# Charging/Running a garmin from the Brompton hub dynamo



## cisamcgu (14 Feb 2019)

I have a Brompton with the Shimano hub dynamo. Is there any way to use it to charge phones/garmins on the road ? Some way of connecting to the output ?

I have had a google search but I am not 100% I know what to look for.

Thanks
Andrew


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## steveindenmark (14 Feb 2019)

I have an Igaro D1 convertor that I connect to the Dynamo hub. I have piggy back connectors on the hub.

I can ride with my GPS always charging up if I want to but I actually have my power bank plugged in all the time during daylight. I usually dont charge anything at night as this does draw some power from the dynamo lights.


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## cisamcgu (14 Feb 2019)

@steveindenmark is this connected to the Shimano Bromton hub ? Do you have any wiring diagrams or photos ?

Thanks
Andrew


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## berlinonaut (17 Feb 2019)

cisamcgu said:


> I have a Brompton with the Shimano hub dynamo. Is there any way to use it to charge phones/garmins on the road ? Some way of connecting to the output ?
> 
> I have had a google search but I am not 100% I know what to look for.



You need a "thingy" that converts the output of the hub dynamo to an USB-port (with the port delivering for one the specified power and secondly offering the possiblity to plug in the devices that are to be charged via USB). Over the last years a tremendous amount of such "thingies" entered the market, with prices ranging from about 20€ to about 200€. As you would guess price is not the only difference, they also vary in efficiency, features, design and reliability. More on that in a minute.

What you should be aware of before buying such a charger are mainly four things:

1. When you charge your device you obviously make use of your dynamo hub. This means that usually you cannot use them while running with the lights on due to the limited amount of power that a hub dynamo produces. So in most cases it is either charge or lights. Not a huge issue in practice.

2. Making use of the dynamo hub for charging also means dealing with the rolling resistance of the dynamo hub in power mode constantly. Not a huge issue (and none at all with higher level hubs like the SON), but as the Bompton Shimano hub is a low level hub with relatively high rolling resistance you may notice the difference. Again not a huge issue but worth mentioning. Basically as if you would run your bikes with the lights on constantly.

3. As you do not travel at constant speed and even worse stop from time to time this means the power output of the dynamo hub is not constantly high enough to charge. This means that your device gets charged sometimes and sometimes not. Expect most devices to charge when you are pedaling more than 12-15 kph. Per se this is not a problem, but some garmin devices as well as some smartphones pop up a dialogue box each time and THIS is annoying. You can work around that with a small buffer battery between charger and device - you charge the battery, the battery charges the device. Some of the chargers offer a built in battery, others do not. You can also use a powerbank for that purpose but you would need one that is able to charge while it is being charged and while those do exist it is not the standard.

4. As power rises with the speed you get another issue: At higher speeds (i.e. downhill) the power output of the dynamo may be too high and able to fry the electronics of your device. Not very desirable but an issue with some of the chargers. Again a buffer battery is a life safer here. Most of the higher quality chargers offer protection even w/o a buffer battery while some of the cheaper ones do not. You have been warned. 

From my experiece (mainly with an iPhone) it is possible to charge the phone while riding. It is however not a very quick process and if you are running with screen and GPS on it is even slower - you are on the safe side in this use case if you calculate with the battery staying at about the same level or charging slowly. Your can basically forget to charge camera batteries or such. In many cases a power bank is the easier an cheaper approach these days - if you use a bigger one and charge it fully at home before starting your ride it may well bring you through the day. Still the dynamo powered chargers are nice and fun and I do not regret to have bought one.

Now for the actual devices. There has been a series of tests over the last years (starting in 2010) in German "Fahrradzukunft" which is a free bicycle magazine available online. As you would expect from a German test  these are sorrowfully done and very technical.  Possibly you can get an online translation with google translate or such - they are the best and most trustworthy source I know of:

https://fahrradzukunft.de/11/steckdose-unterwegs/
https://fahrradzukunft.de/12/steckdose-unterwegs-2/
https://fahrradzukunft.de/13/steckdose-unterwegs-3/
https://fahrradzukunft.de/21/steckdose-unterwegs-4/
https://fahrradzukunft.de/22/steckdose-unterwegs-5/
https://fahrradzukunft.de/26/steckdose-unterwegs-6/

Andreas Oehler who did the tests (and is a very nice guy) works as engineer at Schmidt, the makers of the SON. This may give you an impression on what to expect qualitywise...
There are even more devices on the market than are covered in these tests but they show a relevant amount of what's availble including the most common devices and a lot of less common ones as well.


