Hub Dynamo Systems For Bicycle Touring: Part 2

NB: If you’ve just stumbled upon this post, you may want to read Part 1 first! There is also a Part 3 covering hub dynamo lights.

UPDATE: Since writing this, I’ve switched to the Revolution by Sinewave Cycles. Read my review Revolution vs The Plug.

The most compelling reason for me to use a hub dynamo for bicycle touring is for recharging our various USB devices. Using a hub dynamo USB charger, you can charge whilst riding and your gadgets will be ready for your next wild camping stop in the mountains. Or, if you don’t mind adding some additional weight, you can recharge a cache battery and later recharge at the campsite.

Hub Dynamo USB Chargers

I wanted to build my own voltage regulated USB charging circuit. I found designs posted on Candle Power ForumsRob Dean RacingkLite blog, etc. However, given the amount of time I had to prepare for our trip, I had to be pragmatic and decided to go for an off-the-shelf solution. Fortunately, there are now quite a few products available.

BrandModelDescriptionPrice
Sinewave CyclesRevolutionUPDATE: My weapon of choice! Super compact, waterproof and reasonably priced;$120
Sinewave CyclesReactorSimilar to The Plug, it fits inside the steer tube and replaces the stem cap. $220 USD
IgaroD1Heavy duty touring charger that can be mounted on any bottle cage mount$105 USD (includes INTL shipping)
Busch & MullerLUMOTEC IQ2 LUXOS Uhigh LUX front light with integrated USB charger and backup battery€149
Busch & MullerE-Werkone of the first hub dynamo USB chargers to market;
still well regarded, but a bit bulkier than others
£130
Tout TerrainThe Plug II+Tucks away inside the steer tube; cumbersome to install, but ergonomic and easy to use. Superseded by the Plug III.€159
Cinq5The Plug III
PedalPower v4iIncorporates a battery for recharging off the bike
Comes with lots of connectors;
Rather bulky!
€159
PedalPowerSuper-i-Cable + v4i setAn iPhone friendlier cable + the full v4i set;
Only missing a kitchen sink;
Most expensive product on this list!
€190
Bike2PowerLightChargeQuite compact and very cheap;
mixed reviews online
$68
Think BiologicReeChargeQuite compact and reasonably priced;
mixed reviews online.
$99

Several of these products have mixed reviews online and they are all relatively expensive given what you get. I suppose because they are all quite niche products, you are paying for the R&D rather than the materials in the finished goods.

The B&M LUXOS* is one of the newer products to market and was one of the most attractive options to me. However, it was not yet available when I was planning my trip, so I had to discount it.

* It should be noted that the more B&M E-Werk model is capable of variable power output and higher maximum power (the LUXOS is not). B&M recommend the E-Werk over the LUXOS to those who are primarily interested in charging lots of different devices.

Some chargers have cache batteries built in (eg, Pedal Power). These tend to be bulkier and heavier, but have the added advantage of a battery which allows more constant, sustained charging for devices which are more fussy about minimum input power for charging (eg, Garmin EDGE 800 — see more about this later).

Tout Terrain ‘The Plug II+’

The Plug II+ main body fits inside the top of the stem and connects to the wire harness. Be sure to leave enough clearance between the body and the expander to avoid contact and prevent damage to the connector. You must insert the Plug II+ body before tightening the central vertical stem bolt.

UPDATE: Since writing this, I’ve switched to the far superior Revolution charger by Sinewave Cycles. Read my review Revolution vs The Plug

I decided on the The Plug II+, mainly because it doesn’t get in the way (and because the LUXOS was not yet available when I started my trip). I like the way it tucks away neatly inside the steer tube. The custom PAT (power amplification technology) cable included with ‘plus’ model is intended to provide improved voltage regulation at slower speeds, a potential bonus for steeper climbs and off-road riding. In the absence of a *real* battery, I consider this feature pretty essential for our kind of riding!

Installing The Plug II+

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Slide the PAT cable into the steer tube before inserting the steer tube expander bolt.
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The Plug II+ wire harness passes through a hole in the custom steer tube expander.

Tout Terrain provide installation notes on their website, but I found they were not completely clear. Here are some additional tips based on my experience.

The instructions suggest that you can run the cable through the star fangled nut so long as the parallel holes in the star nut are perfectly aligned (so they don’t slice into the cable). I followed this advice but managed to slice my cable anyway. I would definitely recommend using the custom expander nut instead of a star fangled nut. If you already have a star nut in your existing fork, follow these instructions to remove it.

