wet cell batteries reading 13.7v at rest!

[arafura]

I think I already know the answer but looking for confirmation. Checked the fluid level in the 12 volt deep cycle marine batteries and found a few very low cells, topped off with distilled water and now batteries read 13.7 volts at rest....seems high. Some plates were exposed. Are the batteries toast?

[k1vsk]

sounds more like your voltmeter is wrong or you checked them immediately after charging.

[arafura]

Battery charger has not kicked on since topping them off. Spoke again with my husband to double check and he sheepishly said that it appeared that all the cells in all three batteries were very low. Took 2 gallons of distilled to top off 3 batteries!

[k1vsk]

There is no conceivable way a bad battery could be producing 13+ volts. Either a bad voltmeter or a bad charger (voltage) which cooked the batteries.

[TQA]

When a battery is fresh off charge the terminal voltage can read as high as 14 volts; it will drop quickly to 13.2 V and then slowly to 12.6 V.

This is due to the surface charge. The surface charge must be removed before testing. If the battery has been sitting at least several hours that will do it or the battery must experience a load of 20 amps for 3 plus minutes.

A hydrometer is the best way to test your battery. Get one that reads from 1.1 to 1.28. The ones with little colored balls are worthless.

State of a full charged battery 1.265

Hydrometer readings should not vary more than .05 between cells.

If you have topped up with significant amounts of distilled water the battery should be cycled a couple of times then fully charged before testing.