External Battery Pack for A2

[TigerhawkT3]

I'm planning on making an external battery pack for my A2, but I don't know how many cells to use. The AC adaptor is listed as 5V, so should I use 4 or 6 NiMHs? Does the 12V car charger drop the voltage before feeding current to the A2?

In a nutshell, how does the A2 handle DC input?

EDIT: Please move to PMP Techincal Support... sorry.

[GSV3MiaC]

I am sure the car charger drops the voltage. People have fried PMPs before now with cheap car chargers which say '5v' but actually deliver 6 or 7v.

4 NiMH cells would probably be the right answer, but personally I'd be reluctant to experiment, unless you put a Zener or similar in there to make sure the voltage can't go over 5v (fully charger NiMH cells can be up around 1.45v, briefly .. but will probably drop back quite smartly under load).

Thread moved, as requested.

[BaTu]

Now that you're up for it, regardless of using a power supply or just batteries, I would strongly suggest to include a simple regulator circuit that's build around a 5V DC/DC converter, just in case. A2's internal battery is rated at 5V/4300mA so you'll need a converter with sufficient amperage. (I was going to suggest 7805 IC but it's rated at 500mA).

Just a reminder: Anything you plug to A2 other than the originals will most likely affect your warranty coverage.

[TigerhawkT3]

Whoa, it can't even handle one extra volt? I'm glad I asked!

I've been reading some reviews on Amazon of the Gomadic brand 4AA charger, which does basically the same thing as I was thinking of, and it looks like its power is pretty limited. Am I better off going with a car charger and connecting that to a ~12V source?

[GSV3MiaC]

Some car chargers are pants too (those are what turn out 6v or 7.5v instead of 5v - or in some cases horrible spikes if you turn the ignition on when the charger is plugged in). If you want horror story, go look at/read:

http://www.iaudiophile.net/forums/sh...ad.php?t=16446

(Among others).

The USB plug charging is going to be limited to .5A (500 mA) usually (else the PC USB ports tend to fry); what sort of Amps you can put in through a dedicated DC power port I am not sure - the M5/X5 models are about 2A.

[TigerhawkT3]

The charger I linked to in my above post is from Cowon's official store. Should that one be okay? Maybe I could buy that one and test the voltage with my DMM when it arrives.

[GSV3MiaC]

A Cowon car charger should be perfectly safe, and even if it does fry the unit (which is really unlikely) it will still be Cowon's fault, so they'll have to fix it. Go for it. Certainly lots safer than DIY electrics.

[TigerhawkT3]

I went ahead and ordered it. I'll check Vout, and if it doesn't list a range for Vin, I'll try to find it out.

[TigerhawkT3]

Well, I can't check Vout because of the design of the plug, but it says that Vin is from 9-16V. I used an old AC power cord to make an extension by putting female quick-connect blade terminals on one end (for a 12V SLA) and an ordinary 12V auto-type outlet on the other. I tried it for a minute, and it didn't seem to fry. I'm pretty happy with it.

[TigerhawkT3]

I don't know why I forgot to post a pic of what I made. Sorry about that. It's just an extension cord with both ends snipped off, one wired to a 12V car cigarette lighter-style socket and the other bearing a pair of female blade terminals. This way, I can connect it to a 12V SLA or something like a pair of 6V lantern batts in series (available at most electronics/department stores). Anyway, here it is.



I also just finished this little doohickey about half an hour ago. It uses a pair of 7805 voltage regulators. It's an LDO, so it's not very efficient (current in is the same as current out, no matter what you choose as Vin), but it works. I used two because they're rated at 1A and the Cowon's power supply is rated for 2A and I wanted to be safe. They're soldered to some steel bits for heatsinking. I can use a 9V batt or a 6AA or 9AA carrier with 9V snaps. Here's a pic:



The first setup is quite large, but it only draws 0.25A from the 12V SLA. The second setup is much smaller, but draws 0.5A.