I have a TopDon BT-100 battery tester, and it worked great on my past two cars... I could simply connect it to the battery and it would provide good consistent results, showing a variety of things like charge, resistance, overall health, etc.
But on my new 2025 Land Cruiser, it apparently works very differently -- i.e., it does not provide accurate results unless I disconnect the battery's negative terminal before doing the test. A brand new, fully charged battery that was connected to the car showed failed results for both health and charge -- but when I disconnected the negative terminal from the battery and then retested, the results were 100% health and 100% charge (with good voltage and low resistance). And when I reconnected the negative terminal and retested, it was all fails again. This is fully reproduceable -- I got the same sort of results when testing the original OEM battery that I replaced.
Apparently the parallel path thru the hybrid system (when the battery is still connected to the car) screws up the test results. I haven't seen this before on other cars (and the instructions for the battery tester do not suggest that you disconnect the battery before testing).
But on my new 2025 Land Cruiser, it apparently works very differently -- i.e., it does not provide accurate results unless I disconnect the battery's negative terminal before doing the test. A brand new, fully charged battery that was connected to the car showed failed results for both health and charge -- but when I disconnected the negative terminal from the battery and then retested, the results were 100% health and 100% charge (with good voltage and low resistance). And when I reconnected the negative terminal and retested, it was all fails again. This is fully reproduceable -- I got the same sort of results when testing the original OEM battery that I replaced.
Apparently the parallel path thru the hybrid system (when the battery is still connected to the car) screws up the test results. I haven't seen this before on other cars (and the instructions for the battery tester do not suggest that you disconnect the battery before testing).
