MPPT-Based Lead Acid Charger Using bq2031

Hi Chris,

Thanks for your suggestions.

I got answer for my 3rd question. but first two questions i didn't get the answer.

In that datasheet, there is no comparision between algorithm vise and more ever they didn't specify the selection criteria for the algorithm.

I am still confused with selecting the algorithm , there is no difference in application vise.( Like: all are going to charge the lead acid battery only).

Is there any criteria for selection of algorithm based upon the battery make or battery manufacturer will specify the method of charging ?

In this pdf Simple MPPT-Based Lead Acid Charger Using bq2031,

They are showing some datas in table 1  but they didn't mentioned what was the jumper setting  ?

Regards,

M.Balaji

Hi,

My battery having 6 cells. So now i am able to select RB1 value.

Thank you very much.... You really helped to understand the basic prinpciple of lead acid battery charging methods or algorithms.

I will start build this circuit very soon. if i face any problem , i will come back to you.

Regards,

M.Balaji

hi ,

I Planned to test this board. SO i did PCB desgin and purcahsed some of the components from this circuit.

When i planning to purchase the components, i come to know the the P-channel MOSFET (MTP23P06VG) is obsoleted.

Can you help me to know  the alternative components for this. Because partially purchased and builded i am about begin the test.

Regards,

M.Balaji

It just needs to be a P-channel FET with sufficient size to handle the power loss and sufficient voltage rating to handle the input voltage.  What is your input voltage?

Here is a 30V FET that should work: On  MTP50P03HDL

HI Chris,

Please can you Help me with the Gerber files of BQ2031 Based EVM for Lead acid battery charging.  If Possible please  give me the gerber files and circuit for board  in which MPPT current loop is added.  Also if there is may soln with N-Channep Mosfet insted of P- Fet.

Thanks

Rupesh

Arrow

Hi,

Can I also have  gerber and bom list of the evulation module?

Regards

Sinan

Here are the gerbers and BOM for the DV2031S2 EVM.  I do not believe a special board was built to evaluate the MPPT circuit.  I think the components were simply wired into the existing circuitry.

I am not aware of any design that uses an N-channel FET.  This is more difficult due to the gate drive requirement being above any voltage already on the board.

5482.DV2031S2_BOM.xls

3683.2031S2-B.ZIP

hello chris ,

DV2031S2 EVM gives me specifications what i needed i.e. 2.5 A , 12 V as you have used R20=0.10 ohm.

In your design of "Simple MPPT-Based Lead Acid Charger Using bq2031" you added a current control loop to implement the MPPT using the operational amplifier TLC27L2.b ut that is for 1 A  design. what changes i have to do in that current control loop so that it fulfill my requirement of 2.5 A.

Thanks and regards,

Arjun Pal

You just need to change the sense resistor that sets the charging current.  The MPPT circuit works by looking at the input voltage and reducing the charge current until the input voltage is regulated to the set value.  So, it does not regulate nor care what the absolute value of the charge current is.  It will either reduce the charge current to try to increase Vin or allow the full charge current if Vin is still above the setpoint.

hello chris,

Please complete the BOM list with the current loop resistor as i can't see from the drawing the exact values.  Today i started the work on this project, if any questions i'll try to post them here. Thank you.

R20 was 0.2 Ohm for the app note circuit.  This is a power resistor that needs to be able to dissipate (250mV)^2/0.2Ohm of power.  So, about a half Watt resistor.  I am not sure what exact part number was used here but any 0.2 Ohm half Watt resistor made for current sensing should work.

hello chris,

thanks for your reply.

i have some doubt regarding the design.

1- The level translator  circuit used between mod output and PFET base .How to design it .there is no description given in datasheets so can you help me to understand it.

2- I am using a solar panel for charging the battery and its rating is 30 W,working current is 1.67 A,and short circuit current is 1.9 A. So what should  be the Imax

thanks and regards

arjun

I am sorry but we do not have any design file for generating the level shifter circuit.  You can use what is on the EVM and then tweak it for your specific case.  Basically, the point of this circuit is to not exceed the gate source rating of the FET, especially when the FET is turned on.  With a 30V input, the gate cannot be pulled all the way to ground to turn it on, so a circuit must be added to only pull it down 15V at most.  The 15V zener, D2, accomplishes this.  The circuit also amplifies the bq2031's gate driver capability so that the FET may be switched on and off quickly with few switching losses.

