Overcharging on a BSA?? You better believe it!!

[beezermacc]

I still think the best thing to do is wire the charging system independently of everything else and substitute components until it works! The 40 Watt dynamo is definitely behaving strangely as I've never heard of a short dynamo producing so much juice unless somebody has been tinkering with it, so I would start by substituting a known good E3L, though I also have some suspicions about the battery. In my experience some of the solid state regulators are quite sensitive to battery condition and are prone to register unusual readings on the ammeter even though the system is working fine.

[warmshed]

With the dynamo supporting the headlamp and tail lamp the total is about around the dynamo's maximun output of 40 watts.  With as you say, the battery being 6.19 volts and the dynamo giving 7 volts at 3000rpm, there is no way more than a tiny trickle is going into the battery. I would bet on zero.  It does mean that the dynamo is working at its maximum 40 watts so a 60 watt or small headlamp bulb would be best..  

The indicated reading of 8 amps charge is the thing that's incorrect, so either the ammeter is faulty or your wiring is. It is impossible to deliver 8 amps (or any current) to a battery that is the same voltage as the charge voltage.

On my Velo I was getting a healthy charge indicated on the ammeter at around 3Krpm even though I found out my alternator belt has snapped. The vibration affected the ammeter.

[KiwiGF]

Hi Warmshed, sorry to question your post but Beezageezauk said in his original post

"The voltage across the battery measures 6.19 volts with no engine running, 7.75 volts at about 3000 revs with no lights on and 7volts and about 3000 revs with the headlight on.  It doesn't rise higher than this when I rev it".

So I think Beezageezauk has not said the dynamo is giving 7 volts. Beezageezauk has said the battery is at 7 volts, and I reckon the battery will be taking quite a few amps at that voltage, as that is 0.8 volts above its static voltage. According to the ammeter readings observed it could be taking around 7 amps, which to me sounds sounds unlikely but putting an ammeter in the battery lead would reveal all.....  

My 6ah AGM battery has a static voltage of 6.5 volts when fully charged. When fully charged and being "over" charged at 7 volts it takes 1 amp.

As an aside, I've noticed some electronic multi meters do not give accurate readings when a DC voltage or current is "fluctuating". Depending on the regulator there could be significant fluctuations in the volts being applied to a battery by a regulator, so one should view any measurements made with a multimeter with "caution".

[warmshed]

But he said his battery voltage is 6.19v and at 3000rpm the voltage with headlights on is 7 volts and does not get higher, How can the battery be taking any charge? the difference is 0.01volt. the only draw is the 40watts or so from the lights.

Without the lights I agree the battery may well be taking a few amps but as the battery voltage will rise quickly to 7.2 volts, the nominal charged value of a good battery, (this is correct and not overcharged) you still only have 0.5 volt higher voltage from the dynamo so again you should only be reading max 3 amps. certainly less than 40 watts and no other load. In this state the current would quickly drop to just a trickle.

[KiwiGF]

Hi warmshed, 7-6.19=0.81volts, the battery will be charging at several amps at 0.81 volts over it's static voltage, especially if it is low on charge.

7-6.99=0.01volts

[BSA_54A10]

And one from left field.
Are you believing that your amp meter is accurate ?
have you tested the system with a better amp meter ?
Chances are the original unit is duff.

[Beezageezauk]

Hi again fellas.  I appreciate the input from all of you.

I've now done as Beezermacc suggested and disconnected the wiring harness and rigged up the following:-

The D and F leads from the dynamo to the Voltage Regulator.  The power lead from the regulator to an independant ammeter (one from another bike that I know is working properly) and the other side of this ammeter to the negative side of the battery.  The earth lead from the regulator to the +ive side of the battery.  Guess what!!!.....no difference in the ammeter reading.

I then rigged up my other voltage regulators (one solid state and one mechanical) and got the same ammeter readings from both of them....off the scale at about 2000rpm...but only fired the bike up for about 5-10 seconds.  I couldn't check a reading with the lights on because the harness was disconnected.

Ok, my 60watt dynamo has now been checked out and appears to be in good working order so I'm hoping to get that back today.  Changing the dynamo is the only test I haven't done so I'm now looking forward (apprehensibly) to seeing if this will cure the problem.

Watch this space.

Beezageezauk.

[chaterlea25]

Hi Beezageezauk,
Are you sure the wiring to the ammeter is correct? (bike loom)
wiring up as you have just done will show only the dynamo output
Have you tried another battery?
Another possibility is that the D and F connections are touching / shorted together inside the dynamo end cover
Dissconnect the F connection and see if the dynamo still charges?? this would show that D and F are touching inside the dynamo

HTH
John O R

[beezermacc]

Desperate to know how you get on with the new(ish) dynamo...... the suspense is agonising!

