battery drain rate

[Judith Kennedy]

I recently had my battery fully charged and then monitored for 20 days without being connected to any load.

I recorded the voltage daily and after 20 days found the initial voltage of 12.8 volts had dropped to 12.1 volts. An average of .035 volts per day.

This info might be useful to those who previously were unaware of self discharge or the rate by which this occurs.

The battery is a deep cycle marine wet cell battery.

[Frederick L. Simson]

I might be inspired to replicate your experiment to confirm your results...

[BobB]

Judith,

The rate of discharge seems fast. I would wonder if you have a "parasitic load" such as a stereo. Our battery will stay up 2-3 months in storage with a battery cut-off switch.

[Judith Kennedy]

nope, the uhaul only has two florescent lights which were only briefly ( like 30 sec ) the entire time. The only other load was the meter which was only energized while reading. Bear in mind that the battery was not run all the way down. At that constant rate of discharge, the batt. would reach 11 volts in 34 more days making a total of 44 days.

[peterh]

A battery's discharge rate vary depending on the battery's design and the internal and external conditions of the battery.

Conventional "flooded" or "wet" lead-acid batteries, fr example, have a higher natural discharge rate than Gel-Cell and Absorbed Glass Mat (AGM) batteries do.

All lead-acid (flooded, gel-cells, and AGM batteries) discharge faster at higher temperatures. BatteryStuff.com (which sells different types of batteries and chargers), for example, says that a battery left at 110-degrees (F) for 30 days probably won't start a car.

Low temperatures slow the battery's discharge rate, but also slow the chemical reactions that release energy from the battery down, so cold batteries can't produce as much power as warm ones, either.

As lead acid batteries get older or are abused by excessive discharge they become "sulfated" by the formation of hard lead-sulfate crystals on the surface of the lead plates in the battery. Where the sulfation collects on the plate the battery can no longer store or exchange electrical charges, which also speeds the discharge process.

[Gina D.]

Do you have a 3 way refrigerator? I recently learned from my RV tech that even the older ones have a draw of .04 amps when not in use. There are a couple components on the power supply board that are parasitic.

I had a similar problem and I disconnected the battery via pulling the inline fuse when not in use. No more problem.

[Judith Kennedy]

No fridge

[Joe Z]

Do an amp draw test at the battery via the positive cable and a multitester....... or disconnect the cable and re-do your test without being hooked up to the trailer. Either way you will then know if it's the trailer or the battery.
Joe

[Brian Van Snell]

Judith:

Look at http://www.batteryfaq.org/ in the CAR AND DEEP CYCLE BATTERY
FREQUENTLY ASKED QUESTIONS 2009 section 4. How do I test a battery?
4.4.3 Open Circuit Voltage (OCV) vs. Temperature
at Various States-Of-Charge

it appears that your battery is almost completely discharged.

As suggested by others it would be a good idea to find out whether something in your trailer is drawing power from your battery, and a simple way of doing that would be to repeat the experiment with the battery fully charged but disconnected.

Brian

[BobB]

There is certainly much to learn about batteries!