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Faulty charging system?

5K views 31 replies 14 participants last post by  Caulky 
#1 ·
I have a 70' Trophy with all stock charging system. Also running a Boyer ignition system. My gel battery is only about 1 year old but doesn't seem to be keeping an appropriate charge. I usually keep the bike on a trickle charger and battery reads over 12 volts when I put a volt meter on it. But after a couple of weeks of short trips around town the battery without charging in between wasn't keeping the bike running while at idle. Battery was reading about 9.75 volts at this point. A night on the charger and battery was reading over 12 again and running great. Put the volt meter on while at idle and twisted the throttle and read over 13 which (I think) tells me the rectifier is working properly and the battery should be charging. Zenor diode tests properly. Am I missing something? Are my short trips around town not enough to keep the battery properly charged? Any advice is appreciated.
 
#2 ·
I think you hit the nail on the head, at low revs you have to much being drawn from the battery to allow it to charge. With points fitted you may not have noticed it but the Boyer can be sensitive to low voltage. Nothing wrong with keeping it on the trickle charger, but a good hard ride would do it more good.

Rod
 
#3 ·
Put the volt meter on while at idle and twisted the throttle and read over 13 which (I think) tells me the rectifier is working properly and the battery should be charging. Zenor diode tests properly. Am I missing something?
The rectifier may not be working properly.It would still give you that result if it only gave 1/2 charge.If one of the 4 diodes is blown,you will get 1/2 charge.

Try testing it with the headlight on.At 3000 rpm,you should be getting about 14V.
 
#4 · (Edited)
If you are running a real gel cell battery (not AGM or Lithium) that may be your problem.
Gel batteries have a very different charging program then the usual batteries used on bikes and they also need a specialized charger. They have been typically used in the past on race bike total loss systems, but IMHO are really a poor choice for a street bike.

The AGMs work very well and lots of people use them. I am currently running a lithium-ion battery with a Typanum reg-rect on my TR6C. So far no problems since June, but it is experimental.

What is the exact information on your battery..brand name and model number? It sounds like it is rapidly self discharging which is a prelude to failure.

Start by testing your battery. Charge it up to a least 12.8 volts no load, let it sit for an hour and check it. Now let it sit for a couple of days and check it again.
 
#5 ·
Your battery is shot, buy a new one.
Get the new one tested first before taking it away.
I had two (poor quality ones) that failed the battery test.
Its worth paying a little more for a good quality battery.
If the vendor is any good he can advise you.
 
#8 ·
I need to correct myself. It's not a true gel battery, rather an AGM battery. So I don't think I've damaged it with the charger. It's Westco brand, which I consider to be a quality battery.

I have done most of the charging tests mentioned in the replies. I will perform the one or two that i haven't, but nothing thus far has given me readings of 14 volt output. If I rule out the battery (which I've replaced once before thinking it was the problem; this has been an ongoing issue for a while) I'm going to replace the rectifier which appears to be the original unit.

If I go that route, any opinions on replacing it and the Zenor diode with a Sparx regulator rectifier? I'd prefer to use the single phase (I don't know what that means) unit that looks like the Zenor diode to preserve the original look as much as possible.
 
#9 ·
It's easy to test the rectifier.You can test each diode separately with a multimeter.

The other way is to connect your battery charger to the rectifier in place of the stator leads.The battery should charge.Reverse the polarity of the charger leads,and the battery should still charge.If it charges both ways,the rectifier is OK.
 
#10 ·
<I'd prefer to use the single phase (I don't know what that means.>
Unless it's been changed yours will be single phase. A single phase alternator has 6 coils and a three phase has 9 coils. With single phase you get gaps in the output after rectification, the extra coils with three phase help to fill in the gaps.

<Put the volt meter on while at idle and twisted the throttle and read over 13>
A voltage rise generally means your alternator is charging. But do you normally ride with your lights on John? If so what is the voltage with the lights on? Normally we measure the voltage at 3000RPM.
 
#14 ·
One more thing I probably should have mentioned (and thought of). I installed a Cebie halogen headlamp a while back. Probably around the time I noticed the charging system wasn't up to snuff. I installed a relay with the headlamp, but is that enough with an electronic ignition and 43 year old stock rectifier? Maybe my real issue is I'm drawing too much juice and not providing enough to satisfy the demand. At this point I feel like I've upgraded a bunch of electrical components without upgrading the equipment that needs to supply them.
 
#16 ·
John
No1 I'd say is (assuming the multimeter is reliable) you should have greater than 12.5volt on a decent charged battery (I mean after having disconnected the charger for an hour).
If it's lower, battery is well past its best.

Zener diodes are hard to judge without test equipment, in basic multimeter tests they can say ok, but if they have started to fail in that they allow current to flow at slightly lower voltage, you won't pick up unless you've got the gear.

What will happen in that case, is that a steadily worsening case of undercharging of the battery will occur, which has a dramatic impact on battery useful life.

I have also known the other end of the scale, where the zener has gone open circuit, which caused far greater damage to other components as well.

I can't see any reason to use zeners anymore, or an old rectifier, a podtronics, boyer powerbox and others do a better job, they take the pressure off the alternator having to run at full output all the time as well.

The advantage of going to a 3-phase alternator (with appropriate powerbox) is that the amps build in a quicker curve with revs, so chugging with lights on is less of a problem.

While on the subject, I laugh at all those ammeters we have on british bikes, needle flapping from one side to the other, only true reading you get is when you switch on before starting!
Put a digital voltmeter on it, tells everything you need to know (I know that's not good for all, I am a triton owner! with freedom)
Dave
 
#17 ·
Thanks for everyone’s input. I’ve been out of town all week so haven’t been able to perform additional tests until today. I checked the battery fresh off the charger with no load and it read 13.07. After an hour there was no change. Obviously I haven’t been able to test it after a few days sitting.

