Using a Garmin Edge 305 with external battery

[bikingdad90]

The battery in my Edge 305 is failing and only lasts for an hour or so from full charge.

I could get it repaired for about £30 or for £15 I can lay my hands on an external battery pack.

Is it possible to use the 305 and have it plugged into the external battery pack at the same time so its charging while in use?

Do I need to use a special USB cable to prevent it going into charging mode as I normally use a wall charger?

If anyone is good with electronics I would willingly buy a battery and pay for a repair in return for some beer money.

 

[StuAff]

First off, you can buy a new battery and replace it yourself. Much cheaper, done it twice on 705s. Good instructions here https://www.jimcarson.com/2009/replacing-the-battery-in-a-garmin-edge-305/ and loads of battery suppliers on eBay and elsewhere.
Second, with an external pack, providing that's outputting enough juice, if it's the same as a 705, yes, you can charge up the internal battery while using the Edge. Been using a 3xAA USB pack for some years with my 705. I've never had any problems with the Edge going into computer connect mode, results may vary...