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Sci.Electronics.Basics -> NiMH 1.2V charger
There are 27 messages in this thread.
You are currently looking at messages 20 to 27.
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Author: ehsjrDate: 20:40 30-12-06
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mrdarrett@gmail.com wrote:
> ehsjr wrote:
>
>>mrdarrett@gmail.com wrote:
>>
>>>I'm looking for a good design (with schematic) to charge single 1.2V
>>>NiMH batteries.
>>>
>>>Not two in series, not three or four in series: individual batteries.
>>>
>>>Schematics of chargers which can handle 4 batteries in parallel
>>>(charging individually) would be appreciated too.
>>>
>>>I've got some NiMH batteries on the fritz, and I'd like to take care of
>>>them as much as possible. Dad had a Ray-o-Vac battery charger that
>>>seemed to charge them individually, but I can't find this anywhere
>>>anymore (not at WalMart or Target).
>>>
>>>Thanks,
>>>
>>>Michael
>>>
>>
>>This will do a single cell:
>>
>> -----
>> +5 ----Vin|LM317|Vout---+
>> ----- |
>> Adj [R]
>> | |
>> +----------+
>> |
>> [NiMh]
>> |
>> Gnd ----------------------+
>>
>>I = C/50 forever; I = C/10 for 14 hour rate.
>>If using 14 hour rate, you could use a 24 hour
>>appliance timer like Intermatic TN111C
>>
>>R = 1.25/I
>>
>>Ed
>
>
>
>
> But, what if the battery wasn't completely discharged? Say, 50% or 70%
> charged? Then this (and all timer-based chargers) could overcharge it,
> right?
>
> Thanks,
>
> Michael
>
Nope. The C/10 current won't damage the battery
when limited to 14 hours by the appliance timer,
even if it is applied to a cell that is close to
fully charged for the full 14 hours.
And this is not a "timer based charger" - it is
current based, with the timer to "idiot proof" it
against people who put a cell in a charger and
forget to take it out. 'Course if they leave it
in there for months it can self-discharge, which is
why I also mentione the "forever rate".
Ed
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Author: linnixDate: 22:12 30-12-06
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mrdarrett@gmail.com wrote:
> ehsjr wrote:
> > mrdarrett@gmail.com wrote:
> > > I'm looking for a good design (with schematic) to charge single 1.2V
> > > NiMH batteries.
> > >
> > > Not two in series, not three or four in series: individual batteries.
> > >
> > > Schematics of chargers which can handle 4 batteries in parallel
> > > (charging individually) would be appreciated too.
> > >
> > > I've got some NiMH batteries on the fritz, and I'd like to take care of
> > > them as much as possible. Dad had a Ray-o-Vac battery charger that
> > > seemed to charge them individually, but I can't find this anywhere
> > > anymore (not at WalMart or Target).
> > >
> > > Thanks,
> > >
> > > Michael
> > >
> >
> > This will do a single cell:
> >
> > -----
> > +5 ----Vin|LM317|Vout---+
> > ----- |
> > Adj [R]
> > | |
> > +----------+
> > |
> > [NiMh]
> > |
> > Gnd ----------------------+
> >
> > I = C/50 forever; I = C/10 for 14 hour rate.
> > If using 14 hour rate, you could use a 24 hour
> > appliance timer like Intermatic TN111C
> >
> > R = 1.25/I
> >
> > Ed
>
>
>
> But, what if the battery wasn't completely discharged? Say, 50% or 70%
> charged? Then this (and all timer-based chargers) could overcharge it,
> right?
>
> Thanks,
>
> Michael
Some people will tell you what they think.
Let me show the facts for you to think.
The charging current is nothing more than breaking down
the H2O into Hydrogen and Oxygen.
By definition, the cell is fully charged when it's
no longer able to hold Hydrogen generated at the anode.
All things being equal, Hydrogen is continuously generated
at the same rate.
The difference being that it is no longer chemically absorbed,
but mechanically held in the cell. The pressure will build up
and raise the temperature. The cathode (bigger outer cell)
usually can hold more oxygen, so that is not a problem.
At certain point, the Hydrogen will vent out of the cell.
Lacking components for recombinations, the cell dry-out.
Now, tell me why 0.1C overcharging is not a problem.
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Author: Henry KieferDate: 10:11 31-12-06
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"linnix" <me@linnix.info-for.us> schrieb im Newsbeitrag
news:1167534765.635178.194380@h40g2000cwb.googlegroups.com...
> Some people will tell you what they think.
> Let me show the facts for you to think.
> The charging current is nothing more than breaking down
> the H2O into Hydrogen and Oxygen.
> By definition, the cell is fully charged when it's
> no longer able to hold Hydrogen generated at the anode.
> All things being equal, Hydrogen is continuously generated
> at the same rate.
> The difference being that it is no longer chemically absorbed,
> but mechanically held in the cell. The pressure will build up
> and raise the temperature. The cathode (bigger outer cell)
> usually can hold more oxygen, so that is not a problem.
> At certain point, the Hydrogen will vent out of the cell.
> Lacking components for recombinations, the cell dry-out.
