old portable NES (nintendo) project question

[Izlude]

Hi all, I was cleaning out the closet the other day and came by an old project I had started back in the early 2000s (a ben heck project)  where he tore down a NES and turned it into a handheld. I never did finish it, but want to now. A few days ago, I found a portable Philips LCD for $2 at savers thrift  I couldn't help but want to test it... so I powered both components (the nes and screen) separately (5v for NES and 12v for screen) since I don't yet have a DC DC converter. Regardless, the image and sound are very satisfying. Now on the original schematic for this project, it uses 8AA batteries to produce 12v, then leads to a switched coax power connector, which cuts the power from the battery to prevent drain and instead allows power from a power adapter.

http://nesp.tighelory.com/images/schematic/schematic.gif

Instead of using AA batteries, I'm wondering if I can use this 12v lithium battery:

ebay item 

The battery has male and female connectors. Female for charging and male for outputting to the device itself. I'd like to be able skip the switched coax power connector entirely and have the system run straight from the lithium battery, but still be able to use an external power supply that charges the battery while the game is on. I'm not really sure if the female connector on this battery also acts as an external power input that can power the device while it's playing, or if it's strictly only for charging the battery.

How can I rig such a setup so I can play while it charges? Perhaps a different battery with charging combo similar to this, but listed elsewhere that I'm unaware of?  

[Arceles]

On 22/05/2025 at 15:16, Izlude said:

Hi all, I was cleaning out the closet the other day and came by an old project I had started back in the early 2000s (a ben heck project)  where he tore down a NES and turned it into a handheld. I never did finish it, but want to now. A few days ago, I found a portable Philips LCD for $2 at savers thrift  I couldn't help but want to test it... so I powered both components (the nes and screen) separately (5v for NES and 12v for screen) since I don't yet have a DC DC converter. Regardless, the image and sound are very satisfying. Now on the original schematic for this project, it uses 8AA batteries to produce 12v, then leads to a switched coax power connector, which cuts the power from the battery to prevent drain and instead allows power from a power adapter.

http://nesp.tighelory.com/images/schematic/schematic.gif

Instead of using AA batteries, I'm wondering if I can use this 12v lithium battery:

ebay item 

The battery has male and female connectors. Female for charging and male for outputting to the device itself. I'd like to be able skip the switched coax power connector entirely and have the system run straight from the lithium battery, but still be able to use an external power supply that charges the battery while the game is on. I'm not really sure if the female connector on this battery also acts as an external power input that can power the device while it's playing, or if it's strictly only for charging the battery.

How can I rig such a setup so I can play while it charges? Perhaps a different battery with charging combo similar to this, but listed elsewhere that I'm unaware of?  

The 12 v battery should be fine. However, if you want to play and chage you can perhaps put a switch to disengage the battery from powering the unit and only allow charging whilst at the same time the external power supply would in parallel power the unit.

[Steffan]

Sounds very interesting. Is the end goal for ROMs or cartridges?

[Izlude]

Hi, it's all cartridge. It's a real NES. Yea, I feel bad thinking back on it having torn up a real NES, however it was in pretty crummy shape when I found it (a spare in some garage that my gramps owned back in the day, tenant musta left it behind). I still have my original one though in tip top shape. So I'll give that lithium battery on ebay a try, but still gotta find a way to disengage the battery while it charges/plays. I know the original schematic has the coax power connector with a built  in switch that cuts off the battery entirely, but to still find a way to have it charge from that same wire is a bit mind boggling.