The battery in our TT was 5 years old and I noticed the last couple of trips, the tongue jack seemed to be struggling a bit. I had a trip coming up and for weeks kept procrastinating on getting a new battery.Fast forward to the Thursday before the July 4th weekend. I had 3 nights planned in the TT and we were to leave early the following Saturday morning. Went to the storage lot Thursday after work to turn on the fridge. Get home from work Friday afternoon and pack up a cooler with food for our trip. Run over to the trailer and open the fridge. Not cold! Was upset and was thinking about canceling the trip or at worst having to go out early Saturday morning and see if I could purchase some dry ice. I went back home, started unpacking the food and thought of the battery again. I assumed (my first mistake) that since the TT was plugged into 30 amp power, that the fridge would work. Ended up running out to the auto parts store and got there right before they closed Friday night. $137 later, I had a deep cycle battery and went to the storage lot and installed the battery. Went back early Saturday morning and guess what? Nice cold fridge! The trip before last I needed some hot water and I turned on the water heater on propane. I usually just use it on electric mode but it heats up faster on propane. I could not get the hot water heater to work on propane. On this trip, I tried the hot water tank on propane and it worked just fine.So, I am gathering that the fridge and propane mode on the water tank use the battery whether you are hooked up to power or not. Are there any other appliances that are dependent on the battery? I had always assumed that if I was hooked up to AC power, that the battery wasn't used. I thought that the battery was used when power wasn't available (IE: boondocking). At least this will teach me to not procrastinate on replacing the battery in the future!Burch

Did you happen to check the voltage on the old battery?

If your hooked to 120V, then you should also get 12V from the converter (on board battery charger). Check and make sure the 120V breaker connected to your converter is not tripped, or your battery will be dead again in short order. Now, if the old battery had a shorted or dead cell or to, then the charger can't get the voltage up to around 11.5V or more, then the fridge and WH electronics won't let them turn on and it won't work even on 120V. Likewise for the furnace.

Refrigerator, water heater, cabin heater, some of the sensors Co2, and propane.The refrigerator needs 12v for the electronic control board to switch from 110v A/C to propane and viceversa, the hot water heater uses 12v also for the control board and the igniter and the valves, even when hooked to 110 v if the battery is old, has an internal short or low in water it will not have enough voltage to operate electronic boards.navegator

2oldman wrote:Did you happen to check the voltage on the old battery?I didn't check the voltage because when I opened the battery compartment, one of the water caps was barely on the battery and I didn't see any water on that side of the battery. I did have a volt meter but after seeing the state of the battery (and it being 5 years old) I just went out and got a new one. Burch

ktmrfs wrote:If your hooked to 120V, then you should also get 12V from the converter (on board battery charger). Check and make sure the 120V breaker connected to your converter is not tripped, or your battery will be dead again in short order. Now, if the old battery had a shorted or dead cell or to, then the charger can't get the voltage up to around 11.5V or more, then the fridge and WH electronics won't let them turn on and it won't work even on 120V. Likewise for the furnace.The first thing I checked were the breakers and fuses. As soon as I saw the state of the battery, I knew the battery was bad. I just never thought about things not working if I was plugged into shore power. After seeing the battery (no water on one side), I am sure I wasn't getting anywhere near 12 volts.

Battery - Learned something new | Good Sam Community

15 Replies

wa8yxm
Explorer III
Jul 13, 2016
Some times it depends on the model but the following devices all use 12 volt DC for one thing or another

Refrigerators (Control power all modes, as far as I know all models save residential units)
Water heaters (Some models, control power, all modes)
Air Conditioenrs (Models with remote controls or wall mounted thermostats)

Fans, Water pump, interior lights, jacks, slides and your Television antenna

Radios (Dash type).

Now, converter/battery

Some converters have nice CLEAN output power.. I mean if I accidently disconnect my house batteries my ham radios run just fine off the converter.. I do not notice the lack of the battery at all.

Others... Let's just say I'd notice BIG TIME and fast. The converter is not nearly clean enough to power the radio or anything else

The battery however acts as a filter.. Till it goes bad that is .
wbwood
Explorer
Jul 13, 2016
Many people don't realize that those and other things can draw a parasitic load off your batteries and kill it quickly if it's not disconnected when in storage.
Old-Biscuit
Explorer III
Jul 12, 2016
colliehauler wrote:
MetalGator wrote:
korbe wrote:
When we are on shore power, I can disconnect the batteries and all my 12-volt things work just fine through the converter.

That is the way I expected things to work, but the fridge definitely didn't work with the dead battery. Different trailers must be wired differently.
I would make sure your converter is charging. Converter should run the 12 volt side.

Converter supplies 12V DC System when connected to 120V AC power source.
DC output from a converter is 13.2V DC MINIMUM.

BUT converter can not supply sufficient DC Voltage AND charge a 'shorted/dead' battery

When you disconnected battery cables......converter should have been able to THEN supply the trailer DC System.

New battery allowed converter to not be overloaded.
tplife
Explorer
Jul 12, 2016
MetalGator wrote:
2oldman wrote:
MetalGator wrote:
I just went out and got a new one.
Ok. Because it technically should have worked, but as mentioned, if the battery is completely shot, no, the conv. can't get the voltage up to run things.

An AGM might be a good choice for you next time since your battery maintenance seems to be a bit lacking! :)

I used to check the water levels on the battery frequently, but it had probably been several months since I last checked it. Batteries in the Florida heat aren't known for their longevity. The longest I have ever had a battery last in any of my cars or boats (and now RV) has been 6 years.

+2! :B
colliehauler
Explorer III
Jul 12, 2016
MetalGator wrote:
korbe wrote:
When we are on shore power, I can disconnect the batteries and all my 12-volt things work just fine through the converter.

That is the way I expected things to work, but the fridge definitely didn't work with the dead battery. Different trailers must be wired differently.
I would make sure your converter is charging. Converter should run the 12 volt side.
MetalGator
Nomad
Jul 12, 2016
korbe wrote:
When we are on shore power, I can disconnect the batteries and all my 12-volt things work just fine through the converter.

That is the way I expected things to work, but the fridge definitely didn't work with the dead battery. Different trailers must be wired differently.
korbe
Explorer
Jul 12, 2016
When we are on shore power, I can disconnect the batteries and all my 12-volt things work just fine through the converter.
Sandia_Man
Explorer II
Jul 12, 2016
Actually 5 years is pretty good for an RV battery although if you were plugged into shorepower your converter should have supplied the DC power required by fridge control board. On our rig converter output feeds the battery and DC distribution panel separately. Anyway you are back on the road having fun and that's all that counts. Happy Camping!!!
MetalGator
Nomad
Jul 12, 2016
2oldman wrote:
MetalGator wrote:
I just went out and got a new one.
Ok. Because it technically should have worked, but as mentioned, if the battery is completely shot, no, the conv. can't get the voltage up to run things.

An AGM might be a good choice for you next time since your battery maintenance seems to be a bit lacking! :)

I used to check the water levels on the battery frequently, but it had probably been several months since I last checked it. Batteries in the Florida heat aren't known for their longevity. The longest I have ever had a battery last in any of my cars or boats (and now RV) has been 6 years.
2oldman
Explorer II
Jul 12, 2016
MetalGator wrote:
I just went out and got a new one.
Ok. Because it technically should have worked, but as mentioned, if the battery is completely shot, no, the conv. can't get the voltage up to run things.

An AGM might be a good choice for you next time since your battery maintenance seems to be a bit lacking! :)