Woke up with a dead battery

[knunut]

With no shore power. Batteries read 12.86 V. "In Store" current draw reads .08 Amp. "In Use" current reads .25 Amp. with "Nothing" on. DVM in series with Neg. Batt. Terminal.(DC Amp. function.) Fluke 23 DVM.
I guess this is normal.

[abqdor]

Same problem. Went boondocking last weekend and battery would not hold a charge through the night. Luckily, I have a Honda 2000 generator to get us through. I typically run the generator for an hour in the evening and in the morning and batteries start out at 13.4v, but was down to 9.1 volts when we woke up and we did not run the heater during the night. We try to be frugal with power usage when boondocking

Factory batteries are less than two years old. I keep the trailer plugged in at the house, but keep the switch in the "Store" position and use a trickle charger on the batteries. I check the fluid levels regularly, so I thought I was doing everything right, but am now puzzled as to what is going on with the batteries.

[Al and Missy]

When did you take the 13.4 volt reading? The battery condition is not well represented by voltage unless there has been no charging and no loads for an hour or so. 13.4 volts with the generator/converter running or just after turning off is not necessarily indicative of full charge. 9.1 volts is indicative of dead battery and if discharged to this level repeatedly will shorten the life of the battery. A lead acid battery should not be discharged below 50% for best life.

This chart may provide some useful information. "C" is the battery capacity, for a Group 24 that is around 85 Amp hours, a Group 27 is around 100.


Lead-Acid_Battery_State_Of_Charge_Vs_Voltage_1993.pdf



Al

[uncle_bob]

Hi

If the battery box is sitting outside in freezing weather, a reading of 13V means a battery that is near the "don't use" point. Getting a full charge into a cold battery without a battery temperature probe is tough.

In any case, at any temperature, a battery that is at 9.anything volts is dead. It's been run past it's maximum discharge point. You may have done damage to the battery. If this has been done multiple times, the odds of damage increase. Charging the battery from this point has an increased likelihood of shorting out a cell. Shorted cells are what cause batteries to boil.....

When we talk about flooded batteries lasting for 4 years, that's just an average. Indeed some of them will last six years. Others will not make it to their second birthday. Deep discharge tips the scales towards a short life pretty quick ....

Bob

[DKB_SATX]

Originally Posted by abqdor

Same problem. Went boondocking last weekend and battery would not hold a charge through the night. Luckily, I have a Honda 2000 generator to get us through. I typically run the generator for an hour in the evening and in the morning and batteries start out at 13.4v, but was down to 9.1 volts when we woke up and we did not run the heater during the night. We try to be frugal with power usage when boondocking

Factory batteries are less than two years old. I keep the trailer plugged in at the house, but keep the switch in the "Store" position and use a trickle charger on the batteries. I check the fluid levels regularly, so I thought I was doing everything right, but am now puzzled as to what is going on with the batteries.

9V at the battery terminals likely means they're toast, as has been said. 9V at your battery indicator inside *MIGHT* mean that, depends on your delta. Mine only runs about .2v lower, if memory serves. I'm paranoid and check the delta vs a reliable meter nearly every time we go out.

Do you have an inverter? If so, do you leave it on? I notice significant load with the inverter on but not driving anything... I think it's because the TVs and blu-ray player "wake up" and idle even though apparently off, plus the native inefficiency of the inverter. Still, I run my CPAP all night off the inverter (with the TVs unplugged) and the voltage doesn't drop enough to shut off the inverter, just makes ME feel bad to see it in the low 11v range by morning.

Some models of the refrigerator are said to have an unswitched 12v heating element to prevent condensation. That's worth looking into, if only to protect your next set of batteries.

[uncle_bob]

Hi

When you turn on a "normal" inverter, it generates a 120V AC output regardless of a load being present. Simply generating that output (even with no load) takes power. There are work arounds on some inverters (check for load every 60 seconds and shut off ...). The ones I have seen are more trouble than they are worth.

Bottom line - don't leave the inverter turned on. Also check for switched lights in the outside storage cabinets .... or on the power jack .... or on the water dump area ... I believe I have left all of those on at least once

Bob