Parasitic Loads

Vehicles may have several electrical devices which result in continuous current drains on their batteries. Batteries on vehicles not being used for an extended period may become discharged by these small current drains called parasitic loads.

Any battery discharged by parasitic loading and then allowed to stand in this condition for a period of time may not readily accept recharge. However, if properly recharged, batteries will return to a good usable condition.

Extremely discharged batteries can freeze at temperatures as high as 32 degrees Fahrenheit, and freezing can also cause permanent damage. Permanent damage to discharged batteries can also be accelerated by high temperatures.

A vehicle sitting for 2 months at 32 degrees Fahrenheit most likely will not start due to parasitic load and self-discharge.


EXAMPLES OF PARASITIC LOADS:


DEVICE MILLIAMP DRAW

Voltage Regulator .001
Digital Clock .003-.0045
Quartz Clock .007
ECM .0065-.008
ETR Radio and Clock 7

-AVAILABLE BATTERY POWER:

Figure 1 shows what happens to available battery power and the power required to start the engine at different outside temperatures.

FIGURE 2 - ENERGY AVAILABLE FOR PARASITIC DRAIN:

Figure 2 shows a typical amount of current used in getting a vehicle built and delivered to the dealer, how much is available for electrical devices and how much is necessary to start the vehicle. The battery begins to be discharged at the time it is connected. Current is used during plant build, carrier handling, dealer storage and new car preparation. During this entire period, the vehicle is never driven long enough nor at a high enough RPM to bring the battery back up to a full state of charge.

Chemical reactions take place in all batteries, even if they are not connected to a load. Therefore, a certain amount of self-discharge is always occurring. The higher the ambient temperature, the greater the amount of self-discharge. This explains why the number of discharged batteries increases in very hot weather. The Delco Freedom battery has a much lower rate of self-discharge than conventional batteries. The chart below demonstrates how the increased temperature affects self-discharge.


RATE OF
TEMPERATURE SELF-DISCHARGE
(DEGREES FAHRENHEIT) (AMPS)

120 .0112
100 .0068
70 .0018
50 .0008


To prevent battery damage and difficulty in recharging, any vehicles that are not going to be in service within a 30-60 day period should have ground cable(s) disconnected to remove the constant drain on the batteries. If this is not possible, batteries should be recharged periodically every 30-60 days until the green dot is visible. The longer a vehicle sits with the battery cables connected, the higher the probability that it will have to be recharged due to the drain caused by parasitic loads and self-discharge.