Unregulated Dual 18650 battery questions!

[CalebMonster]

I recently ordered a dual 18650 box mod wired in parallel, I already have a few batteries and I was wondering if it is necessary to buy 2 new batteries and "marry" them together and always keep them together. I've heard you should do that or it's a good idea to do that but I want to know do I need to do that. Plus all of my batteries are different brands and different mah, so is that important.

 

[State O' Flux]

Per Battery University:

Serial and Parallel Battery Configurations

"A high-resistance cell, or one that is open, is less critical in a parallel circuit than in serial configuration, however, a weak cell reduces the total load capability. It’s like an engine that fires on only three cylinders instead of all four.
An electrical short, on the other hand, could be devastating because the faulty cell would drain energy from the other cells, causing a fire hazard. Most so-called shorts are of mild nature and manifest themselves in elevated self-discharge. Figure 4 illustrates a parallel configuration with one faulty cell."

 

[freemind]

Short answer, you don't HAVE to but it IS THE SAFEST way to use your new mod.

A pair of Samsung 25R's is a CHEAP investment. Much cheaper than an ER visit, should something go awry.

 

[BoomStick]

You're talking about high drain lithium batteries. Definitely use a matched pair.

 

[getek]

For a series configuration, yes. Mary the batteries and swap position every charge.
For parallel, much less important. You should, however, use the same brands/models and similar life usage.

 

[KeyserSoze]

As previously stated, it's not absolutely necessary but I would at least use the same kind of battery. I don't have a parallel mod but I would still use a married pair just to be extra safe. Pairs of batteries come with a free case from illumn.com. Cases are a good idea too...