implement 20W 12V solar MPPT tracker - Page 1
Forum section: electronics / projects

author: reyntjensm
author_rank: Regular Contributor
timestamp: January 22, 2025, 10:31:02 pm
content: I'm working on a project powered by a 12V solar panel. My application needs about 10W to work and is powered by a 12V sealed lead acid battery.The easiest way would be to just buy an off the shelf MPPT tracker and install it in the same cabinet.Just to keep everything nice and tidy i would like to implement this MPPT tracker onto my own PCB.A ready made MPPT module (just the PCB) would be perfect but i can't find any suitable products. Any suggestions?Another option would be to design my own MPPT.Is this worth the effort? Could somebody point me to a good application guide for this?

author: thm_w
author_rank: Super Contributor
timestamp: January 22, 2025, 11:20:51 pm
content: You can google "MPPT module", and find some small boards that will work.Or you can search for MPPT ICs and design them in yourself:https://www.lcsc.com/product-detail/battery-management_shanghai-consonance-elec-cn3791_C154992.html

author: globoy
author_rank: Frequent Contributor
timestamp: January 22, 2025, 11:33:16 pm
content: At the risk of tooting my own horn on here, I made one that is for sale on tindie (I don't make much money on it, I mainly wanted to share). It works quite well (there are a lot of them out there).https://www.tindie.com/products/globoy/mppt-solar-charger-for-intelligent-devices/And it's open source if you want to take its ideas and make your ownhttps://github.com/danjulio/MPPT-Solar-Chargerat the very minimum read the manual appendix on how to size your panel and battery for your application. The thing I've noticed about people just getting into solar powering some gadget is that they almost always underestimate what they'll need.

author: reyntjensm
author_rank: Regular Contributor
timestamp: January 22, 2025, 11:36:17 pm
content: Quote from: thm_w on January 22, 2025, 11:20:51 pmMost "mppt module" i find online is only for Li-ion cells. Couldn't find any module for 12V battery.I already came across the CN3791 chip. Sadly enough this is only sold by Chinese resellers, i would prefer to buy genuine parts from trustworthy suppliers.The datasheet is written in Chinese....

author: thm_w
author_rank: Super Contributor
timestamp: January 22, 2025, 11:41:28 pm
content: Quote from: reyntjensm on January 22, 2025, 11:36:17 pmLCSC is a reputable supplier. Datasheet can be easily translated.There are MPPT IC's from western brands of course, but you'll pay more:https://www.analog.com/en/products/lt8490.html

author: MF-jockey
author_rank: Regular Contributor
timestamp: May 01, 2025, 04:49:18 pm
content: For small projects, this adjustable module can be used:https://de.aliexpress.com/item/1005008778407163.html

author: mikerj
author_rank: Super Contributor
timestamp: May 01, 2025, 07:13:54 pm
content: MPPT seems overkill for a 10W application unless you are constrained for size on the panel. A larger panel would be a better investment if practical.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: May 01, 2025, 11:46:54 pm
content: Quote from: reyntjensm on January 22, 2025, 10:31:02 pmYou could buy and test something like this ?https://www.aliexpress.com/item/1005008585183995.html

author: brucehoult
author_rank: Super Contributor
timestamp: May 02, 2025, 05:33:08 am
content: Quote from: globoy on January 22, 2025, 11:33:16 pmOh this is very cool!I couldn't find a BoM but I found the schematic. I'm a programmer not an electronics designer but I'm happy to see there is no black box part there specifically designed as "an MPPT" but just a couple of amplifiers for the current sense voltage drop across a 5 mOhm resistor fed (along with a voltage divider) to ADCs on a good old 8051, and a buck converter PWM'd by the 8051.I could read the C code of course (and glanced at it) but that would be actual work so maybe you can answer a couple of questions :-)- what percentage do you change the PWM duty ratio by to ensure a meaningful change in VS and IS?- how long do you need to let the system settle in the new state?- I assume you start at 0% duty cycle to measure the Voc?- how many iterations / how much time to find the initial optimum? (ok, I can derive that from the previous answers :-) )- how long to find the new optimum when a lovely fluffy cumulus cloud rudely gets in the way? (or moves on)I'm actually quite interested in experimenting with an open source and reprogrammable unit like yours.I'm just starting to dip my toe into the solar waters and bought a cheap Temu kit (my only Temu purchase ever) with 20x 20W flexible panels (which handily have a USB port on the back of the panel, and one charged my iPhone in about an hour with nothing but one panel and a USB to lightning cable). I'm planning to use this to keep my motorcycle battery charged. I used to use a BMW battery tender but my vehicles currently live in a farm shed some distance from the house, with no electricity. The Temu klt came with a small PWM solar controller which I see all over the net under various brand names (e.g.). According to the manual it probably does a pretty good job on the battery bulk charging, absorption, float stuff side, but the basic PWM isn't going to get max efficiency from the solar panel. Which isn't going to matter. The motorcycle has a 19 Ah 12V battery (which I'll probably replace with LiFePO4 next time it needs replacing) and it will typically have more than a week available to charge the battery so even your board's 2A output limit is fine. The problem is just that I don't use it enough (or for long enough each time) to recover from a cold start of an 1100cc twin with 10.7:1 compression ratio.