Dreamcast VMU rechargeble Batteries

[Padoca85]

So i just thought today if wouldnt be great if the VMU had rechargeble batteries.

After some research in google, it seems its a recent topic on several foruns.

Some are just mentioning the use of batteries with an external charger, but i was wondering if would be possibe to make the batteries inside the vmu recharge using the DC controller.

I understand a rewiring would be necessary, and maybe a small rechargeble circuit on the vmu or controller.

Do you think its something viable? and the 5v coming to the controller would be enough?

[Jamtex]

In theory you could but there are some practical problems mainly, you do have to have a circuit to charge Lithium Ion batteries and I am not sure you would have the space to shove it into a VMU unless you have mad surface mount soldering skills. However if you can get two LIR2032 batteries and a USB charger then you can probably use that as a start.

[Padoca85]

The circuit could be mounted inside the controller, should be enough space there.

[APE]

Using SMD components there would be. 100% through hole might be an issue.

[Jamtex]

How would you get power to the batteries then?

The DC would have enough current as you only need 150ma to chrage the batteries and the total draw would be <300ma. I would recommend using LIR2032s as these would be easier to use. There are a number of ICs you can use to charge Li-ion battereis, the MCP73833 is tiny and easy to use and costs a $1.

[K0baltic]

Does the MCP73833 handle overcharging and a shut off switch. Or would you still need your own relay?

[Melchior]

There are some really small LiPO rectangle battery packs - or a small cylindrical cell/pack.

whats the minimum voltage the VMU actually needs anyways, if 3.4 Volts is enough - why bother with extra cells?

[PCB_Master]

Spent a little time thinking and came up with this.


I don't have the balls to solder it, and the design needs checking, but this should, theoretically, work. It has a MAX1555 LiPoly charger and MAX1674 DC-DC boost converter to 5 volts to power the VMU.

Edit: The board is really small, 0.85" x 0.55"

[Annoying_one]

will this go inside the battery spot? if so why not round so it fits

[kendrick]

I've often thought that the way to do this is to double the thickness of the VMU. You'd use a second VMU shell, spaced and connected so that both can fit into an existing controller slot. The original VMU remains mostly unmodified, whereas the second shell contains the batteries and connects to the battery slot of the first. It'd be heavy, and it would block use of the rumble pack, but it would have the benefit of being usable on any VMU interchangeably. That might have been important for save files that couldn't be copied back in the day, even though we can move all that data around at will now.

[PCB_Master]

will this go inside the battery spot? if so why not round so it fits

This won't go in the battery spot, as the battery spot would be dremeled away to fit the small LiPoly battery. Besides getting the board small enough to fit in the battery spot would require Ball Grid Array components or black magic.

[Padoca85]

Cool seeing this thread is giving results, hope to see some one build one of these soon. Can help alot of dreamcast fans in the vmu minigames homebrew scene.

[Annoying_one]

damage the vmu case to do this????


no solution id want to do

[PCB_Master]

You're just removing the battery cavity, the battery cover would still be in place. Not really visible from the outside, unless you have a transparent VMU. I suppose you might be able to mash a smaller LiPoly battery, but you will have less amp hours. I still need to make accurate measurements.

[Annoying_one]

read something about a jouel theft circuit . maybe that could help

[PCB_Master]

Joule Thief circuits store energy in a capacitor, and release it when full. This causes a square wave output as it is pulsing. This works for an LED since the on and off pulse is too fast for the human eye creating the illusion that the LED is lit. However, the VMU wouldn't get enough voltage, and even if it did, it would boot, shutdown, boot, shutdown due to the pulse the joule thief creates.

[Melchior]

After looking for foil wrapped LiPO cells - perhaps it IS better to stuff a PCB+Battery into the back case area - and attach some wires to the VCC from the Dreamcast, so it can charge when connected to the controller.

Would only need to dremel out the round cell holder area, and put the LiPO cell and PCB there.

I'd imagine there are test points for the correct connections on the VMU PCB already...