I asked one of the engineers I work with, and he gave me the following info:
- If you decrease the voltage, you will conversely increase the amperage (ohms law V=IR).
- Increasing the amperage will tend to heat all of the wiring and components, decreasing their lifespan.
- Although it is recommended that the voltage not vary more than 10%, you must also remember that although you have 5V input, that input will also vary, depending on the input from the source. If the unit assumes you have 115V RMS from the outlet and you are only at 110V, it will decrease the output from the power supply to a proportionately lower voltage. There may also be some inefficiency in the generic power supply that may lower the voltage even more.
- The lifespan of the rechargeable batteries may also be affected by a constant low voltage input.
So, that jives pretty well with the comments here. The only thing to worry about is lifespan on your components. Heck, given the leaps that technology makes, maybe it's better if your Axim doesn't last as long...just an excuse to buy the next version sooner. ;)
- If you decrease the voltage, you will conversely increase the amperage (ohms law V=IR).
The resistance can be assumed to be fixed in this case, so decreasing the voltage causes the current to DECREASE.
For an inductive load, like a motor, reducing the voltage can cause an increase in current due to decreasing counter emf, effectively changing the "resistance".
In any case, I'll post the results of charging rate for battery vs charger when it gets here, also the actual supplied voltage for this particular setup. I doubt that it's 5.00v.
__________________
Persistence can pass for brilliance
FFR Roadster on order for 04/3/04.
Mike
Great cross-reference, Mike. I assume from the Gomadic response that the same thing may occur with any 5V power supply that puts out less than 4.86V under load. As such, I look forward to your test results on the Digicom you ordered.
Regarding your earlier comment about resistance, doesn't that change as you attempt to draw more or less power? Since more components are involved, I would expect that to also increase resistance, and vice versa. This seems to me to be what the Gomadic guys are saying--turning off the device decreases resistance so that more current is available. Or am I missing something, here.
I agree, though, that my coworker was incorrect about amperage increasing. That would be from too much voltage, right?
Unfortunately, I couldn't find any details about the specific output voltage of the external battery pack, other than that it's for 5volt cameras. As far as Li ion batteries, 5 volts isn't one of the possibilities ... only 3.7- 3.8, 7.2- 7.4, etc. So, I'm guessing it has an output regulator similar to the tripod mount Digipower unit. The DPS-9000 is a 7.4 volt pack, at 3600 mAh.
The good news is that 3.7 v batteries reach full charge at 4.2 v, so if this rig is only used for emergency boosting of the charge, with the unit off, it should be OK.
My recent research into Li ion batteries seems to indicate the only problem with low power charging is that it takes longer, and possibly not reaching full 100% capacity. No harm done, and enough good to make it through the day when out in the field.
While looking around, I also found this set offered for as much as $150! (and as low as $25) The Digipower with the fuel gage may be a better buy at $40.
__________________
Persistence can pass for brilliance
FFR Roadster on order for 04/3/04.
Mike
Just bought a DPS-9000 at bestbuy; an open pack for just $17.99. I had the clerk re-open it for inventory and to take a look at the paperwork. I have an Olympus Digital Camera and it will work for that and perhaps the bonus of running the Axim. I have found the information regarding the amperage/voltage requirements of interest. Thanks for the info.
Well I got my DPS-9000 In the mail today
and am very pleased! I am glad I did not
order the Dell long-life battery... so far
it has worked great, I only plan on using
it for emergency recharges though...
I was hoping it would work on my sony
camera as well, but the cable they have for
sony cameras is not the same as the jack
on my sony camera...
only thing that bugs me is that when the
cord is plugged into the battery (the one that
connects to your PDA, there is a light on the
box.... and the light is on, even if its not connect
to your pda.... so you have to disconnect everything..
i would rather leave the cable attached to the battery..
anyway all in all, I am satisfied...
__________________
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
My recent reviews:
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
I received the battery pack from DigiCom, and it's a ten-cell Ni-MH pack, (5 x 2) which should be 6v nominal, but fully charged it puts out 6.98v. This is the one listed for 5v cameras.
I thought this might be a little high, so I made a 5v regulator to put in the cord. Actual output now 4.97v, max current 1 amp.
This is still enough voltage to get a green charged light, with the screen at fully bright.
BTW, a four cell alkaline pack puts out 6.36v fresh.
The 5v regulator was so easy to make, anyone thinking of using a booster pack should add this to be safe. Parts from Radio Shack about $5.
+5v voltage regulator, Cat # 276-1770A $1.49
TO220 Heat Sink, Cat # 276-1363 $.99
Small Project Box 3x2x1, Cat # 270-1801 $2.29
Connectors to fit Axim and wire if necessary.
Positive v. from battery solder to pin 1
Positive 5v to Axim solder to pin 2
Negative from battery splice to negative to Axim and solder to pin 3
Bolt heat sink and regulator to inside of metal box cover, bend pins away from metal.
Done.
The regulator will burn out instantly if connected backwards, so a 1amp diode in series w/ pin1 is recommended if using 9v batteries (which can make contact if inserted backwards)
Here is a page explaining it ... although the pin numbers they show (1,2,3) are different from the Radio Shack package (1,3,2) the function is the same (input, common, output) 7805 regulator . You can find ANYTHING on the interweb.
The diagram showing a transformer for the source is more complicated than you need when using a DC source, namely, the capacitors and bridge rectifier can be eliminated, leaving just the regulator!
__________________
Persistence can pass for brilliance
FFR Roadster on order for 04/3/04.
Mike
If that unit comes with a regulator, then ... in my opinion ... it is safe to use. I DO NOT SPEAK FOR DELL! Yo?
I have not asked Dell about any of this.
I do not know what Dell's position is on this.
I will not warranty any units.
I do not endorse Digicom or Digipower.
I have tested a 5 volt regulated power supply on my Axim and it seems to work OK. This may void my warranty. You may void your warranty. You make the call.
The short answer is, only Dell can say if it's safe, since they hold the warranty.
__________________
Persistence can pass for brilliance
FFR Roadster on order for 04/3/04.
Mike
Follow Us
RSS Feed
Follow on Twitter
Facebook
YouTube
Uber Member
Addicted Member
