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Powering your board from battery

All Unexpected Maker development boards come with support for using a Lithium Polymer battery to power your projects as well as the ability to charge that battery off the USB connector (or 5V pin if you are using an external 5V power supply).

The TinyPICO, TinyS2, TinyS3 & TinyC6 come with a separate JST PH connector that you can solder onto the footprint on the bottom of the board, as well as a VBAT header pin next to a GND pin to allow you to connect your battery via the headers.

The FeatherS2, FeatherS2 Neo, FeatherS3 and ProS3 come with a battery connector on the board. The Feather boards have a JST PH connector and the ProS3 has a PicoBlade connector. Both also have a VBAT header pin allow you to connect a battery via the headers.

The TinyPICO Nano and NanoS3 both have a VBAT pin on the headers you can use on your carrier board to allow you to hook up a battery connector if required.

The VBAT header pin on your board is electrically connected to the +Ve pin of the battery connector on the board, so no matter which you use to connect your battery, it will also be charged if 5V is present.

What type of batteries can I use?

Lithium Polymer (LiPo)

You can use any size, single cell Li-Po battery to power your Unexpected Maker boards. Obviously, the larger the mAH rating of the battery, the longer it will last, but the longer it will take to charge. What is the charge rate on my board?

Please use LiPo-Batteries with charge protection included on them. Most hobby RC batteries do not have under voltage protection, and if a battery discharges too much, it can damage it and it might never be able to hold a proper charge again.

NOTE: When connecting a battery to your Unexpected Maker board, please check the polarity of the battery, as not every battery is wired the same way. The IC I use for charging does have in-built reverse voltage protection, but it’s better not to tempt fate!

Lithium Ion (LiOn)

LiOn batteries can be connected to your UM board, but there are a few things you should be aware of.

  1. As LiOn batteries have a slightly different chemistry than a LiPo battery, they also have a different maximum charge voltage. Usually higher than the 4.2V max that LiPo batteries have.

    The Charge IC (PMIC) on your UM board is designed to charge LiPo batteries, so will stop charging at 4.2V so it’s likely your LiOn battery will never get to a full capacity, or they just may not charge properly at all depending on the b battery you use.
  2. It’s common for LiOn batteries to come without any under voltage protection, so they can be more dangerous to use, if you are not experienced using them.

Because of these reasons, I usually advise people that ask about using LiOn batteries to use LiPo ones instead.

Nickel Metal Hydride (NiMH)

These batteries are not compatible with the PMIC on UM boards, and should never be connected to an UM board via the VBAT pin or battery connector, but can be connected through a 3V3 regulator to the 3V3 pin of an UM board.

Alkaline AA & AAA

Alkaline batteries can be a great way to power your projects, as they are cheap and usually easily found around the home or office.. that said, you should NEVER connect an Alkaline battery to the VBAT pin or battery connector of an UM board.

Alkaline batteries are not rechargeable, and if you connect them to the PMIC and accidentally connect 5V, the PMIC will try to charge it and well… DANGER WILL ROBINSON!

Can I run batteries in series or parallel?

Sure, but never connected to the VBAT pin or battery connector on UM boards as the PMIC is designed ONLY for a single cell 3.7V Nominal, 4.2V Max LiPo battery, so it cannot charge a multi-cell battery (multiple 3.7V LiPo batteries in parallel) and it adding them in series will add their voltages, which will be out of scope for the max 4.2V limit.

Running alkaline batteries in series is a great way to use 3x AA batteries (1.5V each) as a 4.5V source that can be connected to the 5V pin on your UM board… but again, never to the VBAT pin or battery connector.

VBUS/5V detection and Reading the Battery Voltage

battery chemistry, lipo, 1s lipo, 1 cell, single cell

Updated on April 28, 2024

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