Is my WFCO converter/charger killing my batteries?

That's great! What current do you read on the shunt when you're charging at sat 40-50% SOC with all your loads off. Shut the WFCO off and back on and under those conditions it should be around 40A.

Something's not right with your charging and/or you're using a huge amount of electricity, or your state of charge is higher than you think.

The WFCO should be producing 40A or so until battery voltage gets pretty high, so in 4 hours you should be getting close to full charge even if you started at a low SOC.

How are you determining state of charge? Don't use the idiot lights, use a multimeter, leave the battery disconnect for an hour or so and use an SOC vs voltage table. Get a meter with a Hall Effect DC clamp on so you can measure your actual charge current as well.

I'm a retired engineer too so I know about overengineering. But with electrochemical stuff like batteries the complexities make it fuzzy enough that its a bit more of an art than a science relative to say electrical or software engineering.

I think its important to recognize that deep cycle lead-antimony batteries are not for everyone. SLI auto batteries generally use a lead calcium alloy which results in lower self discharge and charging rates and would probably be a better choice if you let your pod sit for long periods.

As an example, I have a car here at my Dad's house in Hawaii that due to Covid travel restrictions I was not able to run for two years. I'd left the battery in the car disconnected and uncharged for that period, connected it and it started right up and its run and starts the car just fine. That would definitely not be the case with golf cart deep cycle batteries. They would be dead as a door nail.

So if you need batteries that will tolerate a lot of cycling and either use your pod often or are willing to do the charge, watering, and equalization maintenance, then deep cycle GC batteries are for you. If you mostly camp with hookups and/or use your pod I intermittently and/or aren't much for battery maintence then get SLI or AGM batteries. If you want the best of both worlds then bite the cost bullet and convery to Li batteries, where there are a bunch of different types available as well. Different chemistries for different applications.

Me overengineer?  Software Architect by trade before I retired and that's why.  Thanks for the help.

Or pull the charger module from my wfco 8735 and replace it with something 'smart' that meets the Trojan guidelines.  I've been researching but its becoming difficult to find on for my particular unit.  In addition, I'm wondering if a stand alone unit closer to the battery might be a better option since the wires 20 feet away from the battery to the charger look like #6.  I have not measured the current from the charger to the battery but imagine that with the long run of smaller cable there is quite a bit of resistance.