Posted by: audaxing | January 4, 2014

Not So Smart with Lights

I recently bought two Smart Lunar R1 lights. They are small, lightweight devices but extremely bright. I got them for two purposes:

  • Putting on my winter bike which I will occasionally be riding in fog at this time of year
  • As a backup light for my best bike. I can unclip and put them on the best bike before an event

When I got them out of the box and looked at how they worked I was impressed at the “modes” available. The light has some small LEDs and one large big LED. The 3 modes, which are selected by pressing one switch are big light, small lights only, alternate/flash big/little. The big LED is too powerful for group riding but is impossible to miss, even in daylight. The little lights are good for group riding and the batteries will last longer. So being able to select big or little as alternatives is great.


The “big” and little lights modes



The pair of lights, fitted on the rear stays of the bike

I put them on the bike about a month ago.

The bad news

However, the lights were too good to be true. During the second of two wet days/nights out one of the lights refused to switch off after use. Later in the same ride the other light refused to switch on. I left them over the fireplace overnight, they dried out and started working again.

I asked around and apparently this is a known problem with this type of light. The design flaw is that the switch is placed at the bottom of the light. Any water that penetrates the seal pools near the switch and causes it to go wrong.

My fix

The “smart” (see what I did there) thing to do at this point would have been to return the lights to the retailer as unfit for use. Apparently Astrum and Radobot lights have the switch in a different place and do not have this problem. But sadly I am not sensible enough for this.




To try and mitigate the design flaw I have taken the following counter measures

  • Remove the gasket seal and coat it with silicon grease
  • Apply silicon grease around the switch
  • Apply silicon grease on the seal on the switch cover
  • Wrap red insulating tape around the join of the two halves of the light
  • Mount the lights upside down so that the pooling occurs away from the switch

Will it work and render the light reliable in rainy weather? I don’t know. I suspect I will be finding out quite soon though.


  1. good luck! Hope to hear its a success, I’ve been thinking about getting one of these – someone passed me with one on my commute recently & its a great little light.

  2. That’s odd, I have one like that (but with only two modes: Flashing 2 small 1 big, or Big constant). It’s been working fine on my hybrid/commuter rain or shine for at least a couple of years. Construction looks identical. Gah, it’s a lottery isn’t it?

    I like the silicone idea, btw.

    My Hope Vision 1 has started turning on/off in rain/bumps, so I may see if a similar solution will help there. Not sure I can take it apart though.

    • According to hearsay evidence: if you can mount them higher up and above the mudguards, on the seat post for instance, then they don’t seem to be as prone to failure.

      Turning off on bumps is sometimes the battery connection. Turning off in rain is usually the switch. If I had a Hope light in a similar state I’d put spray switch cleaner in the switch and clean the connections with isopropyl alcohol

  3. Used one as my taillight for TTing as I wanted good daytime visibility and it worked fine until the first wet race, then as yours it wouldn’t switch off and I had to take the batteries out and dry it, then after next wet race it won’t switch on.
    Rubbish. Switch is all corroded inside.
    Which is a shame, as it’s a great bright light, if only it were properly sealed.
    Smart also do (did ?) a kidney-shaped light with the same LED as the 1/2Watt one – I had one of those for ages and with no wet-weather problems until something I had on my carrier dislodged it from its bracket.
    This one on my TT bike I’ve replaced with a Planet-X two-LED thing for £2.50 which looks a bit inelegant but is plenty visible

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s


%d bloggers like this: