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# 251051 6-Jun-2019 11:15
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Anyone been through the process of buying a solar charge controller recently where I can steal your homework?

 

I want to replace ye-olde PVM controller in my rental house with a smarter MPPT controller, seems a lot of the ones I see claiming to be MPPT are really PVM with false labeling.

 

I'm after one that has WiFi so I can feed my stats urges.

 

Thanks!


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  # 2253016 6-Jun-2019 13:59
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Is this an off grid system? What battery bank, panel voltages, panel output etc?





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  # 2253021 6-Jun-2019 14:04
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@raytaylor knows a thing or two about solar.


 
 
 
 




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  # 2253141 6-Jun-2019 14:57
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Small off grid house.  Well semi-offgrid there is an AC feed to the inverter which can be run if power is desperately low.

 

Setup is :

 

Battery bank 24volt  = 4 * 6v 230ampH Lead acid

 

Inverter  = Enerdrive ePOWEREN1120X 24v

 

Charger = Enerdrive  ePower EN32430 24v

 

Panels = 4 * 100 or 125W (guessing)

 

Solar Charge controler = Steca Sigma 20A 24v

 

 

 

Looking to replace the Steca with something smarter and modern.

 

 

 

 

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  # 2253150 6-Jun-2019 15:27
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You are correct, many Chinese brands are advertising MPPT when they are actually PWM. After shopping around for a bit, you get a sense of fair pricing for MPPT and start to realise when the deal is too good to be true. You also get to recognise the shape & layout and realise that the same regulator is being advertised as both technologies. 

 

I have recently switched from PWM to MPPT on a 24v 1300 watt system.

 

If you are not altering the configuration of your panels, there is little energy to be gained. There is a few reviews on youtube where they did direct replacement of PWM with MPPT and saw no gain (or slight negative gain) in efficiency.

 

In my experience/situation the biggest advantage of MPPT is that you can run your panels in series for a higher voltage and lower current, reducing you I2R losses in the cabling. This isn't so relevant if your panels are very closed to your batteries. For me I went from trying to get 50amps @ 24v down from the roof at 15 meters to 90v @ 14 amps which reduced my copper losses a lot, improving efficiency. If the distance was only 2 meters I wouldn't have seen an improvement. 

 

Edit: spelling.


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  # 2253167 6-Jun-2019 15:40
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I have only tried 1 MPPT regulator (a cheap Chinese one) and I'm not sure that I am yet satisfied with it. It seems to target a PV voltage about 20% under the nominal voltage making me suspect it is loosing efficiency. Ideally I'd like to pit it against other brands and see if it behaves the same/better/worse.


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  # 2253183 6-Jun-2019 16:17
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Mark:

 

I want to replace ye-olde PVM controller in my rental house with a smarter MPPT controller, seems a lot of the ones I see claiming to be MPPT are really PVM with false labeling.

 

Because you are looking in the wrong place.

 

Morningstar | Midnite | Outback

 

Take your pick.





Integrity Tech Solutions @ Norsewood, New Zealand




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  # 2253208 6-Jun-2019 17:12
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I didn't twig that you'd have advantages for feeding in more volts to an MPPT controller ... I like the idea of that, more reading needed :-)

 

At the moment I think the setup I have (I didn't install it) has 4 *12v panels configured up for 24v (2 strings of 2 panels each), connected to the PVM Steca.

 

So if I replaced them with 6 * 200W panels, and did 2 strings of 3 panels each I'd output higher voltages which the MPPT controller would soak up and turn into ~24v + extra current ?

 

A small gain on the older panels may or may not happen with a MPPT based controller ?

 

I'd also like a charge controller that plays nice with external chargers .. my current Steca does.


 
 
 
 


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  # 2253218 6-Jun-2019 17:55
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Currently live in a place that's been off-grid for 10 years.

 

 

 

Been rocking 4kW on an Outback MPPT for 10 years, and it doesn't show signs of slowing down soon. It's a pretty big and heavy unit though.

 

Expanded my setup not too long ago and went with the Victron Energy 250/60 MPPT. No regrets at all, it's been rock solid for me and the Bluetooth integration with my phone is really good. Not to mention that Victron has really good integration with all their other products (inverters, battery smoothers, etc.) Their Color Control GX unit is really the brain of all this and allows you to connect it to a 3G modem or the internet via a WiFi dongle or ethernet cable. The software runs on Linux and is open source, so you can flash your own and have full IFTTT integration. You can add this all later if you want by the way The unit is significantly smaller compared to my outback too, and it doesn't need active cooling.

 

Victron Energy also has a good summary and white paper on MPPT vs PWM here

 

 

 

 

 

 


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  # 2253485 7-Jun-2019 02:30
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Mark:

 

I didn't twig that you'd have advantages for feeding in more volts to an MPPT controller ... I like the idea of that, more reading needed :-)

 

At the moment I think the setup I have (I didn't install it) has 4 *12v panels configured up for 24v (2 strings of 2 panels each), connected to the PVM Steca.

 

So if I replaced them with 6 * 200W panels, and did 2 strings of 3 panels each I'd output higher voltages which the MPPT controller would soak up and turn into ~24v + extra current ?

 

A small gain on the older panels may or may not happen with a MPPT based controller ?

 

I'd also like a charge controller that plays nice with external chargers .. my current Steca does.

