Post some good pictures showing how you wired the batteries.  Lithium-x batteries have a battery management system built-in to prevent damage/fires.  That may be affecting your discharge. 

What is each battery's voltage? 

This is a parallel connection, to be used with two 12V batteries, in an R-Pod.

So if you have the standard rpod wiring then the mystery is how did the battery connected to the solar port get charged? Do you have a solar kit connected? If not then it shouldn't be getting charged or discharged, because there should not be anything connected to those wires. Where are you seeing the 90% state of charge reading?

I should have maybe been more clear on the multimeter. Pretty much all multimeters will measure both ac and dc voltage. I was talking about measuring dc current,which is more unusual. That would tell you how much charging and discharging you are getting. 

In any case, you have the meter you have. The two smaller gauge wires are the ones that go to the solar port. Assuming there is no solar connected, disconnect them from that battery and measure the dc voltage on them. Should be zero. If so set them aside. 

Get two battery cables, one red and one black. Minimum gauge should be 6, 2 gauge or 1/0 is better. Connect + to + and - to - of your two batteries. 

Then connect the heavier gauge - cable on the rPod to the - of one battery and the + to the + of the other battery. Verify with your meter first which is + and which is - before connecting. You can plug in the rPod and turn on the charger to be sure, but then shut it down again while connecting.

The reason for attaching + to one battery and - to the other is to better balance current flow between them.

One last question, the standard WFCO charger in the rPod is not designed for lithium batteries. If you overcharge Li batteries you can start a fire. So, you need to be sure that you have a safe system there, either by changing the standard WFCO for a LI charger or being sure that the batteries themselves are internally protected from overcharging.  

Also, you will not be able to effectively charge Li batteries from your tow vehicle without additional equipment. There really is a lot to converting a trailer to lithium batts and you need to understand all of that or it will at best be ineffective and at worst can be very dangerous.

So, you can connect the two smaller gauge wires from the solar kit to the same two battery terminals as the larger wires which lead to the charger/panel.  Again, be sure of your polarity buy using your voltmeter first. That plus the two parallel battery connectors should get you going. 

Next question: 

All three charging sources: solar, rPod charger, and tow vehicle charging (if you want to be able to do that while driving or boondocking) need to be configured for charging Li batteries. This is very important to be sure you are getting proper charging but most importantly, keep you safe from fires and explosions. Have you looked into that yet?

And one last thing, never attempt to charge Li batteries when they are below freezing. That can also cause severe damage or fires. For that reason many folks, depending on what your climate and camping patterns are like, mount their Li batteries in the heated space rather than the standard battery location. 

Re the cold temperatures, its not that the batteries are frozen in some obvious way its that lithium batteries can't accept a charge when the are at cold temperatures. So, if you camp in sub-freezing weather you can have problems. Your batteries may be self-protected from that by their battery management system, you might want to check the specs for the BMS and see.

Sounds like your solar charge controller can be reset for lithium batteries, just be aware that the WFCO charger in your rPod is not set up for them. They have another version that is. If you want to also charge from your tow vehicle you will probably need a dc dc converter for that. 

hi Folks,

My solar panel project this summer has meant I've learned a lot about my batteries but not enough yet.  These are both 12 volt (the batteries are new(er) but they replicate with came with the camper). Can someone please tell me what these two loose wires are and, as unlikely a possibility as that seems, are they supposed to be loose?

No, the solar is just a suitcase portable panel. It's just that before I got that and tried boon docking I left batteries alone (was learning other things). Now I am learning batteries. But this is just the two 12 volt batteries wired in parallel (I believe). I just don't know what these "extra" wires are. Have they become disconnected from somewhere?  A ground wire maybe?

I'm open to instruction on how I should be connecting the renogy panels. I have put them on one of the batteries matching positive and negative 

First, yes it does appear that the batteries are connected in parallel. You can tell that because there is a black jumper wire between the two negative battery posts and a red one that looks like it goes between the two positive posts. 

