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What Should A Car Battery Voltage Be Under Load

What Should A Car Battery Voltage Be Under Load. The ideal car battery voltage with the engine running is between 13.7 and 14.7v. If the battery isn’t fully charged, it will diminish to 12.4v at 75%, 12v when it’s only operating at 25%, and down to 11.9v when it’s completely discharged.

Testing a Car Battery Tontio
Testing a Car Battery Tontio from tontio.com

More or less around 12.7 vdc is resting voltage. Since the voltage will change depending on whether or not the bank is on load the set point can be determined by a specific gravity reading. Lithium polymer cells range from 2.5 to 4.25 volts per cell.

A Gravity Reading Of 1.200 Is Equal To 50% Discharged.


~13.6 volts is float charging (keeping the battery full, but not really actively charging). When the battery is not being charged and not delivering charge to a load, this is the rule of thumb. Lead acid should be charged with float charge voltage of 13,80v or with cycle charge voltage up to 14,40v.

Once The Load Is Removed, It Will Only Bounce Back Up To Its Maximum 10.5 Volts.


With an agm battery, you will be looking for the reading to be as close to 12.8v as possible. Good battery, load of 100 ohms, 1.4 volts. To get a true voltage reading of the cars battery it is important to measure the voltage after the car has been sat for a period with the engine off, preferably overnight, this provides you with the “car battery open circuit voltage” or also know as the “resting voltage”.

I Say And Rested Because Immediately After Being Fully.


Similarly, 6v and 24v agm batteries should have voltages of. The closer the voltage is to 13. The ideal car battery voltage with the engine running is between 13.7 and 14.7v.

Around 14.0 To 14.5 Volts Is Actively Charging.


More or less around 12.7 vdc is resting voltage. Maybe a week or two weeks later it won’t start. If the battery isn’t fully charged, it will diminish to 12.4v at 75%, 12v when it’s only operating at 25%, and down to 11.9v when it’s completely discharged.

Load Testing As Long As Battery Voltage Remains Above 9.6 Volts, The Battery Is Considered “Good.” But If It Drops Below 9.6 Volts By The End Of The Test, The Battery May Be “Bad,” Or The Battery May Have To Be Recharged And Retested If It Was Not Fully Charged Prior To The Test.


If you were discharging at 8a and saw 12.55v you would be at a lower soc than 90%. What’s a car battery load test? A fully charged and rested 12v lead acid (starter) battery should read 12.6 volts.

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