Power µC with 18650? - Page 1
Forum section: electronics / general

author: Winfried
author_rank: Contributor
timestamp: March 12, 2022, 07:20:37 pm
content: Hello,I don't know much about electronics, and would like to power a NodeMCU controller with an 18650 battery and give up the power bank I'm currently carrying.I understood that lithium-ion batteries should be carefully recharged to avoid a fire hazard (BMS.)Do you think the followingpower boardand18650 batterycould work?Thank you.

author: Rick Law
author_rank: Super Contributor
timestamp: March 13, 2022, 06:32:42 pm
content: You didn't say how much current you need. If your current requirement is within what this board can provide, it "should work" if the board works as designed.But there is one issue there. Quoting from their item description:"...If you turn it to HOLD,it will remain on regardless of the situation until the battery is empty(the 2512 resistor on the back will heat up)." (Bold added and I eliminated their typo with "s i tuation")That statement (bold part) implies the board doesn't have over-discharge protection -- implies only, it didn't say if the board has over-discharge protection or not. If over-discharge protection is indeed missing, issue is the battery will be damaged when over-discharged. One light discharge (below 2.6V but not near 0V) and quickly recharged wont hurt too much, do it often or do a deep discharge, your battery is pretty much toasted.You may be better off getting a power bank. If you don't need 5V, you could get a protected battery and a proper recharger. If you do need 5V, you need to equip your protected battery with a boost/buck board.

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 13, 2022, 06:52:05 pm
content: If weight and size for a given capacity is of no real concern to you, I would favor a LiFePo4 variant, as those are much safer to use (and even abuse.)

author: Doctorandus_P
author_rank: Super Contributor
timestamp: March 15, 2022, 05:43:49 pm
content: I would probably also go for LiFePo4.Battery voltage is a bit lower then from Li-Ion, and this means you can probably connect your 3V3 circuit directly to the battery with no voltage regulator needed.

author: Winfried
author_rank: Contributor
timestamp: April 07, 2022, 02:11:16 pm
content: Thanks much. I'll read up on over-discharge protection, and LiFePo4 batteries

author: Peabody
author_rank: Super Contributor
timestamp: April 07, 2022, 02:58:21 pm
content: I believe the different versions of those 18650 shields have completely different circuits. I have both the single-cell V3 and the dual-cell V8, and would only recommend the V3. The V3 has a typical TP4056 charger and DW01 protection chip, plus a separate 5V boost converter and 3.3V LDOs.The V8 I have uses one of the new chips that does everything - both charging and boost converting, and it doesn't do either very well, or switch between the two without glitching. As far as I can see, only the V3 is suitable as a UPS. However, the V3 lacks a load sharing circuit, so it may not terminate charging properly if the load current is too high. Here's a video that discusses that issue:

author: Winfried
author_rank: Contributor
timestamp: April 07, 2022, 03:00:27 pm
content: Thanks for the feedback.Overcharging is a serious concern:https://emariete.com/en/co2-meter-with-battery-well-done/

author: Peabody
author_rank: Super Contributor
timestamp: April 07, 2022, 03:21:48 pm
content: Yes, that link discusses the MCP73871 charger IC. It has the advantage that it has load sharing built in. The problem has been in finding a good module that uses that chip. Perhaps this is the one.

author: tepalia02
author_rank: Regular Contributor
timestamp: April 14, 2022, 02:27:41 pm
content: If it's a one sensor project, it will work pretty well.