Uve Rick's Battery Page
Rescued from Geocities

Peukert Calculation

Step 1: use one of the following methods, A or B, to calculate the Peukert's values (exponent and capacity) for your battery. As an example, the default values below are for a standard 220ah, 105 minute reserve capacity (at 75 amps) golf car battery.

Method A

Enter two different times (in minutes) and currents (in amperes).

Time 1: (min)
Rate 1: (amps)
Time 2: (min)
Rate 2: (amps)

Method B

Enter the 20 hour capacity (C20) and reserve capacity in minutes. Select reserve capacity current (12v: 25a, 8v: 56a, 6v: 75a).

20 hour capacity: (ah)
Reserve capacity: (min)
At RC current: amps


 

Peukert's exponent:
Peukert capacity: ah

Step 2: Using the Peukert's values calculated above, you can now determine your battery's capacity at your chosen rate in amps, or over a given time period in hours. Enter a time and click the left button, or enter a current and click the right button. As a reference, many EVs discharge their batteries in about an hour.

Time: hours
Current: amps
Amp hours:
Given time period, calculate current and amp hours Given current, calculate time and amp hours
 


Frequently Asked Questions

What should I look at when deciding which battery to use?

You should be looking for a low Puekert's number. A high Puekert's number means the battery will not provide good range, and will have a large voltage sag. I would not use any battery which has a Puekert's number greater than 1.23.


Why is the Peukert's number important?

Because it suggests the internal resistance of the battery. Suppose a battery has a high 20 hour amp-hr rating, but a high Peukert's number. At the currents needed for EVs, this may not be a good choice. The amp-hr rating at a 1 hour rate or 1/2 hour rate can even be a lot less than a battery with a lower 20 hour amp-hr rating, but a lower Peukert's number.

When deciding on a battery, use the calculator on this page to calculate the the 1 hour or 1/2 hour amp-hr rating. This will give a better indication of the range you can expect.


If I want to have a lot of range, which battery should I use?

Range mainly depends on the weight of the batteries you have in your car, and what percentage that weight is of the total vehicle weight.


If I want to have an inexpensive low maintenance battery, which battery should I use?

I would suggest one of the Concorde batteries. Note that these batteries, though they are AGM type, cannot take the abuse (high currents) that the Optima and Hawker batteries can.


If I want a high performance car, which battery should I use?

I would suggest an Optima or Hawker battery.


If I want an inexpensive moderate range low voltage car, which battery should I use?

I would suggest a T105 or T125-type flooded lead golf car battery.


Are there any precautions which need to be taken for sealed batteries?

A sealed battery must not be overcharged. If you overcharge a sealed battery, you will greatly shorten its life. You can use battery regulators to keep this from happening.


What is cell reversal?

Cell reversal occurs when a cell in the battery has a negative voltage value. This usually happens when a cell is charged in the incorrect direction, as when the cell is completely discharged and current is still being drawn from the battery. The other cells in the battery force current through it, which charges it backwards.


How do you fix a cell reversal?

Put a resistor across the battery over night to completely drain the battery. Then charge the battery with a low current. The battery may be usable, but it will have diminished capacity and life.


How much current can I draw from the battery without damaging the battery?

This depends on the battery and how long you draw the high current. In general, the lower the Peukert's number, the higher the current you can draw from the battery without damaging the battery.


How do I charge my flooded batteries?

Charge batteries at whatever current is available until they reach 2.4 v per cell, +/- .003v per degree C difference from 25 degrees C. The higher the temperature, the lower the voltage. Once the batteries reach 2.4v (temperature corrected), keep the batteries at this voltage until the current falls to 2% of the 20h amp hour rating, expressed in amperes. As an example, 120ah batteries should be charged until the current falls below 2.4 amps.

Equalizing should be carried out about once a week when the batteries are new or very old, and once a month during the normal life of the battery. To equalize, charge the batteries at 2% of their 20h amp hour rating until voltage stops rising. Make sure you keep track of the water level in the battery while equalizing. Equalizing will use water!


How do I charge my AGM batteries?

Battery Charger (Constant Voltage): 13.8 to 15.0 volts, 10 amperes maximum, 8-10 hours approximate.

Float Charge: 13.2 to 13.8 volts, 1 amp maximum current.

