user6249: For my next project I'd like to use a battery pack to power my Arduino.
I would also like to get a small solar panel and charging module to charge these batteries when possible (during the day).

What is the right type of battery for this kind of application?
What are the differences given this context?
What are the factors I need to consider when choosing a rechargeable battery for this application?


user6959: Look at Battery University for many good ideas.
Both NimH and LiIon are viable for your application.
LiIon are easier to manage well if managed well.
ie do it right and they are easy to manage, but cut corners and they are easier to destroy.
NimH can be abused more with a slow degradation in capacity - although complete destruction is possible. 
As a LiIOn cell has a ~= 3.0V to 4.2V range you'd probably probably need a step up inverter with 1 cell, or a buck regulator with 2 cells, which is 'annoying'. If you are prepared to use the cell over say a 3.4V to 4.2V range with an LDO regulator for a 3.3V system then you lose a significant amount of available capacity but increase battery cycle life substantially. 
Nimh give 1.0 - 1.2 V/cell so eg   

6 cells give 6 - 7.2V for a 5V system,  
5 cells give say 5.25V - 7V if run down to 1.05V for a 5V system with a suitable LDO regulator, and
4 cells give 4 - 4.8V for a 3V3 system.   

NimH are easier overall to build half well and get half good results. 
LiIon are slightly harder to get going with in most cases, work very well if treated well, and are VERY unforgiving of bad treatment past a certain point. 

6249: <p>For my next project I'd like to use a battery pack to power my Arduino.
I would also like to get a small solar panel and charging module to charge these batteries when possible (during the day).</p>

<ol>
<li>What is the right type of battery for this kind of application?</li>
<li>What are the differences given this context?</li>
<li>What are the factors I need to consider when choosing a rechargeable battery for this application?</li>
</ol>
 6959: <p>Look at <a href="http://www.batteryuniversity.com/" rel="nofollow"><strong>Battery University</strong></a> for many good ideas.</p>

<p>Both NimH and LiIon are viable for your application.</p>

<p>LiIon are easier to manage well <strong>if</strong> managed well.<br>
ie do it right and they are easy to manage, but cut corners and they are easier to destroy.</p>

<p>NimH can be abused more with a slow degradation in capacity - although complete destruction is possible. </p>

<p>As a LiIOn cell has a ~= 3.0V to 4.2V range you'd probably probably need a step up inverter with 1 cell, or a buck regulator with 2 cells, which is 'annoying'. If you are prepared to use the cell over say a 3.4V to 4.2V range with an LDO regulator for a 3.3V system then you lose a significant amount of available capacity but increase battery cycle life substantially. </p>

<p>Nimh give 1.0 - 1.2 V/cell so eg   </p>

<ul>
<li><p>6 cells give 6 - 7.2V for a 5V system,  </p></li>
<li><p>5 cells give say 5.25V - 7V if run down to 1.05V for a 5V system with a suitable LDO regulator, and</p></li>
<li><p>4 cells give 4 - 4.8V for a 3V3 system.   </p></li>
</ul>

<p>NimH are easier overall to build half well and get half good results. </p>

<p>LiIon are slightly harder to get going with in most cases, work very well if treated well, and are VERY unforgiving of bad treatment past a certain point. </p>
