18650 solar charging setup for 12V strip  lights, help a newbie out - Page 1
Forum section: electronics / beginners

author: TT_Vert
author_rank: Regular Contributor
timestamp: May 21, 2022, 03:40:37 am
content: I enjoy 3D printing and whenever I have an excuse I'll design and print something. Well I had some spare white LEDS from an old illuminated umbrella I made a case/solar panel mount, etc. and used 3P 18650s config using acheap amazon solar charge controllerwhich would also turn the output on/off based on panel current. I also used onecell protection boardand those work great for the 3P setup I was using for that.I then got ambitious and decided to try my hand at a bit larger solar LED project. I used 12V LED tape. All of these lights together draw about 800mA so I decided I'd go w/ a 3S2P setup so my output would see a max of 12.6ish volts and I'd have about 6000mAh of capacity. Well the problem was my panels I was using were at best 5V 500mA. So with my lack of real knowledge I got a boost convertor thinking I could increase the voltage of the solar panel to ~14V to feed the balancing BMS. I used thislithium protection board. The way I have it wired is 5V from solar panel to the Vin of the boost regulator which is set to 19V (The spec for the charge controller board states 16-22Vin) then the output of this boost regulator to the 3S protection board. From that board the Vout goes to the LEDs. Now this did power the leds and the on/off function worked but it didn't appear to be charging. Probably due to the lack of current the solar panel can provide. I was hoping that the solar panel could essentially trickle charge the 18650s but it seems that this protection board needs 12V to initialize the unit. I have over 12V out of the boost convertor but perhaps not enough current, not really sure. Perhaps there is a different/better way I can do this? I had looked at 12V panels but most of them seem quite large which I don't really want to do. Perhaps I go w/ 3V LED strip lights designed to be powered by three AA batteries? Try to go gently on me here, I think I got in a bit over my head but i'm learning lots in the process.ThanksDave

author: TT_Vert
author_rank: Regular Contributor
timestamp: May 24, 2022, 03:15:23 pm
content: No takers huh? I know that first post was a bit long winded but I went ahead and went with a different boost convertor that uses an XL6009 which seems to be cooperating at a lower input voltage/current. I also did away w/ the solar "charge controller" and went w/ a BMS that does 3S balancing. It has over/under voltage as well as short circuit protection. Basically I am going from the 5V/500mA solar panel to the boost convertor which is boosting the voltage to 14V which is then feeding the two BMS's I have for each set of 3S 18650 packs. Is this an acceptable/safe way to do this? While bench testing I set my power supply to a current limit of 300mA and 5V which was about the average output I was seeing out of my solar panel. With this setup I'm drawing about 300MA from the bench power supply with a voltage of somewhere under 4V as it was current limiting. Based on my calculations using this solar panel (5V/500mA) , with boosting from 5-14V and about 90% efficiency I'm seeing best case 160mA to the pair of BMS's I'm using. Given the capacity of the 2P3S config and the fact the LEDS are only used for a few minutes a week or so and draw 1A I don't think this charge rate will ever be an issue. Is my math accurate here?Here is my finished product, so far it seems to be functioning as design but I'm just paranoid about charging Li batteries unattended. Pay no attention to the bodge wire