Totally bumed out

[Putz]

I have spent many hours trying to figure out why my batteries go flat (10 volts) in less than one day. I've taken them to a battery dealer and they are ok. My only solution so far has been total disconnect, but that is a pain. On the road they last less than one hour if I run the heater, etc., less, if I run the inverter. I always use the on board battery disconnect when storing for more than a few hours, but something is stealing my juice anyway

[mimiandrews]

First, charge the batteries and leave them disconnected for a few days. If they don't hold a charge when disconnected, something is wrong with the batteries. How old are they? Have they been allowed to sit in a discharged state?

With the batteries removed and everything off, connect an ohm meter between the wires for the positive and negative battery terminals. If the meter doesn't read infinity--completely open circuit, something is either always on or shorted. If the meter does read infinity, go back to the batteries.

If you do find that there is a current path between the positive and negative wires, then the laborious process of isolating the bad circuit starts. Pull fuses or open circuit breakers and test each circuit individually until you find the culprit.

[SSquared]

Your batteries may actually be bad. Some battery dealers test batteries by simulating a vehicle starting load--high current (over 100 amps) for just a few seconds. That's a good test for a car battery, whose hardest job is to start the car. In our trailers, we never put such a high current load on the battery, but we run in for hours (or a few days) at low current. A battery can be good for a few seconds but not for a few hours.

There are ways to figure out for sure what is wrong, but that takes more explaining than I can do here.

[Caffeinated]

What year and model is your trailer? If your batteries have gone under 11.5V you risk damaging them.

Mike

[sgschwend]

You could measure the Energy yourself too. Your batteries are rated for so many AH (amp hour). Purchase a $20 volt meter that can measure up to 10Amps of current too.

Using the user manual setup for amps and turn on the trailer lights to obtain a amperage just below 10 amps. Remove the amp meter setup and setup for voltage measurement.

Monitor the voltage of the battery over several hours of run time. A good 100 Ah battery would deliver 50 Ah safely, which would be around 5 hours of testing. You can see the state of charge by the battery voltage reading (this value is temperature dependent, so I won't pass on the value you are looking for, something around 12.5VDC).

Lead acid batteries are strange animals. The performance of the battery is related to the surface area of the lead plates. As a battery ages that surface area continues to become less; while it will still pump out a lot of amps but still not have the storage as specified for that battery.

[brokeboater]

You don't give any specifics on your rig so it's a bit hard to give an opinion but I won't let that keep me. It is quite possible your batteries aren't being charged adequately for a number of reasons. A substandard converter and an overly long run of undersized wire to the batteries from said converter comes to mind. What year and model is your rig? What converter is currently in it? What does a volt meter show at the batteries with the converter on and off?

[cabinetmaker]

Originally Posted by davef

I always use the on board battery disconnect when storing for more than a few hours, but something is stealing my juice anyway

This could be your problem. You must leave the the battery disconnect "on" when you want to charge the batteries from your onboard converter not in "store".

Also, your onboard converter might not be working. Try using a external regular auto 12volt battery charger and see if the batteries come up.