Help needed choosing MPPT charge controller

[Sverige]

I’m hoping some of you can help me find a good candidate to match my needs, which I would list as follows:

- Affordable 40A MPPT charge controller (under $200)
- Can handle my array of 2 x 160W poly panels in parallel (18.1 Vmp). Partially shaded location, hence parallel connections
- Can charge 4S LiFePO4 100Ah prismatic cells via Daly Smart BMS 80A
- Wifi connected with iOS mobile app allowing remote viewing of charge current, logging and graphing of daily power generated and consumed Wh or KWh on monthly charts

At present my attention has been focussed on the Wipanda.com eSmart3 plus iCloud expansion box and “Mygreen” solar app. This device is quite affordable at around €139 here in Europe.

My concern is whether this app will run on the latest iOS versions (some comments online that on iOS 13 and above it cannot connect to the charge controller). Also whether the eSmart 3 can handle 2 panels in parallel at 12V nominal. Finally if the controller will allow programming of charging voltages to suit LiFePO4 4S.

Since I don’t know much about which mppt controllers are available, I thought I’d ask for recommendations.

Edit: corrected panel spec from Voc to Vmp

 

[gnubie]

18 Voc suggests Vmp around 15V. Please post your panel's specs, label on the back or link to same information on a web page. Voltages that low are no good for MPPT charging a 4S lifepo4 battery. PWM would be a better choice if you must connect the panels in parallel.

A boost MPPT charger would not be an option either as it will not be able to fully control charging voltage.

 

[Sverige]

Thanks @gnubie. The panel specs are as follows. I’ll have two of these running in parallel. I was in fact wrong about the Voc as I’d got that mixed up with the Vmp!

rated power (Pmax): 160 W,
max. Voltage (Vmp): 18.1 V,
max. Current (Imp): 8.85A
Open circuit voltage (Voc): 22.32V
Short circuit current (Isc): 9.56A
Max. System Voltage: 1000VDC
Operating Temperature : -45 °C to + 85 °C
Dimensions: 1460 x 664 x 35 mm – Weight: 12 kg.

 

[gnubie]

OK, the Vmp is just doable but you will need to use a Victron or better. The epevers and other cheaper controllers all have too high a voltage difference requirement to be able to keep the panels at Vmp sucessfully. Some of them won't even go into MPPT mode with voltages as low as this instead staying in a pseudo-PWM mode.

Even Victron will be at the limits in terms of voltage. Victron needs 5V over to commence charging, so you get away with it there with 22.32V Voc and 1V over to continue charging and again you just scrape in with 18.1V. As your panels heat up their Voc and Vmp drop usually at a rate of 0.5% / degree C for poly panels, but check yours for their derate. If your cells go to 47C in the sun your Vmp falls to around 16.3V. Fully charged your lifepo4 will be around 14.2V so you can see you are only just squeaking it in with 2.1V difference. If your poly panels have a worse derate than 0.5% that will drop further. Technically it is possible for a MPPT controller to work on the wrong side of the IV curve but power drops off really fast doing that so it's something you want to avoid.

I don't advise doing this with MPPT as you are just too close to the line.

 

[Sverige]

Thanks @gnubie, these are issues I was not aware of, and I see it is marginal at best. Made worse no doubt by the somewhat long cable run I have from my panel location to controller and batteries, so some volt drop should be expected.

Perhaps I should stick with the cheap 20A PWM controller I’ve been using to date, although I’m not sure how nicely this will behave with a 4S LiFePO4 pack. Added to which, the current from my two panels in parallel will push over the 20A rating on the device. Not advisable then.

Maybe I need to look again at the mounting positions to see if I can arrange them so the shade hits both panels at the same time (and more importantly both would then be in sun at the same time), then I could series connect them and use an mppt controller as previously planned.

 

[SolarQueen]

I suggest looking into a quality PWM charge controller, like the Morningstar PS-30. With some accessories, you can also get remote access. I honestly believe, with some exceptions, that you don't truly get the full benefits of MPPT payback until your array is around 400-500W. For your 2 small panels, already in parallel, PWM would be perfect.

 

[Sverige]

I suggest looking into a quality PWM charge controller, like the Morningstar PS-30. With some accessories, you can also get remote access. I honestly believe, with some exceptions, that you don't truly get the full benefits of MPPT payback until your array is around 400-500W. For your 2 small panels, already in parallel, PWM would be perfect.

Thanks @SolarQueen, I will investigate this! I’m currently running just one of the 160W panels via a cheap generic “allpowers” 20A PWM controller, and it seems to work ok. A second panel is en route from the supplier.

Here in Sweden at nearly 60 degrees latitude we get fantastic long, sunny days in summer, but now we are heading into winter where the reverse is true. So short days and often cloudy. I was thinking MPPT might help salvage more power during this coming season during the overcast conditions, but if there are solid reasons to stick with PWM then I will do so.

 

[SolarQueen]

I guarantee you this will spark all sorts of controversy, but manufacturers have said they've even seen some of their small PWM outperform their MPPT with small systems. MPPT controllers do a lot more than PWM, and as such, use more energy doing it. So while you may harness more energy from the panels, you will also use more doing so. The question is when do they even out.

I have on my short list of videos to make is having a duel, same array, same brand (probably Morningstar), same battery, PWM vs. MPPT. I hope to get everything I need together in the next couple of weeks. I'm excited to see the results myself.

 

[Sverige]

That sounds like an interesting experiment - I’ll look out for the video. Thanks for your advice!

