30A Flush Mount PWM Solar Controller

I keep all the old PSUs from obsolete stuff and keep them labelled (handy if looking for anything particular). Found an old HP Transformer that is noted as 32V DC with a 625mA output. Very low current but that high voltage could be handy for testing how well the solar controllers convert voltage to current (the controller output should be around 1.5A on a 12V system on an MPPT system with that input)
 
So the old HP Transformer failed. (Maybe that is why we got rid of the printer?)
So then got a pair of 9V 2A Transformer (labelled Thomson Telecoms. Think they were from BT Home Hub 1s?) and connected them up in Series to make a nominal 18V, 2A (so 36W) "Solar Panel" to fed into the Solar Controller.

Won't be able to do this level of monitoring on the various Solar Controllers that will be checked, but the graph below shows the kind of voltage & current changes that you would want and expect from an MPPT Solar Controller.
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On the point highlighted, the "Solar" coming into the Controller is at 17.88V with a current of 2.2A, giving a power in of 39.3W; Coming out of the Controller, the voltage is 12.88V and a charge current of 2.9A - giving a Wattage of 37.4W, so a conversion efficiency of 95% (this is all very low power. As power increases, efficiencies usually increase).
The key thing of course is that the higher voltage is not wasted but converted into a higher current on the output side.

Anyways, so the above is going to be the benchmark. Once I have my incoming and outgoing monitors setup I will on a separate thread post some pictures of the monitors showing the performance of the various controllers I have available (think I have 5 different models at the moment I can check) and see the differences between the various models of Solar Controllers and TYPES of Solar Controllers.
Now I have not actually specifically done a test like this before so while I *think* I have a good idea of what the outputs will look like, I am very interested to see what happens in practice.
I will probably order one of those units Trevor has out of curiosity to add into the test mix as if they genuinely are MPPT units and have high efficiency, at that price point they would appear very good value :)
 
I've got a really good maplins bench power supply, you should buy one of those. Oh, wait....


I'll have to digest your info another time, my first beer was 0530hrs at the airport this morning:)
 
If wildebus gets to the bottom of this it could save folks a lot of dosh when the truth is out
 
I've got a really good maplins bench power supply, you should buy one of those. Oh, wait....


I'll have to digest your info another time, my first beer was 0530hrs at the airport this morning:)
Maplins have risen from the ashes you know :) On-Line only, but still some good stuff (y)
I could do with a bench PSU with variable voltage and power output but the old transformers will do the job (and at this time of year with the current weather, those two old Home Hub ones are putting in more power than my 400W Solar Array on the van roof!)
 
Didn't realise when I ordered them, but the two monitors are not due to be delivered until 3-4 weeks :( Oh well, that will give me time to get Trevs Controller in probably :)
 
I have a spare one in workshop,just in case one in van goes down,i was going to fit m votronic but if this we yogi works then im happy.
 
I have a spare one in workshop,just in case one in van goes down,i was going to fit m votronic but if this we yogi works then im happy.
I've ordered one this evening. supposed to arrive one day before the monitors arrive :D
Also found another 9V PSU so will be able to run the inputs to the panel as 18V or 27V to see any differences to conversion watts (this should only be that noticable to PWM Controllers, but will be interesting to check across the board)
 
the 3rd 9V Transformer seems to be working fine so I can have a "Solar Panel" running at a nominal 27V and output of 56W as well as the 18V/36W version.
This is what the 27V input looks like:
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So the 2.3A input results in a 4.3A output current at that battery voltage level.
(FYI, the dips every 10 minutes is the controller momentarily shutting the input to do a voltage check to see what the battery state is and this happens to be coinciding with the data sampling. Usually you would not be aware of this.)

Plan is to run each controller at both 18V and 27V if possible (some Solar Controllers have a fairly low voltage limit, for example the Schaudt LR1218 only permits upto 25V input) so the 27V test might not always feature.