2013-05-24-032.jpg
Use a spare headset cap to clamp the stem in place before tightening. This avoids crushing aluminium body The Plug whilst still allowing to achieve a solid fit between headset, steer tube and stem.
  1. Use a spare headset cap to clamp tight the headset, fork and stem in place
  2. Tighten the bottom stem bolt clamp
  3. Remove the spare headset cap
  4. Connect and fit The Plug II
  5. Tighten the top stem bolt clamp

The Plug II+ Power Output

Obviously, power output from The Plug depends on speed. Tout Terrain published a graph in this PDF showing the power output vs velocity. The graph is non-linear, so it’s clear that there is a sweet spot velocity threshold which I try to stay above in order to maximise charging efficiency. The voltage regulating circuitry in The Plug II+ seems to be optimised for casual road cycling speeds on reasonably flat roads. I can charge any of my USB devices reliably at any speed between 12-35 km/hr, though it seems most efficient at around 20-25 km/hr. This range is okay for most flat road riding, but not so good for climbing or off-road riding.

I’ve found that the min and max speed cutoffs for effective charging vary between devices. For example, the Garmin EDGE has a higher minimum speed cutoff for charging (approx 15km/hr). The Sony NEX camera begins charging at around 12km/hr. The documentation on Tout Terrain’s website suggests that the max speed for charging protection cutoff is around 30km/hr. I’ve found it is actually a bit higher at around 35km/hr. The LED on the top of The Plug indicates the current charging status.

UPDATE: I’ve since switched to using the Revolution by Sinewave Cycles, I no longer have to worry about the high speed cutoff above 30km/hr. In retrospect, it seems a bit arbitrary that The Plug has this limitation in the first place.

Recharging USB Devices

Here is a list of USB devices I have recharged with The Plug II+.

  • Sony NEX 5 digital camera
  • Garmin EDGE 800 GPS
  • Kindle (3rd gen)
  • HTC Desire phone
  • AA battery charger
  • USB mini speaker

Quirks and Annoyances

Most the devices recharge without any problems. I just plug them in to the Plug and stick them in my handlebar or frame bag to collect the juice for a few hours. However, there are some minor hiccups, particularly when my speed falls outside the acceptable range for charging (i.e., 15-35 km/hr). It’s bizarre that The Plug II actually stops charging above 35km/hr. This is a really unreasonable limitation, as 35km/hr is really not fast at all!

Every time charging cuts out, the Garmin EDGE beeps and displays a message saying ‘External Power Lost’. This is particularly annoying on climbs when my speed is teetering on the low speed threshold. Whilst the message itself is only a minor annoyance, what makes this worse is that the screen brightness resets to the default value every single time external power is detected or removed! In order to maximise battery life on the Garmin, I tend to use it with the brightness turned all the way down, so I find that I must reset it every time power is lost! I emailed Garmin customer support about this a while back and asked if there was some way around this. Here is their reply:

1. Yes, it is safe. 5V and no more than 1 amp is safe and ok.
2. I’m afraid there’s no option to disable that message. The device was
not designed to be charged from a dynamo.

I have forwarded your email to the design team as they are always
interested in customer feedback. Many of the comments/suggestions we
receive (such as yours) are often evaluated towards potential
implementation into future Garmin products or current unit software
releases. We cannot guarantee that what you have suggested will be
implemented, however we do appreciate you passing along your opinions.

We also have a portal for customers to submit ideas directly to our
innovation experts. Please share your ideas with us at the following
page on our website: http://www.garmin.com/ideas

And in response to my second email pleading for a firmware update to change the behaviour:

I’m afraid I do not have such information. Only developers team and high management involved in the process have information about planned changes.

Well, needless to say, I am not holding my breath, but hope they improve it in a firmware update! Aside from this issue, The Plug II+ charging system does work, but it’s not the best product on the market.

UPDATE: Using a USB cache battery

The most effective way I’ve found to get around the charging threshold issues of the Garmin and other devices is to use a separate USB rechargeable cache battery like the Limefuel. This allows me to trickle charge the USB cache battery during the day and recharge the GPS after I am finished riding for the day. It solves the annoying Garmin beeping / brightness resetting mentioned above.

UPDATE: Plug II+ PAT Cable Failure

Before I could finish writing this post, my Plug II+ mysteriously just stopped working. The charge light came on when nothing was connected, but it cut out as soon as I connected a device for recharging. I contacted Tout Terrain for support and here is their response:

[From] your description [it] sounds like there is a problem with the PAT cable. Can you please provide me with a shipping address so that we can send you a new cable as a warranty replacement?

I was reassured by Tout Terrain’s responsive customer support, but it meant I had to wait a few weeks to receive a replacement PAT cable. I gave them an address for WarmShowers host a few weeks down the road, and low and behold it showed up there a few weeks later. I swapped out the PAT cable and now The Plug is now working again!

2013-07-22-237.jpg
I replaced my original PAT cable with the new PAT II version and now my Plug USB charger is working again!

Helpful Links For USB Chargers

Read The Rest Of This Article

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