 

[Sverige]

I checked the manual on my cheapie 20A PWM controller and although it has a profile intended for 4S LiFePO4 (“B03”) I was dismayed to see the absorb voltage is 14.6V and not adjustable. I think this is going to be too high, and using the BMS to disconnect the battery at a lower voltage will not work as that will just turn off the charge controller which will disconnect my loads.

So one way or another I need to find a controller which will work with my panels and also allow safe charging of 4S LiFePO4. I will look for PWM controllers based on advice above.

 

[gnubie]

Most PWM chargers on ebay, ali*, amazon etc are the same boards in different boxes. If you find one you like, post it here and someone will tell you if that's likely the case. There are some real alternatives for PWM controllers out there. Check with brands like Renogy, theirs are all OEM'd by someone else but they do actually work. I'm not sure who makes their PWM range.

 

[Sverige]

Thanks @gnubie, I’m hunting around right now, seeing what I can find on vendor sites. The morningstar model mentioned by @SolarQueen above is simply beyond my budget, unfortunately.

I did think the epever gomate looked promising as it has an “ebox“ wifi accessory which supports a mobile app, but the reviews in the iOS App Store are damning, and it seems the app simply doesn’t work on the latest iOS versions (13+). The cheaper Epever viewstar range doesn’t appear to support lithium batteries, so that’s out.

I’ll have a look at Renogy. It’s a slow process as I don’t know the product range of any of these manufacturers, and finding the necessary product details on each one takes some digging through manuals when the vendors don’t make the functionality clear on their website. But it’s a fun process and I’m learning, so that’s good!

I may have to compromise on my desire for a mobile app and just get a charge controller with display. Then I suppose the potential options increase.

 

[Sverige]

Ok, this Renogy Wanderer 30 Li looks interesting. Only 30A of course, and I previously said I wanted 40A, but with two 160W panels in parallel, maybe 30A will suffice? There is a plug in Bluetooth module and iOS app “Renogy BT”.

Wanderer Li 30A PWM Charge Controller

The Renogy Wanderer-Li is a 30A PWM solar charge controller that incorporates efficient PWM crediting boost battery life and improving system performance.

www.renogy.com

The price point looks appealing and it says it will charge lithium batteries, but I need to investigate that further to find out if absorb voltage is adjustable and what the default is.

 

[gnubie]

With PWM there's no voltage conversion so current in = current out. Your two panels in parallel give a maximum of ~19A. 30A will cover you.

19A x 12V = 228W. As your battery voltage rises power goes up, so at full charge 14.2 (?) that means about 270W.

 

[Sverige]

Thanks @gnubie. So now I’m seriously interested in the Renogy Wanderer 30 Li. The manual is at this link...

https://www.renogy.com/template/files/Manuals/Wanderer%20Li%20%281%29.pdf

... and my reading of this final page from the manual is that the default absorb charge voltage on lithium setting is 14.2V and all charging parameters are user definable via their iOS app Renogy BT with the use of the optional Bluetooth module.



I’m having a hard time finding fault with this unit at the modest price point of around €35 plus another €25 for the Bluetooth module. Someone please stop me if I’m making a mistake, but I think I might order it!

 

[SolarQueen]

The charge controller is arguably the most important part of your system to keep your expensive battery bank healthy. Why pay top money for the batteries, then risk their health with a cheap controller? The Morningstar PWM is under the price you were willing to pay for an MPPT. Why is it now too expensive? No offense meant at all, but the phrase penny wise, pound foolish comes to mind.

 

[Sverige]

The charge controller is arguably the most important part of your system to keep your expensive battery bank healthy. Why pay top money for the batteries, then risk their health with a cheap controller? The Morningstar PWM is under the price you were willing to pay for an MPPT. Why is it now too expensive? No offense meant at all, but the phrase penny wise, pound foolish comes to mind.

I’m certainly prepared to consider it. I must admit I looked at your website and couldn’t find the expansion module which I believe will be needed to enable mobile app control and monitoring, so my view that the Morningstar gear will be over my budget is an assumption on my part, which is not the best way to take any decision.

How much will a PS-30 with the expansion module which allows iOS mobile app (EMC-1 I think?) cost, with shipping and taxes to Sweden?

Also, is there a reason you think the cheaper Renogy is likely to be a risk to the health of my batteries, or is it just an assumption?

 

[SolarQueen]

I’m certainly prepared to consider it. I must admit I looked at your website and couldn’t find the expansion module which I believe will be needed to enable mobile app control and monitoring, so my view that the Morningstar gear will be over my budget is an assumption on my part, which is not the best way to take any decision.

How much will a PS-30 with the expansion module which allows iOS mobile app (EMC-1 I think?) cost, with shipping and taxes to Sweden?

Also, is there a reason you think the cheaper Renogy is likely to be a risk to the health of my batteries, or is it just an assumption?

I think I came off as harsher than I meant to. Renogy is a known brand, and better than the cheap junk out there. Morningstar doesn't have an app, their remote access is PC based, so Renogy may be the right thing for you. My comment was more targeted to the cheap stuff.

 

[JoeHam]

I think I came off as harsher than I meant to. Renogy is a known brand, and better than the cheap junk out there. Morningstar doesn't have an app, their remote access is PC based, so Renogy may be the right thing for you. My comment was more targeted to the cheap stuff.

Wow!

Take another look around the forum if you think that was harsh ?

 

[fat_old_sun]

I have on my short list of videos to make is having a duel, same array, same brand (probably Morningstar), same battery, PWM vs. MPPT. I hope to get everything I need together in the next couple of weeks. I'm excited to see the results myself.

Good Idea! May I suggest comparing the two types at midpoints of their ratings & at their max end? So, at 15 Amps/35-40 V input (two 100W panels in series), as well as 30 Amps & 4 panels in series for the MPPT?