What makes Battery Voltage Drop?

A bunch of batteries.

Your battery can experience a voltage drop for several different reasons. Knowing what the possible causes are can help you to fix the problem both quickly and effectively. While there are multiple reasons why your battery may be experiencing a voltage drop, there are some more common than others. Below are some tips and hints on what to test and do if the voltage seems to be dropping on your battery with no obvious cause.

Battery and Starter Connections

Of course, the first thing that you should check is the battery and the starter connection. These are the most common problems that you will run into with any voltage drop in a battery. Once you check the starter and the battery connection and are sure that neither one of them is the problem, then you will then need to move on to other tests to see what the cause is.


An excessive resistance of your high amperage circuit is an overlooked problem that can cause your volts to drop in your batteries. Check to see if the cables are corroded, damaged, or loose.

Resistance is usually caused by battery terminals and cables that have not been properly cleaned. Corroded cables or terminals could be a big problem. Sometimes you will not even be able to see the corrosion. Regularly cleaning your cables and terminals can prevent you from having this problem with resistance. A wire brush can be purchased cheaply at any auto parts or hardware store. This is the best method to clean off corrosion.

Battery cables that have ends that are replaced or bent out of shape can also cause a good deal of resistance. There does not need to be much of an increase in the resistance of your battery for there to be trouble. It is important to keep up with these things by doing checks on your cables and terminals often. This will prevent you from having battery resistance problems in the future.

Checking Connections

The connections will need to be connected if you begin to notice that your battery is losing voltage. If you are using an ohmmeter, you may not be getting an accurate reading for your battery. This is because all that this meter will measure is continuity. It does not measure its ability to handle a high amp current load. There are ways around this to be able to get an accurate read on your battery.

A voltage drop test is the most accurate ways to test the connection on your battery. You will not have to disassemble anything, so it can be done quickly. Get your digital volt meter to test the voltage drop once you have successfully created a load in the circuit that will need to be tested. If your circuit or the connection has too much resistance, then some of your voltage is going to flow right on through your digital voltmeter. This will give you a voltage reading.