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A Review of the TOPDON BT100 Battery and Alternator Tester

I'm a tool guy and love to put tools through the test. When I find a tool that can make life's every day projects easier, I like to share.

TOPDON BT100 battery and alternator tester

TOPDON BT100 battery and alternator tester

Upgrading to a TOPDON Battery Tester

I have several machines that use 12-volt batteries. The machines sit around all winter, and by the end of every winter, you never know what condition the batteries will be in.

I have an old analog battery tester, but I decided it was time to update it to something that actually gave me a digital reading, instead of showing me a needle on a graph where I would guess what numbers the arrow is pointing at. I didn't want anything too complicated, and I didn't need to spend the money on a tester with a printer. Since I already owned the TOPDON battery jump pack and I know their customer service is beneficial, I thought I would give the BT100 a shot.

I like to have a unique tool like this TOPDON BT100 in my toolbox because I have three kids who own cars, and I have a wife, so I'm the guy everyone calls when they have a problem with their vehicle. Whether it's just a question or they need me to test something, this little battery tester fits the bill.

The BT100 uses the vehicle battery for power, which at first I thought was a bad idea. Still, after thinking about it, you'll never have a low battery, and you won't have to deal with batteries deteriorating, leaking acid, or damaging the tester.

BT100 Test Results

I used the BT100 to test several batteries. I found that the test results are consistent and accurate to the best of my knowledge, I've gone as far as trying the same battery three times in a row and the test results were very close to exactly the same.

I found when using some of the more expensive battery testers that their test results are not as consistent as the BT100. When using a more expensive battery tester, running the same test on the same battery three times in a row, I would get three totally different test results. These testers cost close to a thousand dollars, and with inconsistent test results, how could I rely on the test results being accurate?

The BT100 Can Test Several Different Types of Batteries

  • Regular flooded (liquid sulfuric-acid-filled, the most common car battery)
  • AGM flat plate (absorbent glass mat)
  • AGM spiral (spiral plates)
  • Gel (electrolyte mixed with fumed silica)
  • EFB (enhanced flooded battery)

My Test Results With the TOPDON BT100

Charging System Test With the BT100

Testing the charging system was easy. I connected the clamps, ran the engine with no load, and used the tester to run a ripple test on the diode and windings. Unfortunately, I didn't have a chance to use the BT100 on a damaged or worn alternator, only on a quality, well-performing alternator.

When running the ripple test, the ideal pattern should be consistent with small ups and downs. High or low spikes indicate there is a problem with the system. Downward spikes suggest a problem with the diode, and upward spikes suggest a problem with the windings. The BT100 should detect either problem during the test.

BT100 Cranking Test

The cranking test measures the time it takes for the engine to start in milliseconds and how low the battery voltage drops during engine cranking. The manual does have a reference table to indicate what voltage is acceptable and at what voltage the battery will need to be replaced.

It would be nice if the BT100 cable was longer so you could hold it during the cranking test, but it's not necessary. When you do the cranking test, it's best to place the BT100 on a secure surface like the hood cowl or shock tower, not on the engine; when the engine starts it creates a lot of vibration, and the tester could drop and become damaged.

A thin rubber or silicone cover would have been a nice upgrade to this tester for better handling and comfort, but at this price, you can't complain.

Topdon Bt100

TOPDON BT100 Pros and Cons


  • Lightweight and compact
  • Easy to use and understand
  • Consistent battery test results
  • Quality battery clamps, good spring tension
  • Backlit display
  • Uses vehicle battery for power (never needs batteries)
  • Alternator test
  • Stores last test result after disconnecting
  • Low price point
  • Language options
  • 2-year warranty
  • Excellent customer service


  • Short cable (personal preference)
  • No printer (typical at this price point)

Common Mistakes When Testing Batteries

I find the most common mistake people make when using a battery tester is to input the wrong battery information like the type of battery and the cold cranking amps (CCA), which skews test results. Battery information like cold-cranking amps and battery type can usually be found on the battery label. If you can't find it on the label, a simple Internet search using the battery group number and brand can verify the information.

This BT100 is a DIY must-have battery tester, it's compact enough to keep in the car glovebox or in one of your smallest toolbox drawers. I have used both expensive and inexpensive battery testers during my busting knuckles years, and this is one of the easiest battery testers to use with the most consistent test results.

If you have any questions that I didn't cover in this article, leave them in the comment box, and I'll do my best to answer them.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2020 Eddie Carrara