AVR-Chat

I want to build a battery charger with a bit of intelligence, just a bit.

I would like the charger to check the battery voltage every so often, one a minute at most, and if it has reached a set value, I would like the charger to shut it self off.

I would also like charging to commence with a push of button to prevent a power interruption from starting a new charging cycle.

To accomplish this I was wondering what device would be appropriate.  All it has to do is control a relay, and have a single ADC.

Any suggestions?

--- In AVR-Chat@yahoogroups.com, "syberraith" <syberraith@...> wrote:
>
> I want to build a battery charger with a bit of intelligence, just a bit.
> 
> I would like the charger to check the battery voltage every so often, one a minute at most, and if it has reached a set value, I would like the charger to shut it self off.
> 
> I would also like charging to commence with a push of button to prevent a power interruption from starting a new charging cycle.
> 
> To accomplish this I was wondering what device would be appropriate.  All it has to do is control a relay, and have a single ADC.
> 
> Any suggestions?
>

As this is an AVR group, how about an ATtiny25, 45, 85.

don

I did this a while back, in a Tiny-26 with the AVR also doing the PWM
constant current buck regulation.   However, if I was to do it again
today, I'd leave the current regulation to an external chip unless
forced to do it this way for cost.

I think that NIMH cells are probably the most complicated of the
common chemistries to work with, if you really follow all the rules.
They are just plain delicate.

I think that pretty much anything with an ADC would be enough.  You  
could also get something with built in PWM so you could vary the  
charge voltage as the charge nears completion.  The ATMega 16HVA, HVB,  
and 32HVA, HVB are designed to be chargers.  You could also go with a  
general purpose device.

Finally, although you can get by with a 6 or 8 pin chip for what you  
want, you might want to go with more pins so you can dedicate pins to  
the programming header.

On Mar 13, 2010, at 11:01 AM, syberraith wrote:

> I want to build a battery charger with a bit of intelligence, just a  
> bit.
>
> I would like the charger to check the battery voltage every so  
> often, one a minute at most, and if it has reached a set value, I  
> would like the charger to shut it self off.
>
> I would also like charging to commence with a push of button to  
> prevent a power interruption from starting a new charging cycle.
>
> To accomplish this I was wondering what device would be  
> appropriate.  All it has to do is control a relay, and have a single  
> ADC.
>
> Any suggestions?
>
>
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>

Yep, I've been looking at the Maxim charger chips that setup up to work with a uControllers.  I have yet to run across any others.

I have a Duracell 15 minute NIMH charger, and was wondering why it killed batteries so fast.  After reading up on the charging methods for the different chemistries, now I know why.

--- In AVR-Chat@yahoogroups.com, David VanHorn <microbrix@...> wrote:

>
> I did this a while back, in a Tiny-26 with the AVR also doing the PWM
> constant current buck regulation.   However, if I was to do it again
> today, I'd leave the current regulation to an external chip unless
> forced to do it this way for cost.
> 
> I think that NIMH cells are probably the most complicated of the
> common chemistries to work with, if you really follow all the rules.
> They are just plain delicate.
>

I'm unsure if I want to go straight to my final design in one step.  I might want to build a simple/limited version first.  For my most simple version I have the current being regulated by a linear regulator, and all the controller needs to do it turn it off when the system reaches a set voltage.

More elaborate versions could include such things as pre-testing charge state, and automatic discharge of any remaining charge before charging.  However, my goal at the moment is just to get a simple one done and working.



--- In AVR-Chat@yahoogroups.com, Philippe Habib <phabib@...> wrote:

