A couple notes on the last few posts.
With regard to the charging current, remember that these numbers are per battery. If you have 2 in parallel, the a 1C charge rate is 200 amps and the "sweet spot" for 2 in parallel is 90-110 amps. So with multiple batteries in parallel, there is not much concern over too much charging current.
I think the terminal thing on the Lion Energy batteries is a bit overblown. The job of the terminal is primarily electrical in nature, not mechanical. Will has clarified that it is not a current carrying concern, just that he prefers the overkill blade terminals, and the more robust, heavier case on the BB. I would upgrade to more appropriate bolts than the included wing nut bolts and torque the terminals carefully per Lion Energy's instructions (12 ft-lbs in my manual.) I would also avoid hanging any heavy items off of them and secure heavy cables rather than letting them hang from the battery.
Alternator charging, which is relatively simple in the Lead Acid world, is obviously much more complex with LiFePO4, drop-in style or not. The question I keep coming back to is: How badly is it needed? I generally drive in the daytime and where I drive is not frequently in the shade, so the solar panels will be charging the batteries, running the fridge, etc., while I am driving. If I'm parked and dealing with a stretch of cloudy days, I'd much rather run my generator for a couple hours than run my engine on high idle for the same amount of time. The main drive engine of a vehicle with an alternator is not the most efficient tool for stationary charging.
I've decided to build my system for now without alternator charging and just cap and stow the current wire coming from the isolater in case I change my mind after I've used the setup for a while and determined if alternator charging would provide meaningful benefit to me. If I find myself arriving places with depleted batteries on a regular basis, I'll consider adding DC-DC to my setup.
Chris W
Your plan certainly makes sense for your situation. Sounds reasonable to me.
In our case, we DO rely on alternator charging. We have a modest 200W solar setup, but frequently boondock, and use park campgrounds, in the woods. So much of the time we could have 600W or 800W of solar and it wouldn't make a difference. Luckily, we tend to be travelers more than campers, so relying on the alternator to charge our 2 Crown CR260s generally works fairly well, although I've noticed that even if we drive hundreds of miles they never really get a full charge. I assume that's because the Sprinter chassis voltage is lower than normal, at about 14V (+/- 0.1V). Also, the cable Winnebago used between the chassis and coach batteries is #1 and/or #2 gauge, so there is voltage drop across it.
So concerns about the load on the alternator aside, it seems that a DC to DC charger would do a better job than the existing straight connection.
A note on solar: I've been into renewable energy since the 1970s. I like to see solar used wherever it's practical. It clearly works well for some people, in some areas of the country. For others, not so much. In a best-case scenario -- summer in the Sun Belt -- people report being able to rely 100% on solar, and often say their batteries are recharged by early afternoon. Of course, a lot depends on their energy usage. For people in areas like the Pacific NW and places with a lot of cloud cover -- or anywhere, if they camp in the woods -- it just doesn't make a lot of sense.
I doubt many people routinely discharge 2 or more UT1300s every day, but charging a pair of UT1300s from close to 0% SOC up to 100% takes a large PV system and a lot of sun! Definitely doable, but only under the right conditions.
You said:
"... I'd much rather run my generator for a couple hours than run my engine on high idle for the same amount of time. The main drive engine of a vehicle with an alternator is not the most efficient tool for stationary charging."
Absolutely!
You wrote:
"So with multiple batteries in parallel, there is not much concern over too much charging current."
I'm not sure I follow. Two UT1300s in parallel will take up to 200A. That's more than the max rating of our alternator, which is 180A.
I haven't received the batteries yet, but I tend to agree with you about the terminals. They appear a bit cheesy, but they will do the job. I'm not overly concerned about it, but I am looking for ideas to lessen the stress on them. I noticed in the YouTube videos that internally, the UT1300s have multiple smaller gauge cables connected to each terminal. That's a good idea. I may do something like that. Run the existing #4/0 cables to remote lugs, and then connect to the batteries using several small cables for neg(-) and pos(+).
️?
