Son 28 - Ewerk - polarity?

[halfmanhalfbike]

Hi,

I'm sure this question must have been asked before on the forum, but darned if I can find it.

I've just bought a SON28 dynamo, Ewerk and B&M cache battery with the principal intention to charge the battery and then in turn charge another device (mobile, GPS etc). Despite reading the instructions for all the component parts several times, I cannot determine the polarity required to charge the battery. The instructions mention that the centre pin on the connector between the ewerk and the battery should be positive, but how do I determine that? Does it matter which way round the connecting wires go between the SON28 and the Ewerk? Etc, etc

In short (and it's all in the word!), how do I make sure I wire up my new kit correctly and avoid an expensive meltdown?

Simple answers for the electrically challenged will be greatly appreciated. 

[JimK]

For starters, the SON hub is AC, i.e. there is no polarity. It doesn't matter which way you connect the ewerk to the hub... of course you need to plug into the proper, AC input, terminals of the ewerk!

The ewerk must have the circuitry to turn AC into DC but I have no idea about the details.

I have an edelux headlight hooked to my SON hub. The headlight turns AC to DC. The headlight also has a DC output to which my tail light is connected. On that connection the polarity is important!

[Danneaux]

Hi, Halfman/bike, and welcome to the Thorn Cycling Forum!

Jim is indeed correct, the hub produces AC, so polarity is not an issue there -- either lead can be attached to either hub terminal.

As for the e-Werk's DC output, it is important. The center pin is positive. If you are using the "custom" leads included to make your own connections, then the white lead is positive and black is negative.

I know from personal experience, having just installed an e-Werk on my Extrawheel trailer, described here: http://www.thorncycles.co.uk/forums/index.php?topic=4953.0 I also checked with my tester and can doubly confirm. This is also described on page 12 of the little booklet included with the e-Werk.

So long as you get the DC leads polarized correctly, the supplied USB connectors will also be wired correctly.

As a closing cautionary note, just as important as polarity is to check to make sure the voltage and current are appropriate for the device you are about to plug in. If your devices have different requirements, be *sure* to check every time before plugging *anything* in to the e-Werk.  I have standardized my on-tour gadgets for 5vdc @ 500mA and have set the e-Werk accordingly as a fail-safe for when I am tired and wet and stoopid at the end of the day, standing by the side of the road in a rainstorm so I won't do something dumb. The cases I've heard of where people fried their gadgets with an e-Werk were all in similar circumstances, so please be careful to make sure the dials are set correctly.

The e-Werk is really a sweet little device, and I am impressed by its design and build quality. I have the Tout Terrain The Plug2+ on my Nomad, and it also works extremely well and is integrated as a stem cap. The choice between the two is really down to preference and application and whether you need only the USB 2.0-standardized ouput of 5vdc @ 500mA for the TTTP2+ or whether you need the variable output voltage and current as supplied by the e-Werk.

I hope this helps.

Best,

Dan.

[halfmanhalfbike]

Aha! The light has dawned! Many thanks to you both.

A quick spin around the block seems to indicate everything working the way it should. Heading for the Sprengisandur next week for a slightly sterner test.

Good advice about choosing various devices with similar power requirements. Although I intend to run all equipment through the cache battery there's always the chance of failure or loss, where I might have to charge directly from the Ewerk (and I wouldn't want GPS to be an acronym for Great Puff of Smoke).......

[Danneaux]

Thanks for the update!

You'll do fine, I know. Very best wishes to you for a safe and happy trip er, "slightly sterner test".  Looking forward to reports on your return.

Best,

Dan.