I found this interesting. Please do share if you know better/bigger batteries:
Mugen Power Batteries announces a new extended battery for HTC Titan. The new extended battery increases the battery capacity by exceptional 22%.
HTC TITAN Battery Life Extended by Mugen Power Batteries
Mugen Power Batteries announces a new extended battery for HTC Titan. The new extended battery increases the battery capacity by exceptional 22%.
HTC TITAN Battery Life Extended by Mugen Power Batteries