How To Measure Battery Voltage Under Load

Be sure each test is completed before removing load clamps to prevent arcing and potential explosion from battery gasses.

How to measure battery voltage under load. If the battery bounces back to less than 75 percent state of charge 1 225 specific gravity or 12 45 vdc then recharge the battery and load test again. The term used to describe the battery s power is cold cranking amps or cca. Battery load testing involves measuring the amperes produced by a charged battery and is particularly relevant for vehicle batteries. The battery in a car or truck needs to produce high amperes to power the starter motor and turn the vehicle s engine.

To put this in perspective when this battery was discharged at 2x 2 5x your average cruising boat house loads the bank is crossing the 50 soc threshold at approx 12 1v. It took approximately 9 hours at a 5 25a load to get to 50 soc and the under load voltage is still 12 11v. Do not attempt to load test or charge a battery under 20 degrees. If the battery has not passed the load test remove the load wait ten minutes and measure the state of charge.

A load tester is a specialized yet affordable piece of equipment used to determine the voltage generated by the battery while a load is placed on the battery. That value will understandably be lower than the standalone voltage test. When performing a load test you should apply a load to a fully charged battery for no more than 30 seconds and. The load from the starter will give way to the alternator producing a charge flowing into the battery once the car starts and the voltage reading will climb again.

Dead battery no load 1 4 volts. If the battery fails the load test a second time or bounces back to less than. So to see if a battery is really usable you must measure the voltage when the battery is connected to a load. If the voltage reading drops below 10 as the car starts the battery likely needs to be replaced.

Never remove load clamps while testing.