There a few misconceptions. I have all three types of batteries between a horse trailer, travel trailer, and truck camper. The flooded lead acid batteries have the cheapest initial cost but over time they're not a great investment. The AGMs are much better, but the Lithium are the best. The only negative is that the Lithium have a higher initial costs, anywhere from 2 to 5 times the cost, but they can last 10 to 20 times longer than the really cheap batteries and 5 to 10 times longer than the higher in AGM batteries. They are rated to be 3000 to 5000 cycles and some manufacturers offer very long warranties. If you have a good working system, I would suggest upgrading to Lithium, until you're ready to replace items in your current system. These are the advantages of a Lithium system:
--Performs down to 0 degrees F better than other batteries. (All batteries degrade in cold temps, but Lithium perform at a higher voltage. It's true you can't charge below freezing (28 for Battleborns), but it easy to keep Lithium batteries warm.
--You can have Lithium batteries in the living quarters getting heat. They don't off gas while charging or discharging. So they can perform at a desirable consistent room temp when other batteries are exposed to the elements.
--Lithiums are half the weight so you can easily remove them when not in use. For some systems like in my TC, I can use one lithium battery at 35lbs and to get the same usable amp hours I would need two AGM batteries at 140 lbs. Saving a 100lbs can be very desirable as many are near max weight on their trucks.
--Lithiums accept a partial charge without degradation, other batteries begin to suffer if they don't get full charges each time, which is the case in periods of bad weather. You may also decide that you don't need as much solar panel if you know you don't need a full charge each day. In my truck camper, can go well over 3 days and only use 30% of my battery and that's running heat all night, fans, and LED lights. I can charge my battery in 3 hours of driving with a DC to DC charger, so I've decided to delay getting solar at this point. When I get a fridge, I'll re evaluate at that point. Lithiums are charge quicker which has similar benefits in that you don't need as much good weather for solar.
-- Lithiums can discharge all the way to 90 or 100% without degradation (aka DoD, depth of discharge), so you may need fewer batteries to get same usageable amp hours which obviously saves on costs, but you don't have to worry about damaging the batteries if you go too low.
--When storing lithiums, you don't need a trickle charger as they don't need to float and they are fine with full discharges. Lots of batteries get damaged beyond repair while in storage.
--When lithiums discharge, they maintain a higher more constant voltage. This is good for gear that relies on the clean power, like some of the newer compressor fridges and laptops, camera batteries etc.
If you can find away to make the initial investment and will keep your rig over time, it will pay for itself several times over. When making the investment, you typically need to upgrade to a lithium compatible converter/charger and you may want some beefier cables coming of the batteries. Essentially you should look at the overall cost of ownership, not just the initial purchase. It's also nice to have a good battery monitor so you can evaluate the performance. This a good idea for all types of batteries, but if you see an issue you can address with the manufacturer.
