Help me mod a chinese 10 led solar light

So I have this light I bought awhile back on clearance before I knew any better. Honestly its not a bad light and I didnt pay too much for it. Its some Chinese 10 led black body aluminum like you can find on dinodirect. Below are the details I found on another site. I'd like to know if I can get anything brighter in it without much investment. I'm ok with DX parts, ok with replacing all but the battery supply. The body and head are thick aluminum so should make for a great heatsink. So with that said fire anyway any ideas. I'd either like to get 12 hours of run time out of it with the same or more light or get a far brighter output for similar runtime.

Features:

Light Source: Ultra-bright 10LEDs ,15000-18000mcd
Flashlight maximum brightness: over 38 (LM)
Maximum flashlight illumination: over 1600 (LUX)
Sustained high-brightness time: over 6 hours
Flashlight Length: 25cm
Flashlight Handle diameter: 3.5cm
Flashlight Weight: 224.5 grams (with battery)
Power Supply: Polymer 3.7V 800MA
colors: black, silver

Details:
Anodized aluminum enclosure high hardness and very durable.
O-ring, water-resistant.
Ultra-bright LEDs, visible from where father than 60m.
Activities Ribbon portable.
Solar flashlight (solar panels sun light direction) placed under the light for 6-8 hours, that is, the sustainable use of 6-7 hours.
Rubber button switch, feel comfortable.