solar

BFL13 wrote:
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EDIT--ok, say I had the same set-up only with LFP so no amps tapering. It all gets done at 75 amps. 184/75 is 2 hrs , 27 min. so I would save 33 minutes (from 3 hours) of gen time. Not quite the same as "four times faster" is it?

How about I do a 50-80 with my four 6s? Now it all gets done at 75 amps where amps start to taper at 80% SOC. 150AH in two hours. Swap to LFP and--oops--still 150AH in two hours.

The "4x faster" component comes from the C rates the batteries are rated for. Most GC2 batteries are rated for C/3 charging while LiFePO4 1C or above. That's three times the speed - not accounting for the "aboves". They also don't have a slow absorption stage at the end (as you alluded to in your edit). If you have the chargers/generators to support the charge rates, they do charge that much faster. If you want the most life out of your lead acid batteries, most manufacturers say not to charge at more than C/10. That means for optimal life, you should be charging your bank of four GC15s at only 46A.

In practical application, you can buy larger chargers (or parallel them), larger generators, and charge off your solar array at the same time - so you can get closer to those theoretical limits. I've seen as much 6.3kW going into the LiFePO4 bank in my fifth wheel from multiple sources - that's a charge rate of over 500A in 12V terms. If I had a bigger genset, I could add more chargers or swap out my current ones to charge faster. A lot of people who upgrade to Lithium also upgrade their chargers at the same time, to take at least partial advantage of this.