Tutorial 8: Powering the UNO R3 PLUS Using Batteries
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In this tutorial we will highlight the items that you will need to pay attention to when trying to power the UNO R3 Plus board using AA battery.


AA battery is the most common type of battery used in portable electronic products.  The voltage and capacity depends on what chemicals they are made from.  These chemicals include Zinc-carbon, Alkaline, Li-FeS2, NiCd, NiMH, and most recently Li-ion.  Off the shelf, the most


common battery that you will find for an un-rechargeable type is the alkaline battery, and the rechargeable type is the NiMH battery.  Typically, their capacity is in the 2300mAh – 2700mAh range.


Useful Note:  The unit mAh means mA-hour.  Assuming you are using a single 2700mA battery, if your application consume 2700mA, your battery will last for about an hour.


Before designing you circuit, you should think ahead on the type battery you will be using, how many battery you will be connecting and how will they be connected, as these will affect how the input stage of the power circuit is design.


Each AA type alkaline battery will output at around 1.5V in normal condition, however, the NiMH battery will output at around 1.2V in normal condition.


If you connect four batteries in series, then you will get 6V when using alkaline battery and you will get 4.8V when using NiMH battery.


Useful Note: The UNO R3 Plus uses a MC33269D-5.0V 5V linear regulator to regulate its input voltage.  This voltage regulator has a 1V drop, when you supply a 6V into the input, it can still output a 5V and function correctly.


Useful Note:  Can I connect four NiMH battery and tap it into the 5V power rail directly?  NiMH battery output a 1.2V normally, but just after charged, it could be outputting at 1.4V, so you could be supply a 5.6V into the 5V rail.


If you want to power your UNO R3 Plus using either type of batteries, you can put in a boost converter into your circuit.  The AA battery holder connect the four AA batteries in series, so you voltage will range from 4.8V to 6V.   You can put in a boost converter that converts the voltage up to 7V, then supply the 7V to the VIN terminal of the UNO R3 Plus.  This method will work, but it is very inefficient.


A better method is to modify the battery holder, so that it will connect the four batteries with two in series.  This will give out 2.4V to 3V.   Using a 5.0V boost convert, you can convert this voltage up to 5V and supply it directly to the 5V terminal of the UNO R3 Plus.   By bypassing the onboard 5.0V linear regulator, this solution will have less power loss and your battery will last longer.

Four batteries all in series                  Four batteries with two in series

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