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Jump Starting and Charging

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Jump starting
See Figure 1

Whenever a vehicle is jump started, precautions must be followed in order to prevent the possibility of personal injury. Remember that batteries contain a small amount of explosive hydrogen gas which is a by-product of battery charging. Sparks should always be avoided when working around batteries, especially when attaching jumper cables. To minimize the possibility of accidental sparks, follow the procedure carefully.

Figure 1 Connect the jumper cables to the batteries and engine in the order shown.
Connect the jumper cables to the batteries and engine in the order shown.

CAUTION
NEVER hook the batteries up in a series circuit or the entire electrical system will go up in smoke, including the starter!

Vehicles equipped with a diesel engine may utilize two 12 volt batteries. If so, the batteries are connected in a parallel circuit (positive terminal to positive terminal, negative terminal to negative terminal). Hooking the batteries up in parallel circuit increases battery cranking power without increasing total battery voltage output. Output remains at 12 volts. On the other hand, hooking two 12 volt batteries up in a series circuit (positive terminal to negative terminal, positive terminal to negative terminal) increases total battery output to 24 volts (12 volts plus 12 volts).

Jump starting precautions

  • Be sure that both batteries are of the same voltage. Vehicles covered by this manual and most vehicles on the road today utilize a 12 volt charging system.
  • Be sure that both batteries are of the same polarity (have the same terminal, in most cases NEGATIVE grounded).
  • Be sure that the vehicles are not touching or a short could occur.
  • On serviceable batteries, be sure the vent cap holes are not obstructed.
  • Do not smoke or allow sparks anywhere near the batteries.
  • In cold weather, make sure the battery electrolyte is not frozen. This can occur more readily in a battery that has been in a state of discharge.
  • Do not allow electrolyte to contact your skin or clothing.

Jumper cables

There are four things to consider when buying jumper cables:

Conductor (Cable)

Cables are usually made from copper, which minimizes power loss due to heating of the conductor, since copper has less resistance to electrical current (more resistance produces more heat). Aluminum is sometimes used, but the gauge size should be at least two numbers smaller to deliver the same power. The package should say "all copper conductor"; if not, push the insulation back to be sure it is copper.

The gauge (size) of the conductor is also important. The smaller the gauge numbers the larger the wire. A larger conductor will carry more current longer, without overheating.

Clamps

Check the feel of the clamps. They should resist twisting from side to side, have a strong spring and good gripping power. A higher amperage rating means the clamps will withstand more current.

Insulation

The conductor is insulated with vinyl or rubber to protect the user. Quality cables will retain their flexibility in sub-zero temperatures without cracking or breaking.

Length

Buy the shortest cables possible to safely do the job. Longer cables mean increased resistance and power loss, but they should be at least 8-10 feet to reach between two vehicles.

Jump starting proceduree

Single Battery Gasoline Engine Models

  1. Make sure that the voltages of the 2 batteries are the same. Most batteries and charging systems are of the 12 volt variety.
  2. Pull the jumping vehicle (with the good battery) into a position so the jumper cables can reach the dead battery and that vehicle's engine. Make sure that the vehicles do NOT touch.
  3. Place the transmissions of both vehicles in Neutral (MT) or P (AT), as applicable, then firmly set their parking brakes.

If necessary for safety reasons, the hazard lights on both vehicles may be operated throughout the entire procedure without significantly increasing the difficulty of jumping the dead battery.

  1. Turn all lights and accessories OFF on both vehicles. Make sure the ignition switches on both vehicles are turned to the OFF position.
  2. Cover the battery cell caps with a rag, but do not cover the terminals.
  3. Make sure the terminals on both batteries are clean and free of corrosion or proper electrical connection will be impeded. If necessary, clean the battery terminals before proceeding.
  4. Identify the positive (+) and negative (-) terminals on both batteries.
  5. Connect the first jumper cable to the positive (+) terminal of the dead battery, then connect the other end of that cable to the positive (+) terminal of the booster (good) battery.
  6. Connect one end of the other jumper cable to the negative (-) terminal on the booster battery and the final cable clamp to an engine bolt head, alternator bracket or other solid, metallic point on the engine with the dead battery. Try to pick a ground on the engine that is positioned away from the battery in order to minimize the possibility of the 2 clamps touching should one loosen during the procedure. DO NOT connect this clamp to the negative (-) terminal of the bad battery.