[warmshed]

KiwiGF, I dont think you read my post

KiwiGF quote" the battery will be charging at several amps at 0.81 volts over it's static voltage, especially if it is low on charge."


I Posted "Without the lights I agree the battery may well be taking a few amps but as the battery voltage will rise quickly to 7.2 volts, the nominal charged value of a good battery, (this is correct and not overcharged) you still only have 0.5 volt higher voltage from the dynamo"   7.75V dynamo with 7.2V battery at this stage is 0.55V, ok I was guilty of rounding it up to 0.5V, no real significance there.

A 6volt battery freshly charged can give 7.2 volts, falling quite quickly to 7 volts if left a short while.  

KiwiGF quote "Hi warmshed, 7-6.19=0.81volts,"  is it????


Back to the problem,
Beezageezauk quote
"The D and F leads from the dynamo to the Voltage Regulator.  The power lead from the regulator to an independant ammeter (one from another bike that I know is working properly) and the other side of this ammeter to the negative side of the battery.  The earth lead from the regulator to the +ive side of the battery.  Guess what!!!.....no difference in the ammeter reading".

Right, wiring it up that way you are reading the dynamo output, so removing any doubt about the wiring.  As Your headlight is 35watt, add to your rear light  at 5 watts  do you have a pilot bulb?   this will equate to 6.6 amps at 6 volts   (40Watts divided by the voltage to give the current) and dependant on the voltage that the rating of the wattage of the bulb is made. If at 6 volts it should be as said, 6.6 amps, If so 7 volts will put the total current up about 16% getting up to your indicated current. To this you will need to add any charge into the battery (minimal)


However this is different to what you got according to the original post, you said with the Headlights on  (your 6-8A as just calculated),  you also got a 8 amp charge showing, this would equate to double the output you show when connecting the charging circuit separately. Your wiring or ammeter is faulty.

Sorry if I my post is not too clear its difficult to when trying to make non ambiguous.

[KiwiGF]

Hi Warmshed, I'll let someone else confirm/deny whether 7-6.19 is 0.81. Nuff said on that.

Beezageezauk, I think Chaterlea/John is onto something with the possibility that the Field and Armature are somehow connected together inside the dynamo. This would most likely prevent the regulator being able to do it's job and cause the overcharging behaviour observed.

From memory the resistance of the field (F terminal to earth) is around 3 ohms (there must be a Lucas service sheet on the E3x dynamo's?). The resistance of the armature is much lower than 3 ohms, so as well as the check John suggested a resistance check of the F terminal to earth would also indicate a possible problem with the internal wiring.

I realise the dynamo has been checked out but you never know.....

If the field resistance is much less than 3 ohms the regulator may get damaged due to a current overload? No telling what a damaged regulator would then behave like?

[warmshed]

KiwiGF yes You are quite right, I read it as 6.91 not 6.19 my appologies, must be dyslexia. I deleted it from the above post so as not to confuse others.
 So yes it will take an amp or two. but certainly not 8 amps, dynamo is acting correctly though being over stretched until the battery is fully charged. this is due to there being no current limiting device in the regulator.
 His remote ammeter shows correctly at around 8 amp, 6+amps for the lights plus the charge to the battery. You need to wait a while with the engine running  to bring up the battery before using the lights if you have a 40watt dynamo with a 35watt headlight, better to get a lower wattage one. 

The regulator will still be trying to get up to its calibrated voltage with its output being pulled down to 7 volts by the load. so it will still be trying to be powering the field coil, so may not be a f-d fault.

everything seems to be working correctly, (though overstretched) except your 8 amps charge reading on the bike ammeter with the lights on.

[Beezageezauk]

Again fellas thanks for all of your input.

I've now fitted my spare dynamo and all is well with the charging rate being what you would expect.  Who would have thought that a process of elimination would be required for this?

The suspect dynamo is now being checked out and I will report back with the results.

At this point I will mention my main concern.  I don't mind running the bike with no charge on home territory but I will shortly be riding to Sweden for the BSAOC International Rally where I will need daytime running lights.  However, I can now get into the habit of riding with daytime lights at home.

Beezageezauk.

[beezermacc]

All is well with the world...!

[Beezageezauk]

Hi again fellas,

Here is the update as promised.

As expected the inspection showed that an internal fault had developed within the dynamo and there were some signs of slight overheating but nothing too serious.  It has now been repaired and tested so I'll pick it up tomorrow and it can sit on the shelf as a spare.

Thanks again to all the knowledgeable members who helped.

Beezageezauk.