Battery discharging

I have a Sportster year 2000 and i put some new Spotlight on it 2x55watt and when i use the light just for half an hour my Battery drops drastically so much that I'm not able to restart my bike. I measured the voltage on the Battery when i switch the light on and the Battery drops down to 9.8volt. question is the Voltagenot enough to recharge and keep the Battery full loaded?? so what can i do to keep my Battery full loaded?????

Thanks in advance to et answers
Regards
helmut
thanks for your kind to give me some idea.
I read all the trouble with the matter of the Battery in the forum and I check again the Stator and measured the output by a round 1000rpm 22.5-24 voltand when i accelerate the engine the voltage increased to 70-80Volt. and the output from my regulator still 12.60-12.80 volt even by accelerating the engine the voltage stays on 12.80Volt. is't now the regulator which is broken even it looks likes he works?? of course he not supply my with 14.4V and that's way my Battery is always going empty special when i use my spot light. Then theloaddrops down to 9.70volt. So what else i can do????
Thanks in advance
Helmut
Ok thanks i will change the Regulator. By the waydo you know how much cost the Regulator in USA just to have a price comparisonto Indonesia. If you cantell mewould be great.
Thanks an when i change the regulator and it work ilet you know.
Regards
helmut



