How To Measure Battery Voltage Under Load

It took approximately 9 hours at a 5 25a load to get to 50 soc and the under load voltage is still 12 11v.

How to measure battery voltage under load.

Without a load it may show an acceptable voltage but when you actually try to use it the voltage drops because the battery is nearly dead. 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. The battery in a car or truck needs to produce high amperes to power the starter motor and turn the vehicle s engine. That value will understandably be lower than the standalone voltage test.

The term used to describe the battery s power is cold cranking amps or cca. Dead battery load of 100 ohms 1 0 volts. Battery load testing involves measuring the amperes produced by a charged battery and is particularly relevant for vehicle batteries. 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.

Allow the battery to warm to room temperature before testing or charging. 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. Do not attempt to load test or charge a battery under 20 degrees. Never remove load clamps while testing.

If the voltage reading drops below 10 as the car starts the battery likely needs to be replaced. Be sure each test is completed before removing load clamps to prevent arcing and potential explosion from battery gasses. So to see if a battery is really usable you must measure the voltage when the battery is connected to a load. Dead battery no load 1 4 volts.

If the battery fails the load test a second time or bounces back to less than.