Rapid Battery Charging

[tAhm1D]

Hi all,

I want to  design a battery charger (SMPS) which will charge a 100Ah 12V battery in about 3 to 4 hrs.

Input: 160VAC - 240VAC
Frequency: 50Hz
Battery: Lead Acid 12V, 100Ah.
Charge Time: 3 to 4 hrs.

I made a charger earlier which take 8-10 hrs. to charge the battery but I require to charge within 4 hrs.

I was thinking of using pulse charging method. But I am not fully aware regarding the mechanism of rapid pulse charging method. Searching internet, I also could not gather adequate working knowledge. If anybody is willing to share knowledge or can provide some link, it will be of great help.

[babatundeawe]

checkout this site i guess u shud be able to get some thing out

www.smps.us they ve got a lot on smps good luck

[HackerNo.1]

Hi,
Pulse charging method is adopted recently to charge battery rapidly with very high current for 1sec on and 2-4 msec off and when voltage of the battery reaches 14.4v, then current is reduced and in this way when battery voltage reaches 14.7, then switched over to Trickle Charge. For this type of charging Micro controller control is essential and the cost of the charger becomes very high in comparison with normal charger and charging method should be perfect. Otherwise the cells of the battery may be damaged. I am having some literature regarding this and hope to help you.

[charnyutk]

Hi TAHM1D and all,
           If you want a low cost system I sugguest a tapple charging, see more at www.bb-battery.com

goodluck,

[arash_tah]

Please share your earlier charger to see what we can suggest u

[waicon]

take  a look at http://www.talkingelectronics.com/projects/BatteryCharger-12vSLA/BatteryCharger-12vSLA.html for adequate working knowledge

i've do some modification refer to : http://cid-43d920b8e0e97821.skydrive.live.com/self.aspx/Public/electronic/12VDC10amp%20pulse%20batteries%20charger.jpg
change to difference amp transformer for higher current pulse charge. this is working version i've made .

chart refer to: http://cid-43d920b8e0e97821.skydrive.live.com/self.aspx/Public/electronic/lead%20acid%20charger%20chart.gif

[charnyutk]

Hi tAhm1D,

              Could you try to use a reflextive-charging, it can charging a battery with a little bit discharging current. The result of reflective charging is the temperature of battery while charging is lower than traditional charging.

[charudatt]

Hi,
Pulse charging method is adopted recently to charge battery rapidly with very high current for 1sec on and 2-4 msec off and when voltage of the battery reaches 14.4v, then current is reduced and in this way when battery voltage reaches 14.7, then switched over to Trickle Charge. For this type of charging Micro controller control is essential and the cost of the charger becomes very high in comparison with normal charger and charging method should be perfect. Otherwise the cells of the battery may be damaged. I am having some literature regarding this and hope to help you.

Hello Hacker,

I am also looking for such a smart battery charger using Pluse to charge a SLA battery. Could you post a working schematic of the same, preferably using a PIC MCU. I have a kit on my desk which does it and uses a PIC16F72. It does every thing.

Your help would be appreciated.

regards

[tAhm1D]

Hi charudatt,
As my knowledge goes, you cannot rapidly pulse charge an SLA battery as SLA type batteries are not meant for that sort of quick charge. As it is sealed it should be charged carefully. Normally lead-acid batteries are suitable for rapid pulse type charging.

[jzaghal]

Hi,

Try this, I think it will help you.

Cheers.

[abcsantosh]

Hi tAhm1D, with some design efforts you can build a Rapid Battery Charger. First you have to understand the battery chemistry.
    Take a look at these links below. These are Unitrode Application Notes. Carefully read them. Then you will find yourself in commanding position. If you didn't find the Battery Controller mentioned in App. Notes, Don't worry you could build one using Micro controller as you already have control over SMPS. <{:-) 

1:) http://www.ti.com/sc/docs/psheets/abstract/apps/slua098.htm
2:) http://www.ti.com/sc/docs/psheets/abstract/apps/slua058.htm

    Have A Good Day 

[tAhm1D]

Hi abcsantosh,
Good application notes. I will study those. Since you are from India, I want to ask one question:
Some of the Indian IPS/Inverter makers charge the Batteries very fast with first rapid current charge and then controlling voltage and other parameters. I have reverse engineered one, and found that, they use Triac/SCR and control current through primary side phase control. For this, they use pot and OPAmp. They use same Transformer for inverter and battery charging(linear mode). I liked the system and thinking to apply the same technique for other fields also,like welding machine current control, digital voltage stabilizer etc.with Pic in place of OPAmp.Do you have any Idea regarding this? What is your opinion?

