I'm having battery problems.  I was be plugged in with the monitor indicating the batteries were full.  Drove 1.5  hours with the fridge set to battery power and arrived with the monitor saying they were empty.

I bought this 2016 camper used and don't know how well the batteries were cared for (I bought it from second owners who'd had it a year and only used it, once so batteries could have just sat there unattended). My first thought was batteries are bad and not holding a charge.  Now I know from the forum that there is also a charger that could be bad. Any thoughts on how to tell which is the problem?

Thanks for advice.  :)

I'm currently set up with two 12 volt batteries. So depletion after only 1.5 hours tells me my first hunch was probably right.

Also, make sure you have power thru the 7-way plug to your charge line on the trailer.

One other thing that could be happening is that the tow vehicle is not supplying power to the batteries. If that is the case, it is not surprising that the batteries are depleted when you arrive. What tow vehicle? Some of them require installing a fuse or breaker before they will supply power to the trailer. You could also check the battery meter when the vehicle is plugged in to see whether it is indicating that the battery is being charged when the tow vehicle is running. Better still is to use a digital volt meter to check and see if the outlet on the tow vehicle is supplying 12V power. A clamp-on ammeter that is capable of reading DC amperage would be better as you could see whether it is charging when the tow vehicle is running with the cable plugged in.

I choose to run the refrigerator on propane when not connected to shore power. That way, my dual 6V batteries are charged when we arrive. I've not had good success trying to run on 12V power as I don't think the vehicle provides sufficient power to run the refrigerator and charge the batteries. By running the refrigerator on propane, I don't have to worry about it.

That being said, take your batteries to an auto parts place, Batteries + Bulbs, or even Walmart and have them test the batteries. That will let you know if they are good or not.

Your fridge uses a considerable amount of power when running on 12v, especially if it's warm outside and it is trying overcome the loss of cold inside due to the exterior warmth.  In all likelihood, your 7 pin system does not have the charging wire size needed to adequately supply the power needs to your fridge.  The voltage drop from the TV generator to the fridge is significant, unless you've installed a pretty heavy gauge cable in your TV to the fridge. 

The 12v power option is not really configured to run the fridge for extended periods of time.  And, unless it's super hot outside, the amount of cold loss over short periods of time, if the fridge is pretty full, is minimal and it's hardly worth the bother to even use the 12v to keep the cold "topped off."  It is far more efficacious to run the fridge on gas when traveling.  If you are at a point where you can't run on gas, such as having to go through the Holland Tunnel at commute time or taking the Black Ball Ferry from Port Angeles to Victoria, then using the 12v system makes sense, but once on the other side, it'd be best to turn the gas back on.  [Actually, I don't know whether you can carry a propane tank on the aforementioned Black Ball Ferry.]

FWIW my tow vehicle is a bmw x3 with a factory tow package.  The 7 pin plug does run the trailer lights etc an I was getting a notification in the car that there was too much draw on my battery, so it seems to me it is connected.  From all that you've said I think I really do need new batteries and had already learned enough here to know that the dual 6 volts is the best option.  Now i just need to fin them at the best price available.  :)

Vann

If you mean the trailer running lights they operate on a separate circuit from the battery charging circuit, so having those lights in itself is not a guarantee that you're getting charging to your rPod battery. To be sure, try disconnecting the battery completely by removing the negative connection (along with unplugging the ac power of course) and see if the trailer interior lights come on when you plug in to the tow vehicle. 

You'll probably need GC2 size plastic battery cases for your new golf cart batteries, they are a different size than the 12V ones. You can get them here:

https://www.amazon.com/NOCO-HM306BKS-Snap-Top-Automotive-Batteries/dp/B00316KU6E/ref=sr_1_fkmrnull_1?keywords=noco+gc2&qid=1557560542&s=automotive&sr=1-1-fkmrnull - https://www.amazon.com/NOCO-HM306BKS-Snap-Top-Automotive-Batteries/dp/B00316KU6E/ref=sr_1_fkmrnull_1?keywords=noco+gc2&qid=1557560542&s=automotive&sr=1-1-fkmrnull

Oh...and from what I've learned here I won;t be running the fridge on battery anymore; just he cpap.  :)

Even though the RV style LiFePo4 (LFP) batteries are marketed as 'drop-in' replacements it's a bit more complicated than that. The converter in the r-pod (and most RVs) does not provide the LFP battery with the proper charge settings. Then there is the added complexity of your tow-vehicle charge line to the trailer if you have installed an LFP bank.

I started down that path and its a bit of a rabbit hole.

So, my trailer now has dual lead acid battery bank for all the normal trailer systems, and its compatible with the r-pod converter and the charge line from the tow vehicle. 

I ADDED an LFP battery to run auxiliary loads, in my case, a laptop, an inverter, and a couple of ham radios. That LFP battery is independently charged by a solar panel and dedicated LFP solar controller.

In fact I'm dry-camping right now in New Mexico and both systems are working well. 

