[Tfug] OT: Batteries

[Don Freeman]

I guess you'd have to weigh the volume of sales to determine if a custom
battery would make sense. Otherwise the cost would become prohibitive. Also
you'd have to consider the cost of the device. After about $10 I don't want
to consider anything disposable and the higher it goes the less 'disposable'
it becomes. If you went the disposable route you'd also have to build in
some protections to insure the device didn't discharge accidently by being
left on unintentionally, etc. Have you considered a fuel cell or solar
rechargeable? ;)

- D

-----Original Message-----
From: tfug-bounces at tfug.org [mailto:tfug-bounces at tfug.org] On Behalf Of
Bexley Hall
Sent: Wednesday, November 25, 2009 1:05 PM
To: Tucson Free Unix Group
Subject: [Tfug] OT: Batteries

Hi,

I'm trying to come to grips with two very different approaches to battery
selection for a device I am designing (there are actually three but the
second is *effectively* the same as the third).

1. Customer replaceable (!) off-the-shelf batteries.
This limits the design to battery form factors, chemistries and capacities
that are "readily available"
(i.e., buy replacements at Target, etc.).  Note that a separate issue is
rechargability (as that complicates design, adds to cost, reliability
impact, etc.).  With COTS batteries, recharging is just a *convenience*
issue.

2. Proprietary battery.  This affords greater flexibility in form factor,
choice of chemistries, battery capacity, etc.  It, however, *requires* the
battery to be rechargeable (or have a VERY long life -- years!) as
replacement would be inconvenient (and possibly expensive since that means
stocking a supply of replacement batteries and allowing people to purchase
them -- adds overhead to each such sale).

3. Proprietary battery *sealed* within the device!  (i.e., option 2 might be
something like a cell phone approach in which the battery *is* proprietary
but the user *could* remove/replace it if he was able to get a replacement
part).
This places even more demands on the battery (from the user's perspective)
as replacing it would be a "factory service" operation.

However, it offers some benefits that can be real wins:
- device can be made far more weather resistant (I've known
  of two cell phones "destroyed" because they "fell" into
  a toilet -- I have no idea *how* but...  :> )
- cost of manufacturing goes down as you simplify the
  design of the case
- cost of *tooling* goes down (since the case has fewer
  pieces, molds become simpler and fewer)
- no need to stock batteries or battery covers as
  replacement parts

Price point seems to play a big part in my initial thinking on this.  E.g.,
a $20 device with a battery that will last a year you can think of the
battery
*and* device as "disposable" (in today's market).

OTOH, how happy would you be about discarding your laptop/netbook after a
year?  (and those aren't actually terribly expensive!)

Comments?
--don


      

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