New reg/rec - Odd voltage

[Welshguzzi]

I've just installed an Electrex RR51 reg/rec on the V11 Le Mans. Voltage readings before/after are:

 

Ignition off  12/12.3

Ignition on   12/12.3

Ignition on, engine at idle  13.5/14.4 (with lights on, about 1V lower)

Ignition on, engine at 4000rpm  13.5/13.5

 

I'm really confused by the voltage drop with the new reg/rec at 4000rpm

 

The unit was originally bought for my old 900SS bevel but never fitted, but general opinion is that it's OK to fit to the V11 (tried asking Electrexworld but they weren't very helpful......)

 

Any ideas as to why I'm getting these anomalies? Assumed that the voltage would climb from 13.5 at idle up to 14.5ish at 3000 - 4000 rpm

 

The reason I changed the reg was that I was getting varied reliability - had to be trailered home once, and then a subsequent trip, i only just made it home from a similar distance (engine died in outside lane of motorway , also stalling at lights and occasional misfire. General opinion was that the fault possibly lay with faulty charging.

[docc]

Ignition on, engine at 4000 rpm with lights on: 13.5?

 

In other words, (lights on), no change from idle to 4000 rpm?

[Welshguzzi]

No, sorry, didn't make it very clear - at idle, with lights on 13.5V, at 4000rpm I get 12.5V

Not what I was expecting.....

 

Just to put more detail in there: Electrex recommend direct connection of the positve and earth directly to the battery. I originally tried just to use the same connections as the OEM R/R but couldn't get the charge light to work. Apart form the wierd output at the battery, the bike seems to run OK. In fact, cranking speed seemed slightly higher when I fired her up.

 

I'm going to re-run the checks again today and get some more accurate readings, but I don;t know if this will help.......

[AndyH]

Careful with these Electrex reg/recs: we've identified a tendency to leak a trickle and flatten the battery if the bike is not run for a couple of weeks. Just had that problem yesterday when I tried to start the bike and forgot to keep on trickle charge.

 

If you follow their recommendations and run a fat red wire straight back to the battery, rather than using the standard V11 loom red wire, add a large 30 amp blade fuse holder into the line (as you should anyway) and pull the fuse when you leave the bike standing.

[Welshguzzi]

Thanks Andy - I've heard similar....

 

Any ideas about the wierd 'inverted' output?

[AndyH]

Have you tested the alternator output AC? I had problems with AC voltage output only when the engine was warm and was not getting sufficient charge to the battery at higher revs, sounds a bit similar. Not exactly the inverted readings you report though.

[Welshguzzi]

OK, got some more accurate numbers now:

 

Ignition off, engine off      11.97V

Ignition on, engine off      12.3V

 

Engine idling (1000rpm)  14.5V

Engine idling, lights on     12.6V

 

Engine @ 4000rpm           14.3V

Engine @ 4000rpm (lights on)     14.2V  

 

So it behaves as expected with the lights on, but not with the lights off.

Sadly, my complete lack of knowledge of electronics means that I can't explain this but out there are greater minds than mine and I summon the powers of the forum!

 

BTW the engine is definitely cranking more freely now when I hit the starter button

 

Edit: I guess with these numbers the alternator is probably OK...... or maybe not?

[docc]

Hey, your numbers look great with a couple exceptions:

 

I would say an AGM battery at 11.97 is totally flat; should be 12.84 full charged. What's odd is your voltage comes up to 12.3 when the lights come on (?)

 

Also, the Veglia tach in notorious for reading higher than actual rpm. Mine is off 300 rpm and I've seen them high by as much as 500 (the only way to check is by reading what the ECU is getting from the crank sensor using a software interface). In that case, your 1000 rpm indicated idle might be 700 or even lower which will not make for decent idle voltages.

 

So, a couple things to consider:

1) For sure those are your key off/key on voltages and not reversed?

2) Give your battery a proper AGM charge which may require bringing the charge voltage to 15.5 with higher amperage than a typical  1 or 2 amp "trickle charger."      Then recheck voltages.

3) Make sure you have a true 1150 rpm idle (I like mine a little higher yet, but "YMMV") You could simply watch the voltage as you open      the throttle until the tach needle is about halfway between the 1000 and 2000 marks.

[docc]

Welshguzzi, I see I had assumed when you turned your ignition on the lights came on with it (US bikes do), but your posted engine off (key off/ key on) voltages may be without the headlamp (?)

[Welshguzzi]

I rechecked the ignition off voltage - actually 12.2V, not sure where I got 11.97.......

 

I'm going to try hooking up the charger tomorrow night as I've been tinkering with the electrics for a few days and the battery may be a bit drained.

 

Thanks for all the help so far

[docc]

Here are some benchmark voltages on a known good battery, a 3 1/2 year old Hawker PC545 having covered 16,500 miles. The Sport had been sitting three weeks at 56˚F/14˚C. All these voltages are at that temperature:

 

Key off - 12.7 vDC

Key on with bright light after 3 minutes -  12.0

Recovery after 3 minutes - 12.6

10amp charge - 14.5 > 15.6 in 2 minutes

Then 2 amp charge -  14.0 > 15.6 in 2 hours and 50 minutes.

Residual voltage after two hours -  13.0

 

This is just a battery/charging summary and does not involve the bike's on-board charging system.

[Welshguzzi]

Thanks docc,

I've no idea how old the battery is - it's actually a Moto Guzzi one and as the bike is 11 years old, almost certainly not the original. I'll put it on charge and see what happens.

 

Only once has it not started the bike so far so my guess is that it's not completely shot....... but may be the cause of the glitches I've had.

[Kiwi_Roy]

Ignition off, engine off      11.97V

Ignition on, engine off      12.3V

 

Where and with what are you measuring those Voltages?

Directly across the battery terminals or at some point in the loom

Or just have them backwards perhaps?

 

The others seem pretty normal, I like the direct connection to the battery, much better than the OEM

 

http://www.electrexworld.co.uk/acatalog/RR51-ducati.pdf

 

It might be worthwhile to check the coil connection to the yellow wires, I found one of mine just hanging by a strand.

[Welshguzzi]

After 2 hours on the charger I now have 12.7V. Will check for any leakage tomorrow. Waterproof fuse holder ordered!

[docc]

 

It might be worthwhile to check the coil connection to the yellow wires, I found one of mine just hanging by a strand.

 

Roy, by this you mean the yellow wires coming from the stator underneath the alternator cover at the bottom of the stator coils?