Here's my recent experience... Had knee surgery late last summer & I hadn't used it for a while and since I was getting knee surgery I took R-Pod to a loca shop to check all the seals etc since I had no time and woudn't be able to after knee surgery.

BTW - I also had them remove the poorly designed plastic spoiler on the top rear that has the red lights. It seemed like it was primarily designed to catch debris, hold water etc and at some point leak. The calking on the exosed screws needed to be redone and I was sick of dealing with the debris and standing water...  they replaced it with 2 red lights and sealed the 20 or so holes that were left by the screws.

Since it had been in the shop all winter - I know at some point they carged battery. Getting ready to leave I pushed the button and it read "100%" - 4 lights so even though I normally charge battery prior to heading out I didn't. 

I got to camp spot and opened up the extension. Later that evening the refrigerator started to beep and I realized it was indicating low power when I checked it since I know the propane was pretty full. I checked the battery charge and it now only showed 1 light or I guess 25%. My main concern was getting the extension back in so I backed the truck up, turned it on and brought the extension back in and left it like that for the rest of the weekend. I was no where near power, stores etc - primitive site.

Later that following night I woke to a beep from the CO2 / propane sensor. It was indicating low power OR that it was faulty. Nothing was on....     I pushed the battery power button and it now displayed 2 lights instead of 1!  After finally removing the sensor and disconnecting the wires the beeping stopped so I went back to sleep. The next morning the battery was completely drained and it showed no lights.

So personally I won't trust that battery indicator again - I'll simply top off charge before I go on a trip & I'm also in process of installing a battery kill switch.

Those lights are not 25, 50, 75-100. There are two scales on the panel. One is for the tank levels. The other is for the batteries. The top light does not indicate 100% charge, but that the battery is charging. The next light indicates that the battery level is Good if not being charged. The next one indicates that the battery charge is Fair and the bottom one indicates that the charge is Low.

I agree that the lights are less than helpful as a general indicator but are not useful for understanding the state of charge. That is why I installed a voltmeter. I installed the battery cut-off switch so I did not have to keep removing and replacing the battery terminal cable.

I installed a simple digital voltmeter right next to the fuse panel. I used this one:

https://www.amazon.com/gp/product/B00B689UGA/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 - https://www.amazon.com/gp/product/B00B689UGA/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

You can install the temperature probe anywhere: in the fridge, inside the cabin, or outside.

https://powerwerx.com/panel-mount-temperature-volt-meter - https://powerwerx.com/panel-mount-temperature-volt-meter

I recently purchased the Victron BMV-712 to ensure I don’t deplete my dual deep cycle batteries to less than 50%.  I’m sorting out how to install it but I think I’m going to place the shunt near the inverter.

I am installing a battery cut off as well.  Did you install it at the converter?  I’m nervous there might be other drains that I’ll miss by not installing it at the battery.

I'd like to add a voltmeter I could push button test on the battery case so it's not another item slowly draining the battery. 

I'm assuming CO2 / Propane alarms are required to have a light so you know they are working but every little bit drains when your not hooked up.

No, a voltmeter is a poor indicator of battery state of charge (SOC).  SOC is measured in percent of total amp hour capacity of the battery. To measure that properly you need an amp hour meter. A voltmeter will give you some idea, but since the voltage of a battery changes with the rate at which you're charging or discharging it and with the temperature is only a rough approximation. I don't find it much better than the little lights. 

If you really want to know where you're battery is, get one of these or similar:

https://www.amazon.com/AiLi-Battery-Monitor-Voltmeter-Motorhome/dp/B07CTKYFTG/ref=sr_1_11?crid=3T5WM4H8JG2KB&keywords=battery+state+of+charge+monitor&qid=1558612467&s=gateway&sprefix=battery+state+%2Caps%2C238&sr=8-11 - https://www.amazon.com/AiLi-Battery-Monitor-Voltmeter-Motorhome/dp/B07CTKYFTG/ref=sr_1_11?crid=3T5WM4H8JG2KB&keywords=battery+state+of+charge+monitor&qid=1558612467&s=gateway&sprefix=battery+state+%2Caps%2C238&sr=8-11

You would be installing a current shunt in one of the battery conductors. This will provide a measurement of the actual current in and out of the battery, which the device uses to track the SOC. 

Don't get one of the cheap battery SOC monitors available that use a hall effect donut instead of an actual shunt to measure the current, the hall effect devices are notorious for inaccurate readings. 

Which box did you get?  I have dual 12V deep cycle batteries and I’m going to get a box so I can install the battery cut-off and Victron shunt out of the elements.  How difficult was it to secure the batteries inside the box?  Are you happy with the quality?

Plenty of room for 2 Costco 6v golf cart batteries.  I also keep 4 wheel chocks in there along with a quart of battery water and the hydrometer.  I'm going to try to resist putting in more, but there is still a little room.  Here's what it looks like mounted on the tongue: 

https://postimg.cc/Xp6vCp8z">

I added a battery cutoff switch that I bolted to the forward wall of the box and I secured the batteries using eyebolt secured in the aft wall and heavy rubber shock cords.  I cut the old plastic battery boxes to make trays to hold each battery.  Absent a trailer rollover, the batteries ain't gonna move.  And if there is a rollover, who cares, that'll be the least of my problems.