Anyway, these tests are something that is not going to happen until November as Monitors not coming until then :( (unless someone wants to send me a pair of Victron BMV-700s, and then I could do the tests AND log the info like above as well on any Solar controller :D )
 
Just about the time of year i will be getting very little charge from solar here,but will see how this we unit compares to my old unit.
Do keep us up to date wildebus as i hate being kept in suspenders. :LOL:
 
I wasn't planning on another update on this thread until the monitors arrived, but thought this following point is worth mentioning when choosing a Solar Controller....

Multi-stage charging
Batteries (talking Lead Acid here. Lithium are a different animal) require different stages when charging to treat them correctly for maximum operational life.
A decent Solar Controller - be it PWM or MPPT - should take account of this and operate in Bulk (CC), Absorption (CV) and Float modes when required. The correct Voltages for Absorption and Float modes should be documented by the Battery manufacturer, and the maximum permissable current for Bulk model should also be documented.
Many Solar Controllers, just like many Motorhome mains chargers are dumb chargers and don't have a float mode, so the battery runs the risk of having a high voltage charge applied to it constantly all the time power is coming into the controller.

The chart below on my test setup with the old power transformers illustrate the kind of behaviour you should look for in a Solar Controller

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Power is applied.
The Battery is fairly depleted, so is in Bulk Mode. The voltage gradually increases and the current is fairly steady (hence Bulk is also known as CC - Constant Current - Mode)
Then once the Voltage reaches the Absorption Voltage Setting, the Controller switches to Absorption Mode. The voltage is now steady (hence Absorption Mode is also called CV - Constant Voltage - Mode) and the current starts to decline as the battery fills up.
Finally, the Controller switches to Float Mode. This can because the battery is fully charged OR it may be because the controller has been in Absorption mode for a certain length of time.
(The maximum length of time a battery should stay in absorption mode should also be documented by the Battery Manufacturer. It is typically between 5 and 8 hours. In this case, Absorption Mode lasted 6 hours and then timed out. This helps protect the battery and is a setting in the controller - this level of control is not that common and usually only found on the best models TBH).
 

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OK, so the testing is going to start in the next few days as my monitors arrived today :)

As a calibration check I connected them up and used the Victron MPPT as above so I could check how accurate the numbers are (these are good monitors but they are cheap as well so a degree of tolerance is only to be expected)

Here is a photo of the monitors (LHS one is the PV input to the controller; the RHS is the Battery output from the controller)

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I think the monitor values are pretty accurate and should give a decent indication of how the various controllers will perform. Of course won't have the computer view,but will have the snapshot info as it shown above, plus a cumulative Wh harvest as well. As I am using a fixed Power Supply and not dependant on sun, that will hopefully mean I can do a actual power harvest comparison as well.

What the testing will NOT do is determine how good a controller is at getting the most out of a panel (the MPPT bit for example) but to do that comparison needs multiple panels and batteries and a reliable sun!
 
Hope you get the we controller im using soon so i can see whats really going on,very good tests so far. (y)
PS i have also found this new one on the market for duel battery charging.solar mppt 20ah charger reg.png
 
I forgot about that controller. Should be within the next 10 days I think?
I honestly would be surprised if it were a genuine MPPT but who knows!

What I cannot test for knowingly is the actual MPPT feature, so that aspect of the MPPT could remain a mystery between the various MPPT controllers. I have the second PWM controller on test currently - looks same kind of numbers as the first PWM so in fact would be an easy check I think to see if a controller is MPPT or PWM .... Put a voltmeter on the PV terminals on the controller. If it very close to the battery voltage it is likely PWM; If it is much higher (> 15V say) then it probably MPPT (do this when the panel is in light and getting some power in).
 
Hope you get the we controller im using soon so i can see whats really going on,very good tests so far. (y)
PS i have also found this new one on the market for duel battery charging.View attachment 50706
Ref the Dual battery charging thing. I am not convinced those are really any different to the controllers that have a "load" connection as well as the battery. With most reasonable ones you can configure the load to be active when the battery is at a certain level of when the PV input is present.
In fact, if you did use the "Load" as a secondary battery connection and set it to be in when the battery is above a certain level, then it could provide a trickle charge to the starter when on mains hookup with a charger? Think I might have to have a look at that?
 
Hopefully you should soon be able to sort the men from the boys,prob as you say many are not what they claim to be but i am very interested on the outcome.
 

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