I took a voltage reading with the bike running at about 3000 RPMs (I don’t have a tachometer so I ran it in top gear at 45 MPH per the manual) with the headlight on (I’m running a 60/55W H4 bulb with relay) and my volt meter was only reading about 10 volts. Even with the headlight off I wasn’t getting up to 14 volts. Keep in mind I only ride this bike around a metropolitan area and rarely get up to 45 MPH and it’s brief when I do. And I’m also using an electronic ignition.
 
#18 ·
10 volts isn't near enough. you Headlight draws considerably more than stock, but it shouldn't be that high of a draw. Check the output at 3000 with the lamp off and see what you get. Be willing to bet it still won't be above 12v.

You need to determine if the zenner has bit it, teh stator, or the regulator. Meter your 2 stator leads for A/C voltage where they plug into the harness. Should see upwards of around 9 volts A/C when running loaded at around 2500-3000RPM on each leg (white/green and green yellow wires if memory serves). If one is low, swap the leads where they plug into the harness and test again. If the low leg still reads low plugged into the different connector you either have a problem with the connection or the stator itself. If the voltage drops on the previously normal stator leg, then you have a problem with the harness or rectifier.

If you check solid on both leads, then you need to check the output going to the zener, after the rectifier before the zener. You will be checking D/C voltage at this point. If the zener is bad and shedding to ground too soon, you will read low period. In essence, you need to disconnect the output from the rectifier to the zener and check raw output through your meter to ground. There are several ways to get it done, but not sure I can acurately describe how to do so, and do not want to risk spiking your Boyer Box (bad news if ti happens). Maybe someone else can step in and describe this step. If not, I will make the attempt, but will reccomend extreme caution doing so to ensure unregulated voltage doesn't reach the Boyer.
 
#19 ·
It might be useful John to spend a few minutes checking over your charging system connections, from the alternator to the battery. Disconnect each one at a time if you can and make sure each one is good. What you are looking for is a weak connection, weak as in it's just about to break.

Charge your battery.

To test if it's the zener, disconnect it. Start your bike and measure the battery voltage. If it's now 14-16v then the zener is duff.

To check your alternator disconnect it and measure the resistance between any two leads. It should be very low, about 0.5ohm. If the resistance is very high then it is broken.

To confirm it is OK start you bike and measure the alternator voltage, still disconnected, between any two leads at 3000 RPM. Make sure your meter is switched to AC for this measurement. It should be high, 30v AC or over.

If this is OK then it looks like you have a broken rectifier.
 
#20 ·
It might even be the same problem i had.The rotor had lost nearly all its magnetism.Looked at that last of course after the rectifier,battery etc.I connected a lamp across the two alternator wires and it barely glowed.I also read up on DerryUk s alternator info which was very useful
 
#22 ·
<It might even be the same problem i had.The rotor had lost nearly all its magnetism>
Thanks for the reminder. I should have said, if the output voltage is low, you have weak rotor magnets. Allegedly if your rectifier fails it can allow battery current to flow through the stator which may demagnetise your rotor.

I tested some Lucas alternators here ... http://www.scribd.com/doc/102021181/Lucas-Stator-Log-4
 
#24 ·
So many opinions and tests etc, bet you're still trying to unravel it all!

In a nutshell, your alternator in new condition is rated at ~120W output, only delivered at high revs, say 5000 rpm. At 3000 rpm (~50 mph in top) it may only output perhaps 80-90W or so.

Your demand on the system is constant 55W headlamp, ~10W tail & sundry, ~35W ignition (not much difference EI or points) - total say 100W.

The equations don't work at those revs/speed usage, even if all the bits (alternator, rectifier, zener) are working 100%.

So if only riding <45mph in town, either do it in 2nd gear, or reduce the demand. Do you need anything more than a halogen 35W dip bulb? Use LED bulbs for tail etc.

IMHO the best solution is a 3-phase alt, with solid reg/rect, which will give the power in the rev range you are using, as it produces more max power(180W) and the output climbs in a steeper curve from tickover upwards.

3-phase uses the same alt rotor. It is unlikely that your rotor has signifiantly lost its magnetism, unless it has been seriously shocked with a hammer or stored in isolation (not inside the stator).

Even if you elect to keep the single phase alt, don't waste your time with zener/rectifier, use appropriate reg/rect box.

Dave
 
#25 ·
I test charging systems every week on a variety of bikes. I cannot stress the importance of checking your battery. If your alt and reg/rect aren't working correctly you can easily ruin an AGM battery. When you put in the new components the bad battery can cause your new components to fail because of increased duty cycle.

Charge your battery. Let is sit for a little over an hour. You need to see 12.8 volt minimum. Better yet, take it down to your local shop. Most of them are now equipped with a computerized battery tester.

I like to use an automotive zero-center type ammeter (not the POS one in the headlight). You can then observe the rpm when the battery goes into positive charge.

If your system checks out good, take the bike out for at least an hour ride and check it again while it is still hot. Both alt and reg/rects can fail after getting hot.
 
#26 ·
<At 3000 rpm (~50 mph in top) it may only output perhaps 80-90W or so.>
Dave I tested a stator that I think is like John's and it gave 129W output at 3000RPM.

True that when unloaded the alternator will double it's output when you double it's speed, see http://www.scribd.com/doc/116748386/Testing-Lucas-Alternators but when loaded the curve flattens off and you don't get a lot of increase above 3000. I wonder if this is why Lucas seemed to choose 3000 RPM for testing or was it just to keep the noise down!
 
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