Yes, it is a good measure of SOC if you know the specific gravity of your battery acid fully charged and discharged. But its inconvenient to use on a daily basis, so more generally used as a means of troubleshooting battery problems. 

The battery SOC monitors are getting pretty cheap now, the one I linked to is only about $32. I don't have personal experience with it but its getting decent reviews on Amazon. The Lexus version is the Victron 712 if you want to spend a couple of hundred bucks on one. 

https://www.trojanbattery.com/tech-support/battery-maintenance/ - Trojan states this on the web site :

Visual inspection alone is not sufficient to determine the overall health of the battery.

Both open-circuit voltage and specific gravity readings can give a good indication of the battery’s charge level, age, and health. Routine voltage and gravity checks will not only show the state of charge but also help spot signs of improper care, such as undercharging and over-watering, and possibly even locate a bad or weak battery. The following steps outline how to properly perform routine voltage and specific gravity testing on batteries.

Below that are instructions on how to do specific gravity readings and how to do open circuit voltage checks. Plus it has instructions on how to water flooded cell batteries and how to clean them. All in all, a very useful web page.

For many of us who don't consume a lot of amp hours having a constant monitoring device for the battery isn't really needed.  For those who use a lot of electrical devices, it sure makes sense.  If you have a CPAP machine that you need to work all night it certainly is reasonable to spend the money for an SOC.  

For myself, I'll just monitor my battery volt meter on the wall and it it's getting down a little too much, I'll open the lid of the tongue box, pull out my handy hydrometer, flip the two cap levers, and make a quick test, all in, as I previously said, less than a minute.  

Thanks for the info!  I see you have a WDH.  Is that an Equalizer?  That is what I have and I wasn’t sure if I could fit the box but clearly you did.  We have have a 179 and I have about 11.5 inches from the back of the propane to the trailer.  Is that about what you have?

The box seems reasonable sturdy, though the lock could be easily pried open by a person with a blaggard's heart.  

All true and a fine way to go for battery maintenance purposes. With three caveats:

You need to know the specific gravity (sg) of your particular battery at full charge and discharged. Different manufacturers use electrolytes with different mix ratios of sulfuric acid to water, depending on the intended application of the battery. So sg on a fully charged lead acid battery can be between 1.26 and 1.30. Also, some battery designs are "plate starved" and others are "electrolyte starved", meaning that some run out of plate capacity first on discharge and others run out of acid. So you need to know the relationship between sg and SOC for your particular battery. Some manufactures provide data for this, some you'll have to work out for yourself the first time and make your own table. Trojan is really good at providing this data. Also, if you want to be accurate then there is a temperature correction to do to your sg measurements. 

For voltage to work as a measure of SOC you have to measure it while the battery is at open circuit (Voc), meaning no charging or discharging can be occurring. And, you can't just stop taking current or or running current in, you have to wait awhile for the battery cells to reach equilibrium. Typically this takes around an hour or so. 

As with sg, you also have to know the Voc of the battery at different states of charge. This. like sg, varies based on the way the battery is designed. Generally the manufacturer will provide a table or graph for this, but sometimes you'll need to create this the first time like with sg. 

The above caveats are why these sg and Voc based readings are good for maintenance purposes. They take  quite a bit of time to do and you have to take your batteries off line to do it.

If OTOH you want an easy way to see the current SOC of your battery at a glance (the equivalent of  little lights except actually accurate) then get a SOC meter. Much more convenient and they're really cheap now.

It doesn't measure pH, it measures specific gravity.  Pure sulfuric acid is heavy stuff, it's  sg is 1.84. Water is 1.0.  A mix of the two will be somewhere in between, and the sg of that mix (temp corrected) tells you what the concentration of sulfuric acid is. During discharge, sulfuric acid is consumed so the sg of the mix goes down. If you know the sg of your particular model battery at 100% SOC and say at 20% (a difference of 80%) and you measure the sg as halfway between the two then your SOC is 60% = 40%+20%. 

The original question was related to what one might use to check battery SOC in lieu of the inaccurate little lights provided by FR. A voltmeter was proposed and I recommended an SOC monitor instead. Both are inexpensive and can be installed where you can look at them from inside the trailer. 

There's nothing complicated at all about reading the SOC from a meter. You just read it, it gives you percent state of charge directly. The complexity is in the one time setup, and its really not that much.

Measuring your battery cell's sg is in contrast a complex and time consuming process, not something most folks want to do on a daily basis while camping somewhere. Nothing wrong with doing it as part of your battery maintenance procedures though, and if you're not using enough of your battery capacity on a daily basis to worry about SOC, then that plus the rough indication the little lights give you is all you need.