>
> I think that pretty much anything with an ADC would be enough.  You  
> could also get something with built in PWM so you could vary the  
> charge voltage as the charge nears completion.  The ATMega 16HVA, HVB,  
> and 32HVA, HVB are designed to be chargers.  You could also go with a  
> general purpose device.
> 
> Finally, although you can get by with a 6 or 8 pin chip for what you  
> want, you might want to go with more pins so you can dedicate pins to  
> the programming header.
> 
> 
> On Mar 13, 2010, at 11:01 AM, syberraith wrote:
> 
> > I want to build a battery charger with a bit of intelligence, just a  
> > bit.
> >
> > I would like the charger to check the battery voltage every so  
> > often, one a minute at most, and if it has reached a set value, I  
> > would like the charger to shut it self off.
> >
> > I would also like charging to commence with a push of button to  
> > prevent a power interruption from starting a new charging cycle.
> >
> > To accomplish this I was wondering what device would be  
> > appropriate.  All it has to do is control a relay, and have a single  
> > ADC.
> >
> > Any suggestions?
> >
> >
> >
> >
> >
> > ------------------------------------
> >
> > Yahoo! Groups Links
> >
> >
> >
>

I just read Amtel's AVR-based Constant Current Supply app note, which left me wondering why would you prefer an external chip for the current regulation.  What difficulty did you have with using just one chip?

--- In AVR-Chat@yahoogroups.com, "syberraith" <syberraith@...> wrote:

>
> Yep, I've been looking at the Maxim charger chips that setup up to work with a uControllers.  I have yet to run across any others.
> 
> I have a Duracell 15 minute NIMH charger, and was wondering why it killed batteries so fast.  After reading up on the charging methods for the different chemistries, now I know why.
> 
> --- In AVR-Chat@yahoogroups.com, David VanHorn <microbrix@> wrote:
> >
> > I did this a while back, in a Tiny-26 with the AVR also doing the PWM
> > constant current buck regulation.   However, if I was to do it again
> > today, I'd leave the current regulation to an external chip unless
> > forced to do it this way for cost.
> > 
> > I think that NIMH cells are probably the most complicated of the
> > common chemistries to work with, if you really follow all the rules.
> > They are just plain delicate.
> >
>

I looked that up already.  It's a 10C rise accompanied by a 10mV drop, at least according to PowerStream datasheets.

The simple voltage cutoff is actually for recharging disposable alkalines, cutoff at 10% of rated voltage.  :)

Fred

--- In AVR-Chat@yahoogroups.com, Dennis Clark <dlc@...> wrote:

>
> Hi,
> 
>    Your method of checking voltage to determine cutoff would work 
> somewhat for LiIon cells but not so well for NiMh.  NiMh have a pretty 
> flat discharge curve and their charge curve is best served by monitoring 
> temperature rise, the "peak" voltage of an NiMh is subtle and not always 
> easy to catch without some pretty good charge circuitry.  I'd have to 
> look up the optimal temperature rise to detect a full charge, I forget 
> the details.  Check out battery sites to get more charge details.
> 
> DLC
> 
> On 3/14/10 6:45 AM, syberraith wrote:
> > I'm unsure if I want to go straight to my final design in one step.  I might want to build a simple/limited version first.  For my most simple version I have the current being regulated by a linear regulator, and all the controller needs to do it turn it off when the system reaches a set voltage.
> >
> > More elaborate versions could include such things as pre-testing charge state, and automatic discharge of any remaining charge before charging.  However, my goal at the moment is just to get a simple one done and working.
> >
> >
> >
> > --- In AVR-Chat@yahoogroups.com, Philippe Habib<phabib@>  wrote:
> >    
> >> I think that pretty much anything with an ADC would be enough.  You
> >> could also get something with built in PWM so you could vary the
> >> charge voltage as the charge nears completion.  The ATMega 16HVA, HVB,
> >> and 32HVA, HVB are designed to be chargers.  You could also go with a
> >> general purpose device.
> >>
> >> Finally, although you can get by with a 6 or 8 pin chip for what you
> >> want, you might want to go with more pins so you can dedicate pins to
> >> the programming header.
> >>
> >>
> >> On Mar 13, 2010, at 11:01 AM, syberraith wrote:
> >>
> >>      
> >>> I want to build a battery charger with a bit of intelligence, just a
> >>> bit.
> >>>
> >>> I would like the charger to check the battery voltage every so
> >>> often, one a minute at most, and if it has reached a set value, I
> >>> would like the charger to shut it self off.
> >>>
> >>> I would also like charging to commence with a push of button to
> >>> prevent a power interruption from starting a new charging cycle.
> >>>
> >>> To accomplish this I was wondering what device would be
> >>> appropriate.  All it has to do is control a relay, and have a single
> >>> ADC.
> >>>
> >>> Any suggestions?
> >>>
> >>>
> >>>
> >>>
> >>>
> >>> ------------------------------------
> >>>
> >>> Yahoo! Groups Links
> >>>
> >>>
> >>>
> >>>        
> >>      
> >
> >
> >
> > ------------------------------------
> >
> > Yahoo! Groups Links
> >
> >
> >
> >    
> 
> -- 
> Dennis Clark
> TTT Enterprises
>

