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kit_714
Joined: 05 Jul 2006
Posts: 63
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 24 Sep 2007 17:40 Intelligent battery charger circuit |
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Dear All,
I would like to build a module of battery charging circuit, better can use microcontroller to monitor the status. Is there any recommendations on those battery charging ICs to acheieve the task?
If yes, kindly leave the information for me.
Thanks.
Kit
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btbass
Joined: 20 Jul 2001
Posts: 918
Helped: 69
Location: Oberon
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| 24 Sep 2007 18:58 Intelligent battery charger circuit |
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| You might find a solution at Microchip application notes
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kender
Joined: 19 Jun 2005
Posts: 965
Helped: 70
Location: Stanford, SF Bay Peninsula, California, Earth, Solar System, Milky Way
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| 26 Sep 2007 5:45 Re: Intelligent battery charger circuit |
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| kit_714 wrote: |
| Is there any recommendations on those battery charging ICs to acheieve the task? |
Kit,
What cell chemistry are you planning to use? What capacity? Charging is different for Lithium and Nickel chemistries.
Nick
Last edited by kender on 29 Sep 2007 2:22; edited 1 time in total |
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nguyennam
Joined: 06 Sep 2006
Posts: 459
Helped: 28
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| 28 Sep 2007 2:27 Re: Intelligent battery charger circuit |
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You should refer to Microchip and Atmel website for PIC and AVR MCUs application notes on charging batteries.
For chemistries and algorithm, as well as excellent ICs dedicated to batteries charging, you should go to Maxim website.
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hamed_sotoudi
Joined: 01 Aug 2007
Posts: 108
Helped: 11
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| 28 Sep 2007 13:16 Re: Intelligent battery charger circuit |
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Hi
go to atmel website. and search for battery charger. there is one document about battery charger with atmega8 and atiny15 and u can download its codes in c and assembly for them. but u should change the codes alittle for your battery types. and u can implement it very easily.
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inventor(y)
Joined: 18 Jun 2007
Posts: 30
Helped: 7
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| 29 Sep 2007 1:30 Re: Intelligent battery charger circuit |
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Don't use the atmel app. It's complete nonsense.
It's designer must have bin sleeping. Just look at
the mosfet driver and the way the program is written.
if you want to use it, make an extra board with a fire extinguisher
trigger circuit. a 10 K PTC and some comparators work fine here.
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ChineseDragon
Joined: 31 May 2002
Posts: 27
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| 29 Sep 2007 8:54 Intelligent battery charger circuit |
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| Go to TI and Maxim website.
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contagiouseddie
Joined: 10 May 2004
Posts: 60
Helped: 3
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| 29 Sep 2007 16:12 Re: Intelligent battery charger circuit |
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Hi There,
I just came back from a Microchip battery charging seminar and lab session.
I have been using TI's BQ series for quite some time and I guess they are better than Microchip's one in term of minimal external components, charging current capability, and wide input range.
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inventor(y)
Joined: 18 Jun 2007
Posts: 30
Helped: 7
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| 29 Sep 2007 18:37 Re: Intelligent battery charger circuit |
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Hi contagiouseddie , what BQ have you used? I tried the BQ2004. But it never worked like it should. Later I came across a battery charger using the same chip having the same problem as my design. I'm now using my own design based on an ATMEGA48. Low part count/low cost. (ATMEGA 0.8 )
Last edited by inventor(y) on 30 Sep 2007 1:17; edited 1 time in total |
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hamed_sotoudi
Joined: 01 Aug 2007
Posts: 108
Helped: 11
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| 29 Sep 2007 20:21 Re: Intelligent battery charger circuit |
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| inventor(y) wrote: |
Don't use the atmel app. It's complete nonsense.
It's designer must have bin sleeping. Just look at
the mosfet driver and the way the program is written.
if you want to use it, make an extra board with a fire extinguisher
trigger circuit. a 10 K PTC and some comparators work fine here. |
I dont know why u say like that. I use it but I made some changes to it and it has been working very well till now.
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inventor(y)
Joined: 18 Jun 2007
Posts: 30
Helped: 7
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| 29 Sep 2007 21:56 Re: Intelligent battery charger circuit |
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Hi,
-NiMh version uses -Delta V technique. This is not suitable for NiMh unless you charge with very high currents. Something the hardware can not do.
-Take a close look at the 0R25 sense resistor in the switching current source and try to find out what PWM resolution you need to get it to work stable.