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## HobbesOnTour (17 Feb 2019)

cisamcgu said:


> I have a Brompton with the Shimano hub dynamo. Is there any way to use it to charge phones/garmins on the road ? Some way of connecting to the output ?
> 
> I have had a google search but I am not 100% I know what to look for.
> 
> ...



Yes you can. @berlinonaut says you need a "thingy" but in the spirit of online discussions I respectfully disagree - what you need is a thingamajig

There was a recent discussion on similar here https://www.cyclechat.net/threads/charging-on-the-move.242089/

It really depends on your needs and how you will be using it. Most people (myself included) recommend using a powerbank - ie. dynamo charges powerbank, powerbank charges phone etc.
If you are just using it for day rides, then a powerbank is really all you need. If longer trips, then the dedicated thingamajig make sense. It's just a matter of picking out one that works for you. For example, dynamo lights are available with a usb port that you can plug in to.

I use a Cycle2Charge.de unit and am very happy with it. I use it with a powerbank. I never charge my phone with it and when I tried a Garmin unit connected directly to it, it went haywire. No issues with my Wahoo connected directly.


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## cisamcgu (17 Feb 2019)

@HobbesOnTour and @berlinonaut 

Thank you SO much for your considered and helpful responses. 

I didn't realise there were so many options  I will have to have a careful look at the Brompton dynamo hub and try and see if I can work out what any of the wires are doing, and how I might connect any of the USB chargers.

Time for some more research

Thank you both again, CC is such a wonderful place


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## HobbesOnTour (18 Feb 2019)

cisamcgu said:


> @HobbesOnTour and @berlinonaut
> 
> Thank you SO much for your considered and helpful responses.
> 
> ...


You're welcome!
I'm not sure what wires you are referring to? Is there a different type of hub dynamo for Bromptons?
Maybe throw up a picture or two?

It can seem terribly complicated at the beginning, but I've done it twice now and I am rather technically challenged. 
Search Youtube for helpful videos about installing/wiring dynamos.

Good luck!


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## cisamcgu (18 Feb 2019)

There are a pair of wires going from the front light to a small plastic connector and then into the dynamo. I imagine I will have to somehow add the wires from the USB charger to these and put them into the connector.

I'll find some photos 

Andrew


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## HobbesOnTour (18 Feb 2019)

cisamcgu said:


> There are a pair of wires going from the front light to a small plastic connector and then into the dynamo. I imagine I will have to somehow add the wires from the USB charger to these and put them into the connector.
> 
> I'll find some photos
> 
> Andrew


That would be the usual situation. You can open the plastic connector (there's a little tab that you need to press in and slide the two parts apart) and make connections for the light and the usb device. 
Does your light have a switch to switch it off?
Most, if not all, of the usb devices need the light to be off to work. If you don't have a lightswitch, then you may need to consider a new light.


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## berlinonaut (18 Feb 2019)

cisamcgu said:


> There are a pair of wires going from the front light to a small plastic connector and then into the dynamo. I imagine I will have to somehow add the wires from the USB charger to these and put them into the connector.
> 
> I'll find some photos
> 
> Andrew



It is pretty easy: the wires are + and - (and with the Shimano Dynamo it is in opposite to others important do distinguish between the two). The little plastic housing on the dynamo hub that they enter can be simply pulled of the hub. Then you can take it apart - it has an inner part and an outer part, secured together by a small knob. Having done that pull the two cables out, drill each of them togehter with the according cable coming from your future charger (care for + and -), put them back into the housing (again care for + and minus), pur the housing back onto the hub and off you go. Pretty easy.


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## cisamcgu (18 Feb 2019)

@HobbesOnTour and @berlinonaut - again many thanks for your replies. The light does have an on/off switch. I will have a good look at the plastic connector and see if I can open it up. If I can, then I will look at picking a USB charger


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## HobbesOnTour (18 Feb 2019)

cisamcgu said:


> @HobbesOnTour and @berlinonaut - again many thanks for your replies. The light does have an on/off switch. I will have a good look at the plastic connector and see if I can open it up. If I can, then I will look at picking a USB charger


Have a good think about what's important to you in your charger. For example, what real estate it will take up on the bike. Where will you put the unit/powerbank? Will it affect the foldability of your bike? Weatherproofing? 
Good luck!


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