Hardware Question: How Much Does Pandora's Power Port Take (volts

[Karel Jansens]

Does anyone know the specs of Pandora's power IN port? What voltage, amps or watts it needs? I'm toying with the idea to make a battery-powered, emergency-type charger for it, but it would be nice to know what to build. Oh yeah, and what kind of plug does it use? The standard, "Nokia-type" 3 mm kind?

If it's the same specs as the USB port (5 volts, regulated), I'd like to build something around 4 C or D cells (rechargeables). With recent model batteries they should provide enough oomph to almost completely recharge Pandora's battery.

Which would be nice on a 12 hour flight to Bangkok...

 

[Miika]

Craig has stated that a PSP supply will work with the Pandora.

 

[Squidge]

Which is 5V 2A Centre Hot, to save you from searching

 

[michield]

Further questions I have regarding the power connectors:

Does it have overvolt / polarity reversal protection?

Planning on getting some solar panel (perhaps a bag with an in-built 1 W USB charge output - or if that is not enough, something else ( Soldius 1 ) or a better panel) and I don't want to blow up the pandora with any experiments.

 

[mali]

Further questions I have regarding the power connectors:

Does it have overvolt / polarity reversal protection?

Planning on getting some solar panel (perhaps a bag with an in-built 1 W USB charge output - or if that is not enough, something else ( Soldius 1 ) or a better panel) and I don't want to blow up the pandora with any experiments.



You should use a solar trickle charger with build in battery, that has the right voltage output and is able to handle the current. The solar charger charges the build in battery also in low light conditions and the battery delivers full power when needed. If you go on a trip, you can let the charger charge the battery and if you need to charge the pandora you can do it even at night. That's the most versatile solution in my opinion.

 

[Karel Jansens]

Which is 5V 2A Centre Hot, to save you from searching

Cool. I'm off to find a 4-cell battery compartiment, a diode and a microswitch. I'll wait until my Panda arrives to get a plug. I've found D-cells that can store 4500 mAhs; with inevitable losses that might be just enough to almost fully recharge Panda once, depending on how tolerant its charging circuits are to undervolts.

 

[sdedalus83]

For most of the life of the battery, it will put out very close to 4.8 volts, which will be fine for something that can use USB input. You will want to have a way to shut the external pack off when it drops below 4 volts, since letting it go much below that can seriously damage NiMH batteries. The Pandora's charging circuit may do this for you, but ask a dev first.

 

[Squidge]

Make sure you download the datasheet for those batteries first. You may find that if you draw an amp from them continuously, that 4.5A may die within the hour, and they require much less load to get the full amperage from them.

 

[mali]

Make sure you download the datasheet for those batteries first. You may find that if you draw an amp from them continuously, that 4.5A may die within the hour, and they require much less load to get the full amperage from them.

Yes, and one could use eight smaller batterys with four, of two in parallel, in series.

 

[Karel Jansens]

Thanks for the suggestions, people. I think I'll just wing it and see how it pans out, it's not as if it's a hugely expensive project.

I did learn that a lot depends on the charging circuitry of the device itself: I have a 4xAA charger (store-bought), originally designed for my Archos PMA430, which I used both with my Nokia 770 and my N800. The 770 would only charge partially from the battery pack and behave rather erratically (would stop charging for no apparent reason and start again), while the N800 charges very well, both charging only and charging while in use. Both Nokia devices have the same type of battery inside.

I'll keep y'all posted on the results.

 

[sdedalus83]

Yes, and one could use eight smaller batterys with four, of two in parallel, in series.

Commericial serial + parallel battery packs aren't very common because it's a lot safer and simpler to use a single, larger cell.

 

[mali]

Yes, and one could use eight smaller batterys with four, of two in parallel, in series.

Commericial serial + parallel battery packs aren't very common because it's a lot safer and simpler to use a single, larger cell.

He wants to make a battery pack himself. NiMh are relatively weak at delivering high currents, so two in parallel are safer in this regard.

 

[nat1192]

Which is 5V 2A Centre Hot, to save you from searching

Cool. I'm off to find a 4-cell battery compartiment, a diode and a microswitch. I'll wait until my Panda arrives to get a plug. I've found D-cells that can store 4500 mAhs; with inevitable losses that might be just enough to almost fully recharge Panda once, depending on how tolerant its charging circuits are to undervolts.

Instead of wasting a bunch of batteries, why not just hook up another one of these to it? It has 6k mAhs with a very small form-factor, though it is a touch expensive to implement (battery + lion charger + plug = ~60USD)

 

[nubie]

Make sure you download the datasheet for those batteries first. You may find that if you draw an amp from them continuously, that 4.5A may die within the hour, and they require much less load to get the full amperage from them.

Is the Pandora going to charge from a standard USB ( 500ma or less)? He could use a mini-USB and take advantage of that to charge maybe.

I don't recall how NiMH worked, I know that they have high internal resistance, but does that go up or down with storage capacity?

I can't find NiMH D size batteries that hold less than 6000mAh, and the rest are over 10,000mAh. http://www.onlybatteries.com/cat_featured_...=3&uid=1416

Would an amp out of these be such a bad thing?

Watch out for the look of the device, I would shrink wrap it in black so that it doesn't look "explosive" like individually taped cells can.

 

[mali]

Make sure you download the datasheet for those batteries first. You may find that if you draw an amp from them continuously, that 4.5A may die within the hour, and they require much less load to get the full amperage from them.

Is the Pandora going to charge from a standard USB ( 500ma or less)? He could use a mini-USB and take advantage of that to charge maybe.

I don't recall how NiMH worked, I know that they have high internal resistance, but does that go up or down with storage capacity?

I can't find NiMH D size batteries that hold less than 6000mAh, and the rest are over 10,000mAh. http://www.onlybatteries.com/cat_featured_...=3&uid=1416

Would an amp out of these be such a bad thing?

Watch out for the look of the device, I would shrink wrap it in black so that it doesn't look "explosive" like individually taped cells can.


But charging with 500mA will take around 10 hours with the device shut off. I think, the power connector approach might be better time-wise.

 

[pelrun]

Just to fix a couple of misconceptions:

You will want to have a way to shut the external pack off when it drops below 4 volts, since letting it go much below that can seriously damage NiMH batteries.

No, that's not entirely correct. Lithium-ion rechargeables get damaged when over-discharged, not NiMH. But if you go too far with a set of (non-matched) NiMH's or NiCads in series, the cell which goes flat first can get charged backwards by the other cells and die.

NiMh are relatively weak at delivering high currents

NiCad does better (by about 2x), but NiMH are still extremely good. Especially the new low-self-discharge types (e.g. eneloops) which get closer to NiCad's specs. Alkalines and zinc oxide are the ones which can't handle high current draw (like 10x worse!) - that's why you don't put them into digital cameras.

I don't recall how NiMH worked, I know that they have high internal resistance

Definitely not right - they have high self-discharge (which means a charge wont last more than a few months, even if unused), but their internal resistance stays about 0.15ohms. Alkalines go from there up past 1ohm!