solar

BFL13 wrote:
... It is really about carrying more usable AH in the same small space in a RV that is weight limited, but IMO the fast charging claim is not realistic.

The charging speed becomes much more important as you scale it up. It doesn't make a lot of difference if you have a small setup with four GC2s or two BattleBorns, but if you have several thousand watts, tens of thousands of Wh of storage, and a load that can draw the bank down significantly overnight, it becomes quite important.

For our 2925W array we can usually harvest around 18kWh of energy per day in AZ in summer. We have a 22.8kWh bank in that rig. In 100F temps, we'll consume right around 22kWh per day keeping the rig at 72F. That leaves us with a deficit of around 4kWh, that we want to cram into the bank as quickly as possible, in the middle of the day so we're not having to listen to it during the evening. It's not unusual to run the genset around lunch time and when the AC compressor kicks off, push 3800W from the generator and 2500W from the solar array to the bank at the same time. 525A of charging if it were a 12V system (it's 48V).

A bank of 16 225AH GC2s has a max charge rate (C/3) of 600A@12V, a recommended charging rate (C/10) of 180A@12V, and an absorb stage that substantially tapers the charge above 85-90%. They also need to be routinely charged to full to retain that ability. We'd either trash the batteries in short order, never make it to full, or more than likely, some combination of both. By contrast, the recommended charge rate (C/2) for our LFP bank is 900A@12V, so we easily make it to full each day and never have to worry about it.

We are far from the only people with setups like this.