And I see what appears to be the negative connection from the batteries going (probably) to the pod panelboard (black wire connected to the battery post just above your hand in the photo).  What I don't see is the positive connector from the batteries to the pod. That should be connected to one of the two positive battery posts (preferably to the battery on the left that the negative lead is NOT connected to, it balances the batteries better if you do that). It could be the red wire you're holding but if that's not  ever been connected then I'm puzzled how you have been getting battery power to your trailer dc circuits. 

As GlueGuy says, I also have two extra wires on my trailer (smaller gauge that the main battery cables) which go to the Zamp solar port. So we have a total of 4, your picture only shows 3 wires plus the two battery jumper wires. Is there another wire somewhere that's not showing up in the picture?

Next, did you rotate the left battery around or is it always set in there on an angle like that? I notice that the right side case is bigger than that battery, I'd suggest getting the correct size for that and placing the batteries in there lengthwise so you can strap them down and everything is stable. Those plastic cases aren't expensive.

Finally, if you connect the suitcase solar kit directly to the battery, is there a fuse at the battery + terminal for that? If not, you should add one for safety. And be very careful working with wrenches and loose wires around batteries. If you've never seen what happens when you short a battery post to post or positive to frame ground you don't want to. You can get a heavy wire or tool red hot in a fraction of a second or even blow the side of a battery case off spraying acid everywhere due to internal heating.  Its best to tape up your wrench(es) so you don't accidentally touch them between posts and also disconnect the negative terminal first when working on batteries. 

Thaks for the detail; this is very helpful.  I'll get back out there later today.

What I don't see is the positive connector from the batteries to the pod. That should be connected to one of the two positive battery posts (preferably to the battery on the left that the negative lead is NOT connected to, it balances the batteries better if you do that). It could be the red wire you're holding but if that's not  ever been connected then I'm puzzled how you have been getting battery power to your trailer dc circuits. 

I see your point! But I do have battery power in the camper. Maybe it's hidden in the picture. I'll check.

As GlueGuy says, I also have two extra wires on my trailer (smaller gauge that the main battery cables) which go to the Zamp solar port. So we have a total of 4, your picture only shows 3 wires plus the two battery jumper wires. Is there another wire somewhere that's not showing up in the picture?

I'll check

Next, did you rotate the left battery around or is it always set in there on an angle like that? I notice that the right side case is bigger than that battery, I'd suggest getting the correct size for that and placing the batteries in there lengthwise so you can strap them down and everything is stable. Those plastic cases aren't expensive.

No, this is how they came to me. I like this idea.

Finally, if you connect the suitcase solar kit directly to the battery, is there a fuse at the battery + terminal for that? If not, you should add one for safety. And be very careful working with wrenches and loose wires around batteries. If you've never seen what happens when you short a battery post to post or positive to frame ground you don't want to. You can get a heavy wire or tool red hot in a fraction of a second or even blow the side of a battery case off spraying acid everywhere due to internal heating.  Its best to tape up your wrench(es) so you don't accidentally touch them between posts and also disconnect the negative terminal first when working on batteries. 

I do always disconnect negative first and am very careful around anything electrical (dad was an electrician).  Honestly if I can find someone to look at this and straighten it our for me I'm inclined to go with (paid) expertise. I think adding a fuse might be beyond my skills at this point.  :)

And again thanks to all of you.

So I did solve one mystery.  There is a red wire (that was not in the photo) that goes from the "other" battery to the disconnect switch and then into the camper.

I'm increasingly thinking that those are the zamp wires. So my priority is to figure out about adding a fuse.  I'll check youtube.

I don't recall if you have a multimeter or not yet, but here's how you could confirm 100% if you want to. 

Leave the two wires loose at the battery end. Put your multimeter on the dc volts scale and touch the two probes to the two ring terminals on the two wires. Confirm there is no voltage on them.  Now you know you can safely connect the two wires together, so put a clip or a bolt through to hold the ring terminals together, or get someone to hold them together for you.

Then go to the zamp output port, insert the meter probes in the two poles of the port and confirm there is no voltage there. Then put the multimeter on the ohms (resistance) scale and check the resistance between the two poles. It should read zero or very low, like about 1 ohm, because you shorted the two wires together at the other end. 