[DINESHjp]

the circuit is available for both primary and secondary winding control ,
the circuit is frequently available in the cost of 200/-(indian rs)
and it is very perfect circuit, i have design a power supply . 13.7v and 20 amp current and it is working ok

[charudatt]

which circuit are  you talking about Dinesh ?

[sohel]

Hi abcsantosh,
Good application notes. I will study those. Since you are from India, I want to ask one question:
Some of the Indian IPS/Inverter makers charge the Batteries very fast with first rapid current charge and then controlling voltage and other parameters. I have reverse engineered one, and found that, they use Triac/SCR and control current through primary side phase control. For this, they use pot and OPAmp. They use same Transformer for inverter and battery charging(linear mode). I liked the system and thinking to apply the same technique for other fields also,like welding machine current control, digital voltage stabilizer etc.with Pic in place of OPAmp.Do you have any Idea regarding this? What is your opinion?

u r right. its a multi task rutine first read ad for set current then limit it. check zero crossing int with rb0 pin from mains. calculate moc on cycle and wait for another zero crssing, like phase cut with 50hz.

MOC_FIRE
    MOVF MOC_ON_VER_FLAG,F
    BTFSC STATUS,Z   
    RETURN
    BSF  MOC           
    MOVLW .0   
    MOVWF MOC_ON_VER_FLAG
    MOVLW .35   
    MOVWF MOC_ON_COUNTER
LOOP
    DECFSZ MOC_ON_COUNTER,F
    GOTO LOOP
    BCF  MOC           
    RETURN

[abcsantosh]

    Hi tAhm1D, you are right. Here markets are flooded with branded-unbranded UPS/Inverters. Among them, some are really good designs. But as you mentioned some circuit's are using primary phase control some using secondary side phase control using scr/triac. Some even still using the series pass regulators. Although these methods and their charging speeds for UPS/Inverters are greatly depends on total output of Device. Because you can't over stress the input power even it is possible to take more input power and rapid charge the battery. The reason behind this is you are simultaneously serving the load from ac mains as well as battery charging. For stand alone or commercial battery chargers you can rapid charge the battery as you desire. B'cuz this is the only load.        
    The best method for UPS/Inverter chargers is secondary side phase control in my opinion. Off course you can use it for any other applications too. If it is stand alone device, you can gain maximum efficiency from phase control method. But obviously, some smart controls which SMPS's offer is not available. (ie, Voltage regulation etc) You can't use it for Voltage Stabilizers, b'caz you are modifying the shape of sine wave. see below link for phase control. Instead you could use servo stabilizer.(Exception for this is if you rectified the ac to dc using phase control and regulate and then converting it in ac using u Controller.) http://en.wikipedia.org/wiki/Phase_fired_controllers
    There are limit less possibilities. Instead covering all in this topic we could go step by step focusing one application at a time. <{:-)  
    Have a Good Day      

[tAhm1D]

Hi Sohel,
You are right. I made the phase control program with pic by using RB0 Pin and ADC. By toggling the RBO edge selection and using ADC, the program and circuit is ready. But I am facing some practical problem for using that for Battery Charging. Hope it can be solved. Your cooperation is highly appreciatable.

Hi abcsontosh,
I am not sure whether it can be used for voltage stabilizer or not. In phase control, I am not modifying the sine wave, rather cutting down some of it and hence will try to use it for voltage stabilizer in near future. I made the circuit and wrote the program for precision phase control and will try soon to apply practically. I made the  smps inverter but the rapid Battery Charger is not finalized yet. Hope to finish it soon with the help of good friends like you all.

[arash_tah]

Hi tAhm1d
I see u are expert in thyristo phase controled rectifier I want to know how can I stablize the control loop. loop consist a PID controlled to measure the output voltage and apply control voltage to phase control to regulate the output voltage there is also a current loop to limit the current in high current condition Exactly like a linear laboratory power supply with two volume to control voltage and current
What I am lookong for is how to desighn the control loop how to model the converter(phase control & output filter including capacitor and inductor)
Do u have any schematic or application note
Thank you very much in advanced
REGARD

[alien]

Hello friends,
first of all the thyristor phase angle controll you all are talking about is very inefficient way of controlling power,,,,it not only distorts the original sine wave`s shape it also degrades power factor.yes its true that millions of inverter units sold here in INDIA employes primary side Phase angle controll for charging lead acid battery but at the same time it also wastes a lots of utility power from grid as no one is aware here that this type of charging degrades power factor hence results in people paying much bills.These products will stand no where in international market where standards are very strict(a manufacturer may even have to pay penalties for such products).....but still it does`nt matter in a developing coutry like INDIA where standards are`nt of much importance.Ok guys this all was about some ethics etc but still scr based fire angle controll charging is cheapest way for bulk charging lead acid batteries,,,even some of my designs have them  

In my view Primary side controll is better as you will have to use small low current scr/triac with only rectifiers at secondry side,these type of schemes are suitable for constant current charging only.  

