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Winfried 06-19-13 03:48 PM

Electrifying a Brompton: Tough? Expensive?

I just saw someone riding a Brompton with home-made conversion kit. He was so fast I could barely follow him on my hybrid :-)

At the red light, he just told me he built it himself, that it took a bit of electronics, and off he was.

The black battery, which looked like my scooter's lead battery, was sitting in the front where the Brompton bag goes, and it looks like the electric motor was in the front wheel.

Google tells me that commercial conversion kits cost several hundred $/'s, so I wanted to ask geeks here:
1. How much would the parts cost to build a home-made solution?
2. What technical skills do you need to do this yourself?

Thank you.

bargainguy 06-19-13 07:13 PM

I'll answer in a different way. The Nano and the FreedomBike conversions seem to be the two biggies, so see if their descriptions work for you.

cpg 06-20-13 03:04 AM

Have a good look at the Pedelecs forum, there is plenty of info on there. Here is one to get you started, I think it was stated by someone who is also a member of this forum.

There are other Brompton threads on there as well as discussions about other folding bike conversions. I have been following one about a Mezzo conversion.

Winfried 06-20-13 07:49 AM

Thanks, I'll check it out.

kamtsa 06-20-13 08:52 AM


Originally Posted by Winfried (Post 15763204)
Thanks, I'll check it out.

Brompton also has its electric upgrade project

Considering their difficulties of bringing products to production (bPod, magnetic water bottle, titanium seat post, etc) I would not hold my breathe.

Winfried 06-23-13 03:34 AM

I wish I had the tech skills to build my own :rolleyes:

jerrysimon 06-23-13 03:43 PM

I have been converting and upgrading ebromptons for over 3 years now. Here is my latest super light M2L-X with a very low assist lightweight (not the Tongxin/Nano motors mentioned which I have already tried) and has the same carry weight 11.5kg as a stock M3L. This motor is about 1.4kg and is not much bigger (about 98mm across) than a dynamo. I have now done over 5000 miles in three years on my daily commute Brompton econversions.

This is the flickr set

As stated there are loads of pedelec posts covering this, some of them mine, plus on the yahoo Brompton forum this was covered extensively very recently.

Note the stock Brompton e conversion has been put on hold with no firm date of when they will go to market. I had extensive discussions with them with mine above and it is clear they will not come to market until they are 100% sure it will work reliably.

As stated it does require a certain amount of skill to undertake conversions depending on if you get someone to do the whole conversion, buy a kit or as I do now source all the parts individually direct from China and build your own wheels. The latter is by far the cheapest option and costs me about 250-300 including a small battery. Getting someone to do it for you can cost almost as much as the original bike in some cases!

Here are the two motors I have tried.


Winfried 06-23-13 04:58 PM

Look really cool :-) Thanks for the infos.

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