Hi, I have a 2007 Honda CRV. This car is a spare so we drive it infrequently at this point in it's life. It does have over 300K miles. Recently we changed the battery because it was not staying charged. Maybe about 2 months after the battery was swapped (at a shop) the red battery light stayed on after the car started. I ran the car at idle parked for a while (15 mins) and eventually more dash lights came on and the engine RPM went to zero (at least on the dash) and I proceeded to shut down everything. I attempted to restart and it would not turn over. I then jumped the battery and started the car up and let it run for a bit while still connected to the other battery. Once I disconnected it looks like the volt meter was putting out around 11 volts while the car was running. Does this indicate no charge and point to a bad alternator?

Thanks

 

One quick, but not thorough check is to use a DVOM (digital Ohm volt meter). While the engine is off, set the DVOM to the 20 volt setting. Put one proble on the positive battery post and the other probe on the negative battery post. It will display the battery voltage. Usually that's around 12.6 to 12.9 volts or so. Then, start the engine and put the probes on the battery posts again. You should see an increase in voltage, say between 13 to 14 volts. The idea is that with the engine running, the alternator will pump out volts to the battery, so the measurement increases.

Another thing you can do is take the vehicle to an auto parts store (like O'Reilly or Auto Zone). They have good equipment which can test your alternator off or on the vehicle. They will be able to tell you if the alternator is not only putting out volts, but if the amperage is good as well.

 

A slight addition to Litzenbaum's very informative post above, if you do the DVOM test yourself, measure the alternator voltage output twice. The first time you measure it, have as many vehicle electrical loads as possible *off*. Take that reading, and then turn on as many electrical loads as you can...turn on the AC, blower fan (on high), high beams, 4-ways, rear defroster, radio, seat heaters if you have them, and then measure the alternator charging voltage again. It'll likely be lower than your "loads off" measurement, but should still be about 13.2 or higher. Sometimes a failing alternator won't show signs of failing unless you're pushing it. If you have another vehicle that's working fine, do the same tests on that vehicle for a reference. It only takes a few minutes, requires no disassembly, and the working vehicle should give you a benchmark for what numbers you should be seeing (most accurately, the difference between charging voltage and loaded charging voltage, assuming you can engage similar loads).