10
Jan
There is a very big difference when a car battery drops even a small amount of voltage. When the engine is running the voltage is typically between 136 and 144 volts depending on the alternators load curve and the state of charge of the battery.
The amount of current a battery can provide at 0F 18C for 30 seconds while maintaining a voltage of at least 72 volts.
Typical car battery voltage. The ideal car battery voltage range will provide you with a relevant interval according to which you can measure precisely what the voltage says about the batterys current charge. A perfect voltage with the engine running is between 137 and 147V. With the engine off you should get a reading of 126 volts.
If the battery isnt fully charged it will diminish to 124V at 75 12V when its only operating at 25 and down to 119V when its completely discharged. 12 volts is the standard automotive battery in todays vehicle and each of the battery has 6 cells with a voltage of 21. A fully charged car battery has 126 volts.
There is a very big difference when a car battery drops even a small amount of voltage. When a car drops for instance from 126 to 120 there will be 75 difference. A fully charged car battery voltage should be 126v or above this is with the engine off.
To get a true voltage reading of the cars battery it is important to measure the voltage after the car has been sat for a period with the engine off preferably overnight this provides you with the car battery open circuit voltage or also know as the resting voltage. I put together the following battery state of charge chart which indicates the state-of-charge percent as it relates to battery voltage or specific gravity. Voltages and Specific Gravity are listed for a 6-volt or 12-volt battery and battery banks of 24 and 48 volts.
The chart is listed below. But first a few important notes and caveats. The key to long life for any battery is to make sure battery voltage doesnt drop below 124 volts.
The combination of a significant parasitic draw and long periods of non-use can easily cause voltage to drop below 124 volts. When that happens sulfation begins to diminish both capacity and performance. A reading of 1265-1277 volts means your battery has a full charge.
1245-1254 volts means you have a 75 charge 1224-1229 is 50 charged and 1199-1206 volts is 25 charged. 1175-1189 volts means your battery is dead. Electrolyte gravity voltage test.
This is the method used for non-sealed lead acid batteries. Most car batteries have a capacity between 550 and 1000 amperes. Matters are further complicated by the fact that youll see two-ampere ratings on most batteries.
The crank amps CA and cold cranking amps CCA. Usually the CA rating will be higher than the CCA rating. Car Batteries will generally read around 126-127 volts when the car has been turned off for a while.
While driving the volt reading will be around 134 to 148 due to the alternator and voltage regulator keeping the battery topped off or charging. The rest of the time the voltage is about 12 to 13 volts and the current draw a few Amps so the wattage is 40 watts. After the engine has been started the battery is recharged by the alternator at a current of maybe 30 amps or a charging wattage of 300 watts.
If the cars battery was completely flat it would take about 35 hours to fully charge 75 divided by 22 equals 34. Thats assuming the charger works at peak power the whole time which. The battery voltage test is especially useful on maintenance-free batteries because it can.
Cold cranking amperes CCA. The amount of current a battery can provide at 0F 18C for 30 seconds while maintaining a voltage of at least 72 volts. Modern cars with computer controlled fuel-injectedengines take no more than a few seconds to start and CCA figures are less important than they used to be.
This rating is based on the number of minutes a battery can provide a specified level of electrical current typically 20 amperes. To avoid electrical system problems and a visit to the repair shop never install a battery with a CCA or Ah rating that is lower than that recommended by the vehicle manufacturer. Fully charged automotive batteries should measure at 126 volts or above.
When the engine is running this measurement should be 137 to 147 volts. If you dont have a multimeter to tell you the voltage of your battery you can do a test of your electrical system by starting the car and turning on the headlights. So when the engine is not running the voltage ranges between 129V and 10V as the battery discharges.
When the engine is running the voltage is typically between 136 and 144 volts depending on the alternators load curve and the state of charge of the battery. Some cars can get up to 15V under normal operation. Final voltage of a full discharge.
The recommended cutoff voltage varies with the discharge rate. Table 1 shows the final discharge voltages per cell. It is important to note that deep discharging a battery at high rates for short periods is not nearly as severe as discharging a battery at low rates for long periods of time.
Generally a car battery pulls approximately 400 amps for small vehicles to start and more than 1000 amps for the large ones. That is why the car manufacturers provide bigger amps in the car battery than it needs to start. The amps in the car battery should always remain close to 0000 to prevent it from damaging.
In DC electric car conversions with very simple inexpensive controllers 6v batteries conserve battery power better than higher voltage batteries so your range ends up being longer with 6v batteries. In AC EV conversions 12 volt batteries are more common. As for 24 volt batteries Ive never seen them.