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Posted by Oren on April 23, 2007, 6:11 pm
>
>> >As I understand it, if you're going to discharge this way, you want
>> >to stop discharge just as the voltage across each cell is around
>> >1V. Which for an 18V battery is 15V. The lamp should be noticably
>> >dimmer at that point.
>>
>> So leaving the flash light switched on over night is not best... no
>> lamp flicker, light, nada...too much drain on the battery?
>>
>I've heard that if you completely discharge a battery it is "possible"
>that it can recharge with a reverse polarity. May be possible with a
>single cell, but I don't think that is possible in a battery pack.
>There may be other new reasons for not completely discharging battery
>packs, but that used to be the way to prevent ni-cad memory problems.
>-Red
Based on my one experience, a complete discharge is not advisable.
--
Oren
"I don't have anything against work. I just figure, why deprive somebody who
really loves it."
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Posted by Dan_Musicant on April 24, 2007, 12:49 am
:
:>
:>> >As I understand it, if you're going to discharge this way, you want
:>> >to stop discharge just as the voltage across each cell is around
:>> >1V. Which for an 18V battery is 15V. The lamp should be noticably
:>> >dimmer at that point.
:>>
:>> So leaving the flash light switched on over night is not best... no
:>> lamp flicker, light, nada...too much drain on the battery?
:>>
:>I've heard that if you completely discharge a battery it is "possible"
:>that it can recharge with a reverse polarity. May be possible with a
:>single cell, but I don't think that is possible in a battery pack.
:>There may be other new reasons for not completely discharging battery
:>packs, but that used to be the way to prevent ni-cad memory problems.
:>-Red
:
:Based on my one experience, a complete discharge is not advisable.
I believe it is possible to reverse polarize one of the cells in a
battery pack such as a cordless drill's. I seem to have read that in a
post somewhere. Anyway, the manuals for the tools always seem to counsel
not draining the pack too far before recharging. It's always possible
that one of the cells is a lot weaker than the average and that would
cause trouble. It's something that would be hard to know unless you
could disassemble the cell pack, which I'm not about to do.
I haven't gotten too far in my experiment (busy today), but will get
back at it tomorrow and this time keep careful records and try to
determine if I'm making real progress in reconditioning my 4 cordless
battery packs.
I don't think I'll bother using a slow discharge method this time. The
batteries don't seem to be getting very hot while I drain them by having
the drills set on low and rubber bands around the switch. I'm careful
not to have the switch partially depressed. The Dewalt's instructions
actually said it was bad for the drill to use very slow speed. I have no
idea why. The drill itself seems to be getting a lot hotter during
discharge than the battery pack, but not alarmingly so.
Dan
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Posted by clifto on April 23, 2007, 6:48 pm
Chris Lewis wrote:
> As I understand it, if you're going to discharge this way, you want
> to stop discharge just as the voltage across each cell is around
> 1V.
As I understand it, if you're going to discharge this way, you want
to stop discharge just as the voltage across *the lowest cell* is around
1V. By the time you discharge until the average cell is around 1V, or
until the pack voltage is about 1V per cell, or worse, until all cells
but one are below 1V, chances are good that you will be able to measure
reversed polarity across the weakest cells. That's an indication that
those cells are no longer cells.
--
Music hath charms to soothe the savage breast.
That's why stereo has two channels.
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Posted by Dan_Musicant on April 24, 2007, 12:50 am
:Chris Lewis wrote:
:> As I understand it, if you're going to discharge this way, you want
:> to stop discharge just as the voltage across each cell is around
:> 1V.
:
:As I understand it, if you're going to discharge this way, you want
:to stop discharge just as the voltage across *the lowest cell* is around
:1V. By the time you discharge until the average cell is around 1V, or
:until the pack voltage is about 1V per cell, or worse, until all cells
:but one are below 1V, chances are good that you will be able to measure
:reversed polarity across the weakest cells. That's an indication that
:those cells are no longer cells.
I agree.
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Posted by SJF on May 12, 2007, 12:50 pm
>
> :Chris Lewis wrote:
> :> As I understand it, if you're going to discharge this way, you want
> :> to stop discharge just as the voltage across each cell is around
> :> 1V.
> :
> :As I understand it, if you're going to discharge this way, you want
> :to stop discharge just as the voltage across *the lowest cell* is around
> :1V. By the time you discharge until the average cell is around 1V, or
> :until the pack voltage is about 1V per cell, or worse, until all cells
> :but one are below 1V, chances are good that you will be able to measure
> :reversed polarity across the weakest cells. That's an indication that
> :those cells are no longer cells.
>
> I agree.
Amen! Been there, done that.
As I read the literature, good multiple cell batteries are made up from
uniform cells all from the same production batch. Then you hope they stay
uniform.
Best to quit using the battery as soon as you detect a slowing speed. But
my wife would take a half discharged device and run it till it stopped.
Hard to recover from that.
I now keep small appliances like hand vacs and grass clippers on chargers
modified to trickle charge (added resistance). For frequently used tools,
the slow charge might not be at all convenient but for occasional use
devices, the resulting full charge adds a large margin of safety. My old
Dustbuster has 10-year old cells used this way and still does its job.
SJF
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