Interesting...  I read in the constant current app note that engineer for ControlTek also found the accuracy of the T15's ADC to be less than sufficient.  So he used a external voltage reference and an opamp to get the current regulation of the PWM within 10%.

I would ultimately like to have some PC communication including charge and discharge logging.

I was using the Duracell batteries with the charger.  Half maybe more start reporting errs in the charger within 10 to 20 cycles.  The ones that survive past that usually last for while although I doubt I've had any make it to one hundred cycles.  

The one that cause the errs in the 15min charger will usually take a charge in a slow c/10 charger, although I think they have reduced capacity after being slammed with so much current from the fast charger.  I would like to be able to measure their charge and discharge curves and capacities.  



--- In AVR-Chat@yahoogroups.com, David VanHorn <microbrix@...> wrote:

>
> On Sun, Mar 14, 2010 at 6:45 AM, syberraith <syberraith@...> wrote:
> > I just read Amtel's AVR-based Constant Current Supply app note, which left me wondering why would you prefer an external chip for the current regulation.  What difficulty did you have with using just one chip?
> 
> 
> 
> Codespace for one, and accuracy for another.  The T26's "precision
> reference" ended up at about 10%, I would have been better off using
> VCC as a reference.   Silicon processes that make good digital
> products generally make lousy analog.
> 
> 
> I would advise a bootloader, and a serial port.  You'll want to know
> what the chip is seeing, and why it's making the decisions that it
> does.  A terminal program can log the output for you, and help
> demystify things.  You could send temperature, current, and voltage in
> CSV format and plot in Excel.
> 
> IIRC the 15 minute chargers are only supposed to be used with their
> cells that are designed for it.  For most NIMH cells, the sweet spot
> is 1C, where the charge termination signals (rapid rise in
> temperature, voltage plateau, absolute voltage) are expressed well.
> HOWEVER: Cheap chinese cells can drive you NUTS because they don't
> have operational vents, cheaped out on the catalyst material, or got
> the electrolyte fill slightly wrong.  For your development, use only
> cells that you are absolutely sure come from a quality Japanese
> source. (Panasonic, Sanyo, etc) Definitely get the data sheets on
> those particular cells.
> 
> When you have a problem cell, you may notice that the temperature
> curve is more or less linear across the charge, without the pronounced
> spike at the end which it should have.
> You don't necessarily need a lot of precision for this, a thermistor
> on an ADC port will do, but for bonus points, look up the Hart
> Steinhart equation, and apply that to your thermistor for maximum
> accuracy. (Or implement a lookup table, after working that out in
> excel. MUCH faster!)
>

On Sun, Mar 14, 2010 at 6:45 AM, syberraith <syberraith@yahoo.com> wrote:
> I just read Amtel's AVR-based Constant Current Supply app note, which left me wondering why would you prefer an external chip for the current regulation.  What difficulty did you have with using just one chip?



Codespace for one, and accuracy for another.  The T26's "precision
reference" ended up at about 10%, I would have been better off using
VCC as a reference.   Silicon processes that make good digital
products generally make lousy analog.


I would advise a bootloader, and a serial port.  You'll want to know
what the chip is seeing, and why it's making the decisions that it
does.  A terminal program can log the output for you, and help
demystify things.  You could send temperature, current, and voltage in
CSV format and plot in Excel.

