Using hub dynamos to charge gadgets and gizmis

[andym]

Getting a SON hub dynamo is on my list of Things to Think Seriously About. They look like the most practical option but I'm wondering if anyone is actually using one in earnest. What can I reasonably expect (eg keep a GPS and iPod charged up?). Any comments on the other bits and pieces eg e-werk etc?

 

[vernon]

The e-werk works well. I have one and ised oty to keep a pda and smartphone charged during a three week tour. I use a Shimano hub - cheaper but it does the job besides - it came with the bike - a Decathlon hybrid.

 

[andym]

The e-werk works well. I have one and ised oty to keep a pda and smartphone charged during a three week tour. I use a Shimano hub - cheaper but it does the job besides - it came with the bike - a Decathlon hybrid.

Cheers. I'd forgotten that Shimano might also be an option.

 

[vernon]

Cheers. I'd forgotten that Shimano might also be an option.

I have two bikes with Shimano dynamo hubs fitted. Both do a great job with no signs of problems.

 

[arallsopp]

Both my SONs have over 8,500 miles on. Both have been ridden through rivers. One has traversed a beach. Neither has ever complained. Both still work 100%. I've never ridden with the Shimanos, but hope they're just as good.

Oh, and the beach one is on a 20" wheel, so has just done its 27 millionth revolution. eek.

 

[yello]

If money were of no importance then I'd give the e-werks a go. Thing is, it's too pricey for me to justify on the grounds of maybe once or twice a year usage. Battery extenders are my solution.

Similarly, I use a Shimano hub rather than a SON. I accept that the latter is the more robust solution in all likelihood but the price difference doesn't justify it for my purposes... and that said as someone who has not long since replaced a Shimano hub because the bearings are difficult to service without knackering the electrics!

 

[Davidc]

I have two bikes with Shimano dynamo hubs fitted. Both do a great job with no signs of problems.

So do I

Similarly, I use a Shimano hub rather than a SON. I accept that the latter is the more robust solution in all likelihood but the price difference doesn't justify it for my purposes... and that said as someone who has not long since replaced a Shimano hub because the bearings are difficult to service without knackering the electrics!

Following warnings on here about delicate wires inside the Shimano hubs, and having downloaded some information on servicing them, I've now stripped and refurbished one of mine. It's working fine, and running smoothly. I bought it cheaply second hand and was warned that it had done over 15,000 miles when I got it, so if that figure was correct it has now done over 20,000 miles.

I have set up a Shimano dynamo for charging 12v of NiMH battery (an RC pack 4000mAH rated for 400mA continuous charge current). The system worked, but couldn't keep up with demand. By the end of the week the RC pack had little left in it, but the phone and GPS were still going. I wasn't - caught flu instead.

The pack was tapped at 6v so it became a +6 0 -6v pack and the two halves charged with raw half wave (Schottky diode) rectified dynamo (one half charging on the -ve half cycle the other on the +ve). Bike dynamos are AC constant current devices, and that setup put roughly 200mA mean into the batteries at anything over about 5 mph.

BEWARE if you do that BOTH ENDS OF THE PACK ARE LIVE TO THE COMMON (FRAME) CONNECTION. Using it with 12v car chargers across the whole pack for phone and GPS has to be done WITH CARE. Fuses are needed inside the battery pack enclosure, one on each end.

Also be realistic over the amount of charge available. The dynamos are rated at 6v 0.5A. If you are actually riding - as in moving - for 5 hours a day you'll only get at best a maximum of about 2500mAH into a 6v system, or 1250mAH into a 12v one. (15WH). Once you've allowed for charging efficiency of batteries (around 60% for NiMH) and electrical losses you don't get very much charge for your phone, GPS etc. The best is when you use as you move, in effect using any pack attached as a voltage stabililser

Best if you can to just charge your kit up from the mains at your overnight stops.

 

[rualexander]

I've just bought a Shimano DH3N71 from here for £36 including postage from Germany, which seems like a bargain. Delivered in three days.
Just have to get it built up into a wheel now to try it out.
Haven't decided on the charging interface I'm going to use yet.

 

[Davidc]

I've just bought a Shimano DH3N71 from here for £36 including postage from Germany, which seems like a bargain. Delivered in three days.
Just have to get it built up into a wheel now to try it out.
Haven't decided on the charging interface I'm going to use yet.

Ooh - it's a better quality one than mine (DH3N30s)

 

[andym]

Also be realistic over the amount of charge available. The dynamos are rated at 6v 0.5A. If you are actually riding - as in moving - for 5 hours a day you'll only get at best a maximum of about 2500mAH into a 6v system, or 1250mAH into a 12v one. (15WH). Once you've allowed for charging efficiency of batteries (around 60% for NiMH) and electrical losses you don't get very much charge for your phone, GPS etc. The best is when you use as you move, in effect using any pack attached as a voltage stabililser

Best if you can to just charge your kit up from the mains at your overnight stops.

That was to some degree what was behind my question. Would I need to maintain high speeds over long distances to make it worthwhile? Good point about charging losses.

 

[Davidc]

That was to some degree what was behind my question. Would I need to maintain high speeds over long distances to make it worthwhile? Good point about charging losses.

No, any decent charger will operate the dynamo much as its design intended, 6v at 0.5A output at speeds of 5mph upwards.

In principle it is possible to get higher voltages but not significantly higher current at higher speeds but safely operating anything outside its normal range needs knowledge of its design which in this case I certanly don't have.

 

[vernon]

That was to some degree what was behind my question. Would I need to maintain high speeds over long distances to make it worthwhile? Good point about charging losses.

A technically ignorant answer is no.

I pootle around at around 10-13 mph on tour and never suffered from depleted cells.

 

[andym]

Thanks guys. I'd forgotten that I think there is. German legal requiremenr that they have to keep the lughts functioning even when rhe bike is going fsirly slowly.

 

[ChrisBailey]

Getting a SON hub dynamo is on my list of Things to Think Seriously About. They look like the most practical option but I'm wondering if anyone is actually using one in earnest. What can I reasonably expect (eg keep a GPS and iPod charged up?). Any comments on the other bits and pieces eg e-werk etc?

Hi Andy

I have a SON dynamo, actually I have two, on separate bikes of course, brilliant devices, got my first over 10 years ago. I bought them for my lights and they are excellent.

Recently I tried to utilise the one on my tourer for extras, mainly charging my mobile phone (a blackberry) and keeping my GPS (Etrex Vista) permanently lit up.

I think I should have bought an e-werk, but instead of £100 I spent £25 and this is what happened...

http://www.crazyguyo...page=1&nested=0

Not a total disaster, but I wouldn't go down this route.

Hope this helps.

Chris

 

[andym]

Chris. Thanks. I must admit I hadn't considered powering the GPS direct.

I was considering the pedalpower cable as most devices are USB-chargeable so the ability to change the output voltage from the e-werk looks a little redundant.