On 10/27/2012 8:50 PM, mike wrote:
On 10/27/2012 4:47 PM, D wrote:
I have this battery charger which I use for NiMH AA cells:
http://www.eastcoastphoto.com/a/283/...-f-AACHAR.html.
Some new cells I just bought do not seem to be holding a charge very
long, and I'd like to check the output of the charger to be sure it's
functioning fully. This charger uses temp to tell when the batteries
are"full" (thermistor is present under batteries), then switches to
"trickle". How can I tell by measurement if the thing is operating
properly? I have access to a multimeter and oscilloscope for testing
purposes.
Any suggestions appreciated.
yep, be more specific.
"not very long"
NiMH batteries don't hold a charge for long.
Especially high capacity ones.
Especially cheap no-name ones.
I'd not expect more than a couple of weeks of
useful storage.
Enloops or equivalent hold a charge much longer.
Temperature charge termination is a BAD way to charge cells.
It can work well if you fully discharge before recharging.
Problem is that if you put in a nearly charged cell, you can
do damage before the cell has a chance to heat up enough to
trigger the termination.
If you mean they don't put out as much energy as expected,
that's a different issue.
Depending on the load current and the device shut-off characteristic,
internal battery resistance can cause the device to shut down long
before it's used up. Cameras are especially bad in that respect.
I've got cameras that run well on one battery vendor, but not at all
on any other.
It's like anything else. If you want long service life, buy
premium cells and chargers.
Dan
Mike - Thanks for the reply. I agree temperature change sensing isn't
as good as sensing voltage changes. The batteries are Harbor Freight,
so they are cheap, but I've been using these types from them in AA & AAA
for years with no issues in things like remote keyboards, lower drain
items. Bought a new set for a CAMERA, as you said. The camera does
have a setting for cell type, and a discharge function, which I've used
to deplete them completely twice with recharging. I know this is
especially an issue with cameras. Interesting about the internal
resistance.
You may be right about springing for better cells, at least in this high
drain usage. Only trouble is my $$$ is a bit limited at the moment ;-/
Dan