Solar charge controllers come in 2 types. The least expensive and argueably the most common is the PWM type. PWM stands for Pulse Width Modulation, and is usually used in lower power systems. 1 panel, and a small tractor battery running a gate, for example is a great application for PWM, as the controller, battery and solar panel all have to match in voltages. The other type is MPPT or Maximum Power Point Tracking. The way these controllers work is to collect a higher voltage from the panel. The panel may be rated for 19 volts, at 5 amps. The controller will take the 19 volts, lower it to 14.5 volts needed to charge the battery, but raise the AMPS to 8 or 9! Where as the PWM controller will never go above the rated 5 amps and the extra voltage is lost.
You might think then, that only a MPPT controller is what you want, and, for a large system that is used a lot I would agree, but, PWM does have some advantages. For example, it has been documented that PWM controllers will help with battery sulfation (the buildup of sulfate crystals on the lead plates of batteries). This is a HUGE advantage in that a sulfated battery will only hold a fraction of it’s normal charge. MPPT controllers (usually) have an equalize function that deals with sulfation by taking the batteries to a high voltage (15.6 volts for a 12v battery is a common setting) for several hours. The debate on which is better is ongoing, and the data on how well each of these work is not really clear..
Tracer 20 amp MPPT Controller
The setup I have this controller in these days is connected to 2 260 watt panels and 2 200 amp hour batteries in a 24 volt configuration. This provides a great backup system for running small loads, testing inverters, and long term battery recovery. It is one of my oldest controllers (I got it about 2014) and it has seen heavy use with no problems at all. I opted for the meter too and it allows programming and best of all, display of volts and amps coming in. The only tiny gripe I can think of is that the backlight does not stay on all the time but i know that is a feature and most will prefer that.
All in all, for the money, I would highly recommend this unit, although if I had it to do over, I might have went for the 30 amp version, but at the time, I assumed for the price it would not last this long, but with it’s over volt / amp protection, easy set up, and ruggedness, if I ever need a small MPPT controller, I would sure buy this brand again.
∙ Cost; For an MPPT controller of this size
∙ Reliable; It has been used for 3 years and still works fine!
∙ Simple setup
∙ The meter is sold separately (usually)
You can get one from Amazon at the link below.
Midnite Solar Classic 150
This is by far my favorite controller for several reasons. The best thing about this controller is not all of it’s features and reliability (more on these later), but the company that makes it. The story goes, in my case, like this: I bought my classic from a local dealer in Mesa, AZ. (Penny Solar) and the cost was, with shipping added, about the same as Amazon (A few bucks more but I got it that day). I brought it to the farm, and hooked it up. This is usually where a problem happens but my install went fine and the midnite worked flawlessly for 3-4 days. Then one morning, I go out and it is showing 0 volts from the panels. After checking everything I contacted Midnite Solar’s tech support. He walked mt thru a couple steps and knew exactly what the problem was. I explained that the system was, at that time, my only source of power! He verified a few things and sent a call tag AND a NEW unit THAT day, even though it was getting late in the day. After they got the unit back, they told me that it had an over voltage on the inputs and that usually there was a charge for a new board (About $300), but that they were going to waive the fee for me as we could not figure out HOW a 100 volt array sent in more than 150 volts. It is THIS kind of service and customer care that makes the unit WELL worth the $650. The fact that it really IS a good and reliable controller is almost a bonus.
The new unit has been in service for 8 months now and has had zero issues. So, on with the hardware part of the review. As for build quality, they use pretty top shelf parts. The body is all aluminum with 4 screws that hold on the face plate. The internals (from what is visible) are not cheap knock offs. The board under the face plate is well laid out and very well labeled with heavy duty plastic screw covers to prevent shorts. Installing the classic is super easy with the included hardware which includes the controller, a cat5 network cable, screws, battery temperature monitor and a couple of cool decal stickers.
After installing the classic, you can configure it in 2 ways. The LCD display on the front panel looks intimidating, but is actually pretty easy to navigate and is well thought out. The display shows you everything that is important to someone on a solar system.
One of the best parts of the classic, is that it can be monitored AND controlled over standard ethernet. The (free) software is downloadable from the midnite solar web site and has a cool gauge meter look. The gauges show (in real time) what is coming in from the array, as well as the state of the battery bank.
From here, you can go into settings and change EVERY aspect of the classic, right from you’re desktop! This is all included out of the box with no special modules to buy.
Right now, I have 2 strings of 3 260 watt 30 volt panels connected to it. This puts 75 amps into the battery bank in good sun, and will adjust from bulk to float charge and is set up to equalize every 30 days. The exact voltages can be set up with respect to the battery manufacturer specs down to a .1 volt resolution. This makes the classic compatible with almost any type and configuration of battery bank including Gel, AGM, and of course flooded lead acid.
The classic is also configurable for WIND and HYDRO power systems, and although I have not tested these, I have read they work great in both cases. In my humble opinion, for the money, I cannot imagine buying any other controller. I do not have any experience with the Outback Flex series, and I have read they are about the same quality and price. (If I can get my hands on one I will review it). So in summary:
∙ Over the top customer service
∙ Reliable with long track record for quality
∙ Good features without being over complicated
∙ I see no downside to this device. If you know of one post in the forums!
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