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Pelican Technical Article:

Charging and Jump Starting your Jetta

Jared Fenton

Time:

1 hour1 hr

Tab:

$60 to $200

Talent:

**

Tools:

Battery charger, multimeter, battery tender

Applicable Models:

VW Jetta (1999-05)

Hot Tip:

Read the article and your owner's manual thoroughly

Performance Gain:

Better operating electrical system

Complementary Modification:

Install battery tender

The electrical system on the VW Jetta can cause a variety of problems when a battery has a low charge. This article will cover the basics of checking the battery condition, hooking up a battery charger and also how to jumpstart the car.

I recommend hooking up a battery charger with at least a 40 amp capability if you will be working on the vehicle for more than 15 minutes, when using a diagnostic scanner, adjusting the headlights and any time the doors, hood and rear hatch will be open for an extended period of time. One-way to reduce the amount of power consumed is to manually actuate the latches for the doors, hood and rear hatch. Simply take a screwdriver and push the latch to the closed position. This will trick the car's computer systems into thinking that the door is closed and it will shut off the lights. Stick a rag in the latch to remind yourself to pull the handle before closing the hood or a door.

Due to the design of the car, the best way to check battery condition is to use the factory diagnostic computer or a good aftermarket software package. Using these methods allows you to monitor the battery voltage as well as current draw and alternator output. Chances are that the vehicle likely has diagnostic trouble codes stored indicating an erratic voltage condition if the battery is on its way out.

You can check the voltage on the connection posts using a voltmeter, however this is a less accurate means of determining the battery's condition. Place the meter's probes on the connection posts. A normal battery should read a voltage slightly above 12 volts with the car sitting still and no electrical devices on. A typical reading would be in the 12.6-volt range when the battery is fully charged. If the reading is 12 volts or less, then the battery needs charging or needs to be replaced with a new one. To be certain, you can remove the battery and take it to your local auto parts store for testing. See our article on Battery Replacement for more information.

When the car is running, the alternator should be outputting anywhere from about 12.5 volts to about 14.5 volts. If you don't see any significant change in the voltage after you start up the car, then your alternator could be faulty. If the voltage is high at the battery (around 17 volts or higher), then the alternator's regulator is likely faulty and needs to be replaced. Overcharging the battery at these higher levels may cause it to overflow and leak acid all over the inside of the battery tray. I have cleaned these out before, and it is not a fun job.

Whenever you're doing any work on your car, but especially when you're working with the vehicle's electrical systems, safety is of utmost importance. Never remove the negative terminal from the battery while the car is running. The battery acts as an electrical capacitor. Filters on the entire electrical system, and the car's electrical components expect it to be there, even if it doesn't hold a charge. Disconnecting the battery terminals while the engine is running can seriously damage the computers and systems of the car.

Automotive batteries are not typically deep cycle batteries, which means they do not like to be fully discharged. If you leave your lights on and drain your battery several times, then you will weaken it each time and have to replace it sooner than later. If you need to jumpstart your battery, begin by hooking the positive cable lead to the positive terminal on the dead battery. Then attach the other end of the positive cable to the positive terminal on the good battery. Now take the negative cable and attach it to the negative terminal on the good battery. Take the other end of the negative cable and attach it to one of the grounding points near the dead battery's negative terminal.

You should choose a quality battery charger with an automatic shut-off function. Pelican Parts is pleased to carry a line of CTEK Smarter Chargers ranging in price from $60-200. The battery charger will usually have two or more amperage settings. Typically, you want to charge a battery at the lowest amperage. This will take a while to do, but it is safer than running a charger at higher amperage. You should only use the higher amperage settings on a charger if you need to start the car and the battery is weak.

Probably the best way to protect your battery from draining is to install a trickle-charger / battery maintainer on it. This charger plugs into the wall when you are not using the car, and constantly monitors the battery, charging it as needed when the voltage runs down. Every car battery has internal electrical leakage that will cause it to become fully discharged over time if not properly maintained. A trickle charger can keep your battery fresh year-round, even if you don't drive the car for months at a time. Beware of cheap chargers though, as they can accidentally overcharge your battery, causing more harm than good. The trickle charger I like to use in all of my cars is the Battery Tender, available for $40-$60 at Pelican Parts.

Open the hood and remove the cover on the battery box so you can access the terminals on the battery.
Figure 1

Open the hood and remove the cover on the battery box so you can access the terminals on the battery. The green arrow points to the positive terminal, while the yellow arrow points to the negative terminal.

Connect the battery charger or jumper cables to the terminals starting with the positive terminal first (green arrow) and the opposite end of the cable on the positive terminal on the good battery (not shown).
Figure 2

Connect the battery charger or jumper cables to the terminals starting with the positive terminal first (green arrow) and the opposite end of the cable on the positive terminal on the good battery (not shown).

Now attach the negative cable to the negative terminal on the good battery (not shown) and attach the other end to a good grounding point, such as the engine cover retaining nut as shown here.
Figure 3

Now attach the negative cable to the negative terminal on the good battery (not shown) and attach the other end to a good grounding point, such as the engine cover retaining nut as shown here. You are now ready to start the vehicle with the good battery. Let it sit for a few minutes. Then start your Jetta.

You can also test the battery voltage from the connection points as shown here.
Figure 4

You can also test the battery voltage from the connection points as shown here. See our article on Battery Replacement for more information.

The battery tender is a great way to maintain the battery charge on your Jetta when not driving.
Figure 5

The battery tender is a great way to maintain the battery charge on your Jetta when not driving. They are easily installed on the battery terminals and have a quick disconnect that allows you to plug it into a standard home electrical outlet. These are available from Pelican Parts for around $40-60.

It is important that you use a quality battery charger when charging the system.
Figure 6

It is important that you use a quality battery charger when charging the system. Most modern chargers will have an automatic shut-off function and monitor the charging rate. Use the higher amperage settings only when jumpstarting the car. Pelican Parts is pleased to carry a variety of battery chargers from CTEK ranging in price from $60-200.

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Page last updated: Sat 12/3/2016 02:49:59 AM