How To Measure Battery Voltage Under Load

When performing a load test you should apply a load to a fully charged battery for no more than 30 seconds and.

How to measure battery voltage under load.

Dead battery load of 100 ohms 1 0 volts. The battery in a car or truck needs to produce high amperes to power the starter motor and turn the vehicle s engine. Allow the battery to warm to room temperature before testing or charging. If the voltage reading drops below 10 as the car starts the battery likely needs to be replaced.

Never remove load clamps while testing. Battery load testing involves measuring the amperes produced by a charged battery and is particularly relevant for vehicle batteries. It took approximately 9 hours at a 5 25a load to get to 50 soc and the under load voltage is still 12 11v. 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.

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. 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. So to see if a battery is really usable you must measure the voltage when the battery is connected to a load.

Do not attempt to load test or charge a battery under 20 degrees. 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. Dead battery no load 1 4 volts. 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.

If the battery has not passed the load test remove the load wait ten minutes and measure the state of charge.