On 5.2.2013 20:11, Josh Koffman wrote:
> Hi all,
>
> As part of the project I'm working on, I'm trying to figure out the
> best way to power it via batteries. In previous projects I've used
> small LiIon and LiPo cells, which have worked quite well for my
> purposes. My applications are typically medium-low drain (say, under
> 300mA max), and the cells I've gotten have worked well, powering the
> device for the desired amount of time before requiring a recharge.
>
> For my current project, I'm thinking about switching to AA NiMH cells.
> The advantage here is that high capacity rechargables are readily
> available (~2500mAH), and if all my cells end up flat, I can switch to
> alkalines with no problem. The problem here is that I was hoping to
> use 4x AA batteries, which while taking up a good amount of room in a
> beltpack style case, is manageable. Due to the cell voltage of a NiMH
> cell, I don't think I'm going to get enough input voltage that I can
> then regulate to a nice 5V. I could go up to 6 cells, but it starts
> taking up a lot of space.
>
> I'm curious what other people have done in this situation. I could go
> to two LiIon or LiPo cells in series, but the cylindrical cells are
> too large for the capacity I'm looking for, and rectangular cells
> aren't easily swapped out (ie no one makes a holder for them).
>
> Any thoughts?

What I would do:

1. 4-cell AA NiMH with good LDO and cheating =3D lower the VCC to 4.5V if=20
possible. Below 1.2V there is very little energy left in NiMH anyway.

2. 5-cell AA NiMH with LDO =3D the simplest solution if you can use 5 cells=
..

3. 2-cell or 4-cell AA NiMH, 2.4V with modern 1MHz boost converter=20
without PFM directly, or boost converter with PFM and additional LDO.

I prefer SANYO Eneloops low self discharge NiMH for any device that will=20
be left uncharged a week or two in normal use. I really dislike high=20
capacity NiMH that will be half empty every time you need them the most.

Djula


>
> Thanks!
>
> Josh
>
--=20
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