-The software doesn't use a watchdog while using while loops for polled IO. It should at least use a watchdog timer for Li-Ion batteries.
-The stable ADC function.
-...
Regards
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PaulHolland
Joined: 15 Jan 2003
Posts: 621
Helped: 59
Location: Holland
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| 29 Sep 2007 22:46 Re: Intelligent battery charger circuit |
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| Design one yourself like I did with discrete components. I designed a SLA battery charger with an 10uA idle current and temperature compensated also. Current and Voltage limited and C-I and C-V charging.
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kender
Joined: 19 Jun 2005
Posts: 965
Helped: 70
Location: Stanford, SF Bay Peninsula, California, Earth, Solar System, Milky Way
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Dexter Dude
Joined: 26 Oct 2007
Posts: 45
Helped: 1
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| 26 Oct 2007 6:43 Re: Intelligent battery charger circuit |
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Check this page:
http://myweb.absa.co.za/eric.brouwer/electronics.htm
It's a good charger. I have built it with an PIC16F628A ( changed the asm code for this PIC but the logic of the charger is the same ).
Good luck.
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RenatoBR
Joined: 25 Feb 2007
Posts: 24
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| 07 Dec 2007 13:53 Re: Intelligent battery charger circuit |
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quote="Dexter Dude
It's a good charger. I have built it with an PIC16F628A ( changed the asm code for this PIC but the logic of the charger is the same ).
Good luck.[/quote]
Hi all,
Congratulations Dexter, a long time looking for a charger with pic 16F628A, but I didn't find it on the web.
I don't have konwledge enough in pics to write or change a source code.
Pls, can you post Your schematic and the source code?
Rgds,
Renato
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sri45
Joined: 12 Jun 2006
Posts: 25
Helped: 1
Location: Hyderabad
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| 08 Dec 2007 10:05 Re: Intelligent battery charger circuit |
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hi
you can go for renesas controller R8C/1A ....
to my choice this can well justify your process.
here you have not mentioned for which batteries and capacities
for processing and reference details
check out this..........
http://www.e-radiocontrol.com.ar/?download=picref-2.pdf
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Dexter Dude
Joined: 26 Oct 2007
Posts: 45
Helped: 1
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| 09 Dec 2007 16:18 Re: Intelligent battery charger circuit |
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This is the schematic for the charger (PIC16F628A / osc int 4MHZ).If needed , one could add at pin RB7 a simple serial intreface to PC.This way you could watch the voltage of Acc. , time , and state of charger using a program like RealTem or Hyperterm .
The charger perform a self test (if batt not inserted) , then checks the number of acc. connected (1-4) and display this number for 2 seconds .Then starts the discharging process till 1V/element .When discharging has finished , it pauses for 35sec(cool down) then enter into Slow charge mode (display indicates S ) for 450sec . After that it triggers High charge mode (display indicates H ) . The algoritm of charging is somehow similar with Eric's Brouwer
http://myweb.absa.co.za/eric.brouwer/electronics.htm .
This charger performs a so called "reflex charging" or "Burp charging" , and it is the most advanced charger I had buid (so far) .I must say , I am very pleased of it.
It is simple , cheap ,robust and works quite well , even with old accumulators .It is suitable for NiCd and Nimh batteries.
This is the latest hex file for PIC16F628A :
http://depositfiles.com/files/2651036 <- tested OK
For burning must use this settings :
IntOsc/ IO WDT=off PWRT=off MCLR=OFF BODEN=ON CPD=Off CP=off
The 7 segment digit display works like this:
- 0 for discharging
- I for battery In
- S for Slow Charging
- H for High (Normal) charging
- P for Fail to detect Peak
- F for Finish charging , or Trickle reflex charging
- E -for Error
- E A - for Error on Acc (battery removed while charging)
This is the schematic used for the 7segment display( I had 2 digits glued together so I made a separate PCB for this 2 digit display but only one connected to PIC )
The the switch (Ra5 to GND) could be omitted .It's function is not implemented yet.
The diode is a cheap 3A (not a Schotky diode becouse you need at least 0.6V on it .)When Lm317 is turned off it still outputs 1.25V-1.3V .So :
1.25V-0.65V= 0.6V on out when Lm317 is turned off.In practice I obtained 0.75V (the Delta Sigma ADC has some influence ).
This voltage is used to detect if at least one element is attached .After you build the circuit , with PIC removed , you must check this voltage to be soure that everything working fine.The software need at least 0.92V to detect one element , so this voltage must be in range of 0.6V-0.92V .
