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After a typical "Classic motorcycling experience" (which reminded me why in the last 20 years or so I've mainly ridden and bought modern Triumphs...) yesterday on a 100 mile run from which I came home on a truck...sigh...my '80 Bonnie was humming along so nicely for the first 80 miles, but then did the stop/start routine for the last 10 miles and finally coasted into my destination, a British bike day at an airfield down south in NZ. Apparently running with the lights on was too much for the whole system and the battery slowly drained. She'll start readily and idle, but won't go far up the road without cutting out.

So, my thoughts:
1. The battery is just old and stuffed and just decided to die yesterday.
2. The alternator isn't pumping enough back into it to run the motor and lights together (it started its life in the US, so lights-on spec).
2. A mysterious underlying short, wiring problem, voodoo, curse, random inexplicable act of a metaphysical being only barely perceptible to me...

My question: the battery wouldn't charge for 6 hours while in the bike, so I pulled it out and connected it on the bench, and it's reading fully charged straightaway.

Something I'm missing? - Stu, Peg, Rambo, TR7RVman?
cheers, Pat
 

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Hi DrPat, Exactly what is your charging system? All stock? Or electronic rectifier/regulator such as Podtronics etc?

What is your battery voltage after charging off bike & sitting overnight on bench?

Without some diagnosis hard to tell what is root problem(s).

If battery failed really bad, it might be cause of problems. However I expect you have a fault in charging system as well or the battery is still ok & charging system is faulty.

It's hard to properly test charging system with failed or weak battery. Known good battery is prerequisite for charging system tests. Fully charged battery will be at least 12.6v. After the battery has been fully charged. Install battery & turn on key for 10 minutes head lamp on, motor off. What is voltage?

However, a quick & dirty test is test the voltage at battery after a good road test & see what you have.

After charging your battery ride the bike several miles to warm up all electrics. Carry volt meter in you pocket. Pull over & test volts motor running all warmed very well. At least 10 miles. Just in case don't stray too far from home. Yes, I've road tested in my neighborhood for 10 miles a few times when I was afraid to go father. That's 40 times around my block!

What is voltage at battery idling head lamp off? 3000 then 4000 rpm head lamp off?

What is voltage at battery idling headlamp on? 3000 then 4000 rpm head lamp on?

Do these tests. Don't spend a penny without testing system. If you don't have volt meter that is your first purchase. Note some volt meters work fine motor off. But with motor running reading goes crazy. That meter won't work. Most quality meters work fine motor running. Doesn't have to be costly, but not bottom of the line. Often the cheapo ones don't.

I don't have wire diagram handy for 1980 Bonnie, it's on DVD which I'd have to dig out. But, hooking up charger to battery with both battery cables hooked up can damage Zener diode, depending on voltage of charger. The Zener when its voltage threshold is reached starts shutting current to ground, which can overheat & damage it. A finger on Zener when charging cables hooked up will show it can get quite hot. I've felt that a few times on different bikes. So it's best to disconnect one terminal, or remove if you choose. In bike, make sure seat can't fall down & create problems, shorts, etc.

On a side note, this is not a typical classic experience. It's just a problem that needs correcting. Overall these bikes are quite trouble free if properly assembled & maintained. Several of us ride these bikes regularly well over 100 miles often. Far from cell service too. Most have stock 2 wire alternator, rectifier, Zener. Most of us use MotoBatt MB9U battery. They have proven very reliable & long lived. If available in your area, I recommend it if you need new battery. (check your size).

Most important is do a good diagnosis best you can & correct all faults. Don't forget to check the fuse for corrosion. Also check all connectors & wiring. Visually look over all wiring for pinched/chaffed wires. Pay close attention to wires, connectors from alternator on up to rectifier, battery. Then go from there.

