Using 18650 Batteries Li-On w/Argon

I have a couple of Particle Argons that I want to use in a project with 18650 batteries. Although I was originally going to use an enteral charger/power board between the batteries and the Argon, in reading the specs I see that the Argon has battery support already built-in (from the Argon spec sheet):

LiPo

If you want to make your projects truly wireless, you can power the device with a single cell
LiPo (3.7V). The Argon has an on board LiPo charger that will charge and power the device
when USB source is plugged in or power the device from the LiPo alone in the absence
the USB.

However, the batteries I use (EBL BRC 18650) are Li-Ion and not Li-Po (Lithium Polymer) batteries, and I think 18650’s typically have nominal voltage rating of 3.6V (depending on source, I’ve seen both 3.6V and 3.7V listed). Can anyone advise if these are compatible with the Argon charge / discharge capabilities and can be plugged directly into the Argon LiPo connector?

Second question: If that does work, if I were to use two (2) 18650s in PARALLEL, is there any issue with charging / discharging through the Argon? I am assuming that using the batteries in parallel will increase my run time? Can I assume that both batteries will charge and discharge (approximately) equally? Or does using two batteries in parallel cause any problems?

To be clear, I’m asking about connecting the 1x or 2x 18650’s directly to the Li-Po port on the Argon (which the Photon does not have), and NOT using a separate charge/discharge board in between the batteries and the Argon. Will that work? Or will the difference in chemistry between Li-Ion and Li-Po cause a problem?

@dfilip , Welcome to the Forum!

You are correct in your assumption.
A 3.7V Nominal cylindrical 18650 Li-Ion is the same chemistry as a 3.7V Li-Po.
They both have a max of 4.2V, and are the same thing in different packages.

It’s also common to parallel these, but good practice is to completely charge each cell individually before paralleling them together. That’s the simple method. You want the same cells, capacity, age, etc.

The 2P 18650 pack will then act as 1 battery, doubling your mAh Capacity as you mentioned.

If using a Cell Holder, make sure you never swap out a cell that’s at a significantly different charge state than the other cell. One 18650 will attempt to charge the lower voltage cell, resulting in extremely high currents. Bad things can happen as a result. No worries if you don’t intend to use a Cell Holder which allows for easy hot-swapping.

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