Last edited by Dexter Dude on 10 Dec 2007 16:53; edited 2 times in total |
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wizpic
Joined: 23 May 2004
Posts: 324
Helped: 22
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| 09 Dec 2007 18:39 Intelligent battery charger circuit |
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Dexter Dude what did you write the software in ?
Want to share source code ?
wizpic
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RenatoBR
Joined: 25 Feb 2007
Posts: 24
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| 10 Dec 2007 1:43 Re: Intelligent battery charger circuit |
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Thank you Dude,
Interesting circuit, wich type of diode can be used for "D"?
If possible share the source code, pls.
Rgds
Renato
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linhnc308
Joined: 19 Aug 2006
Posts: 22
Helped: 1
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| 10 Dec 2007 7:03 Intelligent battery charger circuit |
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| My opinion, diode D is 1N4007 or Shotsky diode, maximum current is about 2 or 3A
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Dexter Dude
Joined: 26 Oct 2007
Posts: 45
Helped: 1
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| 10 Dec 2007 8:28 Re: Intelligent battery charger circuit |
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This is the complete schematic:
The software was written in both ASM and in PIC-Basic .The ADC routine is from AN700 Microchip AppNote . The RS232 interface was only used in the develpement stage.I also used this schematic (striped away unnecessary parts ) as an PC DataLogger.
RS232 settings:
"9600baud Parity None 8 bits driven inverted " ( also known in RealTerminal as "9600 8N1 none" )
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RenatoBR
Joined: 25 Feb 2007
Posts: 24
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| 10 Dec 2007 15:44 Re: Intelligent battery charger circuit |
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Dude,
How to calibrate the 2k5 pot?
Renato
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Dexter Dude
Joined: 26 Oct 2007
Posts: 45
Helped: 1
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| 10 Dec 2007 16:48 Re: Intelligent battery charger circuit |
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There are several ways to calibrate the Pot.
Met1:
Power up the charger with 12V dc , no batt in it.
Use the RS232 connection to watch the voltage readings of ADC .I used "RealTem" software to do this.
http://realterm.sourceforge.net/.
Also connect an Digital Voltmeter on charger Output (Cathode of 1N5401 diode)
Adjust the 2k5 POT till readings from DV and RealTerm match .An error of adjustment of less then 90mV is quite OK.
This is the most accurate adjustment.
Met2:
Feed 12V dc to the charger , no batt in it .
Adjust the POT to min value.Display will read E . Slowly adjust the POT untill display show I , then go back a little till display shows again E .
This method is less accurate but works just fine .
Now put 1 acc in and power up .
The display will show for 2 sec the number of elements to be charged (in this case I and then discharge the acc till 1V (pulse discharging , aprox 300mA for 1 element , 500mA for 2 elements , 600mA for 3 or 4 elements ) . Remember to use 0.8ohmi /10W 1.25ohm/10w resistors .
Normal operation mode :
- first connect the rechargeable batteries to the charger
- power up charger
Reset = Power off charger
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wizpic
Joined: 23 May 2004
Posts: 324
Helped: 22
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| 10 Dec 2007 20:16 Intelligent battery charger circuit |
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so dexter you going to share code or not
we understand if you say no
wizpic
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RenatoBR
Joined: 25 Feb 2007
Posts: 24
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| 11 Dec 2007 0:44 Re: Intelligent battery charger circuit |
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Hi all,
I built the circuit on a potoboard using IRF540, I don't have IRF530.
Display, I have only common catode, no possible to calibrate the circuit, IŽll buy the correct this week.
Each time I power the charger it works for about five minutes (pulse discharge) and then stops using battery full charged or discharged.
I donŽt know how to prepare the RS232 to conect to PC, anyone can help me?
Can I use only one display and one BC251?
Rgds
Renato
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Dexter Dude
Joined: 26 Oct 2007
Posts: 45
Helped: 1
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| 11 Dec 2007 7:38 Re: Intelligent battery charger circuit |
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After discharge to 1V/element the charger rests for 35sec (cool down battery) and then start slow charge for aprox. 6min. So I guess your charger is working but you still need to calibrate . If you do not calibrate , the charger could work but the discharge voltage will be off .I think that's what happening in your case .
The MOS-FET it is not critical but it is better to use one with low "Vgs threshold voltage " like those in PC motherboards .This tipe of fet is important only if you are planning to use only one rechargeable element at a time (so that reflex charging keep working normal at low voltages ).