Don
 

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Hi Pat, Don,

'80 Bonnie
hard to properly test charging system with failed or weak battery. Known good battery is prerequisite for charging system tests. Fully charged battery will be at least 12.6v.
+1.

hooking up charger to battery with both battery cables hooked up can damage Zener diode, depending on voltage of charger.
Uh-uh:-

. Charging the battery on the bike with the rest of the electrics connected is bad practice. It's hardly difficult to disconnect and remove the battery from an OIF for charging?

. Pat's bike might or might not have a single Zener connected across the battery, attached to the airbox for a heatsink (afaict, it was during '80 the Co-op standardised on the 3-Zener strip connected to the three alternator wires). If Pat's bike does have a single Zener, one of the reasons it's fitted is to limit DC system Volts; how would it be "damage[d]" doing what it's supposed to? However, if battery-charging is attempted with it connected to the bike's electrics, the Zener can prevent the battery charging by preventing the system Volts rising high enough.

Zener when its voltage threshold is reached starts shutting current to ground, which can overheat & damage it.
. 'Original Lucas' reckoned a single Zener was capable of handling 12A~12.5A. So, if the above was really true, the charger Amps are much, much too high for the battery. Trickle-charging should be at 1/10th of the battery's Amp-hour rating - e.g. if the battery is the standard Triumph non-electric start 9 Ah, trickle-charging should be at 0.9 Ah.

make sure seat can't fall down & create problems, shorts, etc.
Again, why would anyone charge a battery on one of these old heaps when it's so easy to disconnect and remove it from the bike and that precludes several potential problems?

Most important is do a good diagnosis best you can & correct all faults. Don't forget to check the fuse for corrosion. Also check all connectors & wiring. Visually look over all wiring for pinched/chaffed wires. Pay close attention to wires, connectors from alternator on up to rectifier, battery. Then go from there.
+1.

Hth.

Regards,
 

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Hi Stuart, Charging, battery hooked up. I know it's bad practice, but.... Many do it. I used to before I knew better. On the single Zener, my experience is on my bike & a few other OIF bikes with my Sears 4A charger, when battery is low it works fine. However as battery is charged to voltage goes upwards as expected. Then Zener cuts in and begins to warm. Left overnight next morning Zener is too hot to touch with finger. Apparently air box around Zener cannot pull heat away that fast with no air flow?? I've not tested this on old finned heat sink under headlight. It might be fine??

Doing experiments riding with headlamp off on open highway motor reving near 4000 the Zener is activated. However finger on Zener shows it's warm to touch, but can easily hold finger on it. Actually hard to tell if much warmer than air box which is warmed from motor heat blowing back, but not hot.

It is my experience working with diodes if they overheat, they tend to go open circuit. I don't how hot too hot is for the Triumph Zener. Obviously mine was too hot to touch & still working ok. Or did I just get lucky??

I find with 40w incandescent headlight, tail light, at 4000 the voltage is such Zener is not activated as voltage is not high enough.

Regarding removing battery, I find it a pain for the most part. Disconnecting fuse or terminal is much easier to me. Just person preference. But... you must do whatever is needed to prevent short circuits.
Don
 

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I would try a ride with the headlight off and see how long it will run. I suspect it will keep on going. Lower wattage headlamp bulbs are available. Not sure if headlight on is compulsory but if not, consider the use of an LED day riding lamp which, on my bike, is brighter in appearance than a headlight. It will not light up the road though.
Already covered is the need to charge the battery with zenor disconnected. Battery out or at least, disconnect it from the bike. I have a rubber mat under the seat base making it impossible to contact the battery terminals.
 

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Hi Don,

On the single Zener, my experience is on my bike & a few other OIF bikes with my Sears 4A charger, when battery is low it works fine. However as battery is charged to voltage goes upwards as expected. Then Zener cuts in and begins to warm. Left overnight next morning Zener is too hot to touch with finger.
:eek: A 4 Ah charger is a car battery charger, wa-aa-ay too powerful for any lead-acid battery that'll fit any of these old heaps. As I've posted above, battery-charging should be 1/10th of a battery's rated Ah - 4 Ah is 1/10th of 40 Ah; otoh, original 12V battery fitted to non-electric-start Triumphs (all Britbikes) was 8 Ah, later 9 Ah, the popular Motobatt MB9U replacement is 11 Ah, a similar-physical-size Yuasa is 10 Ah - even the battery the Co-op put in the electric-start twins is only 14 Ah ...

