What's the charging voltage for an Mx Revolution Mouse?
December 15, 2010 7:42 PM   Subscribe

I've lost the charging dock and AC adapter for the Logitech MX Revolution mouse. There's no way to charge this mouse without the dock. I think I can pretty easily build a new dock on my own, I'm just looking for owners of this mouse to answer a technical question to help with construction.

First off I'm posting this anonymously because it's meant as an xmas gift for another Metafilter member, and if they see that I've posted an AskMefi about it, it'll ruin the surprise.

What I need to determine is the correct volatage/amperage to send into the two contacts on the bottom of the mouse. Here's where I'm confused:

On the bottom of the mouse the power rating is 4.1V/800mA.
I know that the (non-removeable) internal battery is 3.7V.
Pretty much every 3.7V battery uses 4.2V to charge, so the 4.1V/800mA rating makes sense.
But the AC adapter for the dock is rated at 8V/500mA.
So somewhere the power is being converted from 8V/500mA to 4.1V/800mA. I need to know if this is happening inside the dock, or inside the mouse.
If it's happening in the dock I need a 4.1V AC Adapter, if it's happening in the mouse I need an 8V AC Adapter.

Essentially I need to know if there's anything inside the dock more complicated than two wires running from the AC input, to the two pins that contact the mouse.

I'm also aware I can find replacement dock/AC units on ebay, but the $30+ that will cost compared to $5-10 in materials just isn't worth it.

Thanks for any help you can provide!
posted by anonymous to Technology (9 answers total)
I just whipped the lid off my dock for you. There's a 100uF electrolytic and a smaller unidentified ceramic capacitor in parallel and both connected between + and - inside the dock. I guess this is for power conditioning.

The power supply is rated 8v, and the base of the dock says "Rating 8v".

However, there is also a 20x30x10mm sealed plastic unit about 100mm down the cable, outside the dock - it could be doing voltage conversion. Sorry I don't have a voltmeter to hand to test.
posted by cogat at 8:22 PM on December 15, 2010

memail me for pics of the capacitors
posted by cogat at 8:22 PM on December 15, 2010

I have the mouse in question. I can answer any question you want short of opening the darn thing up. Tell me what to look for and I will. MeMail me and I will guarantee confidentiality. I can tell you that the dock is not that heavy and I would be surprised if much was happening inside it, but I say that with the caveat that I know nothing about electricity of voltage or converters or ratings. I love the mouse!
posted by AugustWest at 8:24 PM on December 15, 2010

On postview,what cogat said. I always thought the round thing on the cable was a magnet for some reason. I have that too.
posted by AugustWest at 8:25 PM on December 15, 2010

Also, my power supply is hard-wired into the dock (in Australia). If there is more than one PSU design, and the mouse says it needs 4.1v, all these clues lead me to believe that the power going into the mouse is 4.1v and that my sealed plastic box is a step-down unit.
posted by cogat at 8:26 PM on December 15, 2010

Are you sure you don't want a new dock? I have an extra one which is in pristine new condition. I'd be happy to send it to a fellow mefite because it's just sitting in my closet collecting dust. Memail me.
posted by cazoo at 11:17 PM on December 15, 2010

there is also a 20x30x10mm sealed plastic unit about 100mm down the cable, outside the dock

That's almost certainly just a ferrite choke.
posted by contraption at 12:52 AM on December 16, 2010

Is the AC adaptor an AC/DC adaptor, or an AC/AC adaptor? It's possible it's just a step-down transformer and the rectifier is in the base, which would also justify having final voltage regulation in there. It's odd but possible.
posted by chairface at 8:12 AM on December 16, 2010

This is a little late, but I pulled out my multimeter and checked the voltage on the dock. As you look at the dock from the front, there are two gold connectors, one on the left and one on the right. The right one is at +8.65VDC (0VAC) relative to the left one. Note that if you're looking at the bottom of the mouse, right and left will be flipped, so the left contact should be at +8.65V relative to the right. Good luck!
posted by stufflebean at 9:53 AM on December 21, 2010

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