Tank bag loom - Voltage question

[akey]

So with my euro trip coming up later this year I thought I should get a few things sorted for power.

What i needed was a voltmeter, the gps powered and a lighter socket to charge the phone etc.

I didnt want to hardwire all this into the bike so I have built a loom up that takes power from the acc socket on the tiger up to my tank bag, which has the cig lighter socket, tomtom power lead and the voltmeter fitted (I know the voltmeter should connect to the batt etc but the show chrome voltmeter just doesnt look like its that waterproof what with the uk weather I thought it would be best in the tank bag).

anyway finally got it finished tonight and it works a treat, the voltmeter seems to read a little higher than the batt voltage when at 3000 rpm but that could be my cheap multimeter, so will check against a good one at work.  but overall I am very happy with the setup, I will try to get some pics up later this week although its not very neat as I wanted a nice flexible instal, but it seems to work pretty good.

[akey]

Quick update:

Tested this on the way to work this morning and got some confusing results, also tested it with a calibrated Fluke at work to confirm.

Nothing live on the bike and the voltmeter is out by 0.1 volt, happy with that.

With bike running and no accessories on this grows to -0.3v at the voltmeter compared with Fluke on the batt - happy with that.

Its interesting to see how the tiger reg/rect works, idle 13-13.5v at 2000rpm 12.5v, at 3000+ rpm back to 13.5ish.  All of these measured by the Fluke across the batt.

Now the interesting bit, when I put fog lights and heated grips on the voltage drops on idle as you would expect, but when you get the bike up to 3000+rpm the voltmeter reads 14-14.5v and the Fluke across the batt reads 13.5, now I am assuming this is because the voltmeter is taking the reading from the accessory port and therefore the output of the reg/rect rather than the Fluke which is taking the batt voltage (the batt absorbing some of that voltage).

So now I know this I know that if my voltmeter is reading 12.5v with stuff on and I am above 3k rpm I probably want to be turning stuff off  :shock:  :shock:

Overall though I am happy with it, unless anyone is going to tell me I am a biff and that all of this is just rubbish  8)

[oxnsox]

My guess would be that what you're seeing on the fluke is correct. If you were to connect a scope to the battery it would also be quiet smooth, because thats what the battery is good at doing. But put the scope on the Acc. socket and it'll have a noticeable AC component due to the way the rec/reg works. Because the AC frequency will increase with RPM, the lower quality of the tank bag meter is simply averaging the ac different to the Fluke.
(looking at Mr Haines the Acc Socket is connected to the noisy rec/reg side of the bat rather than the Load, or smoothed, side)

[Sin_Tiger]

Good assesement and explanation Oxnsox

[akey]

Thanks for the explanation, sounds pretty good to me.

I only really wanted the voltmeter to give early warning of failures and it seems to work quite well at that. put the heated grips and spots on and leave the bike at idle and you can watch the voltage drop off nicely.

Just the new exhaust to go now  :D