2-3V to 5V boost converter? - Page 1
Forum section: electronics / beginners

author: ElectricPower
author_rank: Frequent Contributor
timestamp: November 02, 2021, 02:39:31 pm
content: I look around on AliExpress for an boost converter for use with one 18650 battery for powering breadboard projects, but i can't see i find something. I need the converter to output at least 2 ampere at 5 volt.Can someone help me find a converter that does that please? If it's exist...

author: Rick Law
author_rank: Super Contributor
timestamp: November 02, 2021, 07:34:08 pm
content: I found on AliExpress 3A, 5A, 15A boost converter first page (see attached). I am in the USA, unless your country's AliExpress has filters, you should find them.May be set your region as USA and see if you can order and if they will ship...Edit: Adding this:Note that most of them don't have heat sink. To really do 2A, you probably should also buy a properly sized heat sink and stick it on the chip.

author: Siwastaja
author_rank: Super Contributor
timestamp: November 02, 2021, 07:43:47 pm
content: 2V -> 5V2A boost is already something that requires actual engineering. It's marginally possible to find a module on Aliexpress/Ebay that works, but more likely it doesn't and glueing a heatsink on "the chip" may not fix it. The Ali modules are really for lower power, and higher input voltage, to charge a phone from li-ion cell at maybe 0.5A.If you want to use 18650 li-ion, why do you need to operate from 2V?

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 03, 2021, 07:25:39 am
content: First, discharging li-ion batteries so much is a bad idea. Tipically the work range is 3.7-4.2V.You might go a bit lower, but by not way 2V.Some batteries have BMS which cut off at 2.9V...2.75V, but that's for protection purposes, discharging them so much greatly reduces their lifespan.So you should be boosting 3.7-4.2V to 5V, not 2V. That's a huge difference when searching a solution for your application.There're lots of circuits made for power banks, which is exactly what you need.This handles both charging and boosting the voltage to 5V:https://es.aliexpress.com/item/32999118705.htmlMH-CD42 datasheet is unknown, but after further searching I got this, same pcb using a IP5306:https://flashtree.com/products/mh-cd42-5v2a-charging-and-discharging-integrated-module-3-7v4-2v-lithium-battery-boost-protection-board-diy-chargingWhich lead me to here:https://techobsessed.net/2019/07/what-ic-does-the-mh-cd42-battery-5v-power-board-use/I translated and attached the datasheet, check it out.You have charging, discharging, OCP, OVP, UVP, everything packed in a very small package.

author: tunk
author_rank: Super Contributor
timestamp: November 03, 2021, 11:23:13 am
content: You could also try to search for this:power bank boardpower bank module

author: Peabody
author_rank: Super Contributor
timestamp: November 03, 2021, 01:44:49 pm
content: Modules featuring the MT3608 are widely available and very cheap. The datasheet claims 2A, but I would doubt it. It might be possible to use two in parallel. Maybe.

author: ElectricPower
author_rank: Frequent Contributor
timestamp: November 03, 2021, 02:29:02 pm
content: Thanks for many good suggestions!I think i need something like this:https://www.aliexpress.com/item/4001132144039.html?spm=a2g0o.productlist.0.0.1fd559d25eargC&algo_pvid=b7ac248a-cdea-48af-be5e-139742e0250a&algo_exp_id=b7ac248a-cdea-48af-be5e-139742e0250a-0&pdp_ext_f=%7B%22sku_id%22%3A%2210000014717408730%22%7DBut without the bells and whistles. (LCD and USB outputs/inputs etc.) I just want som hole for wires in the board and as small as possible.

author: DavidAlfa
author_rank: Super Contributor
timestamp: November 03, 2021, 04:46:38 pm
content: Asking that, it seems you didn't see the AliExpress link...(25x16mm)

author: ElectricPower
author_rank: Frequent Contributor
timestamp: November 03, 2021, 05:31:33 pm
content: Quote from: DavidAlfa on November 03, 2021, 04:46:38 pmI'm sorry. I missed thatCan i connect four 18650 in parallel to this unit, and charge it in same time as its get load etc.?

author: ElectricPower
author_rank: Frequent Contributor
timestamp: November 03, 2021, 05:51:30 pm
content: One more thing...Can i just use for example four TP4056 (the one with protection circuit) for higer input and outputs when i use 18650's in parallel?

author: tunk
author_rank: Super Contributor
timestamp: November 03, 2021, 06:03:29 pm
content: QuoteYou can connect them in parallel. For the second question,is this any help:https://youtu.be/-SJbdPvgQnE

author: Peabody
author_rank: Super Contributor
timestamp: November 04, 2021, 01:27:03 am
content: Here's a video on using four TP4056 chips to charge three 18650 cells in parallel. No protection is shown, and no boost converter.

author: beanflying
author_rank: Super Contributor
timestamp: November 04, 2021, 02:43:02 am
content: Thesehttps://www.aliexpress.com/item/32870411748.html?spm=a2g0s.9042311.0.0.27424c4dx5umkEI have a small stash of them and they work great as an all in one solution. Also check out Audreas's video on them.

author: Peabody
author_rank: Super Contributor
timestamp: November 04, 2021, 02:42:54 pm
content: Something usually missing from these TP4056 charger and boost converter modules is a proper "load sharing" aka "power path" circuit. It provides a way for the input power source to directly power the load whenever it is present. Without that circuit, when the TP4056 terminates charging, the load will be powered by the battery until battery voltage drops below 4.1V. So the battery will cycle between 4.1V and 4.2V even though the input power source could have been providing power the whole time. Also, if the load current is greater than 10% of the constant current setting of the TP4056, it will never terminate charging, and you end up applying 4.2V indefintely to a fully charged battery, which is not a good thing in lithium land.This is addressed in the Microchip application note AN1149. I did a video explaining this and demonstrating a load sharing mod for that 18650 shield V3 in Andreas' video:I should note that Andreas also did a recent video in which he suggested using the standard power path circuit with solar panels. It turns out that doesn't work well because under partial illumination, current provided by the battery goes through the mosfet's body diode, with a 0.7V drop. I found a solution for that for a 3.3V output by adding an opamp:https://github.com/gbhug5a/Solar-Power-Load-Sharingbut for 5V output a buck/boost regulator might be needed instead of the linear regulator shown there. I've just finished testing the 3.3V version, and it works quite well, with no tendency to oscillate, and the input to the regulator is never lower than the battery voltage.