Plus, even if you do charge the battery on the bike, given simply removing the fuse isolates the battery from the Zener, why wouldn't you simply do it? o_O

Doing experiments riding with headlamp off on open highway motor reving near 4000 the Zener is activated.
Normally, it's "activated" well below 4,000 rpm.

As you know, the workshop manual test for the RM21 standard '69-'78 is 9A @ 3,000 rpm; otoh, "headlamp off", either 'all lamps off/ignition only' uses about 3.5A, or 'other lamps on' uses about another Amp; the exact rpm when the Zener starts to convert excess generated Amps to heat will depend on the charge in the battery.

my experience working with diodes if they overheat, they tend to go open circuit.
True, but of what relevance is this to the OP's bike's problem? Your battery charger might(?) be OK for a Gold Wing battery but that's about it and, if you really have to charge your bike's battery without removing it from the bike, you could isolate the Zener from the charger simply by removing the fuse.

I find with 40w incandescent headlight, tail light, at 4000 the voltage is such Zener is not activated as voltage is not high enough.
Your bike has an electrical fault and/or you're confused:-

. The alternator on your bike is still the original RM21? If so, that was rated for 10.5A @ 5,000 rpm so, given the rpm/Amps curve, the alternator should be generating ~10A @ 4,000 rpm.

. Otoh, headlamp 40W = ~3.5A, ignition uses the same, standard pilot, tail, speedo. 'n' tacho. bulbs use ~1A. That's ~8A. Depending on the battery charge, the ~2A difference could be doing anything from charging the battery to being turned into heat by the Zener - you aren't going to feel 2A of heat.

. To charge the battery, Volts per cell must be between 2.3V and 2.5V - i.e. 13.8V and 15V - depending on the battery sub-type. If battery Volts are not declining during a ride, the battery must be being charged, therefore the Zener must be allowing the DC Volts to reach a value that can charge the battery.

removing battery,
Disconnecting fuse or terminal is much easier to me.
must do whatever is needed to prevent short circuits.
The main fuse should be in one single wire actually attached to the battery 'ground' terminal - battery +ve on your bike?

If this fuse is removed during battery-charging with a trickle-charger, not only will any Zener diode across the battery be disconnected, a short-circuit between the battery 'non-ground' terminal (-ve on your bike?) and another part of the bike won't be possible. (y)

Hth.

Regards,
 

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Discussion Starter #7
Don, Stuart, Rambo, many thanks for all these thoughts and discussion, really appreciate it!! I've fairly recently revamped the ignition side with coils, leads and plugs, so she's starting and running very well just around about; as I strayed further afield this problem came up but I was slightly suspicious that there was an underlying electrical fault in there, though everything checks out visually (wires are intact, insulated etc). Clearly though it's a charging circuit thing, hadn't thought about the zener, explains the battery charger puzzle, and the alternator just standard. The motor has been rebuilt by an expert quite recently I gather, but the machine hasn't been run extensively (feels pretty tight still), or (obviously) road tested in the real world - which I guess is what I'm doing.

Guess my fundamental problem is that I don't REALLY understand electrics, simple as they are (my PhD in Classics and Ancient History notwithstanding, wasn't much use on Sunday!), nor do I have a tester yet, and my approach has been to replace suspect parts and scrutinise the wiring for obvious stupidity by previous owners, and do process of elimination.

It is a pain getting batteries out to charge (the one in my recently sold Indian Scout was buried so deep that the Lord might have trouble finding it on judgement day), but might do this on the Bonnie from now on, and I'm also aware of the seat's propensity to short things - I use a rubber mat too Rambo!

