Fortunately, you can easily do a basic health checkup on any type of lead acid battery by hooking it up to a simple-to-use digital voltmeter. If you have an open-cell battery that lets you access the liquid inside, you can do a more rigorous checkup with a battery hydrometer.
Checking an open-cell lead acid battery—that is, a lead acid battery with caps that can be opened to access the liquid inside—with a battery hydrometer is most accurate when the battery is fully charged. Closed-cell lead acid batteries without the access caps cannot be tested this way.
Scope: This guide contains a field test procedure for lead-acid batteries used in PV hybrid power systems. Battery charging parameters are discussed with respect to PV hybrid power systems. The field test procedure is intended to verify the battery’s operating setpoints and battery performance.
Charge the battery fully at least 8 hours before testing it. Lead acid batteries recharge in various manners based on their function and manner of installation. For a lead acid vehicle battery, drive the vehicle around for at least 20 minutes. For a lead acid battery connected to solar panels, let the battery charge fully on a sunny day.
If the voltage reading is lower than the manufacturer’s specifications, the battery may be weak and need to be replaced. If the voltage reading is within the manufacturer’s specifications, the battery is likely in good condition. To get a more accurate reading of a lead-acid battery’s health, you can use a hydrometer.
This is due to the fact that the nominal voltage for lead acid batteries is 2 V/cell while real-world OCV values for 100 % SOC are in the 2.25 .. 2.35 V. Fully charged voltage: see above. Depends on cell chemistry details. More important: do not exceed 2.4 V (lower values for sealed batteries) during charging as this will damage the battery.
Charge the battery fully, then let it rest for 4 hours. If you''re testing an automobile battery, take the vehicle for a 20+ minute drive, then shut off the engine for 4 hours.For other types of lead acid batteries, charge them all the way before letting them rest for 4 hours.