Sparkbright Products Voltage Monitor

I've been meaning to do a post about this for a while, but tomorrow always seemed a good time to do it.

A few months ago, on the advice of someone on an internet forum (yeah, I know) I bought an LED voltage monitor on eBay. The reasoning was this: a couple of years ago, both bikes died on me in the same week. Curiously, for the same reason - a failed regulator/rectifier. The Honda ST1300 died on the lane up to the house after a 50-mile ride (phew) and the Yam failed a diagnostic session with a multimeter after it had only just got me to work and back one day. In both cases, the reg/rec had failed and either no charge or a wildly varying charge was getting to the battery. In both cases, the components were replaced and the bikes ran normally afterwards, without even toasting the batteries. But it occurred to me that I had been lucky, and if this had happened a long way from home I would have been in a right pickle. Early warning of a failure could have prevented a lot of grief.

I started to look for a dial-type voltmeter when someone suggested this indicator LED. It's made by a guy in Glasgow, and everyone on the forum who had bought one raved about it. It's hard to find a place for a dial-type gauge on a bike anyway, so I punted a tenner on one (actually a twenty, cos I bought one for each bike - and I haven't got round to fitting it to the Sprint yet).

Link to the product here. Sparkbright Products shop here.

It's a three-colour LED (red, amber and green) and it displays the bike's system voltage as follows:

Voltage	Output
>15.20	Green/Red alternating (over-voltage)
>13.20	Green (charging)
>12.45	Amber (75% plus)
>12.25	Red slow flash (50% approx)
>12.00	Red 2 flashes, repeat
>11.80	Red 3 flashes, repeat
<11.80	Red 4 flashes, repeat

I mounted it on the bike next to the instruments, but (as it is constantly on when running) out of my direct line of sight. This is the position:



And this is the light when it's working (it's red because the engine isn't running and the battery is half-dead after a lot of circuit testing):



When I fitted it, I just fastened it to the clocks with insulating tape and pushed the wires into a switched live and the indicator earth - a temporary arrangement to see if it would work. It did.

In fact, it is very reassuring. It stays green for 99% of the time, and shows amber for a couple of seconds every so often. So I am in the golden 13-15V area for most of the time, and the voltage dips into the 12V area occasionally. I anticipated that this might happen, as the connections to the bike's electrics are hardly robust and may well be a bit flaky. And, let's face it, the XT is a shed - 99% good is 50% better than I have the right to expect. But the key thing for me was that it stayed green even with the lights on. It's an old-skool thing, from the days of dynamos, but I always have the sneaking suspicion that having the lights on is draining the battery. It isn't.

Today, I have been checking all the wiring and the earths on the XT to try to locate an intermittent and peculiar fault, and I decided to make an honest component of it and wire it in permanently while the tank and the plastics were off. A longer earth wire was soldered on and connected to the battery negative, and I used a Scotchlok (yeah, I know) to tap into a switched live at the ignition switch.

All seems well, although a true test will be the commute to work tomorrow night. Will it stay green all the way? Watch this space. In fact, I suspect it has already proved itself. On the two journeys between home and work before the intermittent fault appeared, it was going to amber far more often then usual, indicating that the voltage is dropping lower than it should. The bike's performance remains the same with no cause for concern, but perhaps this little device was giving me an early warning of trouble?

As far as the product itself goes, I would recommend it wholeheartedly. It's well-made, robust and waterproof, and the wires to connect it are neatly tinned. It seems to work perfectly. Running along with the light showing green is reassuring, and (hopefully) I will know about any charging problems before they leave me by the side of the road. The maker, Dr Andrew Ferguson, is a helpful guy, and his communication is personal and friendly. I will probably fit one to every bike I own from now on, as a tenner is not much to pay for peace of mind. The only thing I would do differently is that next time I will get a smaller unit. The 10mm standard bulb is a bit too big for something that is on all the time, when all you need is a speck of light in the corner of your eye. When I mount the other one to the Sprint, I will be careful to mount it well out of my line of sight, as it can be distracting, especially at night. Next time, I will probably go for the 5mm version.

Highly recommended.