best way to test house batteries ?

Sir Traveller wrote:
What’s the most accurate way to test house batteries using multimeter and hydrometer?

Depends what you are trying to test. The hydrometer works great to determine how much of a charge the batteries will accept. Which will also give a rough idea of capacity remaining for the batteries.

It wont really tell you the voltage drop under load. For that you could buy a load tester. Or you could load test at home. Put a multimeter on the batteries and then have someone flip on lights and run the water pump. Note how much voltage drop occurs. I dont want to give out voltage numbers because i dont know the correct numbers to give. But lets say you turn on the water pump and your voltage drops to 11.9V. That would indicate the batteries are getting older and sagging too much under load.