Affordable MPPT Charge Controller

[travellerw]

WARNING - HIGH RES IMAGES.

I wanted to share an affordable (yes chinese) charge controller I found. I picked this controller (20A version) up with the optional control panel for $155USD on Aliexpress.com. You can buy the controller without the control panel for $125. A computer can be used to control all the settings if you don't order the control panel.

FIRST - I will say, I have not mounted it on a boat, so I have no experience in the marine environment.

This particular controller is made by EPSolar, which has made some so-so controllers in the past. This one is a complete redesign from the ground up. Here is a link to the manufactures site with specs (there is a 10A, 20A, 30A and 40A version).
Tracer****BN-Products-solar charge controller—Beijing Epsolar Technology Co., Ltd

So before I even plugged it in, I cracked it open to look that the build quality and design. Here is what I found:

1. A nice double sided board that is properly screwed down to provide good contact for the MOSFETS to the chassis (for cooling). Notice the beautiful potting on the coils. The red wires are silicone based and very flexible. Finally, you can't see it well in the image, but the entire board is conformal coated (protected from moisture). They actually went the extra mile on this controller.


2. After unscrewing the board and flipping it over, I found the MOSFETS positioned nicely and covered in thermal paste, with more paste on the chassis (excellent). Take notice of the nice solid screw terminals.


3. Of course the thing I was most interested in were the CAPs since these are BY FAR the most common failure in Chinese electronics. Imagine my surprise when I found quality brand name CAPS (United Chemi-Con and Jamicon).


Alright... I can't do much functional testing as I don't have access to a high output PV array. You can find a nice video about the functions on youtube. This Aussi does a great job and there are 3 parts to the video.

https://www.youtube.com/watch?v=dFuZ...ADmvmJEAbbzX1Q

However, I put it back together and fired it up on a test rig (small gel cell and a bench power supply emulating the PV cells). I played around with the control panel, but found it a little confusing and lacking. So instead I plugged in the USB - RS485 cable ($4 option) and installed the Windows based software. Although the software is very simple and basic, it gave access to all the features and settings.. INCLUDING USER SETTABLE CHARGE VOLTAGES.. This controller should be capable of safely charging LiFePO 4 battery banks. Here are a couple of screen shots.





Frankly... I think this controller might be a winner... Anyone care to buy one and test it on a boat.

[travellerw]

Just a quick update...

I tested how much power this controller actually draws while running. It draws about 0.04A at 13.50V, so about 1/2 a watt.

I'm pretty sure any controller on the market draws under 5W which is negligible, but I was curious.

[whiskthecat]

If you haven't already mounted this unit out of the way perhaps you could tell me some of the IC model numbers they are using out of curiosity. Particularly the Mosfets, the quad flat pack I assume to be an MCU, and the SOIC's I assume to be gate drivers.

About how hot does the unit get? It seems like an excessive amount of heatsinking considering how low resistance modern mosfets are. It would also be great to know the switching frequency if you have an oscilloscope on hand.

The number of mosfets is also somewhat puzzling. It appears to be single phase so you should only need 2 for switching. Maybe some are in parallel or some are for switching the "load" terminal many of these controllers often have. Either way thanks for the review and the youtube link.

[travellerw]

Originally Posted by whiskthecat

If you haven't already mounted this unit out of the way perhaps you could tell me some of the IC model numbers they are using out of curiosity. Particularly the Mosfets, the quad flat pack I assume to be an MCU, and the SOIC's I assume to be gate drivers.

About how hot does the unit get? It seems like an excessive amount of heatsinking considering how low resistance modern mosfets are. It would also be great to know the switching frequency if you have an oscilloscope on hand.

The number of mosfets is also somewhat puzzling. It appears to be single phase so you should only need 2 for switching. Maybe some are in parallel or some are for switching the "load" terminal many of these controllers often have. Either way thanks for the review and the youtube link.

I do have a scope and will try to get you a frequency when I have a moment.

I wasn't too interested in bending the mosfets up so I could read the brand as I plan to use this on my boat and didn't want to damage it. So unfortunately, that will have to remain a mystery.

As to heat, I haven't ran this anywhere near the rated capacity (520W for 24V) and I'm guessing it would get pretty warm at that PF. You also need to consider that these devices are designed for use in tropical environments, usually shoved in some small compartment. Heat build up is a big issue.

I haven't reverse engineered it (not worth my time at $100 retail) so I don't know why they have so many mosfets.

[whiskthecat]

It appears they are using this same enclosure from the 10A all the way to the 60A model. Perhaps that explains some of the heatsinking. It doesn't seem too difficult to keep the total system resistance under 10 milliohm. 1mohm mosfets are common now and that leaves you nearly 10mohm for the inductor. For the 20 amp verion thats only 4 watts; the 60 amp version that's 36watts and the heatsink goes from being overzealous to possibly just adequate. Of course there's nothing stopping you from using components that drastically increase the resistance above 10mohm and therefore the watts needing to be dissipated.

If you've pushed 20 amps into your 12v batteries that should produce as much heat in the unit as pushing 20 amps into 24v batteries. The only heat coming off the heatsink should be (the resistance of the mosfets and inductor times the current)^2

You will likely have a very hard time reading the laser chip markings through the conformal coating. Don't worry about it if it is any trouble. Was just to satisfy my curiosity.

