Charging issue - high revs equal low volts??

Post Reply
BlackIP2
moderator
Posts: 76
Joined: Thu Jan 12, 2017 1:32 am

Charging issue - high revs equal low volts??

Post by BlackIP2 » Wed Jun 26, 2019 5:03 pm

Having finally resolved my fuel leak after rebuilding the carbs once, but the petrol tap six times and then reverting back to its original diaphragm, I now have a bizarre charging problem in that as revs rise the volts drop off.

The standard (I assume) Kokusan alternator is on my IP2, along with the XJ Yamaha/Commander regulator/rectifier, fitted at the front of the bike in the open air to help cooling. I have had to fit a Lithium-Ion battery due to reduced space in the battery box. It's the recommended replacement for the standard 14ah battery but physically smaller. It shows 13.7v at the terminals with everything off and this also corresponds to the reading on a digital voltmeter I fitted (to ensure it does not get over-charged) when the ignition is turned on.

At tickover, after a few minutes the charging system goes up to 14.8v and stays there. Even with the sidelights on it holds 14.1v at tickover.
Sidelights and charging.jpg
When riding the bike it charges at a steady 14.4v with no load and 13.4v with sidelights, but as the revs rise beyond 3,500, the voltage starts to drop. However, the real problem starts when the headlight is on as it drops to 12.4v and as the revs rise the charging light comes on as it dips below 12.3v. Applying the brake lights and indicators also registers a corresponding drop of about 1 volt on the gauge.

I thought I’d cracked the problem after the last time I rode it back from my local branch meeting in the dark with the charging light on almost all the way home, when I discovered two of the alternator wires were almost broken off at the connector to the main wiring harness. I made up a new connector, soldered all the joints and thought that was it.

Unfortunately, today’s ride proves it’s not as simple as that. Any suggestions please?
Cheers
Mark
You do not have the required permissions to view the files attached to this post.

Clive603
moderator
Posts: 10
Joined: Mon Oct 15, 2018 9:42 pm

Re: Charging issue - high revs equal low volts??

Post by Clive603 » Wed Jun 26, 2019 6:19 pm

Had similar issues with my second Commander. But not as bad.

First fix was a new section of wiring loom running direct from the alternator to th regulator and then to the battery. Which seemed to work for a while.

Next try was an aftermarket "improved" regulator which made less than no difference. Improved in this case missing the "dis" on the front as in dis-improved. Something regrettably all too common around the aftermarket where folk are better at the sales pitch than the engineering.

Third try was to re-make the multiple earth ring connector hooking onto one of the bolts holding the right hand transfer port casting to the frame. Which seemed to work well enough.

Hafta say I'm no fan of permanent magnet alternators with power waste regulators. The devices are not quite as simple as they seem and high, unbalanced, currents can affect the interaction between magnets and coils. Something Lucas tried to use in the early 6 volt versions of their 6 coil system where 4 coils were shorted together in the daytime running condition with no lights on. The heavy current in the shorted coils interfered with the magnetic circuit reducing the output of the remaining two, working coils so the battery didn't boil. With pilot lights on the short was removed releasing a bit more power for the lights. Which all worked about as well as, or not as well as, you might expect. I'd be unsurprised if the Kokusan alternator systems proved to be capable of similar tricks under obscure fault conditions once the revs got high enough to generate overload level currents.

One day I shall get round to sorting a car type alternator conversion for mine. But I said that about 6 weeks after buying my first one in 1989 (I think!).

Clive

johnbirchjar
moderator
Posts: 1230
Joined: Sat Mar 07, 2009 11:20 pm

Re: Charging issue - high revs equal low volts??

Post by johnbirchjar » Wed Jun 26, 2019 11:08 pm

Sounds like it your R/R could be on the blink.
I expect you have checked all the Earth Wires are good?
Although the Kokosan alternators are pretty bomb proof,mine went on the blink on the Commander and I had to have it re-wired,(but my syptoms were nothing like yours,it just stoped charging exclaim)no real answeres, just food for thought,good luck,J.B.

User avatar
Richard Negus
moderator
Posts: 948
Joined: Mon Jun 18, 2007 5:11 pm
Location: Wilds of Lincolnshire

Re: Charging issue - high revs equal low volts??

Post by Richard Negus » Thu Jun 27, 2019 8:44 am

BlackIP2 wrote:
Wed Jun 26, 2019 5:03 pm

The standard (I assume) Kokusan alternator is on my IP2, along with the XJ Yamaha/Commander regulator/rectifier, fitted at the front of the bike in the open air to help cooling.

Mark,
As JB has mentioned, more often than not it's a fault in the earth wiring that causes charging problems. When you relocated the regulator, did you also add a decent ground wire, preferably back to the battery -ve?
R.
Slower slower, no faster faster - the joys of old fogey mode to hooligan mode at the flick of a switch

BlackIP2
moderator
Posts: 76
Joined: Thu Jan 12, 2017 1:32 am

Re: Charging issue - high revs equal low volts??