Your fast charge current depends on what voltage your solar cell outputs and what voltage you pack is.  The current from the solar cell will be the input current to this buck converter which equals the charge current * pack voltage divided by input voltage from the panel times an efficiency.  Iin = Vbat * Ichg / (Vpanel * eff).  Your fast charge current also depends on what the batteries can handle.

Please take a look at the app note below for the bq24650:

http://www.ti.com/litv/pdf/slva437.

hello chris,

                   I have made the battery charger controller for a max 2 A current and i am using PWM charging algorithm in it. my pv panel has rating V(operation)=16V ,Isc(Short circuit current)=1.7 A

1-My first doubt is how i should go for efficiency calculation. what i did ,i took a variable load across the output of battery charger controller and by varying load i was taking the output voltage and current  and also input voltage and current. so i started from high load(500 ohm) and make it lower the current at this point was only 0.05 A around  and  and upto 70 ohm current didnt change very much and output voltage was just 1V below from input voltage.but as i go below 50 its changing pretty fast current starts increasing and voltage starts decreasing but around 30 ohm the battery charge controller suddenly gone into Fault state so i cudnt able to get the maximum efficiency calculation .

2- when i am charging one 20 Ah battery  from PV panel through battery charger controller.i check  input V=13.4 V,I=1.5 V  and output voltage V=12V,I=1.4 A for battery charger controller.

Now i want to use MPPT (maximum power point tracking) so i applied mppt ckt and i design it for mppt  voltage=15.5 V 

so when i applied it there the input voltage change to 15.5 V and current was around the same(as it was on constant current  in I V curve of PV and this shows its taking power from solar panel at higher efficiency) and out put voltage was still 12 V .

My question is how does mppt is efficient for battery charging as it is still giving almost same current and same voltage  to the battery as in the case of without using mppt.

please help me .

thanks and regards 

pal

1) Yes, efficiency is Vbat * Ichg / (Iin * Vpanel).  But for a solar charger, you don't care about efficiency but instead about delivering the maximum power to the battery.

For a battery charger, you can't just use a resistor as the load.  You need a voltage source that can sink current.  This can either be a 4-quadrant power supply or a 1 quadrant power supply and a load.  Figure 2 in this user's guide shows how to emulate a battery: http://focus.ti.com/lit/ug/sluu464/sluu464.pdf

2) What was the battery current with your MPPT circuit?  The circuit works by reducing the charge current to reduce the input current drawn which allows the panel to float up to a higher voltage.  Can you measure exactly how much power was delivered to the battery and drawn from the panel in each case?  It may be that the MPPT point is very close to where you were operating and that there is only a small change in the amount of power drawn from the panel.  Finally, you are very close to dropout with a 13.4V input and 12V output.  Dropout is very efficient.

Hello Chris,

I think it is a difficult choice.  MTP50P03HDL has VGS_ON  up to 2volt and RDS_ON  25milli ohm.   With 16 volt input and Battery close to 13.5 volt   there is only a window of 2.5 volt for the MOSFET gate(VGS). If   you consider drop due to temperature at the panel and drop in the driver transistor/coil  it would be hard to switch on the MOSFET.  Do you think still it can work?.

Hashim

This thread is quite old.  Could you rephrase your question?  I am unclear what you are asking.

If you are referencing a circuit, please attach a schematic.

Hello Chris,

I refer  your answer about   MPPT-Based Lead Acid Charger Using bq2031  reference design which reads as below.

""

It just needs to be a P-channel FET with sufficient size to handle the power loss and sufficient voltage rating to handle the input voltage.  What is your input voltage?

Here is a 30V FET that should work: On  MTP50P03HDL ""

The battery voltage is irrelevant to the PFET.  The controller, bq2031, will drive a level shift circuit that will apply between ground and Vin to the FET's gate.  So, the key thing to watch for is the VGS rating of the FET--make sure this is above the input voltage.  This gate drive circuit is shown here, http://www.ti.com/lit/ug/sluu023b/sluu023b.pdf, where Q4 switches the gate between (nearly) ground and Vin.