Voltage Drop Correction
As the winter season approaches there will be a flurry of posts about weak batteries and starting trouble. I've been through measuring the voltage at the battery when the bike charges and wasn't really impressed with the results. Here's what i got on my bike:
Voltage at rest 12.56V
Ignition turned on: 12.17V
Ignition on + heated grips full: 11.95V
Bike running @ idle (grips off): 13.0V (rose from 12.3 up to 13 after a minute)
Bike @ 4k RPM: 13.3V
Bike @ 4k RPM + heated grips on full: 12.97V
My voltage should be up to 14V and in the winter i wouldn't really be charging the battery when using the bike. The manual states i should get 14.1V to 14.9V out of the Regulator/Rectifier (with no load on the bike, i.e. lights off etc)
I went through the diagnostics and measured the magneto wire resistance, then the resistance to earth then finally measured the voltage into the RR, i got 11.4VAC on all three lines. This is within spec. I also measured the resistance of the pickup coils and they were within spec as well. So why did i have a low voltage coming from the RR to the battery ?
I then measured the voltage drop from the output of the RR to the battery, we'd be hoping for less than 0.2V ... but i measured 0.8V drop from the +ve output of the RR to the +ve battery terminal. mmm, not ideal. I measured a 0.1V difference on the -ve circuit. A drop on the -ve circuit would suggest a bad earth point on the bike.
This voltage drop is due to the long wire run from the RR back to the battery and the cost cutting on wire thickness by manufactures. A common mod is to run a dedicated wire back to the +ve battery terminal, basically this lets the power out of the RR to get to hte battery without losses in the wiring loom. After i fitted this wire i then remeasured the voltages at the battery and got this:
Voltage @ idle: 13.5V
Bike @ idle, grips on full: 13.8V
Bike @ 4k RPM: 13.9V ** Good - this is with lights on **
Bike @ 4k RPM, grips on full: 13.6V ** Good - with lights and heated grips **
Although i'm not quite getting > 14V out of the RR i am seeing a much small voltage drop when there is load on the system and this should help the battery in the coming cold months as more charge will get to the battery.
I've been running this since May 2012 and all has been well with the better charging voltages ! Let's see how winter goes on the battery.
Note: I also pulled the fuse for the headlights (to take almost all load off the system - i've an 03 Fazer and don't have a headlight switch) and the measured voltage out of the RR was 14.1V, which is just within specification, and the RR is stated as 14.1V to 14.9V with NO LOAD.
Googling around on this shows other owners forums (triumph was one that had lengthy discussion on this). Also the very clever chap that produces the MultiGauge for the fazer discusses fitting a better RR and the voltage drops due to the wiring on the bike. We should upgrade to a more modern MOSFET RR , such as the one fitted to the 2007 R1. Models like the FH012, FH011, FH010 are common.
This is a simple Mod that may help people who have re-occuring battery / charging issues.
<< click on images to view at full resolution, then you can read the notes i added >>
The white plug will have 3 white wires (they carry the AC voltage from the generator) and a Red and Black wires which are the +ve / -ve for the battery. The RR is the black finned item under the left hand side fairing panel. If you kneel down next to the bike, you'll see it by looking up under the fairing infill panel. Warning be careful touching it as it gets hot, don't burn yourself.
By running a new wire from the RED (+ve) output of the RR we get the power back to the battery rather than losing it on it's journey through the default route. Remember to solder any joints, use heate shrink and use a ring connector for the connection to the battery.
