fanfaron is absolutely correct. The gen 1 Civic hybrid does not have an alternator.

In all likelihood you have an electrical problem on your downstream 12V system or your DC-DC module is operating outside its specs (needs replacement) and that is causing an inadequate charge to be delivered to the 12V battery. Bad NiMH battery packs are also known to cause these types of issues. Heck, even a faulty BCM could cause this.

Charging occurs when the voltage baselines at 13.6 to 13.9 volts.

So, I would suggest it is time to take it to the dealer for 20 minutes worth of HDS diagnostics. They'll tell you for sure what's up and what needs to be done about it.

Cheers;

MSantos