[sohel]

I have told that its a multitask.
1.read battery volt high cut like 14v peak. 13v for tricle charge
2.read mains ( u mention 160-230 )
3.read current
4. make calculation for pwm.
5.then u may decide which topology u want. (pri or sec)

[tAhm1D]

Hi,
I am not concerned about multitasking job. I am just playing in my mind with the Idea to use the AC phase controlling method to be applied to infuse required current, necessary to charge the battery rapidly and I prefer in input side. This can be done in 2 methods. One is AC Phase Angle Cutting and another is Burst Firing Triac/Pulse Skipping Method. Not clear which will be of best use.

[Ichan]

My understanding about Lead Acid batteries is they can not be charged fast, 100AH battery charged in 4 hours will mean 25A charging current - the electrolyte can be boiled.

Just found with google:
http://www.batteryuniversity.com/partone-13.htm

-ichan

[Walkura]

Dear Tahmid.

I done experiments a few years ago with primary side regulation of charging current .
In itself it is possible although i chosen not to use it in the form of phasecutting .
Phasecutting on the primary side of transformers causes heating in the transformer .
(ringcores seem to heat more then oldfashioned blocktransformers)
When you detect aswell zerocrossing as phaseshift you can make a smart *dimmer* for this .
Elektor published around 1993 or 94 a powersupply using this method .
(tomorrow i'll have a look for the article ,it will be in Dutch but at least you will have a schema to show you their method)
What we after our tests did use is primary side choose windings (3 triacs to choose 190 ,220 or 230 Volt winding) & secundary side charging control logic by MCU .
This way you have control over charging current primary (and secundary) and you prevent the transformer problems due to phasecutting (and avoid more complex primary control).
How you do secundary is a matter of choice ,thyristors ,mosfets ,what ever you feel most comfortable with .

(Last but not least (I assume you know this ,but better safe then sorry)
Do keep in mind that highcurrent pulses can damage a battery with a low cell voltage (of lets say <1,9 Volt cell (standard wet leadacid).
You can charge with high current pulses within the bulkcharge region (till gassing voltage),but do keep a pre-charge and absorption phase .
Actualy i think that charging this way might even have benefits in the matter of leadsulfides .
(as long as you keep the pre-charge phase)
This book gives a little explanation about the processes within the battery (have a look at page 18)
http://www.victronenergy.com/upload/documents/Book-EN-EnergyUnlimited.pdf
But have a look at their section about how to treat accu's it might give you idea's .

Good luck .

[tAhm1D]

Hi Walkura,
I have undergone deeply what you have written basing on practical knowledge. Yes, you have initiated good points to be kept in mind. All your points are valid. I have studied few rapid battery chargers and found that rapid charging for a certain period and voltage can be applied safely and then change to charging in constant voltage to be done till floating charging stage.
I have in mind some other applications of AC Phase Control and hence interested in that. This Phase control is for Linear Application.
For Switch mode Application, Current control will be done by an external simple circuit with Op Amp and using the Compensation Pin of SG3525 PWM IC.

Hi Ichan,
Lead Acid batteries those used for charging Inverter/IPS never discharge 100%. Normally 50% is discharged and hence bigger battery is used. So,Current is required less to charge. Other then Deep Cycle Batteries, more than 60% discharge will damage the battery itself.

[andig]

Hi,

I designed a battery charger in 2005 implementing Phase Angle Control for two different sections a Boost Section (Meant to Charge the Battery) and a dedicated Float Section (Supplying Load while battery is being charged). I did it in PicBasic Pro and assembly. I have seen programmers overlooking the capabilities of the compare module which triggers upto two thyristors running in the background using interrupts. Done on a PIC18F452 it still runs without a single breakdown since commissioning.

I used dv/dt charge termination with 20 cycle auto adaptation , charge timer and VA calc.

Best Regards
Sougata Das
Andig Technologies