Batteries in Series Adapter

[JThiessen]

Update: I measured each battery at 8.14V, connected them to the adaptor, and measured 16.28. So that tells me the adaptor is good. I tried adjusting the settings on the charger again, and actually got an error on it!
So I sent an email to Enerland (MRC), hopefully they can tell me what settings to put in on to charge them both. I've also searched these forums, RC Universe, RCTech, and RC Groups for a "settings" overview for the 989, but found nothing.
The batteries I charged individually ran great - seemed to have more punch than with my old charger (Vision Peak). Had a hard time keeping the front wheels on the ground!