IIRC the 15 minute chargers are only supposed to be used with their
cells that are designed for it.  For most NIMH cells, the sweet spot
is 1C, where the charge termination signals (rapid rise in
temperature, voltage plateau, absolute voltage) are expressed well.
HOWEVER: Cheap chinese cells can drive you NUTS because they don't
have operational vents, cheaped out on the catalyst material, or got
the electrolyte fill slightly wrong.  For your development, use only
cells that you are absolutely sure come from a quality Japanese
source. (Panasonic, Sanyo, etc) Definitely get the data sheets on
those particular cells.

When you have a problem cell, you may notice that the temperature
curve is more or less linear across the charge, without the pronounced
spike at the end which it should have.
You don't necessarily need a lot of precision for this, a thermistor
on an ADC port will do, but for bonus points, look up the Hart
Steinhart equation, and apply that to your thermistor for maximum
accuracy. (Or implement a lookup table, after working that out in
excel. MUCH faster!)

Hi,

   Your method of checking voltage to determine cutoff would work 
somewhat for LiIon cells but not so well for NiMh.  NiMh have a pretty 
flat discharge curve and their charge curve is best served by monitoring 
temperature rise, the "peak" voltage of an NiMh is subtle and not always 
easy to catch without some pretty good charge circuitry.  I'd have to 
look up the optimal temperature rise to detect a full charge, I forget 
the details.  Check out battery sites to get more charge details.

DLC

On 3/14/10 6:45 AM, syberraith wrote:
> I'm unsure if I want to go straight to my final design in one step.  I might want to build a simple/limited version first.  For my most simple version I have the current being regulated by a linear regulator, and all the controller needs to do it turn it off when the system reaches a set voltage.
>
> More elaborate versions could include such things as pre-testing charge state, and automatic discharge of any remaining charge before charging.  However, my goal at the moment is just to get a simple one done and working.
>
>
>
> --- In AVR-Chat@yahoogroups.com, Philippe Habib<phabib@...>  wrote:
>    
>> I think that pretty much anything with an ADC would be enough.  You
>> could also get something with built in PWM so you could vary the
>> charge voltage as the charge nears completion.  The ATMega 16HVA, HVB,
>> and 32HVA, HVB are designed to be chargers.  You could also go with a
>> general purpose device.
>>
>> Finally, although you can get by with a 6 or 8 pin chip for what you
>> want, you might want to go with more pins so you can dedicate pins to
>> the programming header.
>>
>>
>> On Mar 13, 2010, at 11:01 AM, syberraith wrote:
>>
>>      
>>> I want to build a battery charger with a bit of intelligence, just a
>>> bit.
>>>
>>> I would like the charger to check the battery voltage every so
>>> often, one a minute at most, and if it has reached a set value, I
>>> would like the charger to shut it self off.
>>>
>>> I would also like charging to commence with a push of button to
>>> prevent a power interruption from starting a new charging cycle.
>>>
>>> To accomplish this I was wondering what device would be
>>> appropriate.  All it has to do is control a relay, and have a single
>>> ADC.
>>>
>>> Any suggestions?
>>>
>>>
>>>
>>>
>>>
>>> ------------------------------------
>>>
>>> Yahoo! Groups Links
>>>
>>>
>>>
>>>        
>>      
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
>    

-- 
Dennis Clark
TTT Enterprises

According to an electrochemist I talked to with TI, you can also
charge NIMH cells with a constant voltage with a current limit.. I
don' t remember what the voltage per cell was though.

I can recommend the CBA-II for checking discharge capacity.

--- In AVR-Chat@yahoogroups.com, David VanHorn <microbrix@...> wrote:
>
> I can recommend the CBA-II for checking discharge capacity.
>
GOOGLE found:  Results 1 - 10 of about 567,000 for CBA-II. 

Did you have anyone in mind ?

don

http://www.westmountainradio.com/CBA.htm

On Sun, Mar 14, 2010 at 8:19 PM, Donald H <donhamilton2002@yahoo.com> wrote:
>
>
> --- In AVR-Chat@yahoogroups.com, David VanHorn <microbrix@...> wrote:
>>
>> I can recommend the CBA-II for checking discharge capacity.
>>
> GOOGLE found:  Results 1 - 10 of about 567,000 for CBA-II.
>
> Did you have anyone in mind ?
>
> don
>
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
>

Look here:  http://www.angelfire.com/electronic/hayles/charge1.html

I built a couple just like this...works very well.  Good information on this site, anyways.

