Hey, for a project I'm working on, I need to charge 4 different 18650 battery cells. Which of these 2 would I need?
https://zaitronics.com.au/products/tp4056-type-c-18650-lithium-battery-charger-protection
https://zaitronics.com.au/products/2s-3a-5a-18650-bms-li-ion-battery-charger-protection-board

 

Welcome to AAC.

Those are two different things. The first is a 1SnP charger. That is, 1 Serial and some number of Parallel cells. It produces the correct voltage for the single cell (1S) and can be used for more than one in parallel with an important caveat.

In practice such chargers are often used for parallel pairs of cells, while this isn‘t ideal, it ”works”. The problem becomes much worse when you go to 3+ and increases with the number. Cells are not identical, and the rate at which they discharge is not identical. For this reason, boards designed for multicell battery use include a “balancer“ facility.

The balancer is wired to the pack in such a way it can measure the voltage of, and charge, any individual cell in the pack. This prevents the danger of a cell over discharging and being reverse charged by the other cells in the pack. This is actually a fire hazard which is where the second board comes in.

First, that’s not really the right board for an 18650. Those are designed to accommodate the form factor and tab terminals of a pouch cell like a Lithium Polymer (LiPo) cell. 18650 protection boards are round and mount to the bottom of the cell. This is what protected cells have and why they are a little longer than unprotected ones.

If you start with protected cells you don‘t need to worry about it at all. The protection is against over-discharge, over-current, and over-charge. The board uses a small, specialized chip and a MOSFET to literally turn off the cell if any fault conditions are encountered.

If you are using four cells as a pack, you want to get a BMS (Battery Management System) that is designed for your configuration. If you have the for in parallel you would want a 1S4P BMS. For series you want a 4S1P board, and so on.

Please be very careful and certain you understand the potential dangers of Lithium chemistry cells and batteries. They can and do cause fires with devastating effects. If you do this after eliminating ignorance it‘s not very dangerous—if you don’t learn first, it is.

Good luck.

 

You mention that you need to charge four different 18650 cells. Are these to be charged separately or are they connected together?
The first charger you show is for charging a single cell from a USB source.
The second item is a charge control and protection device for charging two cells wired in series. It requires an external supply but it gives no details of the required voltage.