SUNNYSKY Solar MPPT Solar Charge Controller 12V/24V/48V 60A Solar Charge Controller for Lithium Battery and Lead-Acid Batteries with Intelligent LCD Display

I strongly recommend this machine. I tried the "sunnysky" chargers, plural, off ebay, same as the "powermr," the cheap little $100 ones in the aluminum case. They technically work but they are so incredibly delicate that I roasted two of them despite being as careful as possible. The first one was roasted when I connected a battery charger to my BANK, I think 5 at that time, lead acid batteries. The tiny amount of ac coming from the charger, and I don't think it was a lot, demolished the solar controller.This device, by comparison, is so much better built, gigantic toroidal chokes, monstrous relays. The connectors for the wires are pleasantly large. I am using multiple smaller cables, but I'd estimate you could fit one cable of up to roughly 2 gauge or so.The features on this machine are killer. The power tracking graph is a feature I will never be able to live without. No computer required. I suspect I'll be able to tell the difference between shading and cloud cover just buy looking at the graph. I can do sooooo much more accurate math knowing exactly how many kilowatt hours have been collected.This machine does everything I could have ever wanted.One thing you should know is the voltage meter on mine was not the most accurate. It reads about 0.20 volts below actual, roughly. This is not an issue because you can compensate for that in the voltage parameter settings. If you want 14.4 charge, set the machine for 14.2. Don't let that bother you, this machine is the best solution for your project at the price. You won't find a cheaper controller that is half as effective. Even more expensive machines require a computer hookup. This controller offers a computer hookup, but it is not required to view graphs.So far my sole criticism is simply that at dawn and dusk, when stating up or cutting out, the relay clicks a handful of times instead of once before staying on or off. This may be my fault for mixing poly- and mono- crystalline panels. The relay clicks slowly and I doubt it will affect the life of this machine. Just less satisfying a noise than a single click.

UPDATE:11/27/20 2 years later and Its still going strong every day without issue. Still Highly recommend.Awesome charge controller. I have been using this charge controller for over 2 months with Lithium Ion batteries now and love it. All terminals are large and make excellent connection I purchased the 60 Amp version. I have 6 310 watt panels and 230 amp hours 7S 100P 18650 28.7 volt lithium ion batteries hooked up to it and it charges them like a dream and stays cool while doing so. The fact I can program all the charge parameters without the need for a computer is simply awesome. The manual is pretty clear and easy to understand even though I think its simple enough to understand by just playing with the menus on the unit itself. The fan kicks on at just under 20 amps and stays on until the current falls below 19 amps. My favorite feature is being able to limit the current output to whatever I want while charging, this can be crucial with lithium ion batteries as you don't want to charge them above a certain C rating. I haven't used the power output side of this unit and can't say anything about it other than it does put out voltage. The whole unit is sturdy and well put together. I will be buying more in the future.

Update 2/26/21: I have used these for two years now- I have not had any down time during that two year period, and no faults to the units. Again as I mentioned below I never "run these to the max", and being smart (and correct) about their usage is a better way to ensure long life of a product. It is very easy to mis-wire or make a mistake in your solar setup, so it hard to know if the controller or other issues are to blame.I have gotten smarter since my initial review, and I now have a better sense of how the charging function works on these controllers. No, it is not a "three stage" charger. Really what it is is a Current-Limited Constant Voltage charger. Which, this is a perfectly appropriate charging method for most lead acid batteries. I will try to explain but better to find an article on it. Basically the charger tries to provide a constant charging voltage (settable). When the battery is discharged the current demand is past the limit and the voltage will droop accordingly. As the battery gets more charged and its resistance goes up the current demand goes down, and the voltage increases to the setpoint. At the end you approach a float/trickle as the current decreases and the voltages equalize. For me, I am perfectly OK with this charging schema.I have two of these units now, running in parallel from two solar panel arrays into one battery bank. I can vouch for their ability to pass the rated current (60A) and so far they have held up fine with no problems. To me the settings and menu system are pretty straightforward, the manual is hardly needed. I am content and happy with the money spent.The only reason I give 4 stars as others have noted is that it is basically a constant voltage charger and is does not do multi-stage charging. For my use, under constant load and daily use cycling of sun during day, running off batteries at night, I am not sure that you would truly ever realize multi-stage charging even if the unit had the capability. Hence the decision to add a second unit after I had experienced the first one and realized that it did not offer multi-stage charging. I guess it was good enough to buy another! Hah. Anyway I am happy with the reliability and robustness so far, and that means a lot when most of the products are "unknowns" as to what you will get in terms of real current handling capability. As with any electronics, don't expect to misuse and run them at the breaking point continually. I am hopeful that by using this unit conservatively it will hold up for a couple years.