Garmin Edge USB Chargers

The twelve hour battery life of the Garmin Edge 205/305 is a shortcoming that needs addressing if you do daylong rides such as Audaxes and the like. There are a few options out there similar to the emergency mobile phone chargers such as Cellboost and PowerMonkey etc and the Homebrew route that I tried.

Part of the problem when your Edge gets down to one blob of battery life is recharging it on the move. On the Audaxes time was a bit tight in the control points and the Edge doesn’t recharge in 5 minutes. You dread seeing a low battery warning after 100 of 125 miles I can tell you.

My Edge is mounted on the stem but there is also a clearance problem with USB connector. Its a tight fit and any pressure on the cable means the Edge won’t take a charge. This tight fit rules out the use once Emergency Mobile phone packs like CellBoost (£5 at Tesco,s). Riding colleague and Garmin route planning mentor Ray has a pack from Akhter that works that cost him about £20 I’ve been told, it gets put in a pouch that gets looped onto the handlebar. His setup works but I still like the Heath Robinson efforts that abound.

There are two methods of regulating the voltage to your Edge charger first is the step down method. You start with a higher voltage and drop it down to 5v through a regulator . The excess voltage generates heat and is not efficient. It’s easy to do though and the parts are cheap. Cheap enough for the Cellboost pack to be thrown away.

The other method is DC-DC conversion. This is what I think is in the more expensive chargers like Ray,s. This is the blood out of a stone method and is more efficient than the step down method. Without going in to too much detail it allows you to extract all the energy out of a set of cells to top up your Edge. You can quite literally charge your Edge from a single AA cell.

The Energiser Energi to Go charger looks like it might work Ok . I might end up getting one instead of faffing around but where would be the fun in that.

To be continued. The solution is out there.
Mustn’t forget to mention Andy Walshes charger from Poundland. Cost need you ask £1. Battery under the seat, with a switch. He completed a 12 hour Race with it.

MK 2 battery pack is coming up with a 5 volt regulator in it. Been to Maplins for the bits.

Fabricated the Regulator side of the charger into a PP3 cell top. Then potted it in Araldite. The regulator is a 78s05 5volt regulator that I’v had since the days when I used to do computer repairs. I bought a 6 x AA cell battery pack from Maplins whech should supply 7.2 v if fitted with Nicads or Ni-Mh batteries. All thats required now is to fit the mini USB plug to cable and test it.

Usb Charger1.jpgUsb Charger 2.jpg

A 7805 voltage regulator needs around 6 volts before the regulation starts to suffer and is good for 1 amp of current on a heatsink. One final word of warning Nicads and Ni-Mh batteries generate large currents when shorted due to having next to no internal resistance. Take care to insulate any exposed metal or you could end up with more than a melted jersey like I did.  If you’ve poor soldering skills don’t attempt to solder a mini USB connector.

The Edge is quite a hungry beastie drawing 380 mA from the PSU falling back to 190 mA after an hour. The regulator draws 4 mA without the Edge connected so it would eventually flatten the batteries if left connected.

Like I have mentioned before the Edge USB port is a very tight squeeze when the Edge is mounted on the stem. The Madone is fitted with an oversize stem and the Maplin USB connector just comes in to cantact with it. It is going to need a bit of adjustment to make it foolproof.

Next project is likely to be a LED headlight unit. The price of the LEDs must be at a level where it is cheap enough to play around with them.

Next test: Field trials.

The field trials in the Discovering Shropshire Audax went fairly well but they weren’t the full onbike trial. The Edge was down to two blobs by the final control and a 15 minute or so charge put another blob back on the battery charge indicator. The exposed part of the 7805 regulator is hot to the touch but these are robust devices incorporating various methods of protection. I also used the pack to charge up the mobile phone on the way home as it is also fitted with a mini USB connector.
Cost without rechargeable batteries is around £2.50. The regulator was in the junk box.

Maplin Part Number

L53AZ USB 2.0 Mini Plug 5p   £1.79
HQ01B 6AA Battery Box            74p
UJ54J  L78S05CV  2A reg           77p

Or if you’ve no soldering skills don’t posses a soldering ironyou could try one of these for £1.99

Edge 705 update. Not going to be available until 1st Quarter 2008 !!!!!!


13 thoughts on “Garmin Edge USB Chargers”

  1. Thanks Dave,
    I’ve been through that thread a couple of times and a few more besides. Only one post seemed to pick up on the problem I had of charging the Edge on the move. Rest stops and Audax control points don’t give you enough time to put a decent amount of charge back into the Edge. I’m looking towards the step up chargers for the project. My first try had the pack shorting out on change in my pocket and melting a hole in the jersey with me still in it.


  2. Hi Frank,

    Its a problem that the stem mount does become a hazzard when trying to plug the usb cable into the Edge. The handlebar mount doesnt have the same problem but has a precarious look in that position and could risk being kneed! I used a bridge between tri bars in the 12 hour which meant it was well out of the way, the battery pack functioned as a battery extender rather than a “take off, charge and replace” process. And as for the storage of the battery, a bit of duct tape sufficed!


  3. Hi Frank, great site! Returned to cycling this year after 5 out through my own idleness. Looking to drop 4 stone, and I intend to do this more scientifically with the Garmin. Doesn’t the simple answer involve getting a second battery? Just a thought, haven’t priced them up, maybe they’re not cost effective, but surely there are some imitations from the far east around on the net?



    PS originally from New Brighton as a child, many a family day trip spent along your routes, and many a holiday spent in North Wales, I envy you all those roads on your doorstep (am in Berkshire now where it is more rolling countryside, and roads are constantly busy)!

  4. Neil,

    The Garmin internal battery is not user replaceable (it’s sealed, like an iPod), that’s mostly why we’re all running around trying home-brew workarounds 🙂


  5. Hi Frank, I’ll be interested to see how you get on with the MKII charger. I used a 4 cell usb unit, no regulator, but it did not do much at all. I think 4 rechargeables barely give 5 volt though.
    Keep up the good work.
    Regards Graham

  6. Graham, the 4 cell unit suffered because it could only charge the Edge until the potentials were equal. At best it would probably only put 50% back into the Edge. You can’t do it instantly either so it has to be done on the move.
    I like the idea of the blood out of a stone DC-DC converter chargers and at under £20 they are the way to go without all the hassle.
    I can’t find a retailer that stocks the Energizer Energy To Go chargers even though they stock the batteries.

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  8. This product looks like it might work with the garmin 705 etc.

    From the their FAQs I nabbed the following

    Q: How do I know the powermonkey-eXplorer is safe to use with my device?
    A: The powermonkey has an output voltage of between 4.5v and 5.5v. Please check your device’s documentation to ensure your device requires a voltage within the powermonkey’s range. The powermonkey will then auto adjust the voltage as required by your device, it will also know when your device is charged to prevent overcharging.

  9. Hi Graeme, It’ll work OK but at a price. The Camelion charger from Maplin was only £3, works fine. It’s over a year since I’ve posted on this and things move on all the time. They were clearing out the Camelions but even at £6 they ar good value.

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