Regulated power supplies, soldering in capacitors? That's the beauty of 4 NiMH AA's in series. Fresh off the charger they'll give you just over 5 V (not enough over to do damage), then almost immediately settle down to 4.8 V of steady output for a long time. Anything that'll take a charge off the constant 5 V provided by USB won't fry (unless you hook up the wires backwards). Here's a simple way to do it without getting the wires backwards: get one (or two) 4-AA battery holders from Radio Shack or equiv., the ones that have tabs to fit a 9 V battery clip. Buy one (or 2) 9 V battery clips, too, and then get a USB extension cable. Cut the cable, strip the wires on the female end, and connect the black or brown wire on the USB cable to the black wire on the 9 V battery clip(s), then the red to the red. Solder the connections if you like, use twist connectors, or just twist them tight; then tape or epoxy the connections and the ends of the two unused USB wires, just so they don't make electrical contact with anything else. Put the clips on the battery pack(s), put your charged NiMH batteries in the pack(s), and you're ready to charge anything that has a USB sync/charger cable--it'll work with ANY PDA as long as you have a cable for it--and there's no risk of hooking up the wrong wires and reversing the polarity, or of overloading and frying your equipment. 15 minutes of effort, tops, even for the novice. IMPORTANT NOTE: Use only NiMH rechargeables; four alkalines will kick out 6 V which may be enough to damage your device--four of those spiffy Energizer 1.7 V lithium AAs will kick out almost 7 V and will almost surely fry your device.
Note that I DID specify a sync/charger cable in the how-to. If there's one available for your PDA and you've got it, you should be able to charge on it.
Darkdestroyer, 2 comments:
1. Ditch those puny black and red wires that came with the battery holders and solder in some thicker wires instead. The original wiring is not designed to pass 1A+ current comfortably and will probably cause the screen to flicker when the axim's battery is a little low.
http://www.powerstream.com/Wire_Size.htm
Wire size AWG 22, max. 7 amps for chassis wiring. Note that transmission amps rating is for long distances, not the 4" from the batteries to the Axim.
I'm currently posting this from my X50, with green light on, plugged into a radio Shack 4-AA switched battery box. Playing MP3''s on TCPMP. < US$5 for box and plug. Using 4 Energizer 2500mAH AA batteries ($10 at Target).
In the battery holder, I pried open the compartment with the switch and noted that it's double-throw. You could wire the "off" position as a "charge" position, with an external socket for power-in.
Hey, DIY is easy.
(X)
http://www.powerstream.com/Wire_Size.htm
Wire size AWG 22, max. 7 amps for chassis wiring. Note that transmission amps rating is for long distances, not the 4" from the batteries to the Axim.
I'm currently posting this from my X50, with green light on, plugged into a radio Shack 4-AA switched battery box. Playing MP3''s on TCPMP. < US$5 for box and plug. Using 4 Energizer 2500mAH AA batteries ($10 at Target).
In the battery holder, I pried open the compartment with the switch and noted that it's double-throw. You could wire the "off" position as a "charge" position, with an external socket for power-in.
Hey, DIY is easy.
(X)
Typical wiring that comes with generic battery holders is not AWG 22, but more like AWG 27, which makes it rather borderline for running and charging the Axim in short lengths and completely unsuitable in long lengths.
Take you dell CD, install the Dell Axim Diagnostic tools. Under those tool's run the "battery" test. That'll show you
1. Voltage required for your axim to run
2. mAh it's using
This way you can best change the battery voltage's to accomadate your usage. The battery i made charges the axim fine when it's running at around 300-375mAh usage. Any higher, (usually gfx intensive, microdrive intensive, or processor + bt + wifi+ microdrive + max backlight will cause the charging to flicker. Although charging does flicker, the usage with the battery pack plugged in drops dramatically. Instead of "charging" the pda, the Axim is actually using the battery power from the AA batteries. This is apparent when your PDA is not "charging", but the usage is down to 100mAh and you have everything turned up max.
A few of the batterys leaked and everything, except for the pda, died. Oh and I no longer have my axim as I traded it for an iPAQ 4700. I havn't been able to wire up some old Li-Ion batteries yet, do any of you know what I can use to connect them together? Unlike batteries I can't find holders with the right pins for this pile of old Li-Ion batteries that I have. Should I make my own holder with my own pins? If so do these Li-Ion batterys require a special way to wire? If pictures are required of the few Li-ion batterys that I have I can take them and see if you guys can help me out. (If I do get these Li-Ion batterys wired together tightly I may just slip it in a leather case, put a cord on it, and sell it as a "Mobile Power Pack" :D )
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li-ion batteries do not charge normally like nihm's do. from what i researched, li-ion batteries (bare) needs a regulator circuit of their own. if you attempt to charge them without it, it may kill your batteries. that is... unless u have the circuits in there already.
xnetc9 is correct li-ion batteries need very careful charging, they won't stand even mild abuse.
The use of Li-ion batteries was held back for a long time due to the dangers associated with not controlling the charge rate correctly, these include fire and explosion.
The use of Li-ion batteries was held back for a long time due to the dangers associated with not controlling the charge rate correctly, these include fire and explosion.
It's easier than you think. Use a fuse/circuit breaker to prevent fire from short circuits, a special charge controller to prevent hydrogen buildup, and a low voltage cutoff to keep the cells lasting long.
I have actually built a universal USB power pack using some surplus cell phone batteries (about 2000-3000mAh total). I used a simple charge controller chip to allow it to charge from a PC or wall wart. The circuit breaker and voltage cutoffs were already in the original battery packs, so I didn't need to worry about that. A Maxim digital power supply chip steps up the voltage to about 5.2v. As an extra feature, I included two white LEDs so it's also a flashlight. All of it fit into the case from a toy MP3 player. There is still some room left, so I'm thinking about adding something like a WiFi field strength meter or clock.
BTW, I had to change the coil in the voltage regulator circuit. Once, when I let my friend Jessica Simpson (who has a X30 with an extended battery) borrow my power pack, the breaker kept on tripping. I just told her to leave her PDA off for a few minutes (while borrowing mine to do the work) to let it collect enough charge so the breaker doesn't go off. When I got back to my electronics lab, I figured out that at load currents over about 1.2A, the resistance of the inductor reduced efficiency to the point where the current drawn from the batteries tripped the circuit breaker. I replaced the inductor with one from a broken laptop. I tested the power pack with a 2A load, and it worked fine. It's also much more efficient.
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Originally Posted by A friend of mine who has a Linux kernel named after his girlfriend.
If I was VirtualBox, I could load my virtualization module into Hannah and boot up another kernel in the same address space.
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