Magicshine MJ-818 Is the Most Advanced and Reliable Rear Bike Light Unit

It also has the most irritating on/off mechanism of any light on the market.
Aforementioned pain in the a ris can also lead to the light failing as there's no way of knowing where the limit of the constant twisting to work the thing is.
This can eventually lead to the user twisting too far and shearing off the puny soldering that connects the internal wiring.
Once that happens it's done for.
It also has extremely stiff connecting plugs which with frozen hand can lead to pressure being put on the cable crimp which quickly turns into a fail or requires fiddly work with a cable tie.
Also not worth lugging around a battery pack with all the associated annoying cabling unless you're using a front light at the same time.
Magicshine batteries are hopeless and will overcharge at will, requiring incredibly annoying surge of power to bring it back to life. A trick I still can't manage.
I have 2 dead batteries, one of which is barely 2 months old.
You also have to store the things with just the right level of charge otherwise it buggers up.
The chargers are a joke.
Had 2 in a year.

It is incredibly bright though. Perfect winter rear light if you can handle all of the above which I can't.

The whole magicshine experience - MJ 880 + 818 has cost me over £200 if you include all the various battery and charger malfunctions, new rear light unit, extra cables plus postage.

I've had to buy extra stuff to put together a viable saleable solution.
I will not go down the magicshine route again.

Buy yourself a couple of Crees off Ebay for a total of £20, some decent 18650 batteries and a bright cable free, lightweight rear light and you'll manage to keep your blood pressure below the critical level.....