TYPE47 : Battery

General Description

The battery type is the same as the one described in the TRNSYS manual except for an addition of self discharge and a change in parameter input. The parameters have been divided in two groups; a group that describes the battery cell (specific for the type of battery) and another group that describes the setup of the batteries. The first group of data is given in a data file and this will make it possible to select different batteries from a data base.

The self-discharge model is implemented at Fraunhofer Institute in Freiburg, Germany by Wilfred Griesshaber and Fredrick Sick.

Nomenclature

a - Factor for temperature and voltage

b - Factor for temperature and voltage

I_0sd - Self discharge current at T = T₀ and U = U₀

Q - Capacity of battery (Ampere hours)

Q_max - Maximum capacity of battery

T - Battery temperature

T₀ - Temperature for I = I_0sd and U = U₀

U - Battery voltage

U₀ - Voltage for I = I_0sd and T = T₀

Mathematical Description

The mathematical equations used are the same as in the TRNSYS manual except the self discharge model which is calculated from the following equation:

Isd = I0sd * Q/Qmax * e^{[a(T-T0) + b(U-U0)]}

TRNSYS Component Configuration

PARAMETER NO. DESCRIPTION

1: mode - mode for calculations (all modes need the battery data even if the data are not needed)

2: lud - Logical unit number for the battery data base.

3: C_p - Cells in parallel

4: C_s - Cells in series

5: N_batt - Number of the selected battery in the data base

6: T_batt - Surrounding temperature of the electrolyzer

7: V_c - Maximum charge voltage

8: V_contr - < 0 => V_d is calculated >0 => V_d = V_contr

9: I_ctol - Iteration accuracy in Amperes

INPUT NO. DESCRIPTION

The inputs are the same as in the TRNSYS manual

OUTPUT NO. DESCRIPTION

The outputs are the same as in the TRNSYS manual except four more outputs:

13: I_sd - Self-discharge current

14: Q_sd - Self discharge ampere hours

15: P_sd - Self-discharge power

16: P_wfull - Power wasted because the battery is full

The data for a battery cell has to be given in a separate file. The first line in this file will give the number of battery cells given in the file. The for each different cell will have two lines; the first line will give the number of the cell in the file, the second line will give the data for the cell. The last three parameters in the file have to be given even though the mode does not require it. It does not matter what values they are given in this case. The data file for the battery cell will be like this (the third line (P1-P18) should not be in the file, but are included here to show which data means what):

1,Batterycell

417 .9 2.5 29.3 2.00 1.18 .1 .1 1. -.0087 20. .1 2.07 2.13 2.2 0.0834 417 -417

P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 P15 P16 P17 P18

P1 = Q_max : Rated capacity of battery cell [Ah]

P2 = Eff : Charging efficiency

P3 = i₁ : Parameter used to calculate the additional voltage term from a given current in the Hyman model

P4 = k₁ : Parameter used to calculate the additional voltage term from a given current in the Hyman model

P5 = m_d : Cell type of parameters which determine the shape of the I-V-Q characteristics for discharging

P6 = c_d : Factor for capacity parameter on discharge [-]

P7 = s_d : Factor for internal resistance at full charge for discharge [-]

P8 = g_d : Coefficient of (1-F) in voltage formulas for discharging

P9 = m_c : Cell type of parameters which determine the shape of the I-V-Q characteristics for charging

P10= c_c : Factor for capacity parameter on charge [-]

P11= s_c : Factor for internal resistance at full charge for charge [-]

P12= g_c : Coefficient of (1-F) in voltage formulas for charging

P13= e_sd : Extrapolated open circuit voltage for discharge

P14= e_sc : Extrapolated open circuit voltage for charge

P15= U₀ : Basic voltage for self-discharge [V]

P16= I_0sd : Self-discharge-current [A] at tbat=temp0(=20 C) and v=volt0 (2.2 V for lead-acid battery)

P17= I_Qmax : Maximum current (charge) [A]

P18= I_Qmin : Minimum current (discharge) [A]

OUTPUT to file logical unit 6 will look like this:

Parameters from file to battery, unit xx:

Qmax = 4.1700E+02 Eff = 9.0000E-01 i1 = 2.5000E+00

k1 = 2.9300E+01 md = 2.0000E+00 cd = 1.1800E+00

sd = 1.0000E-01 gd = 1.0000E-01 mc = 1.0000E+00

cc = -8.7000E-03 sc = 2.0000E+01 gc = 1.0000E-01

esd = 2.0700E+00 esc = 2.1300E+00 volt0 = 2.2000E+00

I0sp = 8.3400E-02 IQmax = 4.1700E+02 IQmin = -4.1700E+02