[whiskthecat]

The only heat coming off the heatsink should be (the resistance of the mosfets and inductor times the current)^2

That should have been resistance * (current)^2. Sorry about that. (I^2)*R

[ullar]

Thanks for your review. Looks like a usable device and I'm looking for one like that right now. Got a couple of questions.

I noticed that software shows also battery temperature. Is battery temperature sensor included or is it an option? Or does it just use an ambient temperature?

What's you bottom line about the display? Useless?

Regards,
Ullar

[travellerw]

You need to order a temperature sensor on top of the controller. Its a $7 item and plugs into the controller. You then attach it to the battery. This controller has also dropped in price and can be had on AliExpress for $97 now (without display).

Sigh.. I'm not sure what to say about the display. Once you get used to it, its convienient, just not super user friendly. However, It does save you from having to plug your laptop or tablet in everytime you need to look at the data. I'm glad I have it when I want to quickly look at some data.

[ullar]

Thanks for your comments. Just ordered controller, display and temperature sensor. Will install them as soon as they arrive. Word of caution about the temperature sensor. It looks to be generic type of quite stupid cylindrical construction. It would have been better to have a proper bolt on type.

[DeepFrz]

I don't think that is an MPPT controller. If it is where is the transformer?

[ullar]

According to OP the electronics looks OK, so, I'm more worried about software here. Anyways, would be interesting to test it.

[whiskthecat]

The transformer is actually an inductor as there is only one winding. It is encased within that black rubbery looking compound so as to help dissipate the heat coming off of it. As shown in the linked youtube video the unit does work as MPPT, although the software is slightly sketchy in the way that it seeks the maximum power point this probably only causes a minor loss.

[ullar]

Originally Posted by whiskthecat

As shown in the linked youtube video the unit does work as MPPT

Good you confirmed that. I just can't get myself watching those. Get bored during first 10 seconds. (With the exception of the ones featuring beautiful young ladies, of course.)

[socaldmax]

I watched the youtube test of that controller, and frankly, I was very disappointed.

A good MPPT controller should be able to establish MPP within a few seconds - not 4.5 minutes, and it shouldn't get confused at 3 minutes and reboot itself. When he did the towel test (changed the panel output) it took forever for it to track, meaning that as clouds pass overhead, this thing is nearly incapable of maintaining MPP.

There's another 20A Chinese controller that I think is better. I've installed several of them, and I'm very impressed. It has the menu and display built in, and shows PV voltage and watts, in addition to battery voltage and amps. It establishes MPP within a couple of seconds and sweeps every few minutes, very responsive to input power changes. It uses a nice sized toroid and conformal coated PCB, in addition to gold plated contacts.

It sells direct from Eco-Worthy.com for $102 delivered. I have one with 410w of panels installed on it (max rated PV power is 300w for 12v battery, or 600w for 24v battery) but it regulates itself at 22 amps and after a yr of this ,just won't burn up. Another thing I like about it is the charging voltage can be adjusted in .1v increments all the way up to 15.5v if desired.

Here's a youtube video of a guy taking it apart, reviewing it's construction and testing it out on a bench.

https://www.youtube.com/watch?v=3Okm50rgAWg

Another review:

https://www.youtube.com/watch?v=pzZS93i2SRQ

[travellerw]

Originally Posted by socaldmax

I watched the youtube test of that controller, and frankly, I was very disappointed.

A good MPPT controller should be able to establish MPP within a few seconds - not 4.5 minutes, and it shouldn't get confused at 3 minutes and reboot itself. When he did the towel test (changed the panel output) it took forever for it to track, meaning that as clouds pass overhead, this thing is nearly incapable of maintaining MPP.

There's another 20A Chinese controller that I think is better. I've installed several of them, and I'm very impressed. It has the menu and display built in, and shows PV voltage and watts, in addition to battery voltage and amps. It establishes MPP within a couple of seconds and sweeps every few minutes, very responsive to input power changes. It uses a nice sized toroid and conformal coated PCB, in addition to gold plated contacts.

It sells direct from Eco-Worthy.com for $102 delivered. I have one with 410w of panels installed on it (max rated PV power is 300w for 12v battery, or 600w for 24v battery) but it regulates itself at 22 amps and after a yr of this ,just won't burn up. Another thing I like about it is the charging voltage can be adjusted in .1v increments all the way up to 15.5v if desired.

Here's a youtube video of a guy taking it apart, reviewing it's construction and testing it out on a bench.

Yup the software has some bugs, but I fully expect the manufacturer to release a firmware update that will solve most of those problems. Actually I'm running a beta firware that was supplied, I just haven't had time to test it out. That is one of the features of this controller, it is firmware upgradable in the field.

I have watched the ECO-Worthy teardown numerous times and I can assure you, the build and construction of that controller is no where near equal to this one. Since I know people will as why, here are a few examples.
- The screw terminals on the EPSolar controller are much beefier
- The heat disipation design on the EPSolar controller is WAY better (potentially longer life)
- EPSolar is using name brand made in USA or Made in Japan components
- A remote panel allows you to check setting without conforming yourself to some wierd location in the boat.
- Has a temperature probe (although a crappy one)
- Software settable.
- Can support LifePo4 batteries.

Now don't get me wrong.. The ECO-Worthy controller is not crap, but I beleive this one is a better build. Software needs some work, but it will get there.