I've had a quick look at reflex charging.
First impresssion: great for NiMH (memory effect) and lead-acid (loosen phosphate deposits).
I'm designing a charger for LFP batteries (obviously the best DIY choice
The high LLC resonance (transformer) leakage inductance
(cause: large distance between primary and secondary for isolation)
means that the Q factor will be extremely high
when a battery is directly connected to the LLC output.
This presents a major challenge for the frequency setting. Not practical.
Solution: a hysteresis controlled SiC buck stage between output and LLC.
Results in a high Rac load for the LLC. (Q=SQRT(L/C)/Rac)
The Q factor still remains high for LLC (~7 at max load).
Allowing ZCS doubles the bandwidth for frequency setting (gain>0.95).
To prevent high losses, it's going to be an all SiC design.
LLC frequency: 135 kHz