Higher current MT3608 boost converter board? - Page 1
Forum section: electronics / projects

author: mct75
author_rank: Regular Contributor
timestamp: November 30, 2019, 04:29:37 pm
content: Hi All,I'm a huge fan of the dirt-cheap MT3608-based boards for boosting Li battery voltages to ~5-12 volts, or for converting all my 'wall-wart' 12V appliances to use micro-USB. They can be had for like $1 each so I keep a pile on hand.I've got a few applications that call for 1A+ and the little SOT23 package gets too hot and the output drops. Is anyone aware of a similarly cheap and effective board with all the ancillary components? The closest thing I can find are these XL6009 boards that claim they can output 4A but the operation with an input voltage below 5V is spotty, so Li batteries probably won't work.I'm sure there's a commodity board out there made for boosting an 18650 to higher voltages that can handle some more current. I don't really have the time or the money to roll my own PCBs so I'd like something that's a plug-and-play as the MT3608's. I thought about just running the smaller boards in parallel but that seems like it would open up other issues like feedback and load balancing.Thanks!

author: Hiemal
author_rank: Regular Contributor
timestamp: December 01, 2019, 12:07:01 am
content: You could give replacing the MT3608 a try.I'd seriously doubt whether or not the chips contained on the boards are "legit". They're likely black market knockoffs and don't actually perform to spec.Since the pinout of the chip on it is relatively standard you can search pretty much any SOT-6 boost converter and see if there's one that has better efficiency (hint, there will be) that you could replace it with.

author: mct75
author_rank: Regular Contributor
timestamp: December 01, 2019, 01:29:25 am
content: Thanks for the reply! Unfortunately the highest current SOT-23 boost converter on Mouser only does 1.1A. I'd really like something that's more turn-key as well. I get these cheap MT3608 boards for less than $0.70 each to my door so the economics are hard to beat. They do work well up to 500-1000 mA, depending on output differential. 3.7V to 5V works great and 5V to 12V is okay up to about 750 mA or so. It's looking like just doubling them up and hoping for the best is going to be my only option.I was hoping there's some chip lifted from a power bank that could do 2.4A since most are rated at that.

author: jhpadjustable
author_rank: Frequent Contributor
timestamp: December 01, 2019, 09:44:19 am
content: OP's chips are most likely meeting spec, and they're cheap enough in volume through legitimate channels that it's not economically favorable to fake them. However, sellers on the online flea markets use keyword-spam and don't necessarily know what they're selling, and, frankly, OP's asking for quite a lot.It's often not fully appreciated that the boost converter's switch bears theinputcurrent, not theoutputcurrent. Since power is conserved across a switched-mode converter, a boost from 3.0V (low battery condition) to 12V takes in 4A (plus losses) for every 1A output. It takes a pretty low Rds(on) to pull that sort of power, and I bet the battery doesn't like it very much either.Maybe it's easier to just put two batteries in series so as to reduce the boost ratio (and input:output current ratio).

author: mct75
author_rank: Regular Contributor
timestamp: December 01, 2019, 03:17:41 pm
content: Very true. For less than a dollar I don't expect much. For example I have a ham radio charger that calls for 10V at 400 mA, and instead of having to keep track of the one wall-wart that outputs 10V I just hot glued one of these boards to the back and now I can charge it just fine with a microUSB phone charger. Very cool for less than a buck invested.My current project is a ground station for an RC drone, I have three ~6.5V loads of 200mA, 690mA, and 350mA and I would have liked to have a common 6V5 bus with a converter that has plenty of headroom for this, but I'm thinking three discrete MT3608 boards will make more sense.Going to a 2S pack brings balancing and charging problems into the equation, as my current design uses a tp4056 charging/protection board. Using four 18650s in parallel affords plenty of discharge current.