Post by BlackIP2 » Thu Jun 27, 2019 5:46 pm

I think I might have solved it - or at least know where to look next.
I checked for earth continuity between the rectifier and battery -ve and it's fine, but to reinforce it I have added a separate lead.
The same readings are showing as before.
Then I thought it worth double checking what was actually happening at the battery, so I put a voltmeter across the terminals and it showed 13.7v with the ignition on, the same as the digital one on my dash. But lo and behold, when I put the lights on, the dash mounted display dropped, but the readings across the battery stayed the same!
I reckon I have wired the digital volt display (and the LED charge light) into the wrong feed, so that's what I'll look at next and report back.

BlackIP2
moderator
Posts: 76
Joined: Thu Jan 12, 2017 1:32 am

Re: Charging issue - high revs equal low volts??

Post by BlackIP2 » Fri Jun 28, 2019 4:12 pm

This is proving to be tricky. The charging system appears to be working at the battery end, which is probably the most important bit, but the warning light and digital voltmeter within the wiring loom say otherwise, which isn't too bad but annoying as they should really tally with the battery and defeats the object of having fitted them in the first place.
I tried the voltmeter on one of the wires going to the battery from the fusebox, thinking this would give a more accurate reading of what is happening at the battery. However, the main ones are all live even with the ignition off, and when I tried the ones that weren't, they showed the same symptoms of the volts dropping off even though the multi-meter across the battery terminals shows the volts rising.
With the knowledge that the battery is being charged by the engine I can continue to ride it, but I obviously need to delve further into this as there is obviously at least one duff connection somewhere and/or a dodgy earth. I'll also check the alternator and reg/rectifier too.
I don't suppose it helps that having had a closer look at the wiring loom I can see wires have been chopped off and taped up, which suggests it's still got the original police spec wiring loom on it, so God knows what other horrors are in there!

Clive603
moderator
Posts: 10
Joined: Mon Oct 15, 2018 9:42 pm

Re: Charging issue - high revs equal low volts??

Post by Clive603 » Fri Jun 28, 2019 10:11 pm

If you have some doubts as to the quality of the original loom probably the best fix would be to make a complete new set of wiring for the charging and metering system running direct to the battery. Dunno how your warning light works but if its anything other than a simple equipotential system I'd leave it off and rely on the voltmeter.

I've done this a few times when folk have bought intractable electrical problems on elderly or messed around with vehicles to me and its proved effective. Life is too short to go hunting dodgy splices or three parts broken wires in the middle of a loom.

Clive

BlackIP2
moderator
Posts: 76
Joined: Thu Jan 12, 2017 1:32 am

Re: Charging issue - high revs equal low volts??

Post by BlackIP2 » Sat Jun 29, 2019 7:54 pm

I agree Clive. I was going to do a full rewire over this next winter anyway even before I saw how bad the harness was, but looks like I will need to do something sooner.
Regarding the warning light, I added it before the voltmeter, as the XJ/Commander reg/rectifier on my IP2 does not have any warning light wire. It was from Improving Classic Motorcycles (https://www.improvingclassicmotorcycles ... oducts.htm) and can recommend it for anyone else who does not have a charging light. The guy who runs it, Graham Blighe, is very helpful too.
Cheers
Mark

Anthony Duffield
moderator
Posts: 155
Joined: Sun Aug 11, 2013 8:13 am

Re: Charging issue - high revs equal low volts??

Post by Anthony Duffield » Sun Jun 30, 2019 7:45 am

Mark,

An issue that my Commander and from what I can determine most others suffer from is volt drop between the fuse block and a 12 volt + that can be found in the harness at front of the bike.

There are modifications detailed on this forum whereby a relay is used with additional direct connections from the battery to ensure that when all the lights are on and the headlight is on full beam there is still 12 + volts at the headlight.

After fitting a voltmeter to my Commander I noticed that with just the daylight running lights on and with engine speed above tick over the new voltmeter showed a normal reading of 13.5 volts, switching on the lights and with full beam the volt meter dropped to 11.5 and with the rear fog lights on it dropped to below 10 volts, checking directly at the battery I found a normal 13.5 volts.

I have a background in electrical engineering so checked for bad earths and poor connections, not finding any obvious problems I checked the readings from the new analogue meter I had fitted with my Fluke digital meter confirming my suspicions that there is considerable volt drop inherent in the harness of my Commander.

My Commander is not a show piece, I have owned it for a number of years having covered many thousands of miles I live in Aberdeen and so far this year have used it to visit the IoM and the NOC International Rally in Holland.

Your original post is similar to my findings:

When riding the bike it charges at a steady 14.4v with no load and 13.4v with sidelights, but as the revs rise beyond 3,500, the voltage starts to drop. However, the real problem starts when the headlight is on as it drops to 12.4v and as the revs rise the charging light comes on as it dips below 12.3v. Applying the brake lights and indicators also registers a corresponding drop of about 1 volt on the gauge.

