I've got probably 4500km on my SP PV-8 and it has performed great so far. 
That said, I really don't want to tear down my wheel at 20,000kms:( To 
state the obvious, no matter how bright and economical a rechargeable 
battery light is, they all have the same downside: you have to remember to 
charge them. When I need my lights, I really need them, and I need them for 
the whole trip home. For me, the lack of worrying about charging, mounting, 
and re-mounting lights, is worth the price of even the most expensive 
dynamos. For me, it's about the freedom to go wherever I want, and stay as 
late as I want, and having a dynamo has increased the number of trips I 
make on my bike 2 fold. Summer night riding in Tucson is so nice. My dynamo 
set-ups are my most valuable components--I don't consider them an 
accessories. That said, if you are disciplined about recharging, you might 
be a good candidate for USB lights. I'm not. 

Scott Calhoun
Tucson, AZ

On Friday, October 3, 2014 10:56:16 PM UTC-7, hangtownmatt wrote:
>
> Wayne,
>
> I'd like to add a third reason:
>
> 3.  They are not user serviceable.  Here's what I found on the Shutter 
> Precision FAQ:
>
> *How often do SP hub dynamos require service?*
> SP hub dynamos employ sealed bearings that do not require service until 
> the bearings are require replacement. We already have customers that have 
> logged over 10,000 kms without any problems and we expect that under normal 
> use the service life of these bearings should be well over 20,000 kms. 
> Should they ever need servicing, they can be sent back to SP and replaced 
> with new ones for roughly USD 30 including the cost of return postage.
>
> *Are SP hub dynamos user serviceable?*
> Alas, SP hub dynamos are *not* user serviceable and indeed we are aware 
> of no hub dynamos that are based on manufacturer’s recommendations. *Any 
> attempt to service a SP hub dynamo will **void its two-year warranty* 
> <http://www.sp-dynamo.com/Support.html>*.* We have received quite a 
> number of requests from consumers on how they might service their hubs even 
> accepting that attempting to do so would void their two-year warranty. They 
> accept this risk thinking that this would save the need to disassemble and 
> rebuild the wheel. Unfortunately, the design of SP hub dynamos like that of 
> many other brands requires disassembly of the wheel for bearing 
> replacement. Furthermore, the delicate generator mechanism housed within 
> the hub body must be re-calibrated to tolerances of less than a millimetre 
> each time bearings are replaced. Failure to carry out this operation 
> properly (which is likely without expert knowledge, experience and tools), 
> will generally result in catastrophic failure of the generator mechanism 
> after a period of use. SP engineers have considered making their hubs user 
> serviceable (with much prodding from IDC at the behest of our technically 
> savvy testers). But the expertise and equipment required to carry out 
> recalibration of the generator mechanism each time the bearings are 
> replaced presents a technical hurdle that SP engineers, and indeed all 
> other hub dynamo manufacturers we are aware of, have so far declined to 
> attempt.
>
>
> Did you catch the part about having to disassemble the wheel in order to 
> replace the bearings!  20,00kms is roughly 12,000 miles.  So every 12,000 
> miles you need to tear down your wheel, ship it off for new bearings, pay 
> $30 + return shipping, and than rebuild your wheel.
>
> WOW.  That combined with the initial buy-in makes dynamos a pretty 
> expensive proposition.  I suppose if you really need it than there is no 
> substitute.  But by comparison, just tonight, I replaced the original 
> lithium-ion rechargeable battery in my USB-charged NiteRider Cordless 600 
> for a total cost of $10.99. This light was purchased in 8/2011.  I use it 
> light 5 days-a-week, year round on my early morning commute.  With an 
> initial cost of $108 it has proved to be a pretty good value.
>
> Matt
>
>
>
>
>  
>
> On Wednesday, September 24, 2014 10:11:18 AM UTC-7, Wayne Mesard wrote:
>>
>> I'd like to anti-recommend the dynohub approach. I considered it when 
>> building my Sam, but rejected it for a couple of reasons:
>>
>> 1. They're expensive!
>> 2. You pay the wattage tax whether you're using the thing or not. The 
>> Interwebs say that the drag costs anywhere from 2 to 15 watts of additional 
>> pedal power. That's not a lot. But it's not nothing either.
>>
>> Instead, I bought a USB battery (
>> http://www.amazon.com/gp/product/B00IP1MQNK/), which I'm quite happy 
>> with. That way I have backup power for all my devices, since they all 
>> accept USB power (front and rear lights, GPS, cell phone, AfterShokz 
>> headphones). With the money I saved, I could have bought five of them, but 
>> one was more than enough.
>>
>> On my most recent tour, I had no problem keeping the battery charged by 
>> plugging it in overnight and opportunistically at lunch stops. But just to 
>> be safe, I also got a solar panel (
>> http://www.amazon.com/Goal-Zero-11800-Nomad-Solar) which mounted easily 
>> to the rear rack. Like I said, I didn't need it; but I was glad to have it 
>> as a backup.
>>
>> Wayne();
>>
>>
>>

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