Measuring SG

Arkansasoffgrid

Other than being in Float mode/fully charged, do all loads need to be disconnected to get a true SG reading?

Dave Angelini

NO as long as when you are in float the battery is not being discharged. Being in float from a display that says float does not mean the battery amps in and out are nulled.

BB.

Are you asking about measuring SG of electrolyte, or by estimating "resting" voltage?

In general, float is a very gentile charge and as long as the electrolyte is well mixed (either after a "hard charge" with bubbling/mixing of electrolyte, or no short term large charge/discharge current spikes for "awhile"--electrolyte needs time to "equalize"--Electrochemical reactions take place on the surface of the plates, not in the bulk electrolyte), measured SG (via hydrometer) should be pretty accurate.

Of course, you have to take electrolyte temperature into account (in either case). I have always wondered what the actual electrolyte temperature is after you suck it into a glass hydrometer (does heat sinking of glass, evaporate cooling bring down the temperature pretty quickly to room temperature)?

-Bill

Arkansasoffgrid

Trying to get accurate specific gravity measurement of electrolyte using hydrometer.

Dave Angelini

This is not rocket science. Overthinking this can hurt your brain. Buy a second good  hydrometer if it will help you sleep.