I want to share inside look at cheap Chinese solar charge controller CMTP02 (CMTP-02). I have a 30A (charging current) variant, but it has also 5A, 10A, 15A, 20A versions. It should be a PWM controller. Maybe even not that (like Didier pointed out in the comments section). I have not learned all the terminology regarding solar controllers and how to identify their type. But one thing is sure- MPPT should have DC to DC converter inside it (am I right?).
Some eBay users sometimes put MPPT int the title – but it’s misleading. It’s not that kind of charger. I thought also that it is but was bit disappointed (didn’t do my homework before buying it). Well- the price should ring bells if nothing else does. Anyway- I hope this post helps other people to choose their controller when stumbled upon this cheap charger. And get some inside info before considering to buy it.
Please note this post is written in the year 2014 and it’s possibly not that accurate anymore. They probably have changed their design also by now. But the basic concept is most likely the same. I If anyone can confirm please feel free to comment.
There is also pictures of 5-ampere version posted by Didier. You can look at them here. Also one user manual (10A version I suppose). It uses irfb3206 mosfets to do the heavy lifting as seen on photos.
How CMTP02 works?
If you are looking how this charger actually works you are in luck. Alan reverse engineered a 20A variant’s circuit and operation. You can read more info from his comment below from his website.
What is inside of CMTP02
Well, check out these photos. I just opened it up and made some shots to overview it’s content.
CMTP02 30A Solar charger controller backside opened
Here you can see that mosfets are heatsinked to the backside (but not firmly). Just little contact with pressure. Someone who has used it with higher loads can comment- is it enough and how well it works.
CMTP02 30A Solar charger controller top view
CMTP02 30A Solar charger controller frontside
CMTP02 30A Solar charger controller main board, chema, circuit, front
A closer look at chips on board. Probably controlling? I didn’t look up their datasheets.
Mosfet irfb3206 closer look
Here we can see what kind of mosfets are used to drive current. All three was the same (if I remember correctly)
And finally- picture of manual. Just in case.
CMTP02 Solar charger controller user guide manual