    After sending my faulty one back to them they took about a month to send it back - no change -it still did the same thing - I'm not sure they had even looked at it- and no feedback from their engineers:grr

    Sean from their service dept was very helpful and had me send it back -this time with note included asking for them to contact me to let me know what they did or did not do to fix or replace it before a return. After waiting 2 months with no word I called and spoke to Sean again who just said they would replace it with a new one -he called to update me when it shipped and it arrived a few days ago... They did replace it free under warranty at least.

    So the mystery remains - and Wattsun (Array Technologies) gets a C grade in customer service......(But Sean gets an A!)
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