Handtops, UMPC - Proprietary power supply?

10/11/04 + vadsoom

Greetings,

Do any of you with hands-on OQO experience have any knowledge about the power supply? Will the OQO require it's own or will an off-the-shelf replacment function?

Like some PDAs, is it possible to charge the OQO through it's USB port?

Thanks in advance!

Recent Blog: I finally did it.., went on a business trip with only my OQO

10/16/04 + DoC

@vadsoom: It's got a seemingly propietary connector. And since it's a USB host controller not a usb device, you could dammage the unit by applying reverse voltage on the USB connector.

There is actually another possibility about the pin usage. The connector profile looks similar to a Combo D (Power+data D-SUB). It's got two large pins at the wide point and 3 small pins at the skinny point. That suggests that maybe it's not just multiple voltages but maybe they moved the entire charge controller outside the unit to save space. If that's the case then there's probably a GND and a voltage slightly higher than the battery voltage and the other three small pins would be used for detecting the temp for controlling the charge. That could also account for a buzzing since you'd need a PWM to control the amp flow and keep the temp down for optimal charging.

I've been unable so far to find a similar connector from DigiKey or some of the other suppliers.

10/17/04 + garylm

DoC said: "maybe they moved the entire charge controller outside the unit"

That rings true. From what I've read about lithium polymer batteries, there's some science involved in the charging process to get the maximum number of lifetime charge cycles.

If the charge controller is in the external power supply, why couldn't they come up with a simple connector to charge all my spare batteries? At this point it looks like the battery has to be connected to the UPC to charge it.

Recent Blog: Travelling With the OQO

10/17/04 + DoC

Lithium is one of the most difficult battery types to charge. It's exceptionally touchy about overcharging and there is an associated fire risk. The latest crop of lithium formulations aren't as risky but they still work through a lot more cycles if you charge them right.

They could probably come up with an external charger either way but it wouldn't be an initial priority from a financial standpoint.

10/18/04 + vadsoom

DoC,

That would make good logical sense and, as already stated, cut down on size and heat inside the OQO chassis. If this is the case, it's likely not wise to circumvent any engineering OQO has already invested trying to make my own. Needing a proprietary power supply is a bit of a let down, ruling out the "iGo" or other one-power-supply solutions, but it's not a killer in my book.

What does concern me is the mentioned difficulties running the power supply from an inverter. Can anyone verify this, please?

Recent Blog: OQO model 02 hands on mini-review

10/18/04 + DoC

Most inverters shouldn't be used with laptops... They don't output pure AC and can cause problems. It MIGHT work ok with one of the expensive ones designed specifically for laptops and other devices that don't normally do well on inverters.

And you are right, if they moved the charge controller out of the OQO then building your own would be exceedingly difficult.

10/18/04 + garylm

I guess the output of the inverter intended for laptop use would have to be a sine wave, whereas most cheap ones put out a square wave. The UPS that I have my desktop computer on puts out a square wave too. I guess there's plenty of room inside a desktop computer's power supply for circuitry that filters out the high frequency component of a square wave. There's not much room in a laptop power supply for heavy duty RF chokes.

I've also got a UPS intended for use with high-end audio that puts out a beautiful sine wave.

Recent Blog: Travelling With the OQO

10/19/04 + DoC

The battery has a 5 pin connection. Obviously it's a different design than the power cable but the pins may be the same. It might actually just be a matter creating an adapter to make a separate battery charger. That would seem to indicate that it's even more likely that the charge controller is external to the OQO.

10/19/04 + DoC

Also, in case anyone is curious. The battery is a 3.7VDC nominal 4000mah Lithum Polymer. It sounds like a single-cell lithium or parallel cell lithum battery which means it likely charges at around 4.2 volts. It makes me wonder how they support the 5v requirement of USB and firewire. If it's using a Cockcroft-Walton voltage multiplier in such a small device then the amp output on the USB port is likely very minimal and not very smooth.

10/19/04 + Chekote

The Firewire is 4pin so there is no power supplied via that port.

Recent Blog: Flipstart Camera

10/19/04 + DoC

USB requires at least 4.35V 100ma on the +5 pin but devices can negotiate up to 500ma with the host. Maximum charge voltage on a 3.7v lithium cell is 4.2V.

10/19/04 + DoC

I wonder if it will negotiate 500ma. If it doesn't then you don't have to worry about battery powered USB devices sucking power from your OQO because they won't be able to charge in any significant way when the load maximum is 100ma. However, that would mean that you wouldn't, under any circumstances, be able to charge a device off the USB port including when you have th OQO plugged in. I seriously doubt they would go that far. I have, however, run across laptops that wouldn't negotiate higher than 100ma with my cell phone and thus wouldn't charge it in any significant way.

10/19/04 + DoC

I just got a weird reply from OQO about the car/air charger question.

There are no air/car adaptors provided by OQO. An adaptor to plug the 2 prong AC adaptor will work.

Either this guy is smoking crack or it's a switching power supply with a voltage sensor that'll actually take any voltage above it's output voltage either DC or AC. It's possible to build such a supply but I'd be suprised if they did.

If that's actually the case (and I'm trying to get clarification) then charging in a car or plane should be a simple matter of buying any cheap 2 prong AC laptop cable ($10) and chopping the end off that goes to the wall socket and wiring it up to a radio shack cigarette lighter plug ($3.49) . Of course for airplane use you would still need an air adapter ($10). I'm not recommending those sites specifically, they are just the first online stores I could find with the parts.

10/19/04 + MrX2999

I am sure they mean a DC to AC converter

10/19/04 + MrX2999

like these

link

10/19/04 + DoC

I know about invertors.. OQO says specifically that you should NOT use invertors with the OQO power supply. I responded asking about that, though.