Is battery shot?

scotty0424

Astrophysics, trigonometry, electricity. These are among the things I have a complete mental block about. Nevertheless, we took our new T@B on a shakedown cruise to the Lake Placid area and plugged into the campground power. I read up on battery readings and was getting 13.6 and 13.7 readings from the in-house monitor. However, somehow, the plug came out of the post and the trailer ran its refrigerator and lights on the battery for an undetermined amount of time. I happed to check the monitor at one point and it read 11.6. I discovered the plug disconnection and fixed it. Afterwards the reading went back to 13.6. However, we were running on shore power and not the battery. I don't know how to tell now whether the battery was over-discharged or not. Please help. Thanks

rfuss928

You should be fine.  Not a good practice to run the battery to those low levels regularly but an occasional oops won't destroy anything.

scotty0424

Thanks

Sharon_is_SAM

@scotty0424,  whenever you are on shorepower, your voltage will read 13.6 as it is reading the AC current not the battery.  Check your battery voltage when not connected to shorepower or you can test it directly with a voltmeter when your cut-off switch is OFF.  Before checking battery voltage, ideally you should have rested the battery (no load) for at least 30 minutes.  The battery will typically read lower when under load, higher when rested.  You should use a surge protector or better yet an Electrical Management System whenever on shorepower.  

rfuss928

Sharon_is_SAM said:

@scotty0424,  whenever you are on shorepower, your voltage will read 13.6 as it is reading the AC current not the battery.

Better stated as "your voltage will read 13.6 as it is reading the DC voltage being supplied to the battery by the AC converter.

BTW - The Progressive Industries EMS shows you the  AC current.

pthomas745

A battery has a "lifespan" determined by how many times it is discharged and recharged.  You will often hear "don't discharge below 50%" as a good practice to extend the life of a battery.  This does not mean you cannot go below 50%, but it will "shorten" the useful life.  Look over the "Cycles Vs Lifespan" section of this FAQ.

https://www.solar-electric.com/learning-center/batteries-and-charging/deep-cycle-battery-faq.html#Cycles vs Life

And, add Voodoo, Astrology, and Alchemy to your "mental block" list.  We may know plenty about the science of a battery, but the behavior of a battery is sometimes shrouded in deep mysteries.

MuttonChops

A few things to consider.

scotty0424 said:

. . . trailer ran its refrigerator and lights on the battery for an undetermined amount of time.

When on shore power switch the refrigerator to AC Mode. If your Shore Power connection fails then (a) the fridge won't kill your battery and (b) if your fridge model has an AC Mode light its being off might alert you.

. . . happened to check the monitor at one point and it read 11.6.

To get a more accurate battery voltage with the SeeLevel monitor turn-off all DC voltage loads in the trailer (lights, water pump, fridge, radio, fan) as the displayed voltage is lower when DC powered items are turned-on.  It is possible your 11.6 was because the fridge was in 12VDC Mode and not actual battery voltage.

. . . how to tell now whether the battery was over-discharged or not. Please help. Thanks

When in doubt take your battery to an auto supply store, they can do a quick test and tell you how healthy the battery is.

scotty0424

Thanks to everybody who offered advice.