The BSA A7-A10 Forum

Technical => Lucas, Electrical, Ignition => Topic started by: Beezageezauk on 08.07. 2012 20:28

Title: Overcharging on a BSA?? You better believe it!!
Post by: Beezageezauk on 08.07. 2012 20:28
Yes, my 1958 A10 is overcharging and for the life of me I don't understand why.  Can any of you electrical Gurus on the forum suggest why and advise me of a possible cure.

Ok, the details:-

I'm on a 6volt system using the early 40watt dynamo driven by the standard chain and sprockets.  I've recently fitted a new 6v. 13AH battery, a new -8 to +8 ammeter and a new 6volt positive earth solid state regulator.  This is wired up as per the instructions with a 15 amp inline fuse fitted between the regulator and the ammeter.

Unfortunately I don't have a rev-counter so when I mention the revs it's and educated guess.

The symptoms:-


As soon as I fire the engine up the ammeter shows about a 6 amp charge at about 1500 revs??  More than this and it goes off the scale.  So I put my headlight on (6volt 35/35watt quartz halogen bulb) and I get the following readings.

30mph.    -2amps.
33mph.   compensating
40mph.    4 amps
50mph     5/6 amps.
60mph.  8 amps plus. (off the scale)

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.

The dynamo istelf is producing about 14 volts at about 3000 revs.

I've tried another ammeter and get the same readings.  I've also tried a second solid state regulator and an original mechanical type regulator and again I get the same readings.

Any suggestions guys?  Other than a sign in the garage that reads "Bang Head Here".

Beezageezauk.


Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: warmshed on 08.07. 2012 20:42
The regulator (solid state or mechanincal) limits the voltage output by the voltage it applies to the field coil.  As it happens with different regulators, this limits what the cause can be.
 If you needed to re-arange the dynamo connections when fitting the new regulator then have a look to see if you done it correctly
  It seems your field coil has an earth on one side (correct) and the other is connected to the dynamo output, tag D. (not correct.)
so,  Basically, one side of the field coil should go direct to the F tag and not touch anything else. It seems this F tag wire is touching the D tag/wire as well.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: bsa-bill on 08.07. 2012 22:05
I'll echo warmsheds comments and add a comment regarding the battery !! 13 amp/hour!! is about twice the norm, can't see it should be a problem though unless your regulator is having a tizzie fit having to deal with a battery that powerful, maybe needs a tweak
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: beezermacc on 09.07. 2012 00:18
According to my information 13 amp is about right. Original battery was Lucas PU7E, on early models, rated to 12 - 13.5 amps, BSA service sheet 805. This is confirmed in Haynes manual.

I'm interested in Beezagezauk's problem. The only time I've come across excessive charging is when the battery has been virtually dead. I can remember getting up on a cold morning and when first starting the bike seeing the ammeter swing almost to the full extent then gradually settle down to about two amps as the battery charges. Basically, because 'amps' is a measure of flow (my physics teacher used to call them 'ants' for a laugh - as he didn't have a sense of humour- but it did remind us of ants marching towards the battery), one coulomb per second and a coulomb is simply a quantity of electrons. Logically this can only occur if the battery has the capacity to accept the charge. The regulator seems a bit generous, delivering 7.75 volts but this would not account for the dramatic increase in amps. According to the information provided various regulators have been utilised, all giving the same result, so it is reasonable to assume the fault lies elsewhere. When wiring a bike up from scratch I usually wire the charging system in isolation before attaching any of the lighting leads. There are only four components, dynamo, regulator, ammeter and battery so it should be possible to identify the culprit by substitution.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: wilko on 09.07. 2012 00:28
Whatever the reason dont keep using it until diagnosed or it will throw the solder from the commutator.Disconnect the two leads from dynamo if you go for a ride.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: warmshed on 09.07. 2012 00:30
According to my information 13 amp is about right. Original battery was Lucas PU7E, on early models, rated to 12 - 13.5 amps, BSA service sheet 805. This is confirmed in Haynes manual.

13a/h at 6 volts is only half the capacity of 13a/h at 12 volts. so your battery is double the size you need. It will work fine and give you plenty of reserve capacity.

I agree also that you should not use the bike until you get it sorted, you risk damaging the Dynamo and the battery even for a short running time.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: beezermacc on 09.07. 2012 00:53
Service sheet 805 specifies 13 amp / 6v. Beezageezauk is on 6v, not 12v


....time for bed says Zebedee...........
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: warmshed on 09.07. 2012 00:56
oops, sorry cant read, but will try harder.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: KiwiGF on 09.07. 2012 02:43
Here's some thoughts/questions...

