Thank you dt. I am aware of 6 vs 12 volt batteries. One of my 6 volts had 205 ah, so it took two to get 12 volts at the same amps. My 8 6-volts, gave me a bank of 4 12-volts at ~820 ah, with weight at ~500 pounds. That’s about the limit of my knowledge. I’ looking at 12 volt lithium, 300 ah each, at 55 pounds. So 6 of them would give me 1800 ah, at about 330 pounds. But are the 12’s as good as the 6’s? Are they as good with longevity? Do they hold their charge without discharging too quickly?
You are going to love the lithium! Lithium 12v are way better than your old 6v in series/12v parallel setup. First is the obvious weight savings - always nice. But your planned six 12v lithium batteries giving you 1800 ah is actually not just doubling your usable capacity, but actually it will basically quadruple your old capacity. The really nice thing with Lithium is the very flat voltage curve. Unlike lead acid batteries that lose voltage as they discharge, lithium voltage stays really consistent until they are nearly 100% discharged. For this reason, you can run them until they are virtually 100% discharged without damaging them, where lead acid begins to see long term damage anytime you go below 50% capacity and are considered dead at that point.
They will also hold a charge a lot longer than lead acid while in storage. It is best to store them at 80% or less charge, but they will hold that for months. I had some that sat on a shelf for 22 months and only dropped to from 80 to 73%.
As for longevity, most are rated at a minimum of 4,000 full cycles. That means the approximate equivalent of discharging from fully charged to less than 10%, 4,000 times. So if one is fully charged and discharges to 50%, that is eqivalent of a half cycle - doing it twice equals 1 of the 4,000 cycles. In a nutshell, if you fully discharge the batteries every day of a year (365 times), they will last eleven plus years! Longevity is a strong point!
When you install them, you do not want the negative and positive cables from the RV going to the same battery. It's best to have the positive cable on one end of the bank and the negative on the farthest away negative terminal. Also use as large cables as possible and make sure all the cables are the same size and length. The reason for all of this is that lithium batteries are very sensitive to resistance and will pull power from the battery with the lowest resistance if possible. By putting the cables at opposite ends, it fools the batteries into "thinking" they are just one big battery - and equal size and length cables make that equation even stronger.
One other plus is that lithium batteries do not off gas and there is no corrosion of the terminals or cables. If you are investing in six lithium batteries, I would advise you to invest is a couple of other items. See below:
1. A "shunt" with either a readout or Bluetooth (or both) capability. This is a unit (I prefer Victron brand personally) that tells you the status of your battery banks charge. Unlike lead acid, where you can watch voltage drop for the battery's state of charge, as described earlier, lithium batteries maintain an almost flat voltage curve until the very end and then they shut off quickly. The shunt mounts on the negative terminal between the negative RV cable and the post. By doing this, it reads the actual amp hours/wattage consumed and tells you the accurate status of your available power. It is definitely worth the expense.
2. All new battery cables. If there is any corrosion in the old cables, and after 6 years it is almost a given that there is, there is no way to balance resistance. New, big cables are worth the spend.
3. A Converter- Charrger that is lithium compatible. A non compatible one will still work, but will only charge the batteries to 80-82 percent of capacity. This is not a huge problem if you don't need 100% of the amp-hour capacity, but it does impact that by about 20%. Also lithium can charge a lot faster than lead acid batteries and a compatible unit aids the faster charging benefit.
4. Finally, if you don't already have it, solar charging works phenomenally well with Lithium. You can go mild to wild on a solar system, but even a modest system will add substantially to your power storage - and greatly lessen generator or plugging in requirements.
Two last items. I did not catch where you live or the type of camping you do, but lithium does have one, fairly major, drawback. That is extreme cold weather. They will discharge just fine down to -4 degrees Farenheit internal core temperature and will then taper off fairly quickly, but you absolutely cannot charge them below 32 degrees Farenheit (freezing) internal core temperature. Trying to charge at colder temperatures will quickly destroy the battery. Make sure that whatever batteries you are looking at have built in low temperature protection. Some also have built in heaters, but if they are discharging or charging, they create their own heat. I definitely don't want to destroy my batteries and would not buy a new battery today without built in freeze protection, but I'm not yet sold on the benefit of internal heaters unless you know you will be camping in those extreme temperatures.
Finally, some will tell you that you cannot start your generator with Lithium and some manufacturers warn against it. This is due to their low ability to provide short term, high end rush, voltage, and is a problem in small battery banks. I started an Onan 7KW gas generator in our last 5th-wheel toyhauler with just two Lion 1300 100AH 12v batteries in parallel operation just fine. I currently have a motorhome with a 12.5KW Diesel generator and also start it with my lithium bank, but it is a substantial bank of batteries. As long as you go with your current plan, you will be able to start any RV generator you may have!
I absolutely love our solar/lithium system on our RV and truly hope you find it to be everything you were looking for. I think I've about depleted my limited knowledge on this topic and if others correct me, that is great as we all learn, but this is what I've learned in 5 years of dealing with Lithium and I would never consider a lead acid battery as a suitable replacement.