CAUTION
Be very careful to keep the jumper cables away from moving parts (cooling fan, belts, etc.) on both engines.


  1. Check to make sure that the cables are routed away from any moving parts, then start the donor vehicle's engine. Run the engine at moderate speed for several minutes to allow the dead battery a chance to receive some initial charge.
  2. With the donor vehicle's engine still running slightly above idle, try to start the vehicle with the dead battery. Crank the engine for no more than 10 seconds at a time and let the starter cool for at least 20 seconds between tries. If the vehicle does not start in 3 tries, it is likely that something else is also wrong or that the battery needs additional time to charge.
  3. Once the vehicle is started, allow it to run at idle for a few seconds to make sure that it is operating properly.
  4. Turn ON the headlights, heater blower and, if equipped, the rear defroster of both vehicles in order to reduce the severity of voltage spikes and subsequent risk of damage to the vehicles' electrical systems when the cables are disconnected. This step is especially important to any vehicle equipped with computer control modules.
  5. Carefully disconnect the cables in the reverse order of connection. Start with the negative cable that is attached to the engine ground, then the negative cable on the donor battery. Disconnect the positive cable from the donor battery and finally, disconnect the positive cable from the formerly dead battery. Be careful when disconnecting the cables from the positive terminals not to allow the alligator clips to touch any metal on either vehicle or a short and sparks will occur.

Dual Battery Diesel Models
See Figure 2

Figure 2 Diesel dual-battery jump starting diagram

Diesel dual-battery jump starting diagram

Some diesel model vehicles utilize two 12 volt batteries, one on either side of the engine compartment. The batteries are connected in a parallel circuit (positive terminal to positive terminal and negative terminal to negative terminal). Hooking the batteries up in a parallel circuit increases battery cranking power without increasing total battery voltage output. The output will remain at 12 volts. On the other hand, hooking two 12 volt batteries in a series circuit (positive terminal to negative terminal and negative terminal to positive terminal) increases the total battery output to 24 volts (12 volts plus 12 volts).

WARNING!!!
Never hook the batteries up in a series circuit or the entire electrical system will be damaged, including the starter motor.


In the event that a dual battery vehicle needs to be jump started, use the following procedure:
  1. Turn the heater blower motor ON to help protect the electrical system from voltage surges when the jumper cables are connected and disconnected.
  2. Turn all lights and other switches OFF.

The battery cables connected to one of the diesel vehicle's batteries may be thicker than those connected to its other battery. (The passenger side battery often has thicker cables.) This set-up allows relatively high jump starting current to pass without damage. If so, be sure to connect the positive jumper cable to the appropriate battery in the disabled vehicle. If there is no difference in cable thickness, connect the jumper cable to either battery's positive terminal. Similarly, if the donor vehicle also utilizes two batteries, the jumper cable connections should be made to the battery with the thicker cables; if there is no difference in thickness, the connections can be made to either donor battery.

  1. Connect the end of a jumper cable to one of the disabled diesel's positive (+) battery terminals, then connect the clamp at the other end of the same cable to the positive terminal (+) on the jumper battery.
  2. Connect one end of the other jumper cable to the negative battery terminal (-) on the jumper battery, then connect the other cable clamp to an engine bolt head, alternator bracket or other solid, metallic point on the disabled vehicle's engine. DO NOT connect this clamp to the negative terminal (-) of the disabled vehicle's battery.

CAUTION
Be careful to keep the jumper cables away from moving parts (cooling fan, belts, etc.) on both engines.


