Moon Shield-X Auto Rear Light

I recently threw out no fewer than six lights that have failed in some way, and the Moon Shield-X Auto will soon be joining them. Three weeks into the test, I went to turn it on and found the on/off button was no longer there. Reason suggests it must have been attached when I last switched it off, so I scoured the garage floor but it never reappeared, leaving me to resort to the distinctly low-tech measure of turning it on and off with a biro lid.

Worse, it leaves the interior vulnerable to water ingress. Modern lights, with their sophisticated electronics, seem very sensitive to this and most of those dud lights were either refusing to switch on, failing to switch off, or randomly doing both after exposure to wet conditions. I subjected the Moon Shield X to an 'instant winter' in my kitchen, dripping some salty water into the hole left by the missing button. The results were spectacular – within minutes the light was blazing like the sun, then flashing randomly until the battery died. I left it to dry out for 24 hours but as soon as I plugged the charger in, it came back on full-power and wouldn't be turned off or switched between modes, with or without a biro lid.

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I confess I was a bit relieved it had gone wrong because picking my way through the nine steady and flashing modes was beginning to drive me mad. Fair enough, if you only have one light then you'll get used to how it operates, but for me using the light tended to go like this: clip it into the bracket, turning it on accidentally in the process. Jab the button in an effort to turn it off; but this just switches it to a different mode. So prod the button again repeatedly to get back to where you were. Try two jabs to turn it off – no, this switches you between steady and flashing...

Ah yes, I remember now, to turn the light off you press and hold the button – not unusual among front and rear lights – but only for two seconds because if you hold it for three, it switches to 'Auto' mode. Now try doing all of this while riding along. Not helped by the on/off button being a bit inaccessible on the back of the light, once it's mounted in the bracket.

That Auto mode refers to the built-in light meter which allows you to set this to come on automatically in low light conditions. This sounds a good idea, but since it was so complicated to get there I hardly bothered with it.

I also wonder whether it might lead to accidental draining of the battery... Picture the scene: you set your Shield X Auto to switch itself on in poor light conditions but when you get back from your ride, the sun is out and your Shield X has turned itself off. You put the bike in the garage and shut the door. Darkness falls. Your light turns itself on automatically and shines all night. By morning you have a flat battery. (In its defence, Moon does warn you: there it is in the instructions, the section about auto on/off – a warning triangle with a '!' in it. 'Remember to switch off the light when you do not use it.')

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It's a shame because the Shield-X Auto is essentially the same as that reviewed by Stu Kerton here. With the addition of a ring of 20 tiny LEDs around the central one, Moon has been able to add an extra 30 lumens and a useful option to run a steady red light with a pulsing middle light.

The steady modes go through bright, brighter, brightest and brightester. If the light was blinding at 50 lumens, imagine what it's like now it's been cranked up to 80. The lowest setting is plenty bright enough for general riding in traffic; the maximum should really only be considered as a fog light.

It's a similar story for the flashing modes. Then a fifth push of the button gives you 'Day Flash' – a maximum brightness double-blitz that lights you up like an aircraft's landing gear. It's excellent for riding in daylight, especially those frightening low-sun, wet-road conditions that seem to take drivers by surprise every winter.

The 210-degree angle is not as wide as Moon's own Arcturus Auto but still offers plenty of side visibility.

The light comes with three brackets: a belt clip, seatpost mount (with two lengths of rubber band) and a saddle rail bracket. All are well made and sturdy as well as being easy to fit. It makes it a simple matter to move the light between different bikes. A helmet mount and a rear rack mount can be bought as optional extras, so all bases seem to have been covered. The mount uses a square clip which means you can use the light either horizontally or vertically with equal ease. A USB remote control is also available, which I would say is almost essential if you want to make full use of all those different modes (or if the button falls off).

> Check out our guide to the best rear lights

Moon has addressed the issue of the previous model switching itself off when the battery goes flat. The Shield-X includes an 'auto safe mode', which means it will continue to run at reduced output for up to an hour. The claimed run-time (1hr 20mins at full power with an extra hour in 'auto safe'; recharged in 2 hours) seemed pretty well spot on. On my test sample, the supplied USB charger cable was faulty.

It's very easy, in the pursuit of offering something new each year, for manufacturers to spoil a perfectly good product with unnecessary upgrades, and I have to say I think that's what has happened here – not helped by the Shield-X's inability to hold together for more than a month.

Verdict

Build quality issues and such a fiddle to operate it's a turn-off