LED battery pack schematic and PCB review - Page 1
Forum section: electronics / beginners

author: mathew
author_rank: Newbie
timestamp: March 21, 2021, 03:21:38 pm
content: Edit. No idea why the images aren't inline. The titles should point you in the right direction.Hi everyoneAnxious putting my schematics and PCBs out here for review, so I'll try and give as much information as I can. I've got some questions to ask at the end as well.ContextI'm working on an LED bicycle of which you can see the start of on Vimeo.The current setupAn Arduino UNOA 10W power supply (5v)5m of SK6812s (60/m)The idea is for the forks to have to have LEDs, along with the other side of the bike, but ...The problemI don't have enough wattage to power more LEDs without voltage drop / dimming. I also need to make the power portable.RequirementsI've done some basic measurements on a small run of LEDs (10) and extrapolated out the numbers. So looking at the ability to deliver between 10A to 15A for the finished setup. That's when all LEDs are driven at full brightness, but I'll be using a lot of patterns so don't see a sustained 10A draw happening. I'll be using alotof left over NIMh (MH-D110) batteries from a former project (I'm reusing what I've got), I've attached the spec sheet since it's no longer available online.MH-D110 Spec Sheet.pdfWhere I'm atSo I'm working on two things. Firstly ...A battery pack that gives me between 3v and 3.6v with a capacity of 44,000mAh.I don'tthinkI've done anything majorly wrong here, but do let me know. Curved traces?!Secondly ...A boost converter, designed with Webench.https://webench.ti.com/appinfo/webench/scripts/SDP.cgi?ID=3CABF6C09A790975(LM3481MM/NOPB 3V-3.6V to 5.00V @ 15A)This is still in progress, but I want some input so I'm not going completely in the wrong direction before I have to redo it all.QuestionsWebench specifies x8 as a quantity for Cout, do I need 8 or can I get x1 with the combined capacity? Same question applies to Cin.The battery pack traces narrow to the pads (a feature of DipTrace), will this cause problems with the load?Anything simpler? I used webench because it was easy for a beginner like myself to whack numbers in, but if there's something that is more beginner proof (i.e. less components) I'm all earsI'm grateful for any feedback and constructive criticism. I'll be around to answer any questionsPS. Love building physical things, so nice to design something, have it manufactured and work. Makes a change from writing software.

author: mathew
author_rank: Newbie
timestamp: March 23, 2021, 06:30:50 pm
content: Bump.If I posted in the wrong place let me know. Otherwise I'll crack on with my design, taking into consideration the design guidelines from the LM3481 datasheet and give it a go!

author: mvs
author_rank: Frequent Contributor
timestamp: March 23, 2021, 07:20:45 pm
content: 1. Webench should calculate ripple current and propose you caps that can handle it. If you change part number and/or quantity of caps, verify ripple current in the datasheet.2. You can readjust trace width with right mouse click or use copper pour for high current traces.3. I do not like this webench design. 3V supply is very challenging, since not so many MOSFETs can operate well with such low gate voltages.There is an option to power controller from output, 5V drive is a lot better then 3V, or from a small auxillary boost converter with 6-10V output. But still i would prefer to build battery pack with higher voltage and use buck converter with synchronous rectification to get 5V.