 

 

Most MPPT controllers use a buck converter to do the actual voltage stepdown. You want the panel string voltage at MPP to be 1.5 - 2X the battery charge voltage. Assuming that you will be using the type of solar panels which are used for grid connect systems. You will need to configure your panels as 3 strings of 2 panels each. And you will need a 60A or so rated MPPT controller. You will quickly be getting to the stage where a 48V battery bank will make better sense than a 24V system.

 

If you want to buy cheap controllers from Aliexpress, I can confirm that "Make Sky Blue" brand are actually MPPT. And they are one of the few where 1 controller will support 12V, 24V, and 48V battery banks.

 

https://www.aliexpress.com/item/32808021790.html?spm=a2g0s.9042311.0.0.51b74c4dro4MpQ

 

If you measure the voltage produced by your solar panels during full sun and cloudy conditions. (measure with enough load on your batteries so the controller thinks that your batteries are part charged). An actual MPPT controller will keep the panel voltage close to the panel manufactures quoted MPP voltage. If the controller is a PWM unit, panel voltage will be similar to battery bank voltage. In both cases, the panel current will vary depending on the amount of sun.

 

MPPT controllers allow you to use panels that are intended for grid connect systems (which are cheaper to buy than panels that are designed for cheap battery systems). If you are buying panels and a controller together. Spending extra to get an MPPT controller compared to a PWM controller allows you to save money on buying solar panels (when comparing equivalent system outputs).






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  # 2253551 7-Jun-2019 08:34
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We have a 24V 300W panel charging two 12V 105Ah batteries at our bach (for running a 240V fridge and 12V LED lighting - the rest of the place is off grid and uses gas).

 

We have an Epever Tracer 30A MPPT controller. We bought it from a crowd up Silverdale way, but they are available on AliExpress.

 

As mentioned earlier in this thread, you get to know the real ones from the mis-badged ones by the pricing.


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  # 2253564 7-Jun-2019 08:57
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I have a small solar set up in the corner of my garage.  Charge Ebike, Emower, 18v battery tools, 12v led work light.

 

80w panel, Epever Tracer 20 MPPT (Replaced Steca 6 or 8 amp PVM). Charging 2 old 40ah scooter batteries. Cheap 240v inverter.

 

I need to find new batteries.  I recently changed to the Epever smart controller as it gives flexibility to upgrade panel(s) and different battery voltage & chemistry types in future.

 

Does not charge significantly better with one panel in my setup.  Does have led display panel and option to add bluetooth, wifi, ethernet, battery temperature sensor. 





:)


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  # 2253969 7-Jun-2019 16:53
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EPSolar Tracer A series - I have about 50 of them in service. 

 

They are chinese but damn good quality and beat the jaycar one hands down. 

 

You will definitley get more out of your old panels on a rainy day if you switch to an mppt controller. 

 

 

 

You dont want to be putting more than 23amps into that battery bank (Amp hour Capacity / 10 = max charging amps) so I would suggest a 20amp model tracer. 

 

If the panels are 100 watts then its most likely they are 12v panels - so two strings of two series panels to get the voltage up to 24v (sending down 34v). This would be the optimal setup. 

 

You could put them into one string with an mppt controller, sending approx 68v into it, and it will then put out the 24v for the batteries. However if a bird craps on one of the panels, that brings down the performance of the whole string. 

 

So by keeping the panels in pairs, a crap on one panel wont affect all four panels - only the two panels in that string. 

Some newer panels have bypass diodes to help avoid the effects of a partial shade but personally I find once you have them a string of the right voltage, your best to run them in parallel. Longer strings of higher voltage are only really helpful on larger systems - but a small sub 800w micro system with short cables its not enough benefit to worry about. 

 

Something that you will find helpful is that when using the Tracer controllers, if you expand your solar panels to say 8x 100watts then you can have a theoretical 33amps at 24v of capability but the Tracer controller will still self limit its flow to 20 amps very safely. The benefit of doing this is on a rainy day you can extract more from the sun without the risk of overloading your batteries on a sunny day by charging too quickly. 

Make sure all panels are the exact same specifications, otherwise you need a second controller in parallel. 
The tracer series are designed to detect each other and will work when connected in parallel without any fancy data cables etc. But at the moment you are approaching the maximum charge rate at 400 watts so you would be best to increase your battery capacity before increasing your maximum charging amps or going above a single 20a controller. 

 

 

 

Your current panels assuming they are 12v 100w (17VoC 5.88A) would mean you are sending in 34v at 5.88A when you put two in series. 
A pwm controller will remove 10V when they are dropped to the battery voltage which equates to 58 watts.
So for 400 watts of panels, you are only getting approx 284watts max out of them simply because they are hooked up to a PWM controller (74% efficient) 
If you connect them to an MPPT controller it would get closer to 380 watts (90-95% efficient). 
And you will really notice much more performance out of them on an overcast day. On a rainy day, every watt counts so getting an extra 15% out of them makes more of a difference and if the sun comes out for an hour you get to make the most of it. 

 

 

 

So yeah EPSolar Tracer A series is what i recommend. They have a wifi / bluetooth module and a RS482 interface (using an RJ45 plug) which you can extract 

 

 

 

Tracer 2210AN is the one i recommend. 





Ray Taylor
Taylor Broadband (rural hawkes bay)
www.ruralkiwi.com

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For my general guide to extending your wireless network Click Here






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  # 2254150 8-Jun-2019 08:40
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Thanks very much, got some more homework to do now 😀


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