--- In AVR-Chat@yahoogroups.com, "syberraith" <syberraith@...> wrote:

>
> I looked that up already.  It's a 10C rise accompanied by a 10mV drop, at least according to PowerStream datasheets.
> 
> The simple voltage cutoff is actually for recharging disposable alkalines, cutoff at 10% of rated voltage.  :)
> 
> Fred
> 
> --- In AVR-Chat@yahoogroups.com, Dennis Clark <dlc@> wrote:
> >
> > Hi,
> > 
> >    Your method of checking voltage to determine cutoff would work 
> > somewhat for LiIon cells but not so well for NiMh.  NiMh have a pretty 
> > flat discharge curve and their charge curve is best served by monitoring 
> > temperature rise, the "peak" voltage of an NiMh is subtle and not always 
> > easy to catch without some pretty good charge circuitry.  I'd have to 
> > look up the optimal temperature rise to detect a full charge, I forget 
> > the details.  Check out battery sites to get more charge details.
> > 
> > DLC
> > 
> > On 3/14/10 6:45 AM, syberraith wrote:
> > > I'm unsure if I want to go straight to my final design in one step.  I might want to build a simple/limited version first.  For my most simple version I have the current being regulated by a linear regulator, and all the controller needs to do it turn it off when the system reaches a set voltage.
> > >
> > > More elaborate versions could include such things as pre-testing charge state, and automatic discharge of any remaining charge before charging.  However, my goal at the moment is just to get a simple one done and working.
> > >
> > >
> > >
> > > --- In AVR-Chat@yahoogroups.com, Philippe Habib<phabib@>  wrote:
> > >    
> > >> I think that pretty much anything with an ADC would be enough.  You
> > >> could also get something with built in PWM so you could vary the
> > >> charge voltage as the charge nears completion.  The ATMega 16HVA, HVB,
> > >> and 32HVA, HVB are designed to be chargers.  You could also go with a
> > >> general purpose device.
> > >>
> > >> Finally, although you can get by with a 6 or 8 pin chip for what you
> > >> want, you might want to go with more pins so you can dedicate pins to
> > >> the programming header.
> > >>
> > >>
> > >> On Mar 13, 2010, at 11:01 AM, syberraith wrote:
> > >>
> > >>      
> > >>> I want to build a battery charger with a bit of intelligence, just a
> > >>> bit.
> > >>>
> > >>> I would like the charger to check the battery voltage every so
> > >>> often, one a minute at most, and if it has reached a set value, I
> > >>> would like the charger to shut it self off.
> > >>>
> > >>> I would also like charging to commence with a push of button to
> > >>> prevent a power interruption from starting a new charging cycle.
> > >>>
> > >>> To accomplish this I was wondering what device would be
> > >>> appropriate.  All it has to do is control a relay, and have a single
> > >>> ADC.
> > >>>
> > >>> Any suggestions?
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >>> ------------------------------------
> > >>>
> > >>> Yahoo! Groups Links
> > >>>
> > >>>
> > >>>
> > >>>        
> > >>      
> > >
> > >
> > >
> > > ------------------------------------
> > >
> > > Yahoo! Groups Links
> > >
> > >
> > >
> > >    
> > 
> > -- 
> > Dennis Clark
> > TTT Enterprises
> >
>

I guess he doesn't supply the source code for the PIC?
:-(

Zack

On Mon, Mar 15, 2010 at 10:38 AM, Terrance <evilterrance@hotmail.com> wrote:

