I can't say if your Sinewave Revolution has a glitch in it or not, but I have three different ways to charge things from a dyno hub. Sinewave Revolution, AXA Luxx 70 Plus and a B&M Luxos U, each on different bikes.
I find that the Sinewave and the AXA put out comparable power up to something like 20 to 25 km/hour. At speeds higher than that, the Revolution will keep putting out more power, but the AXA seems to have hit a peak.
I can't really compare those chargers to the Luxos U because it has a pass through cache battery built in, so trying to measure USB port output at different speeds is meaningless, as the battery is free to discharge or charge while in use.
This might provide some insight on how much power a Sinewave should deliver:
http://fahrradzukunft.de/bilder/21/steckdose-unterwegs-4/13.pngI cited that link with the graph at the following link some time back.
http://thorncyclesforum.co.uk/index.php?topic=11774.0I have several digital current meters, similar to the one Dan cited (he listed an Ebay link) and I find that the current flow out of the USB chargers varies quite a lot on these USB chargers when not using a pass through cache battery. They appear to give a new reading about every second and some of those readings are far from what they were during the previous reading. Not sure why, but as long as I see a healthy number of milliamps flowing through it, I will not worry about fluctuating current flow. It might be a function of the power source being a low hertz AC source?
You are fortunate that your Garmin will charge without the pass through cache battery. My Garmin (model 64) requires a pass through cache battery for my Sinewave or my AXA chargers to directly charge the Garmin, but the Luxos U has a built in pass through cache battery so it will charge the Garmin 64 fine.
I have not used the Cinq unit so I have no knowledge of it. Instead I use some pass through cache batteries that are no longer sold, so I am not citing a brand or model of them. And some of the ones that I have used have quit working.
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A side note on the Luxos U, the rate that the pass through cache battery in it is charged is of course a function of the ability of the hub to deliver power to it. And some of the newer USB charged devices will draw power out of the Luxos U faster than the power comes out of the hub. When that happens, eventually the pass through cache battery becomes depleted and then the charging out of the Luxos U becomes intermittent as it stops charging your device until some charge is put back into the pass through cache battery, then it starts charging your device again for a few more minutes. When this happens, I unplug whatever I have been trying to charge and let the pass through cache battery accumulate more charge than it otherwise was getting before I go back to charging whatever I was trying to charge.
Not sure if this is pertinent to your charging or not. The Luxos U has a tiny pass through cache battery compared to most other batteries, so it is easy to discharge it in use.
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If your Sinewave will directly charge something without needing a pass through cache battery, you might be better off directly charging the device without the battery in the circuit. As you charge or discharge a battery, heat is generated and that heat was produced by wasting power that was not put to good use. That is the only reason I say you might be better off without the pass through cache battery, as you might improve the energy efficiency of your charging.
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When I am on a bike tour, I try to keep all my batteries charged up the best I can, so I am frequently checking my charging progress on things. I carry an Android phone or tablet, GPS, battery powered taillights, camera, headlamp (for my head in the campsite), plus spare batteries.