Rapid Charge (Constant voltage charger): Maximum voltage 15.6 volts for a 12 volt battery (2.6 volts per cell). No current limit is necessary as long as the internal battery temperature remains below 50 degrees C. Current will taper as the battery becomes charged. When the current falls below 1 amp, the battery will be close to a full state of charge. Recharge time will vary according to temperature and charger characteristics.

Cyclic application or series string applications (CV/CC) only: Constant Voltage with Constant Current finish: 14.7 volts (2.45 volts per cell), temperature < 50 degrees C, no current limits. When current falls below 1 amp, finish with 2 amp constant current for 1 hour.


EV Batteries

WARNING: These data are not current. Uve compiled them in the mid to late 1990s. They're reproduced here strictly for historical interest. Please don't try to use them to select new batteries for your EV.

Flooded Batteries

Model

Volts

Weight (lbs)

lngth

width

height

20 hour (ah)

rsrv cpcty

cost

Cycles (80%)

Trojan SCS225

12

66

 

 

 

135

225

$85

 

DEKA 8G27

12

62.5

 

 

 

 

 

 

 

Trojan T-105

6

61

10.38

7.13

11.19

225

447

$55

733

Trojan T-125

6

66

10.38

7.13

11.19

235

488

$80

650

Trojan T-145

6

71

10.38

7.13

11.5

244

530

$95

625

Trojan T-875

8

63

10.38

7.13

11.19

150

295

$102

 

Trojan T-890

8

69

10.38

7.13

11.19

165

340

$122

 

US 8VGC

8

64.5

10.38

7.13

11.9

165

318

$50

 

Trojan 5SHP

12

86

13.56

6.75

11.5

165

272

$220

 

Eveready DC27-850

12

55

12.5

6.75

9.5

120

180

$55

 

Douglas 31EV

12

66

13

6.81

10.17

135

200

 

 


Sealed Batteries

Model

Volts

Weight (lbs)

length

width

height

20 hour (ah)

rsrv cpcty

cost

Cycles (80%)

Optima D750S

12

44.9

10.0

6.8

7.8

65

125

$130

220

Optima D750U

12

46.1

10.0

6.8

7.8

65

125

$119

220

Optima Group 31

12

72

13.0

6.8

9.5

100

190

$140

 

Concorde GPC-1234

12

23

7.68

5.15

7.22

33

50

$58

 

Concorde GPC-1248

12

32

9.41

5.45

9.35

48

84

$85

 

Concorde GPC-1260

12

43

10.2

6.6

9.35

60

106

$102

 

Concorde GPC-1272

12

50

11.82

6.6

9.35

72

114

$114

 

Concorde GPC-1280

12

53

10.2

6.6

9.35

80

149

$118

 

Concorde GPC-1285

12

61

 

 

 

85

159

$138

 

Concorde GPC-1295

12

63

11.82

6.6

9.35

95

176

$152

 

Concorde GPC-12105

12

68

12.95

6.75

9.25

105

190

$166

 

Concorde GPC-4D

12

130

20.73

8.66

10.27

210

380

$301

 

Concorde GPC-8D

12

158

20.62

10.95

10.17

255

561

$376

 

Concorde GPC-6180

6

55

10.4

7.11

10.91

180

317

$145

 

Exide Orbital 34XCD

12

38

10.175

7

7.44

50

95

$98

 

Hawker Genesis G12V38Ah10VP

12

32.9

7.75

6.5

6.69

46

66

 

500

Hawker Genesis G12V70Ah10EP

12

58

13.02

6.62

7.68

72

180

$200

500

Hawker Odyssey PC1200

12

38.2

7.87

6.66

6.8

40

78

 

 

Hawker Odyssey PC1700

12

60.9

13.02

6.62

6.93

65

142

 

 

Hawker Odyssey PC2150

12

75

13

6.8

9.4

88

200

 

 


NiMH Batteries

Model

Volts

Weight (lbs)

lngth

width

height

20 hour (ah)

rsrv cpcty

cost

Cycles (80%)

Ovonic (85ah)

12

35

16.1

3

4

112

200

 

800

Ovonic (150ah)

12

49.5

15.16

4.1

8.54

185

384

 

800


LiPoly Batteries

Model

Volts

Weight (lbs)

lngth

width

height

20 hour (ah)

rsrv cpcty

cost

Cycles (80%)

Mid term

12

21

12.5

6.75

9.5

70

140

$266

600

Long term

12

19.5

12.5

6.75

9.5

145

309

$177

1000

Saft VL Module

10.65

17.6

7.5

4.9

9.5

100

216

$177

1500