Before you go out and buy new golf cart batteries please do a gravity test on each one with a hydrometer. This will make sure you don’t waste your money by replacing a good battery the just hasn’t been charger properly.
Here is a quick look at you how to use a battery hydrometer for 6 volt deep cycle golf cart battery. Specific Gravity is an accurate test on a deep cycle batteries health, state of charge and future output.
This method assumes a hydrometer with glass float and body.
Put on eye protection and rubber gloves.
It is recommended to disconnect the battery.
Remove vent cap. Carefully insert the hydrometer into cell, not pushing down on the top of the lead plates.
Slowly draw liquid into the hydrometer and avoid shaking the hydrometer. Be careful the float is not flooded with too much liquid or sticking to the sides of the glass tube.
Check a reading by looking directly at the float.
Steps 3-5 to should be repeated to reconfirm reading.
Write down the cell number and result of test.
If it is very warm or very cold correct the specific gravity for temperature. If the ambient temperature is fairly consistent and original gravities are taken when the batteries are put into service temperature correction is not as critical and only necessary if problems arise. Make sure electrolyte is not hot if just taken out of service. Let it reach room temperature.
Specific Gravity of acid is temperature dependent. If the temperature is very cold or very hot this can lead to incorrect readings. To correct for temperature use the following equations the equations or below 70ºF subtract points (0.03 per 10ºF) and above 70ºF add points.
Correction factor = (0.331 x Cell Temp ºF – 23) / 1000 or 0.003 pts per 10 ºF
Correction factor = (0.595 x Cell Temp ºC – 12.5) / 1000
Charged Specific Gravity
SG = Mass (g) / Volume (ml)
SG of specific gravity can only be tested on a battery that has been charged. 1.224 SG is not sufficient charge to load test a battery. Most batteries are considered bad because they are tested without a full charge.
Battery Hydrometer just like he uses in the video can be found here on the cheap.