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: 25 56 75 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

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