On Sun, 23 Oct 2005 23:13:05 -0500, "homepc"
wrote:

I have 4 Degen rechargeable batteries that came with the DE1103.

I borrowed my son's Sanyo quick charger and found the batteries got very
hot. I'm worried about killing these batteries with a cheap charger.

Sanyo doesn't make "cheap" quick chargers. It is normal for NiMh
cells to get warm during charge (exothermic chemistry) and get
quite warm during a quick one hour or less charge. The quick
chargers all have voltage, and some also, temperature, sensing
circuits to stop the charge to prevent overcharging.

However, for maximum cell cycle life the cells should stay as
close to normal room temperature as possible. For that, a 2-4
hour smart charger is just the ticket. My current favorite is the
compact Sanyo NC-MQR03 but the Powerex models you mentioned are
also fine.

I've
read that charging the batteries within the radio isn't a good idea as it
could damage the radio if the batteries leak.

Don't know what the charging control circuit is in the radio but
it's probably just a simple low constant current overnight charge
and that won't cause leakage unless non- rechargeable cells are
inserted. The manual should give the cell capacities it is
designed for? On the other hand, the cells may not be fully
charged or overcharged so I agree, it's prudent to use a good
external charger.

Also, if the batteries charge
too slowly, crystals will form in the batteries and shorten their service
life.


Believe this what you mentioned in your original post:
http://data.energizer.com/PDFs/chm4fc.pdf

The trickle charge rates shown are okay once the faster rate full
charge is finished. However, NiMh and NiCads should not be
trickle charged from a fully discharged state as that does cause
dendrites, to form unless the cells are immediately discharged
again.

This also appears to be a simple timed constant current charger
so it will properly charge cells only if they were fully
discharged (1V per cell), and if they are the right nominal
capacity -- but the manual does not state what that is. The box
might give the cell capacities.

From the AA charge current in the manual it seems the NiMh charge
is 420mA for 5 hours then going to a trickle (maintenance) 20mA
charge. I f so 1400mAh cells will fully charged and not be
overcharged even during continous trickle charging.

More than 1400mAh cells will be undercharged (to only about
1400mAh) but that is not a problem for MiNh chemistry and will
actually result in very long cell cyclel life. Less than 1400mAh
cells will be overcharged and that ruins the cells i.e, less
cycles.

Standard 600-700mAh NiCad AAs will be correctly charged and the
inexpensive NiMh 2500-3000mAh C and Ds will fully charged.
The key to this kind of charger is fully discharge the cells and
use the right capacity cells for it. Then, it is perfectly fine.