Battery replacement

Ask anything your want about Mega/SegaCD programming.

Moderator: Mask of Destiny

Post Reply
Charles MacDonald
Very interested
Posts: 283
Joined: Sat Apr 21, 2007 1:14 am

Battery replacement

Post by Charles MacDonald » Sun Feb 10, 2013 11:37 pm

The Sega CD 2 uses a Sanyo ML2016 rechargeable battery. This is a horizontal mount battery with solder tabs. You can cut out the battery with shear cutters, desolder the remaining tabs, and put in a regular battery holder if needed.

For the adventurous I can confirm that a CR2032 does work as a replacement in a pinch. It is not a rechargeable battery, however, so this is technically an unsafe replacement to use - do so at your own risk. Lithium batteries can overheat, leak, and explode when being charged.

The battery monitor is a Fujitsu MB3790: ... 427502.pdf

The control pin (pin 1) is tied to ground and the ML2016 is connected to the Vbat2 input. It charges the battery by supplying 2V at 2mA when the Sega CD 2 is powered up.

This chip does not charge the primary battery. In theory I think you could disconnect the Vbat2 input and connect the battery to Vbat1. This way there would be no charging and it should be safer when replacing the original battery with a non-rechargeable battery such as the CR2032 or CR2016. VBat2 would likely need a pull-down resistor instead of being left open. The MB3790 is a surface mount chip so this is a tricky change to make.

I'll update this post in case there are problems, like if the CR2032 drains abruptly or explodes. :)

Post Reply