Wasn't bagging Classic biking really, just laughing at myself. I had an '80 Bonnie and a TSS in the 1980s, and an 82 Tiger in West Oz in 1998-2000, which was tatty as hell compared to my present Bonnie, but gave very little trouble.
I hope to get this thing everyday running and reliable, I know it can be done, though my confidence took a hit there. I like the 'round the block 40 times' idea...

Anyway, thanks guys for the help - I appreciate it hugely, and will put it to good use!! - cheers, Pat
 

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Hi DrPat, I'm assuming your bike used to work fine with current battery & head lamp etc. Is that correct?

Sounds like you have standard rectifier & Zener. Unless you do extended city riding the original system works good enough even with headlamp on at all times. In California we were required to run with headlamp on even before laws required lamp to come on all the time key is on. I covered 30k miles with original charging system. Then I went to LED headlamp, not to cure an electrical problem, but it's brighter & much more visible to motorists. Not to cure charging faults. I've used the LED for 3k miles now & it indeed helps greatly in extended city miles.

It is a mistake to use LED lights to overcome charging faults. That is false repair, that will ultimately lead to another towing of bike.

The original Triumph charging system is very simple. Rotor, stator, these produce the electricity. Rectifier, this changes AC from alternator to DC that can charge battery. The Zener which shunts excess current to ground & turns it into heat. The Zener keeps battery from overcharging. That's it.

The battery is only to store electricity for bike to use at times when alternator cannot put out enough electricity. Of course battery is important.

To do a full test charging system you need a 1 ohm resistor of at least 100w. (Stuart has shown me 300w is better).Shop manual shows how to make this at home. I got mine from Ebay. Not very costly. You need an ammeter 0-15A. Mine is Mac tools 0-40A digital. You need a voltmeter. Mine is Extech instruments MA200 multi meter, which means it can test both volts, ohms, diodes & some other things. We only care about volts & ohms in the multi meter.

Also know good battery as discussed earlier. With a good battery & those 3 tools you can do the factory test which tests the entire charging system. Once you have the tools set up you can do the entire test in about an hour or less.

Several faults can cause your symptoms.

However, after saying all this you can learn most of what you need to know with a known good battery & a multi meter. This quick & dirty testing I suggested in prior post is simply hooking volt meter to battery + & - terminals. Red lead to +, black lead to -. Record the readings on a piece of paper. Make sure meter is set to DC.
What ever conditions the test step asked for, simply record reading on meter. For instance screen on meter might read 13.10 or maybe it will be 13.104. Read instructions on meter to set scale to volt range you want. Some are auto ranging so you don't even need to do that. Just hook up the leads with meter set to DC.

Be careful to not set to "OHM" on meter with battery hooked up. It can blow fuse or smoke meter. OHM cannot take battery power to it. OHM is used for different tests not discussed here yet.

So don't think you are electrically challenged. That is nonsense. You just haven't learned about the electrical system yet that's all. If you can hook red & black wires to battery you can do this basic test.

The voltages you get will lead to the next test or show system is working ok. Again you must have a good battery during testing.

Notice I said will lead you to next step, not tell you what's wrong. Individual component tests pin point problem area(s). Even then thoughtful use of volt & ohm meter can give clues about what's wrong without the 1 ohm resistor or amp meter. To be clear you need to have 1ohm resistor & amp meter to fully diagnose, but start with the simple voltage tests first.

Also question, following wiring up from primary case to the bullet connectors. How many wires/connectors come out of sheath? 2 or 3.

On a side note do you know exactly what head lamp bulb you have? Just out of curiosity.

Pretty much every Triumph owner will have use for volt/ohm multi meter if they have bike very long if they do their own repairs.
Don
 

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Hi Don,

Sounds like you have standard rectifier & Zener.
Don't forget Pat The OP's bike has (should have) a 3-phase alternator and rectifier. The rectifier is (should be) square with three separate 1/4"-wide AC spade terminals, the DC spade is 3/8"-wide (same as the Zener).

Standard headlamp was a 45/40 (Watts main/dip) P45t (H4 3-spade electrical connection).

Regards,
 
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