40amp Solar Charge Controller mppt 12V 24V AUTO Solar Regulator w/LCD Display for Lead-Acid Lithium, Input 60~960W 100V Solar Power MPPT 40a Charger

6 month update: It's still working perfectly and my batteries are in great shape. I would definitely recommend this one over the others that I have tried.I have 48v 12s batteries and attempting to find a unit that can handle this is difficult. Most of the units that charge "48v" don't actually charge or have a way of charging 48v but instead are for 13s 52v batteries and with no option to set it up for a 12s battery. This one can do it but it's a little confusing as to how to make it work with a 12s battery or to change the parameters of the user settings for more than a 12v system but it does have the ability to do it. If you are running a 48v system you have to set the user settings for 1/4 of what you want the parameters to be, same goes for a 36v system but 1/3 and a 24v system 1/2. I don't know why they didn't just go the extra mile and let you input the numbers that you want instead of having to do a conversion between 12v and what you system really is but what can I say, I'm not in charge of systems design. Either way, it works. I had to divide all of my settings by 4 and enter them into the user setup and everything was fine. All of the other types of batteries are presets that you just select unless of course you want to keep your battery charged at 80% to extend its life like I do. Then it's off to the user settings. However, they give you all of the parameters for each battery type so you can set it up like they do but at lower numbers so that you can limit your charge if you want to. So far, this thing is perfect but I will do another review in a few months to let you know how it's going. I am expecting good things and for now, it's 5 stars.

I'm happy with the way this 20 amp solar charge controller works, but should have paid more attention to the power rating shown in the Amazon ad. The current and voltage rating seem to indicate it could handle all four of my 100 watt, 5 amp, Renogy solar panels. It's rated higher if charging 24 volts of battery, but my inverter is for 12 volts, so I can't just put the batteries in series.I can get by using the PWM charge controller built into my 2200 watt Giandel inverter for two of the solar panels, but wish I'd paid a little more for a more capable controller. In fact, if I ever upgrade I'll probably get the old style 60 watt PowMr controller. A YouTube video mentions that their new version has a connection for a fan on its motherboard, but no fan. The old version, with a metal housing, has a fan.Edit: Note, when comparing solar controllers, be aware that the amp rating is for amps OUT. My mistake was thinking it was amps IN from the solar panels. Even in parallel, my four 100 watt panels should produce just 20 amps INTO the charge controller, but the voltage IN is greater than the voltage OUT, so it overheated and shut down (luckily it works again, after cooling off). Note: to find the amp rating you need, for this or other charge controllers, just divide the total watts of your solar panels (400 in my case) by the nominal battery voltage (12 in my case) to get the rated amps you need (33.3 in my case).Edit 2: At a later date, the price of my 20 amp controller went up so high that the 30 amp model wassignificantly less, so compare prices before ordering. Wish I had that 30 amp model.Edit 3: I have now purchased two more 100 watt solar panels, plus the 60 watt controller I mention above, and couldn't be happier.

So, I bought this a little bit over a year ago. I used this only once on a 2 day trip. Seemed to work just fine then. Second time using it and before my trip, decided to ensure everything is in working order. I switched on the solar panels and the charge controller started up nicely. Was charging my LiFePo4 batteries on the right setting and everything as it did before. The batteries are working and running the controller for 1 day and over night, the charge controller was not charging. It was giving me a nighttime mode symbol on the top left of the screen as if the panels were not producing any power. This was happening all day long. My batteries were dying and the controller was not charging. I decided to disconnect everything and place it directly onto just my panels. My panels were producing 18.6 volts. No problem with them. When i reconnected the panels, the controller turned back on, showed like 14 volts, believe its the voltage its producing for the batteries, but the batteries are not connected, and after about 10 seconds, the controller screen turns off and can see the volts dropping as its turning off. the panels were still producing 18 volts with no fluctuation as i had my multi meter connected to them. The controller, after about 30 seconds, turned back on again. This kept happening over and over. Off then on, then off, then on. I tested the battery output and when it turned off, the battery output produced around 1 to 2 volts when it turned off and back to 14 ish. I am not sure what happened, but after only using it once, twice if you count me testing, it became clear I should invest in a more expensive charge controller in which instructions are clear and the device is not poorly made. Since this is most likely out of warranty, I decided to open up the controller. One HUGE major flaw that the manufacturer should have never done is place a metal plate directly behind all of the terminals where you insert the striped wires in at. It is just one long plate. There is no insulation or barrier to prevent the terminals from shorting each other. Its possible some wires may have moved or became loose and had touched the plate, but am not entirely sure. My stripping is not that long, but is possible due to the manufacturing error. Anyways, I am buying a new charge controller, but not his one again.i plan on testing some components within the controller and maybe replace them if needed as it seems to work, but continuously cycles its power on and off. Worked great for two days, but can't do much about design flaw since the manufacturer decided its best to short the terminals if wires are more than 1/4" striped.

Tried multiple ways of connection always following instructions and never got a fair amount of power for my four one hundred amp hour batteries they would appear to charge and loose thirty percent overnight with no load involved bought a lower price unit and it works great and recharges all my batteries to full daily note I have four hundred watt of solar panels.