I have read of many concerns regarding Garmin Edge 305 relative short battery life [Garmin battery specifications: 800 mAh rechargeable lithium-ion battery; 12 hours typical use] as it relates to so called ultra events. That is any activity where you need the device beyond its running capacity determined by charge you begin the event with. Note, the use of the speed/cadence sensor, heart monitor, GPS, backlight, etc. deplete the battery at a faster rate. I use both the speed/cadence sensor and heart rate monitor.
To meet this challenge, I am using a Socket Mobile Power Pack purchased from Comalco. In its leather case the dimensions are 4.5 x 3.4 x 1.4 inches or 114.3 x 86.4 x 35.6 millimeters and it weighs 13 ozs. or 360 kgs. I found Internet prices range from $149 to $89 [US Dollars]. I did not find the $89 price when I purchased mine]. Some will say the Socket Power Pack is pricey, although I purchased mine for $93 [the lowest price I found at the time] from Comalco. This price is reasonable for me, considering other options discussed below, the pack’s reliability, and the ability to use my Garmin for extended periods. In addition to providing power for my Edge, the power pack can be used to charge other 5 or 6 volt devices such as my cell phone, iPod, etc.
Here are user experiences, as written in threads at BROL Forums:
- Battery Life for Edge 305
- Battery Edge305/FR305
- What power supply for more than a day trip?
- For those who bought a spare battery from USBGeeks
You get the idea.
Many solutions have been adopted. Some use 4 AA batteries to feed the Edge’s USB port and others use home-brewed devices to answer the call. In my mind, I wanted, and found, a lithium-ion device that will give me days of continuous GPS running. In use, at the end of the cycling day, I will turn off my GPS. The Socket Mobile Power Pack meets my needs, and exceeds my expectations.
In reality, with this setup, the Edge never goes to its internal battery. So, I have a 5-8 hr. reserve, should my power pack battery be depleted or fail. Of course, the Socket can be charged [replenished] overnight [if you have access to AC], then I’m back with full potential. I cannot think of a circumstance where this combination will not meet my Edge battery requirements.
So far, the Garmin has run uninterrupted [not turned off] for ~60 hours before the yellow LED on the power pack began to flash indicating it low battery state. If not charged at this point, the power pack will shut down. Also, when the power pack went to a low battery state, the Edge 305 began to use its battery. So, the GPS is still running, and should for at least 5-8 hours.
My judgment is this combination will keep me with a working 305 throughout my tour, especially with me turning if off at the end of the day. Other users my want to consider this option.