So, I reordered the 60 volt 6 Amp rapid charger, plugged it into my AC outlet and it immediately alarmed my computer UPS, indicating a significant voltage drop in my house circuit. Didn't actually trip the breaker and was only momentary, but this beast pulls some serious power when first plugged in.
Anyways, I started reading the manual, and was initially perplexed by the charging times for the different capacity batteries. The 6 Ah battery recharges in 60 minutes, but the 2 Ah battery takes 30 minutes, which should be only 20 minutes assuming a 6 A current flow. Except that this is not how these batteries work. The 2 Ah, 2.5 Ah and 3 Ah batteries consist of a single assembly of battery cells connected in series, whereas the 4 Ah, 5 Ah and 6 Ah batteries consist of two assemblies that are then connected in parallel. Therefore, a 6 Ah battery is actually two 3 Ah batteries, and the 6 A charging current is split equally between them, such that each battery sees a 3 A charging current. However, a 2 Ah battery would see the full 6 A charging current, and apparently Greenworks has determined that this would be an excessively high charging rate, so they reduced the charging current to 4 Amps, resulting in the 30 minute charging time. The same thing applies to the 2.5 Ah and 3 Ah batteries, which recharge in 37.5 and 45 minutes respectively.
The same principles apply to the dual port chargers, such that the 10 A charger never delivers more than 4 A to the smaller capacity batteries and 6 A to the larger capacity batteries with two internal battery assemblies, which see only a 3 A internal charging current. Therefore, the fastest you can ever recharge a 2 Ah battery is 30 minutes and the fastest you can ever recharge a 6 Ah battery is 60 minutes.