>
>
> Look here: http://www.angelfire.com/electronic/hayles/charge1.html
>
> I built a couple just like this...works very well. Good information on this
> site, anyways.
>
>
> --- In AVR-Chat@yahoogroups.com <AVR-Chat%40yahoogroups.com>, "syberraith"
> <syberraith@...> wrote:
> >
> > I looked that up already. It's a 10C rise accompanied by a 10mV drop, at
> least according to PowerStream datasheets.
> >
> > The simple voltage cutoff is actually for recharging disposable
> alkalines, cutoff at 10% of rated voltage. :)
> >
> > Fred
> >
> > --- In AVR-Chat@yahoogroups.com <AVR-Chat%40yahoogroups.com>, Dennis
> Clark <dlc@> wrote:
> > >
> > > Hi,
> > >
> > > Your method of checking voltage to determine cutoff would work
> > > somewhat for LiIon cells but not so well for NiMh. NiMh have a pretty
> > > flat discharge curve and their charge curve is best served by
> monitoring
> > > temperature rise, the "peak" voltage of an NiMh is subtle and not
> always
> > > easy to catch without some pretty good charge circuitry. I'd have to
> > > look up the optimal temperature rise to detect a full charge, I forget
> > > the details. Check out battery sites to get more charge details.
> > >
> > > DLC
> > >
> > > On 3/14/10 6:45 AM, syberraith wrote:
> > > > I'm unsure if I want to go straight to my final design in one step. I
> might want to build a simple/limited version first. For my most simple
> version I have the current being regulated by a linear regulator, and all
> the controller needs to do it turn it off when the system reaches a set
> voltage.
> > > >
> > > > More elaborate versions could include such things as pre-testing
> charge state, and automatic discharge of any remaining charge before
> charging. However, my goal at the moment is just to get a simple one done
> and working.
> > > >
> > > >
> > > >
> > > > --- In AVR-Chat@yahoogroups.com <AVR-Chat%40yahoogroups.com>,
> Philippe Habib<phabib@> wrote:
> > > >
> > > >> I think that pretty much anything with an ADC would be enough. You
> > > >> could also get something with built in PWM so you could vary the
> > > >> charge voltage as the charge nears completion. The ATMega 16HVA,
> HVB,
> > > >> and 32HVA, HVB are designed to be chargers. You could also go with a
> > > >> general purpose device.
> > > >>
> > > >> Finally, although you can get by with a 6 or 8 pin chip for what you
> > > >> want, you might want to go with more pins so you can dedicate pins
> to
> > > >> the programming header.
> > > >>
> > > >>
> > > >> On Mar 13, 2010, at 11:01 AM, syberraith wrote:
> > > >>
> > > >>
> > > >>> I want to build a battery charger with a bit of intelligence, just
> a
> > > >>> bit.
> > > >>>
> > > >>> I would like the charger to check the battery voltage every so
> > > >>> often, one a minute at most, and if it has reached a set value, I
> > > >>> would like the charger to shut it self off.
> > > >>>
> > > >>> I would also like charging to commence with a push of button to
> > > >>> prevent a power interruption from starting a new charging cycle.
> > > >>>
> > > >>> To accomplish this I was wondering what device would be
> > > >>> appropriate. All it has to do is control a relay, and have a single
> > > >>> ADC.
> > > >>>
> > > >>> Any suggestions?
> > > >>>
> > > >>>
> > > >>>
> > > >>>
> > > >>>
> > > >>> ------------------------------------
> > > >>>
> > > >>> Yahoo! Groups Links
> > > >>>
> > > >>>
> > > >>>
> > > >>>
> > > >>
> > > >
> > > >
> > > >
> > > > ------------------------------------
> > > >
> > > > Yahoo! Groups Links
> > > >
> > > >
> > > >
> > > >
> > >
> > > --
> > > Dennis Clark
> > > TTT Enterprises
> > >
> >
>
>  
>


[Non-text portions of this message have been removed]

No, however, I would use an AVR anyways.  Not too hard to figure out what it needs to do once you read through his project.

--- In AVR-Chat@yahoogroups.com, Zack Widup <w9sz.zack@...> wrote:

>
> I guess he doesn't supply the source code for the PIC?
> :-(
> 
> Zack
> 
> On Mon, Mar 15, 2010 at 10:38 AM, Terrance <evilterrance@...> wrote:
> 
> >
> >
> > Look here: http://www.angelfire.com/electronic/hayles/charge1.html
> >
> > I built a couple just like this...works very well. Good information on this
> > site, anyways.