The difference being “but as the revs rise beyond 3,500, the voltage starts to drop” if this happened on my bike I would suspect high resistance (bad connections) between the alternator the regulator/rectifier and/or poor earth connections or the regulator/rectifier itself, from your subsequent posts it seems that you did find poor connections in the alternator output leads, however the problem persists.

My advice would be to remove or ignore the charging light and to connect the digital volt meter direct to the battery terminals (you may want to include a 1.0 ampere fuse in the + lead) take the bike out for a good run and if the volts drop off when the engine is running at speeds above 3.5k try changing the regulator/rectifier.

I hope the above helps.

Tony

BlackIP2
moderator
Posts: 76
Joined: Thu Jan 12, 2017 1:32 am

Re: Charging issue - high revs equal low volts??

Post by BlackIP2 » Sun Jun 30, 2019 10:17 pm

Tony.
Yes, very useful, thanks very much and it's reassuring that it's not just my bike.
Having checked all the earths they seem fine. I was toying with the idea of feeding the voltmeter directly from the battery anyway, which I will now sort out.
The other thing I thought might be a cause is if the leads from the alternator might be frayed or breaking up nearer the engine - ie, out of sight, but I will try the easier stuff first.
Cheers.
Mark

BlackIP2
moderator
Posts: 76
Joined: Thu Jan 12, 2017 1:32 am

Re: Charging issue - high revs equal low volts??

Post by BlackIP2 » Fri Jul 05, 2019 5:21 pm

I have now wired the digital voltmeter direct to the battery, with fuse, and taken the bike out for a run.
At tickover it first shows 13.4 volts and quickly rises to 14.7 volts, and then stays between 14.4-14.8 volts riding along with no load. Side lights drops it down to 13.8 volts and with the headlamp on it drops to 13.4 volts. When revving past 3,500 the meter shows 13.4/13.3 volts, but it always rises as the revs drop. As there is no big drop as shown previously when the volt meter was wired through the harness, I am confident the charging system is working and putting 13+ volts into the battery at any time. The rewire can now wait till the winter.
With the volts being 14.7 at tickover, I assume this is a legacy from the bike's police origins in needing a high charge rate when the bike is left ticking over at the side of the road with lights and sirens on?
The other thing I noticed today, perhaps down to simply watching the tacho more, is an intermittent odd reading on the tacho. When slowly building up revs, as it gets to around 3,500 sometimes the needle swings back down to zero and wavers, then as soon as the throttle is rolled off, it picks up again. As my tacho is wired into one of the alternator wires, I wonder if this might be a sign that there is indeed a fault in the alternator wiring nearer the engine? I couldn't see any correlation between the tacho needle dropping down and the voltmeter reading changing. Perhaps it could simply be a dodgy tacho.
Anyway, thanks to you all for the advice. I can now hopefully put some more miles in this summer without worrying about the battery, then have a closer look at tackling the other bits during the winter rebuild.
Cheers
Mark

User avatar
Richard Negus
moderator
Posts: 948
Joined: Mon Jun 18, 2007 5:11 pm
Location: Wilds of Lincolnshire

Re: Charging issue - high revs equal low volts??

Post by Richard Negus » Fri Jul 05, 2019 6:27 pm

Hi Mark,
Tacho wired into the alternator means it's either a Veglia (says 'Made in France' on the face), or the Motometer replacement ('Made in Germany').
Early examples of the latter, with a round terminal block on the back, were prone to the sort of needle flutter you're seeing. Later ones have a rectangular plastic block on the back and are less prone to this fault.
R.
Slower slower, no faster faster - the joys of old fogey mode to hooligan mode at the flick of a switch

BlackIP2
moderator
Posts: 76
Joined: Thu Jan 12, 2017 1:32 am

Re: Charging issue - high revs equal low volts??

Post by BlackIP2 » Fri Jul 05, 2019 9:31 pm

Thanks for that Richard.
Mine is the French one so I guess I will just have to live with it.
Cheers
Mark

User avatar
Richard Negus
moderator
Posts: 948
Joined: Mon Jun 18, 2007 5:11 pm
Location: Wilds of Lincolnshire

Re: Charging issue - high revs equal low volts??

Post by Richard Negus » Fri Jul 05, 2019 10:51 pm

Mark,
If you've got a Sparkrite ignition unit with a single yellow wire not connected to anything, or a MiniMag ignition, and a deep pocket, Andover have stock of the later Motometer, part no. 55.0569.
If you haven't got either of those ignitions, you're stuck with the old Veglia.
R.
Slower slower, no faster faster - the joys of old fogey mode to hooligan mode at the flick of a switch

BlackIP2
moderator
Posts: 76
Joined: Thu Jan 12, 2017 1:32 am

Re: Charging issue - high revs equal low volts??

Post by BlackIP2 » Sun Jul 07, 2019 9:35 pm

Yes, mine is still on the Sparkrite system and now I know what that loose yellow wire is for. However, as you say, deep pockets needed for stumping up almost £160 to replace the tacho from AN, but as it only occasionally stops working I can live with that so in the meantime I will keep an eye out for a used one instead.
Thanks again Richard.

Post Reply