Use high-quality solder with a flux core and avoid using additional acid-based flux (solder paste), as it can corrode the connection or battery over time. See my solder recommendation here. Before soldering, it's best to discharge the Li-Ion battery down to 3V. The more energy stored in the battery, the more dangerous when things go wrong. 3V is the minimal safe voltage for 18650 to be discharged to. Even slightly lower voltage is okay but might be bad. “Tin” both sides of the batteries with a small amount of solder, allowing it to cool down before soldering the wires. Keep the time your soldering iron touches the battery terminals to a minimum. The longer the iron is in contact with the battery, the more heat will. Before soldering, use sandpaper to scratch the top and bottom sides of the cell, removing the oxide layer. This will help the solder adhere better.
[PDF Version]
How to solder lithium batteries?
If you are going to solder lithium batteries, apply lots of flux to the cell before touching it with the soldering iron. This will ensure that the cell surface is in the best possible state to be soldered which will require less soldering time for a good connection. In this article, we will discuss how to solder lithium batteries.
The problem with soldering lithium batteries is that the heat from the soldering process damages the cells to some degree. Not only does it damage the cells, but it damages the cells to an inconsistent degree in most cases. This can cause the battery pack to come out of balance later on.
How do you solder a Li-ion battery?
Use high-quality solder with a flux core and avoid using additional acid-based flux (solder paste), as it can corrode the connection or battery over time. See my solder recommendation here. Before soldering, it's best to discharge the Li-Ion battery down to 3V.
How do you solder a battery pack?
Step 1: Disassemble the battery pack, if you need to, so you can get to the cells. Step 2: Clean the cell ends so that when you solder, you will be able to make a secure, strong connection. Step 3: Turn on the soldering iron and allow it to heat up all the way.
How much power do you need to solder a lithium battery?
To solder a lithium battery, you're going to need at least 100 watts of power at the tip. Having triple-digit watts at your disposal is required to be able to get in there, form an excellent connection, and get you- quick. It may seem counter-intuitive, but the best soldering iron-to-solder lithium-ion batteries is going to be the hottest one.
How do you solder a battery with a soldering iron?
“Tin” both sides of the batteries with a small amount of solder, allowing it to cool down before soldering the wires. Keep the time your soldering iron touches the battery terminals to a minimum. The longer the iron is in contact with the battery, the more heat will build up.