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[OM] Re: OT (of course!): "outdated" NiMH charger?

Subject: [OM] Re: OT (of course!): "outdated" NiMH charger?
From: "Jeff Keller" <jrk_om@xxxxxxxxxxx>
Date: Thu, 12 Jan 2006 09:54:52 -0800
Probably any charger that does something other than a trickle charge is 
labeled an intelligent charger.

Basically a charger forces a current into the battery. That can be done at a 
low rate without worrying about the battery's voltage. If the battery is 
charged quickly with a high current, the charger should look at the voltage 
while the current is forced in and reduce the current when it believes the 
battery is near full charge. If the charger were designed for a different 
type of battery it might no't correctly tell when the battery is charged. It 
could reduce to a very low current or even shut off too soon.

I bellieve some "intelligent" chargers just used a timer. A higher capacity 
battery wouldn't be completely charged but should be charged up to the 
capacity of the battery that the charger expects.

I briefly had a Panasonic intelligent fast charger that used a timer. It 
would dramatically over heat the batteries.

If you are using batteries of the same type (ex NiMH) that just have a 
different capacity, I am surprised that it charges the higher capacity 
batteries to a lower level. My MAHA charger sometimes thinks the batteries 
can not be charged, and starts flashing a red light after a couple minutes. 
Often just removing the battery and putting it back in will cause it to 
accept the battery and charge it. When the battery dies of "old age", the 
charger refuses to charge it rather than forcing a current into the battery 
potentially causing leakage or other problems.

-jeff

----Original Message Follows----
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>

snip

When I first tried the Panasonic charger I was running it and the Maha
side-by-side and was quite surprised that the Panasonic finished sooner.
   Out of curiosity I took the supposedly fully charged batteries out of
the Panasonic charger and put them in the Maha.  Much to my surprise the
Maha continued to charge them for quite some time.  Maybe an hour or so
as I recall.

Anyhow, I still use the Panasonic charger as additional capacity when
needed but the batteries ultimately go into the Maha charger later for a
top up.

ps:  The ebay sourced Maha charger was not only much cheaper than Thomas
Distrbuting but also came with a cigarette lighter adapter for charging
in the car.  Also, 2 or 3 of the PowerEx 1800 mah batteries from Thomas
have given up the ghost.  Life was probably about 2 years.

Chuck Norcutt

ScottGee1 wrote:

 > We seem to have a couple list members who have the correct background
 > to answer this so . . .
 >
 > A few years back I bought an "Intelligent" battery charger from Radio
 > Shack for my NiCad and NiMH cells.  Been working well for years.
 > Recently bought some Everready 2300 mah NiMH cells, charged 'em up for
 > use in a shoe mount flash to shoot pix at a party.  First set of four
 > pooped out at around 25 shots, same with the second set.  Normally, I
 > get ~200 shots in such a situation from a set of cells with lower
 > capacity.
 >
 > Called Everready and they were very polite but blame my charger,
 > saying it probably doesn't have the ability to charge the newer, high
 > capacity batteries.  Suggest I get one of theirs.  I guess I don't
 > understand the process.  I thought an intelligent charger would simply
 > increase voltage and/or time to make sure a cell was completely
 > charged.
 >
 > Is Everready correct?  Do I need to buy a new charger?  And will I
 > need to buy a new one every time I buy higher capacity cells?
 >
 > ????/ScottGee1



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