REMOTE SOLAR MONITORING SYSTEM - A solution to make battery life extend by 300%

AIM OF PROJECT

Battery Monitoring System

Efficient usage of Battery

Integrating solar panel real time data with building computer

Storage of data

Like EGAUGE

METHODS OF S.O.C MEASUREMENT

Voltage Measurement

Specific Gravity Method

Quantum Magnetism

Integrated Current Method

PROBLEMS ASSOCIATED :

Better S.O.C Measurement :

Capacity changes :

Temperature

Depth Of Discharge Effect

Charge / Discharge cycles

Self Discharge

Charge Rate (C-Rate) dependence

HOW TO INCORPORATE THESE FACTORS ?

Piece Wise Linearization :

Temperature effect

C-Factor effect

Depth Of Discharge effect

Number Of Cycles effect

Incorporate these factors through feed back control into Simulink Model

1. REMOTE SOLAR MONITORING SYSTEM Mamoon Ismail Khalid Mohammad Ahsan Azim Mohammad Hamza Khawaja

2. Battery Performance is not reliable. State Of Charge is not accurately known. Unawareness of Load / Consumption data by consumer. Problem Statement

3. Storage is the most expensive of all expenditures in Solar PV : 1 00 AH Gel Regulated sealed Batteries: 28,000 RS/- 3 Batteries usually used We worked with 45 AH --- Cost 9200 Rs .

4. Aim of Project Battery Monitoring System Efficient usage of Battery Integrating solar panel real time data with building computer Storage of data Like EGAUGE

5. Methods Of S.O.C measurement Voltage Measurement Specific Gravity Method Quantum Magnetism Integrated Current Method

6. Problems associated : Better S.O.C Measurement : Capacity changes : Temperature Depth Of Discharge Effect Charge / Discharge cycles Self Discharge Charge Rate (C-Rate) dependence

7. How To Incorporate these factors ? Piece Wise Linearization : Temperature effect C-Factor effect Depth Of Discharge effect Number Of Cycles effect Incorporate these factors through feed back control into Simulink Model

8. Temperature Effect & C-Rate PIECE WISE LINEAR APPROXIMATION 0.05c 0.1c 0.2c 1c 2c

9. Charge/Discharge Cycles & D.O.D For 30% D.O.D

10. Efficiency Algorithm Set a 30% Depth Of Discharge floor! Use Parallel Battery Banks Connected through Power MOSFETS If Battery 1 S.O.C == 70 % ; Discharge Battery 2 If Battery 2 S.O.C == 70% ; Discharge Battery 1 again Continue repeatedly

11. Battery Cost Feasibility : If 1 cycle = 1 day (assumption) 50 % D.O.D : Approximately 650 Cycles 30 % D.O.D: Approximately 1700 cycles After 1700 days : Cost 1 = (1700/650)* 3 *30000 = ~ 235000 Rs Cost 2 = 3(30000) = 90,000 Rs !!

12. Simulink Model CHARGE INTERGRATOR No Of Charge Cycles Of CYCLES RELAY Battery SWITCHING Charge Cycles Capacity Temperature Effect and FINAL CAPACITY

13. EXPLANATION OF Individual BLOCKS

14. Source Charging = 8Amp Discharging = 9Amp C-rate = 0.2

15. function inst_charge2 = fcn (current2,storedCharge2) if (current2>0) inst_charge2=storedCharge2+current2*0.001; if(inst_charge2>=1620) inst_charge2=storedCharge2;%protect from over charging end elseif (current2<0) inst_charge2=storedCharge2+current2*0.001; else inst_charge2=storedCharge2; end end Stored Charge is the Charge that is previously stored in the battery. Ceiling of 1620 – Prevents Overcharge If CURRENT + ve : INCREASE the charge stored in the battery using q=it vice versa for discharging. If CURRENT = 0 : Charge kept constant. 0.001 is the sampling time. Charge Integrator Coulomb counting/State of charge

16. Stored Charge on the battery. STATE OF THE CHARGE vs Time

17. Relay Decision of which battery to discharge. 30% D.O.D floor - to maximize the life of a battery. After 30% discharge – RELAY will shift the load to the other battery!

18. Shifting Between two batteries Y=0; load on battery 1. Y=1; load on batter 2.

19. Calculating number of discharge cycles No_Cycles = fcn ( previous_storedCharge,next_storedCharge , inst_capacity,u3) if( next_storedCharge / inst_capacity <= 0.7 && previous_storedCharge / inst_capacity > 0.7 ) No_dischargeCycles =u3+1 ; else No_dischargeCycles =u3; end end If the state of charge is 70% we count that as a complete discharge cycle. Hence if the state of charge decays to 70% we know that one cycle has been traversed . CHARE CYCLE COUNT

20. Number of discharge cycles Discharge cycle number progressively increases due to continuous discharging and charging of the battery

21. N umber of cycles and Capacity function y= fcn ( capacity_feedback,no_cycles,initial_capacity ) if( capacity_feedback <=0) y=0; elseif ( no_cycles <=4 ) y= initial_capacity ; elseif ( no_cycles >4 && no_cycles <=6) y= initial_capacity *(-.025* no_cycles *100+110)/100; elseif ( no_cycles >6 && no_cycles <=8) y= initial_capacity *(-.0375* no_cycles *100+117.5)/100; elseif ( no_cycles >8 && no_cycles <=10) y= initial_capacity *(-.05* no_cycles *100+127.5)/100; else y= initial_capacity *(-.0875* no_cycles *100+165)/100 ; end < 400 discharge cycles : capacity ~ UNCHANGED 400 -600 600 – 800 800-1000 >1000 linear piecewise approximation

22. Decrease in capacity with number of cycles Governed by Piece-Wise Linear Transformation

23. Dependence of capacity on c-rate and temperature function y = fcn (y1,temp,capacity,rated_capacity_ah,c_rate,c,rated_capacity, current,capacity_charging ) rated_capacity =1620 ; rated_capacity_ah =45; temp=45; if(current>0) y= capacity_charging ; else c_rate =(-1*current)/ rated_capacity_ah ; if( c_rate >= 0 && c_rate <=.2) c=-.75*c_rate+.85; elseif ( c_rate >= 0.2 && c_rate <=1) c=-.50*c_rate+.80; elseif ( c_rate >= 1) c=-.05*c_rate+.35; end y=c; c=100*c; y1 = 0.72 * temp + c; C-rate has an inverse relationship with the capacity of battery. Standard testing condition at 25 o C Capacity increases as temperature changes from 25 o C to 40 o C Capacity decreases as temperature decreases from 25 o C .

24. Calculating the final resulting capacity of the battery y= rated_capacity -(1-y1)*( rated_capacity )-( rated_capacity -capacity); End if(capacity<=0) y=0; Output final capacity =y Final capacity incorporates the change due to : No. of Cycles Temperature C-rate This final capacity is then fed back into the starting blocks as our capacity is now altered !!

25. Simulation Working and Results

26. Charge Capacity State Of the Charge No of Cycles Charge Capacity State Of The Charge No Of Cycles CHARGE CAPACITY OF BATTERY STATE OF CHARGE CHARGE CYCLES