The chemical reactions have a great dependence of temperature and pressure.
- Henry
--
www.ehydra.dyndns.info
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Author: linnixDate: 11:53 31-12-06
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Henry Kiefer wrote:
> "linnix" <me@linnix.info-for.us> schrieb im Newsbeitrag
> news:1167534765.635178.194380@h40g2000cwb.googlegroups.com...
> > Some people will tell you what they think.
> > Let me show the facts for you to think.
> > The charging current is nothing more than breaking down
> > the H2O into Hydrogen and Oxygen.
> > By definition, the cell is fully charged when it's
> > no longer able to hold Hydrogen generated at the anode.
> > All things being equal, Hydrogen is continuously generated
> > at the same rate.
> > The difference being that it is no longer chemically absorbed,
> > but mechanically held in the cell. The pressure will build up
> > and raise the temperature. The cathode (bigger outer cell)
> > usually can hold more oxygen, so that is not a problem.
> > At certain point, the Hydrogen will vent out of the cell.
> > Lacking components for recombinations, the cell dry-out.
>
> The chemical reactions have a great dependence of temperature and pressure.
Assuming that it is charge/discharge in the same manner (same
temperature),
the lack of Hydrogen will lower the capacity. Depending on the
specific battery,
once the Hydrogen is vented, the cell is not in the same condition any
more.
>
> - Henry
>
> --
> www.ehydra.dyndns.info
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Author: Henry KieferDate: 15:35 31-12-06
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"linnix" <me@linnix.info-for.us> schrieb im Newsbeitrag
news:1167583983.781245.92880@n51g2000cwc.googlegroups.com...
> > The chemical reactions have a great dependence of temperature and
pressure.
>
> Assuming that it is charge/discharge in the same manner (same
> temperature),
> the lack of Hydrogen will lower the capacity. Depending on the
> specific battery,
> once the Hydrogen is vented, the cell is not in the same condition any
> more.
Yes. Overloading opens the valve. Sligthly overloading is reversible as the
gas recombine with the help of an catalysator. Varta makes a cell where
loading is controlled with an internal pressure sensor.
- Henry
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Author: ehsjrDate: 17:34 31-12-06
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linnix wrote:
> mrdarrett@gmail.com wrote:
>
>>ehsjr wrote:
>>
>>>mrdarrett@gmail.com wrote:
>>>
>>>>I'm looking for a good design (with schematic) to charge single 1.2V
>>>>NiMH batteries.
>>>>
>>>>Not two in series, not three or four in series: individual batteries.
>>>>
>>>>Schematics of chargers which can handle 4 batteries in parallel
>>>>(charging individually) would be appreciated too.
>>>>
>>>>I've got some NiMH batteries on the fritz, and I'd like to take care of
>>>>them as much as possible. Dad had a Ray-o-Vac battery charger that
>>>>seemed to charge them individually, but I can't find this anywhere
>>>>anymore (not at WalMart or Target).
>>>>
>>>>Thanks,
>>>>
>>>>Michael
>>>>
>>>
>>>This will do a single cell:
>>>
>>> -----
>>> +5 ----Vin|LM317|Vout---+
>>> ----- |
>>> Adj [R]
>>> | |
>>> +----------+
>>> |
>>> [NiMh]
>>> |
>>> Gnd ----------------------+
>>>
>>>I = C/50 forever; I = C/10 for 14 hour rate.
>>>If using 14 hour rate, you could use a 24 hour
>>>appliance timer like Intermatic TN111C
>>>
>>>R = 1.25/I
>>>
>>>Ed
>>
>>
>>
>>But, what if the battery wasn't completely discharged? Say, 50% or 70%
>>charged? Then this (and all timer-based chargers) could overcharge it,
>>right?
>>
>>Thanks,
>>
>>Michael
>
>
> Some people will tell you what they think.
> Let me show the facts for you to think.
You need to learn the facts before you can show them.
http://www.powerstream.com/NiMH.htm
> The charging current is nothing more than breaking down
> the H2O into Hydrogen and Oxygen.
> By definition, the cell is fully charged when it's
> no longer able to hold Hydrogen generated at the anode.
> All things being equal, Hydrogen is continuously generated
> at the same rate.
> The difference being that it is no longer chemically absorbed,
> but mechanically held in the cell. The pressure will build up
> and raise the temperature. The cathode (bigger outer cell)
> usually can hold more oxygen, so that is not a problem.
> At certain point, the Hydrogen will vent out of the cell.
> Lacking components for recombinations, the cell dry-out.
>
> Now, tell me why 0.1C overcharging is not a problem.
>
http://www.powerstream.com/NiMH.htm
http://data.energizer.com/PDFs/nickelmetalhydride_appman.pdf
See page 19 of the Energizer Application manual
Ed
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Author: David LesherDate: 20:57 01-01-07
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I have a 4x1 cell Eveready that I hate. For reasons not explained,
it does not like some cells and just goes to "BAD" mode [blinking].
Sometimes you can fool it into starting, and then it's OK for a
full charge.
--
A host is a host from coast to coast.................wb8foz@nrk.com
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433
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