In this article, you will learn how to check the charging system on a vehicle. This procedure allows you to test the car battery and alternator.

Using a battery tester you will be able to determine if the battery is good or needs to be replaced. We will show you how to perform a load test which tells you if the alternator is providing the required voltage.

If your car won't start or doesn't stay running, usually one of the first troubleshooting steps is to check the battery and alternator. Checking the battery is very easy when you have the right tools.

What you will need

Tips for buying a car battery tester: 

  • Ideally, it should tests battery on the car directly without removing it
  • Can check 12 and 24-volt charging system
  • Works on AGM, Lead-acid flooded batteries and GEL. 
  • Cold Cranking Amps Range: 200 - 1000 CCA
  • Detects bad cells
  • Can load and test an alternator 

How to test your car battery

In this guide, we used Foxwell BT-705 Battery Analyzer which is able to test 6 volt and 12 volts batteries. It can test AGM, GEL or Lead Acid and can test charging systems 12 and 24 volts.

It is a great tool if you are looking to quickly and easily perform a load test on car batteries. It also checks charge status and determines if there are any problems with the charging system.

This is a great tool even for mechanics. It has a built-in Bluetooth chip that allows you to send reports to any Bluetooth printer. You most likely won't use the print function unless are an auto repair shop.

Instructions 

  1. Remove the key from the ignition. Locate the battery in your car. 
  2. Connect the red clamp to the positive terminal on your car battery. possitive battery termnial test car battery holding charge
  3. Connect the black clamp to the negative terminal of your battery. The battery analyzer should turn on automatically and boot up. If you get an error message saying "Check Connection" make sure the battery posts have no corrosion. test car battery
  4. Hit the MENU button and you should see the Battery Test option.  Press enter
  5. Select the battery voltage. Most cars use a 12-volt system. 
  6. Select Battery Location. In this case, we select In the vehicle. You can also test a battery that is not on the car by selecting "Out of vehicle".foxwell battery tester bt 705
  7. Present enter and choose post type. In this case, we have Top Post
  8. Next, select the battery type. Here you can select Regular Flooder (Lead Acid), AGM or GEL battery. automotive vehicle tester
  9. Enter Cold Cranking Amp CCA which you can look up on top of the battery that you are testing. automotive auto circuit tester
  10. Hit enter to get test results. car battery load tester

Possible test results. 

Good Battery The battery is in good condition.
GOOD-RECHARGE The battery is in good condition but low current. Fully charge the battery and return it to service. About 75% charge.
CHARGE & RETEST Fully charge the battery and retest. Failure to fully charge the battery before testing may result in inaccurate results. If you still get CHARGE & RETEST message after you fully charge the battery, replace it. Around 50% charge.
REPLACE BATTERY The battery is almost dead or the connection between the battery and battery cable is poor. Replace the battery and retest; or disconnect the battery cables and retest the battery using the out-of-vehicle test before replacing it
BAD CELL The battery may be damaged such as a broken cell or short circuit. Replace the battery and retest.

How to perform a load test/cranking test

car battery alternator tester
  1. Perform all instructions in Step 1 above. 
  2. When the battery results are displayed press Enter
  3. Start the engine. 
  4. Read results of the cranking test. 

Possible test results

Cranking Normal  The starter voltage is normal and the battery is fully charged.
Low Voltage  The starter voltage is low and the battery if fully charged.
Charge Battery The starter voltage is low and the battery is discharged. Fully charge the battery and repeat the starter system test
Replace Battery The battery must be replaced before the starting system can be tested.
No Start No vehicle start detected.
Cranking Skipped A start was not detected.

How to test the charging system and alternator

car battery amperage tester
  1. Perform instructions in Step 1 and Step 2. 
  2. Once the results for the Cranking Test are displayed press Enter
  3. Rev up the engine as instructed. 
  4. Turn on lights and blower fan. If your car has LED lights the tester may not detect that you turned on the lights. Try turning on the high beams or the rear defroster instead. 
  5. Rev engine while leaving the lights, blow, defroster on. 
  6. Determine the status of the charging system. 

Possible test results

No Problems The system is showing normal output from the alternator.
No Output No alternator output detected. Check all connections to and from the alternator, especially the connection to the battery. If the connection is loose or heavily corroded, clean or replaces the cable and retest. If the belts and connections are in good working condition, replace the alternator. (Older vehicles use external voltage regulators, which may require only replacement of the voltage regulator.)
Low Output Alternator not providing sufficient to power the system's electrical loads and charge the battery. Check the belts to ensure the alternator is rotating with the engine running. Replace broken or slipping belts and retest. Check the connections from the alternator to the battery. If the connection is loose or heavily corroded, clean or reparable the cable and retest.
High Output Alternator voltage output exceeds the normal limits. Make sure there are no loose connections and the ground connection is normal. If there are no connection problems, replace the regulator. Most alternators have a built-in regulator that requires replacing the alternator. In older vehicles that use external voltage regulators, you may need to replace only the voltage regulator.
Excessive Riple Excessive AC ripple detected. One or more diodes in the alternator are not functioning or there is stator damage.

Where to buy a Battery Analyzer

Check out these highly-rated Battery Analyzers online. 

Conclusion

A good battery tester should not only be able to measure the voltage but also measure the Cold Cranking Amp (CCA) of the battery. CCA is a better way to determine if the battery is good or not.

best battery analyzer

Many cheap battery testers are not able to perform a load test or a charging system test. Foxwell battery tester also has printing capabilities which is great if you need to print results at your repair shop. If you are a DIYer you probably won't need to use the printing function.

Modern vehicles are sophisticated and very sensitive to battery malfunctions and voltage drops. That's why testing your car battery and charging system is critical, especially if you are experiencing electrical problems or unexplained electrical issues. You can save yourself a trip to the mechanic by using a battery analyzer to determine if the battery is good or not.