Reusing smartphone batteries (+ with built-in NFC?)

[CRImier]

I recently received an email, telling about batteries with built-in NFC antennas and how we could use them in our project. Initially, it was suggested that we could use those antennas for GSM/WiFi, however, we've figured out this is unlikely. However, we could add an adapter for those batteries that would also contain a NFC reader (interfaced through I2C). Here are some of the batteries, with dimensions:

• EB-BG800BBE, 2100mAh, 71 x 34 x 6,5 mm (Galaxy S5 Mini)
• EB-BN915BBC, 3000mAh, 92.92 x 40.63 x 5.80 mm (Galaxy Note)
• EB-BN910BBE, 3220mAh, 98.80 x 41.40 x 5.60 mm (Galaxy Note 5) (not suggested, see below)
• EB-BG900BBC, 2800mAh, 84 x 42,5 x 6 mm (Galaxy S5)

The mAh ratings are quite reasonable, and dimensions fit the ZeroPhone very well. Potentially, we could even use two of such batteries in parallel with a purpose-built holder (which would be ~1cm in thickness, still less than the current 18650 pack). So, with a simple 3D-printed/lasercut sleeve (to protect the battery from punctures), a 4-pin connector and a NFC-I2C breakout board (using either MFRC522 or PN532), we could have a great DIY solution for adding a flat, yet easy-to-source, battery to ZeroPhone - as well as NFC!

[CRImier]

Got a BN910BBE for my own research, however, it's not very usable. At 99mm height, there's no way we can fit it inside the ZP outline safely - even without the springy contacts, which I'm sure we'll need at some point. So, I wouldn't suggest it, even though the mAh rating is very good.

[CRImier]

Nokia BL-5H could work: 7.8 x 3.7 x 0.5cm, could even have 2 in parallel.

[CRImier]

Ordered 2x BL-5H, should arrive next week. Need to think about connectors - can't even solder to these batteries, so I certainly should have some kind of breakout.

Also got myself an EB-BG900BBE, seems to be very similar to EB_BG900BBC. It sticks out of the outline a bit (as expected), but that can probably be worked around. However, it will require a Type-C mod - with the full-size USB port mounted, it certainly won't fit inside the ZP outline when it comes to the "height" dimension. Will think about creating the battery connector breakout in the meantime - will certainly require some sort of case to keep it connected.

BTW, I have a (puffy) EB-BG800BBE on hand. While it does fit inside the outline and looks like it could work - even with the full-size USB port! -, the capacity is limited - and you can't fit two parallel cells due to increased thickness. I will see if we can do something.

[CRImier]

Got the BL-5H, they're great! Connectors (from i.e. Nokia 5800) are very cheap on Taobao, and fit very well - no need to apply pressure onto the battery from side opposite to the connector, unlike Samsung, just need to keep the battery in place. Designing some boards for these - dual battery support, with batteries on both sides, ATTiny44 for management&protection and maybe I2C voltage/current readouts.

The boards should also work out for the EB-BG900BBC after changing the connector and small tweaks. Not sure we could fit NFC support on the EB-GB900 PCBs though, wouldn't hurt to try but I have no idea where to start and it will probably be a hassle, will think about it.