Actually you could connect the display like this (no need for transistors) :
I used 2 digits becouse I intended to display more information , but that is for future development .
The RS232 terminal should display something like this :
For RS232 connection you could use this :
http://picprojects.org.uk/projects/simpleSIO/ssio.htm
or
http://www.kmitl.ac.th/~kswichit%20/MAX232/MAX232.htm
I used MAX232 , but the transistor version should work fine.
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RenatoBR
Joined: 25 Feb 2007
Posts: 24
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| 11 Dec 2007 10:48 Re: Intelligent battery charger circuit |
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Tanks Dude,
You're helping a lot.
I'll build the RS232 with transistors, but I have one more question:
+3 to +5 volts conect on LM7805 (out).
PIC TxD conect on RB7.
PIC RxD where to conect??
GND conect on ground from charger.
Sorry for asking a lot of question, I'm not expert in pics.
Rgds
Renato
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Dexter Dude
Joined: 26 Oct 2007
Posts: 45
Helped: 1
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| 11 Dec 2007 11:02 Re: Intelligent battery charger circuit |
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"+3 to +5 volts conect on LM7805 (out). " <- correct
You don't need PIC_RXD .The communication is unidirectional : from PIC to PC.
"GND conect on ground from charger. " <- correct
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RenatoBR
Joined: 25 Feb 2007
Posts: 24
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| 12 Dec 2007 13:46 Re: Intelligent battery charger circuit |
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I built the RS232 interface with transistors and did the calibration.
On the screen of the RealTerm after the calibration I read:
V=7791 mv read=742 status=err, and on multimeter 0.773 volts, is it correct?
The value to compare with multimeter is read?
What means V=7791?
I connected one cell and start dischargin, when finished, the RealTerm showed
"no B" and did not start charging.
My calibration is correct?
May be I have a problem because no all parts available:
For 27k using 22k
For 0.8R using 2.2R
For 1.25R using 4.7R
For pot 2k5 using 2k2
For IRF 530 using IRF540
The resistors for charge and discharge are criticals or I can change the values?
What do you say.
Renato
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Dexter Dude
Joined: 26 Oct 2007
Posts: 45
Helped: 1
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| 12 Dec 2007 20:25 Re: Intelligent battery charger circuit |
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"The value to compare with multimeter is read? "
No.That is the 10bit value ADC reads (0-1023 max).You calibrated the wrong way.You should use V=xxxxmV variable instead (not read variable from RealTerm.( I guess you also changed the POT or the 2k2 resistor connected to it )
The ADC is 10bit precision but it it feed thru an voltage divider aprox 2:1 (2k5 Pot and 2k2 resistor. The resistor needs to be a little lower value then the POT )
* For 27k using 22k (OK values 22K-56K )
* For 0.8R using 2.2R (important for discharge current , not critical but direct proportional with charge resistor , in order to correctly use the "reflex charging technique"
* For 1.25R using 4.7R see above , not critical
* For pot 2k5 using 2k2 not critical
* For IRF 530 using IRF540 not critical
This are the voltage thresholds used by charger :
V_batt read
0.877V ----- 90(units) <-you need to adjust the pot to read this value 90 +- 5
1V ----- 100 (units)
2V ----- 200 (units)
3V ----- 300
4V ----- 410
8V ----- 850 ....................(1023 units max)
V=7791 <- the voltage ADC sense (or 742 x ADC_resolution )
So 7791/742 ~10mV resolution.
How exactly did you calibrate ? Where did you connect DV? If DV reads 0.773 volts then you should adjust the POT until Realterm reads 0.77-0.8V or "read=77" .Then if you put a batt in the DV and Realterm readings should match.
It is impossible to get 7.791V reading with no batt atached .Check the LM317 , the BC173 and the resistor connected to its base (decrease 1K5 resistor).
Also , if you power up the charger with no batt attached , the display should read E
Check protection diode orientation.
"Met1:
Power up the charger with 12V dc , no batt in it.
Use the RS232 connection to watch the voltage readings of ADC .I used "RealTem" software to do this.
http://realterm.sourceforge.net/.
Also connect an Digital Voltmeter on charger Output (Cathode of 1N5401 diode)
Adjust the 2k5 POT till readings from DV and RealTerm match .An error of adjustment of less then 90mV is quite OK.
This is the most accurate adjustment. "
Last edited by Dexter Dude on 12 Dec 2007 20:48; edited 1 time in total |
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