Battery Discharging

Electrolyte(water) level?

Low level will give your indication.

The charger does not have a desulfation mode on it. There is a setting for a smaller battery so I could try putting it on that mode. I have used this charger since I purchased the Interstate group 29 deep cycle battery.

That charger should normally work okay for your batteries. The problem is that the charge program you are using does not work on the sulfated battery. It senses that the battery with less capacity is reaching a full charge. Sp.Gr. check shows otherwise.

Were this batteries charged with this charged since purchased new? What brand and type of battery are you using? Does the charger have a "desulfation" mode to help desulfate the battery?

Does the charger have a 2 amp charging mode? Using that will allow the charger to run a charge over a longer time. Smart chargers get fooled by a battery that looks like 70% or higher in charge state, and hit the cutoff voltage to soon. The 2 amp rate overcomes that problem.

The voltage reading seen on the meter should have risen to 13.7, or 14.4, when in bulk mode. It looks like the charger is either bad, or shut down due to a bad battery.

The charger is Nascar Advantage fully automatic micropressor controlled and after an hour the charger light indicates that it is 100% fully charged and I assume it will not charge any more, so no sense in leaving it on for 24 hours. Correct? After sitting overnight in my shop with no load, the SG was still 12.20 but the voltage was a decent 12.57. How can I charge it for 24 hours if the indicator light indicates that it is fully charged.

jimlouisesophie wrote:
I tested the battery with a hydrometer and after charging only for an hour, as the battery charger indicated that it was fully charged at 100 % and reached 13.25 the SG was only 12.20....would assume the battery is shot..true? the battery is only 14 months old and has never been discharged below 12.25.

After one hour the battery was just starting to charge (the indicator "Idiot lights") is just showing charging current was flowing through the battery. The battery was in terrible shape since the voltage should have reached 13.7 volts in the first 10 minutes.

Charging should have been done over a 24 hour period. 13.25 volts indicates that the charger sensed a problem with the battery and never started a charge. What kind of charger are you using?

SG needs to be at 1.275 or higher. SG at 1.220 indicates your battery is actually ~65%. Like was mentioned, your batteries are probably sulfated from chronic undercharging.

I tested the battery with a hydrometer and after charging only for an hour, as the battery charger indicated that it was fully charged at 100 % and reached 13.25 the SG was only 12.20....would assume the battery is shot..true? the battery is only 14 months old and has never been discharged below 12.25.

NinerBikes wrote:
You need a better charger, that puts out 14.8V, and your battery voltage, fully charged, and disconnected, should be at 12.73V

+1 this

At 13.3 your battery has been chronically undercharged and is probably a bit sulfated. Battery is in desperate need of an equalization and hydrometer test.

You say that shore power is unavailable. How are you charging the battery?

jimlouisesophie wrote:
My group 29 battery is discharging down to 12.34 after only 2 hours while dry camping with the fridge on propane. The fridge is 3 way, but is turned to automatic, and the gauge shows propane being used, which it actually is. The battery seems to be okay when not hooked up to the rig as I have charged it, left it aside and it still holds it charge. I put another battery in and it also came down to 12.34 after 2 hours, so the battery is not the problem. The only other thing I have on the trailer is a propane detector which is hooked up to 12V. After 12 hours the battery goes down to 12.24. Suggestions please.

It sounds like both of your batteries are "garbage". If they actually dropped from 12.7+ volts to 12.34v (70%) that fast they may be sulfated from never getting recharged fully after dry-camping. Their actual capacity may only be around 70% of new.

A 3-way refrigerator should follow: 120v ac to propane to 12v dc in normal selection. Your current usage would have been only a few amps for each of the hours.

How many hours do you allow for recharging batteries after dry-camping? Is it done right away after returning home? Is a generator used each day for 2 or more hours while dry-camping?

Recharging batteries could take up to 12 or more hours to reach full charge. Any time spent below full charge allows for sulfation to build and send a battery to an early death.