The new C4+ seems to be having some odd behaviour. According to its manual the maximum charge rate is determined by the internal resistance. So far so good. But when you put in a 18350 high current battery (e.g. Vapecell / Aspire) the C4+ would charge it with insane 2.5 amps, i.e. 2.5-3C! Of course, you can set it to a lower value manually but I would rather prefer it the other way around in order to avoid cell damages due to improper charge rates.
Another important fact is that LiFePO4-batteries that must not be charged with the standard profile (3.6V instead of 4.2V) may be at risk when you encounter a sudden power outage without any supervision. Once power is restored the C4+ would automatically start to charge the LiFePO4 battery up to 4.2V, i.e. there's an immanent risk of explosion. I am aware that this is probably a design flaw on more or less any chargers that can handle both 3.6V and 4.2V. Anyway, it's something that should not be disregarded when charging LiFePO4 batteries.