[yoyoyoda]

Originally Posted by echo-francis

Every Time I charge a battery pack I manually check the balance of each cell and it is between 0v and 0.01v

Just be sure that you are taking into consideration the long term view.

The one day that you skimp on this required procedure is the day that something could go wrong.

If you are going to keep on using these kinds of batteries then get a proper charge controller which does all of these tasks which you are doing automatically.

And stop soldering directly to the 18650 cells, the thermal runaway temperature threshold for Lithium Ion is only a mere 120 degrees centigrade, a temperature which your Soldering Iron can EASILY exceed.

http://batteryuniversity.com/learn/a...afety_concerns

Lithium-ion cells with cobalt cathodes (same as the recalled laptop batteries) should never rise above 130°C (265°F). At 150°C (302°F) the cell becomes thermally unstable, a condition that can lead to a thermal runaway in which flaming gases are vented.

During a thermal runaway, the high heat of the failing cell can propagate to the next cell, causing it to become thermally unstable as well. In some cases, a chain reaction occurs in which each cell disintegrates at its own timetable. A pack can get destroyed within a few short seconds or linger on for several hours as each cell is consumed one-by-one. To increase safety, packs are fitted with dividers to protect the failing cell from spreading to neighboring cells.

This is the reason why the batteries explode upon charging, getting them too hot will cause thermal runaway, so not only do you have to monitor voltages but you also need to make sure that each battery isn't getting too hot.

Manufacturers generally recommend keeping them under 60 deg centigrade.

There is also only a certian voltage range that you can forseeably use them in, generally below 3.5 volts is going to cause permanent damage to the cell, causing reduced capacity.

Any one, or all of the above. If the cell discharges below a certain voltage, cell damage will occur. This is permanent damage and cannot be reversed. Depending on the manufacturer and the particular cell, damage begins to occur to LiCo/ICR Li-Ion cells at somewhere below 3 Volts OC (open circuit voltage). A LiCo cell is considered "dead" at about 3.50 Volts OC. From this voltage level it really doesn't take very long for the cell to drop below 3 volts, for whatever reason, as there is very little capacity left.

http://www.candlepowerforums.com/vb/...n-safety/page4
http://www.fortbendrc.com/tips/Lithi...erySecrets.pdf

Also, use fuses!!!

I want to make sure you are aware of the dangers involved and the fact remains that you could easily use much less dangerous cells like NiMH, there is absolutely no hard requirement to be using Lithium Ion batteries in your setup.

Be safe! and here is an idea, register an account over at candlepowerforums.com and ask the experts there what to do.