  1. Start the engine on the vehicle with the good battery and run it at a moderate speed.
  2. Start the engine of the vehicle with the discharged battery.
  3. When the engine starts on the vehicle with the discharged battery, remove the cable from the engine block before disconnecting the cable from the positive terminal.

Battery chargers
See Figures 3 and 4

Before using any battery charger, consult the manufacturer's instructions for its use.

Battery chargers are electrical devices that change house Alternating Current (AC) to a lower voltage of Direct Current (DC) that can be used to charge an auto battery. There are two types of battery chargers-manual and automatic.

On diesel-engine vehicles, do not operate the glow plug system while using an external battery charger to charge the battery.

A manual battery charger must be physically disconnected when the battery has become fully charged. If not, the battery can be overcharged, and possibly fail. Excess charging current at the end of the charging cycle will heat the electrolyte, resulting in loss of water and active material, substantially reducing battery life. As a rule, on manual chargers, when the ammeter on the charger registers half the rated amperage of the charger, the battery is fully charged. This can vary, and it is recommended to use a hydrometer to accurately measure state of charge.

Automatic battery chargers have an important advantage-they can be left connected (for instance, overnight) without the possibility of overcharging the battery. Automatic chargers are equipped with a sensing device to allow the battery charge to taper off to near zero as the battery becomes fully charged. When charging a low or completely discharged battery, the meter will read close to full rated output. If only partially discharged, the initial reading may be less than full rated output, as the charger responds to the condition of the battery. As the battery continues to charge, the sensing device monitors the state of charge and reduces the charging rate. As the rate of charge tapers to zero amps, the charger will continue to supply a few milliamps of current-just enough to maintain a charged condition.

Figure 3 Battery charging time chart.

Specific GravityCharger Rated Output
Before Charging* 4amps 6amps 10amps
1.250 ----Charge at 2 amps or less----
1.225 2-4 hrs 2-3 hrs 1/2-1 hr
1.200 5-7 hrs 3-5 hrs 1-2 hrs
1.175 8-10 hrs 5-7 hrs 2-4 hrs
1.150 10-14 hrs 6-8 hrs 3-5 hrs
*Temperature corrected-check with hydrometer
NOTE: Due to condition temperature, etc.
a given battery may require more or less time.
This chart is only a guide.
Check the state of charge periodically
with a hydrometer.

APPROXIMATE CHARGING TIME

Figure 4 Typical battery charger hook-up with battery in the vehicle (negative ground vehicle). Connect the positive (+) cable to the battery and the negative (-) cable to a good engine ground.
Typical battery charger hook-up.

Battery and charging safety precautions

Always follow these safety precautions when charging or handling a battery.

  1. Wear eye protection when working around batteries. Batteries contain corrosive acid and produce explosive gas a byproduct of their operation. Acid on the skin should be neutralized with a solution of baking soda and water made into a paste. In case acid contacts the eyes, flush with clear water and seek medical attention immediately.
  2. Avoid flame or sparks that could ignite the hydrogen gas produced by the battery and cause an explosion. Connection and disconnection of cables to battery terminals is one of the most common causes of sparks.
  3. Always turn a battery charger off, before connecting or disconnecting the leads. When connecting the leads, connect the positive lead first, then the negative lead, to avoid sparks.
  4. When lifting a battery, use a battery carrier or lift at opposite corners of the base.
  5. Be sure there is good ventilation in a room where the battery is being charged.
  6. Do not attempt to charge or load-test a maintenance-free battery when the charge indicator dot is yellow or clear, or otherwise indicating insufficient electrolyte..
  7. Disconnect the negative battery cable if the battery is to remain in the vehicle during the charging process.
  8. Be sure the ignition switch is OFF before connecting or turning the charger ON. Sudden power surges can destroy electronic components.
  9. Use proper adapters to connect charger leads to side terminal batteries.
  10. When turning the charger ON, slowly increase the charge rate. If gassing or spewing occurs, turn the charger OFF.

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1998 W. G. Nichols - Chilton's Easy Car Care