Solar panel regulation & parasitic draw?

May 15, 2023
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I have just put a new battery on our recently acquired 2014 Sterling Eccles Sport. No external power connected, however it has a factory fitted solar panel. As I fitted the battery there was some very small sparking. Prior to fitting I had the battery on my CTEK charger until it was fully charged. The sparking prompted me to put an ammeter in the circuit, and too my surprise the battery was receiving about 1.2A of "charge" for about 2 seconds then 150mA discharge for about 0.5 of a second, this appears to alternate in this fashion indefinitely, my concern is that 1.2A in for a fully charged battery, even if it is intermittent seems odd?

So I thought that I'd see what the solar panel was up to; the direct output of the solar panel is 19.14V , that seems ok? Solar panel direct output.jpg
however measuring the output after the Sargent regulator and its only 6.55V, now this is clearly with no load, so the regulator may give a different output with a load? I intend to find something that loads it with a few Watts and see what the result is.Solar output after regulation no load.jpg

With the solar panel disconnected I went back to the battery, and again with the power switched off I am seeing a 150mA drain, if this was a car I'd call it a parasitic draw. I'm assuming with the power turned off, and the solar paned disconnected, nothing should be drawing any current, or am I incorrect in this assumption?

I have dug out the schematics and will ponder over them tonight with a glass or 2 of wine, and tomorrow will disconnect circuits to see if I can isolate the current draw, but would appreciate any advice or thoughts that may save me some time.

Incidentally, as you can see I was using my trusty analogue meter when measuring what I'm calling the parasitic draw, and there is a constant very slight flicker of the needle, again odd, but at least illustrates one benefit of using an analogue meter when fault finding! Current draw solar disconected.jpg
 
Jun 16, 2020
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Could the draw be from alarm circuits?

I read that it is good practice to disconnect the solar panel before disconnecting the battery. when I installed mine, I fitted an isolator switch to both panels. But I must admit, there was a few times I forgot to use them when removing the battery, luckily, with no harm.

John
 
Mar 14, 2005
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Without knowing what circuitry the Sargent employes its difficult to know exactly what its capable of or if its working correctly.

However I have seen similar behaviour from a DC to DC Switched Mode Power Supply where the voltage source was current limited. and it seemed to be related to the speed at which the bulk charge capacitor could be charged up due to the limited input current.

Nice to see good quality meters being used, and yes there is still a place for moving coil meters in this digital world.
 
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Reactions: littlebasher
Nov 30, 2022
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There are quite a few things that could be responsible for this parasitic load, tge ones I can think of (in no particular order) are....
  1. Radio station memory
  2. Alarm
  3. Fridge not fully switched off (control panel needs power)
  4. Aftermarket thermometer
  5. USB supply socket not isolated from 12v
  6. Clock on a cooker
I am sure there are a few things I have missed, but hopefully this list will start you on your quest?

Do keep us posted when (if?) you track it down.
 
Jun 16, 2010
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I wish i had something to contribute, other than it's nice to see an Avometer being used in anger, and not just as a piece of decoration !
 
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Reactions: Hutch
May 15, 2023
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Thanks for the input this far, I need to get to the bottom of this, as an overcharge or parasitic drain are both going to compromise battery life and performance.
 
Sep 26, 2018
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The Sargent will be a Pulsed Wave Modulation (PWM) controller. I suggest that this looks like a controller failure to me. Parasitiic drain will usually only occur with a direct to battery connection of a low power panel... The controller is there to stop such a drain. A 30A PWM is available for less than £20... When/if you replace it, try to cover the panel to minimise output, disconnect the panel, then disconnect battery (take the battery terminal off, otherwise you're at big risk of shorting the two connections to the controller). Install the new one, do the battery connections at the controller, replace the battery termnal connection, then connect the panel connections, then remove the cover over the panel
 
May 15, 2023
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I have temporally replaced the Sargent PWM unit with some canalised bits from a smart charger that had a damaged case and display; now have a decent output from the solar panel. I will order and fit a new PWM controller module .

I'm pretty convinced that what I was calling a parasitic drains, are not actually faults, but simply a combination of various standby current draws, the majority of which go away if the main Sargent Power controller an EC400 is shut down. One standby draw that is always present is the mover (not controlled by the EC400), it sends a pulsed signal looking for the mover remote every 5 seconds or so, however this draw is very low , circa 10mA.

With the Sargent not in standby mode and without a trickle charge from the solar panel, I estimate the battery would be flat in around 6 weeks.

When we bought the van in April the seller was very honest and said that the battery didn't appear to hold a charge, they hadn't used the van for a year, so with a faulty regulator from the solar panel it easy to see why the battery went kaput.

The lesson is to check the battery every month, I can't see any reason why you wouldn't shut the EC400 down when the van is not in use, we don't have an alarm and there is nothing else that need power during idle periods, unless I'm missing something?
 
Nov 6, 2005
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The mover shouldn't be permanently powered - it should be switched off at the isolator after use to eliminate any parasitic draw.
 
Nov 11, 2009
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I have temporally replaced the Sargent PWM unit with some canalised bits from a smart charger that had a damaged case and display; now have a decent output from the solar panel. I will order and fit a new PWM controller module .

I'm pretty convinced that what I was calling a parasitic drains, are not actually faults, but simply a combination of various standby current draws, the majority of which go away if the main Sargent Power controller an EC400 is shut down. One standby draw that is always present is the mover (not controlled by the EC400), it sends a pulsed signal looking for the mover remote every 5 seconds or so, however this draw is very low , circa 10mA.

With the Sargent not in standby mode and without a trickle charge from the solar panel, I estimate the battery would be flat in around 6 weeks.

When we bought the van in April the seller was very honest and said that the battery didn't appear to hold a charge, they hadn't used the van for a year, so with a faulty regulator from the solar panel it easy to see why the battery went kaput.

The lesson is to check the battery every month, I can't see any reason why you wouldn't shut the EC400 down when the van is not in use, we don't have an alarm and there is nothing else that need power during idle periods, unless I'm missing something?
I never even considered leaving the EC400 on when the van was not being used.
 
May 15, 2023
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The mover shouldn't be permanently powered - it should be switched off at the isolator after use to eliminate any parasitic draw.
I'm pretty sure there is no isolator switch for the movers, there really should be one and a fuse... I'll need to take another look, and possibly fit one.
 

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