Re: (ET) cordless electric mower

["David Roden" <etpost drmm net>]

On 24 Jul 2006 at 21:33, David C Robie wrote:

> NIMHs   -  don't believe the hype.

Like anything else it depends on what you're doing with them.  Nicads can 
take overcharge much better and I'd guess that's why the tool mfgs went 
back 
to them.  

Users want fast charges but low tool prices.  The mfgs bundle about the 
cheapest, crappiest junk chargers they can buy at low bid.  With 
relatively 
high charge rates (in some cases) and essentially no charge control they 
trash NiMH in short order, but nicads can stand this treatment better.

Self discharge is higher on NiMH but not that much higher!  Cheap cells or 
failing cells *will* have bad SD though.  I use Nexcell/Powerex/Maha and 
sometimes Energizer NiMH for my digital cameras.  One of the cameras sits 
in 
my briefcase for weeks or months without being used, and only once has it 
let me down when I wanted it.  As I said, good cells are higher SD than 
nicad but not by *that* much.

NiMH is quite decent - better than nicad but not as good as lithium based 
secondary cells - where you need small size, low weight, lots of energy on 
board.  Darn few AA size nicad cells will yield a real world 2.2 ah, but 
NiMH can and does.  (Though high capacity comes at the expense of cycle 
life.)

I don't know how useful this exchange is to trakers since I doubt that 
anybody here is going to use NiMH in his tractor - but we do have a couple 
of people using nicads.  Flooded ones, that is - not AA cells!


David Roden - Akron, Ohio, USA

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = 
Note: mail sent to the "etpost" address will not reach me.  To send 
me a private message, please use "evadm at drmm period net."
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Americans are satisfied with things because they are large; and
if not large, they must have cost a great deal of money.
 
                            -- Lepel Henry Griffin, ca. 1885

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =