It's probably too late to help you with your issue, but I'm adding this comment for any future reference. We just joined the club yesterday but we were members years ago and were Fleetwood Ambassadors in the early 2000's.
Anyway, we have a 2020 Fleetwood Flair 32S with a residential refrigerator and the supplied dual Harris batteries which I replaced last year. I'm a retired electrical engineer so have a little better background than some might, but I had to do a lot of research before making my decision. RV electrical systems was not my major.
There were several options:
1. Convert to Lithium. In the same compartment it would be possible to install 200 AH of lithium batteries which can be run to about 80% discharge before possible damage to the battery. However, the converter/Charger in my unit does not support Lithium so this would have needed to be replaced also bringing the total cost to between $1200 and $1500 depending on the quality of the Lithium battery. This is the cheapest long-term solution and the best, but the most expensive. WFCO told me that newer coaches all have converter chargers capable of charging Lithium batteries. Check this out before you convert. (Note: all my prices assume I am doing the work.)
2. Install 2 AGM batteries in the same space. This eliminates the need for periodic maintenance (water replacement). However, does not help improve your energy density concern because of your residential refrigerator. Cost $500-$600.
3. Install 2 RV/Marine batteries in the same space such as the Harris (made by US Battery). These typically last 3 years. I don't know the cost since I didn't consider this alternative.
4. Install 2 Golf Cart batteries in the same space. Golf Cart batteries can be taken down below 50% discharge without harm, but it is not recommended to do so on a regular basis. Golf Cart Batteries actually outperform AGM's by quite a bit and can take more abuse, but they need to be maintained (add water as needed (I usually only need to add every 3 to 4 months but check monthly). There are many good quality batteries available. I checked with my golf cart store and bought their recommended units. Total cost was under $400. A true deep discharge battery takes from 50 to 150 discharge/recharge cycles before gaining its maximum power potential and if properly maintained, will last 6 to 7 years. The brand I went with was Thunderbolt Xtreme. they are 225 AH@20HR 115min@75 amps. They are still building up to their full potential. It's the same brand as I have in my golf cart, but the golf car uses 8 volts versus 6 volts in the motorhome.
At the FMCA International Convention in Perry in 2021, I learned how much draw the Residential Refrigerator actually takes. During the second day my batteries were so low the inverter quit working. I had to use the aux start to fire up the generator. Now if you're new to this, pay attention. I ran the generator until the Precision Circuits panel indicated the batteries were fully charged (13.2 volt for FLA). However, they were not. This was just a "surface charge", once a load was applied, the voltage dropped to its actual which was still severely discharged. In a few hours, the same problem occurred. Even though I am an electrical engineer, I finished school in the 1960's and forgot about this phenomenon until it happened several times, then I caught on. At the rally, I talked to Fleetwood and every other expert I could find, including the "ask the experts" seminar with no solution. One of the experts suggested I get the unit plugged in for a day or two to see what was happening. I ran the generator for the rest of the day, and the batteries made it through the night.
To summarize, and this is anecdotal evidence mixed in with partial facts (all the information is hard to come by) it is necessary to run your generator between 6 to 7.5 hours a day to keep the batteries charged when you are boondocking with the residential refrigerator and two flooded lead acid batteries (FLA) (Lithium recharge quicker due to the chemistry of the battery). I believe the total load I am using is about 100-to-150-amp hours per day which must be replaced by either the generator or some other means. The WFCO is capable of putting out 40-55 amps depending on your model, but the batteries are not capable of absorbing that much power, so you can't just divide 150 by 50 and think you can recharge in 3 hours.
In 2022, we went to the Albuquerque Balloon festival and knew we would be boondocking for 9 days along with our other dry camping trips, so I decided to add some solar to the rig. I got a price at the FMCA SEA rally of about $5,000 which would have been everything including the upgrade to Lithium, batteries, but we couldn't justify spending this much money for 20 to 30 days user per year. When boondocking, we typically will run the generator for running the microwave since it is not set up to run off the inverter due to only the 2 supplied batteries. I designed a system that includes two 100-watt Renogy panels mounted to the roof, and two 100-watt portable panels that can be set up once stationary. Initially I purchased a Renogy 30-Watt PWM Wanderer controller. My total investment was about $500. It will supply enough power to keep the batteries topped off-as long as the sun shines. In Albuquerque, last year, there was very little sunshine. I had to run the generator an average of 5.5 hours per day which was an improvement, but not enough to justify the expense. After returning home, I caught a sale on a 40-amp Renogy MPPT controller which I installed in place of the PWM. I will find out if I get the desired improvement when we attend this year's FMCA international convention in Perry next month.
If you want to learn more about FLAs, go to the Trojan batteries' website. There are some great video single point lessons that can help you make the best decision. I've had Trojans in several of my previous coaches and had no problems with them. They are very expensive. I have to be careful here to avoid being sued but talk to your battery supplier and find out which batteries they have the best luck with and which ones to stay away from.
If you want to learn more about solar, check out Will Prowse on YouTube. I bought his book, the electronic version which he sells very inexpensively.
Your decision needs to be based on your available funds, the length of time you will own that coach, and whether you can justify the expense.