Finally, go back to the terminals you connected together and disconnect them. If you now read high resistance (thousands of ohms) at the zamp port you know you have found the other ends of the same two wires. You can just set those two wires off to the side as you are not going to be using them.

For a fuse for your solar kit, you could use something like this

https://www.amazon.com/AutoEC-Inline-Waterproof-Fuse-Holder/dp/B013JG8GIY/ref=sr_1_5?dchild=1&gclid=CjwKCAjwh7H7BRBBEiwAPXjadutaHvmIldvbv2uuieK3JzjJn8ocXJHpzuTvu9jNk3_jAI85cfiuOxoCHKQQAvD_BwE&hvadid=409942933092&hvdev=c&hvlocphy=1027077&hvnetw=g&hvqmt=e&hvrand=4245082082120251410&hvtargid=kwd-9532746121&hydadcr=24657_11410751&keywords=20+amp+fuse+holder&qid=1600962560&sr=8-5&tag=googhydr-20 - https://www.amazon.com/AutoEC-Inline-Waterproof-Fuse-Holder/dp/B013JG8GIY/ref=sr_1_5?dchild=1&gclid=CjwKCAjwh7H7BRBBEiwAPXjadutaHvmIldvbv2uuieK3JzjJn8ocXJHpzuTvu9jNk3_jAI85cfiuOxoCHKQQAvD_BwE&hvadid=409942933092&hvdev=c&hvlocphy=1027077&hvnetw=g&hvqmt=e&hvrand=4245082082120251410&hvtargid=kwd-9532746121&hydadcr=24657_11410751&keywords=20+amp+fuse+holder&qid=1600962560&sr=8-5&tag=googhydr-20

You would need to crimp a ring terminal on one wire so you can connect it to the battery + terminal, and probably use a butt splice connector on the other end to connect it to the positive lead going to your solar charge controller. Get one of these to cut, strip, and crimp the wires. Use the strip holes and crimper for the size of wire you have, squeeze hard when you crimp, and tug on the wire to test to be sure it doesn't pull out of the crimp later on. 

The ring terminals, butt splices, and crimp tool are available at your local big box, you might want to get a kit of assorted splices and terminals for your pod tool box. That way the next time a crummy connection somewhere on the rpod comes apart you can fix it. 

https://www.amazon.com/VISE-GRIP-Stripping-Cutter-8-Inch-2078309/dp/B000JNNWQ2/ref=sr_1_5?dchild=1&keywords=wire+cutter+crimper&qid=1600962817&sr=8-5 - https://www.amazon.com/VISE-GRIP-Stripping-Cutter-8-Inch-2078309/dp/B000JNNWQ2/ref=sr_1_5?dchild=1&keywords=wire+cutter+crimper&qid=1600962817&sr=8-5

I have also learned that the renogy alligator connectors already have a fuse!

I might like to use the zamp connector so I dobn't have to keep opening the batteries. I think I need this: https://www.amazon.com/SolarEnz-Adaptor-14AWG-Connection-MC4-SAE/dp/B07GL9X3B5/ref=sr_1_1_sspa?dchild=1&keywords=sae+adapter&qid=1600964226&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFHQVdVNUw1TjJGOVEmZW5jcnlwdGVkSWQ9QTAzOTI5OTAxWDc1NzFVVldEVkgyJmVuY3J5cHRlZEFkSWQ9QTA1NjIyMzVXWkxJT1E5N0szUEsmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl - https://www.amazon.com/SolarEnz-Adaptor-14AWG-Connection-MC4-SAE/dp/B07GL9X3B5/ref=sr_1_1_sspa?dchild=1&keywords=sae+adapter&qid=1600964226&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFHQVdVNUw1TjJGOVEmZW5jcnlwdGVkSWQ9QTAzOTI5OTAxWDc1NzFVVldEVkgyJmVuY3J5cHRlZEFkSWQ9QTA1NjIyMzVXWkxJT1E5N0szUEsmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl

I guess I would have to still figure out how to connect those two loose wires to the batteries though. Can I just leave them connected?

If anyone sees any mistakes in my thinking I'd appreciate a heads-up.

YAY!!!!

Confirm the polarity you have is what you expect at the zamp port using you multimeter before making your final connection to the Renogy system.