1. A 40w rated dynamo can supply around 6.7 amps at 6volts (volts x amps = watts).
2. A 6 volt 35w bulb takes about 5.8amps
3. With the engine off and your lights on does your ammeter show around - 8amps? (it should, if it is wired to show the current drawn by the lights).
4. Pointing out the obvious, your battery should gradually flatten when the lights are on. This is because there is no (or should not be) any spare dynamo capacity to charge the battery when the lights are on.
5. I'm surprised the dynamo can provide more than it's rated 40w output at its nominal 6v but your measurements indicate it can.
6. Your measurements seem to indicate the dynamo can supply the lights and charge the battery at 8 amps, which is more like 90 watts (which would surely damage it!).
6. In simple terms, if the dynamo can supply more than its 40 watt rating at 6 volts then "something" has to prevent it doing so, either:
       a. The regulator or:
       b. The total current drawn by "everything" on the bike must not (ever) exceed the dynamo rating (40 watts or 6.7 amps).        
7. The flatter the battery the higher the amps it will require from the dynamo, the "worst case" (of a flat battery) should be designed for.
8. As a battery becomes fully charged the open circuit voltage across it rises, the effect of this being it draws less amps at a given voltage.
9. It might be worth looking up the specs of the regulator to see if it (just) regulates voltage and not current drawn from the dynamo. If it does not regulate current then I guess you may have to select a battery and bulbs to ensure the dynamo does not (ever) get over loaded. I suspect you will have to downsize the headlight bulb.
10. I've heard that most of the electronic regulators available do NOT limit current, a by product of that is that it's advisable to put a fuse in the dynamo output wire as otherwise a short in the charging circuit (that bypasses the main fuse) can cause a wiring melt down.
11. If you do not want to downsize the headlight bulb it is probably possible to rig up something to stop the battery drawing current when the lights are on.

I don't think I've got things wrong but if I have I'm sure someone will correct me!
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: warmshed on 09.07. 2012 10:05
If the dynamo is rated at 40watts (early dynamo, later ones 60watts) that does not mean thats all it can supply but rather thats its design limit any greater demand will overheat and damage it, windings or solder/commutator.
The limiting device is normally the regulator, it monitors the Voltage and puts voltage to the field wire to increaser the field electromagnet which gives greater output from the rotating armature. As the voltage rises the regulator will reduce the voltage to the field therefore balancing the output to the designed maximum.

Better regulators also monitor the current preventing too higher demand from causing too high a current from being drawn. I agree with you that a large flat battery could easily draw a higher current from the dynamo than it was designed for.

I Have just re read Beezageezauk original post I think I have misread the question. He states that   "The dynamo istelf is producing about 14 volts at about 3000 revs" and this is what i was replying to. How was this achieved? with the  F and D terminals together and no regulator? if so this is correct.



If the maximum output from the dynamo with the regulator connected then 7.75 is on the slightly high side of correct. I know the DVR2 I have also gives this output and does not have a current limiting circuitry. A fully charged battery gives off 7.2volts so you should be getting a trickle charge only even without lights, don't know why it should read 8 amps I would have thought around 1amp would be right.

 KiwiGF is correct, ensure you do not load greater than the output,  Remember too that the calculations should be done using 7.2 as nominal volts not 6 volts, so try to aim for something just less than 6 amps max.  

Always wise to run the initial few miles without the headlight on, so the battery can charge up before adding headlight load.  You should think about a 25 watt headlight, a LED rear light is also a wise investment to limit load.  Whatever you do you are running at around the maximum output for the dynamo.
A later 60 watt dynamo is also worth considering, it would give that bit extra leeway.

The readings you get , "7 volts at 3000rpm with the headlight on" should mean that the dynamo is balancing out your load  (minus battery charge) with the battery at 6.19V there should be no or very little charge going into the battery as the dynamo voltage is only 0.01V greater. (as  later pointed out by KiwiGF I mis-read this as 6.91! so it will be 0.81v sorry) The ammeter should be balancing around zero.  Are you sure you have the ammeter connected correctly? a 8 amp reading at this state is incorrect.
The ammeter on the bikes are notoriously inaccurate.

Just as a check, if you switch on the headlights with the engine not running do you show a correct discharge on the ammeter, it will tell you if its wired correctly.
Sorry for not reading you post correctly in the first place but it was getting rather late.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: BSA_54A10 on 09.07. 2012 17:27
When I had my Dynamo done it worked well for a few months then packed it in.
Took it back to be told that the regulator was the wrong one or the dynamo.
Scotty whipped them both off then did the adjustments on his work bench.
The difference between not working and melting the solder was less than 1/4 of a turn.
He had a box full of armatures waiting to be rewound. not a pretty sight.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: Beezageezauk on 09.07. 2012 18:35
Thanks for your input so far guys.  At present your suggestions seem to be pointing to a fault with the dynamo and I will be having it checked out at the weekend.

But to give an update and to answer a couple of your queeries:-

The 14 volts I referred to was a test with both the F and D leads together.

When I switch my lights on with no engine running I get about a 1amp discharge on parking light and about a 5amp discharge with the headlight on.

I bought myself a 6volt 35/35watt QH bulb in an attempt to put more of a resistance across the circuit, giving me a brighter light and hopefully reduce the reading at the ammeter.....it didn't work.  The readings were about the same with the original bulb fitted.

I have a spare 60 watt dynamo which is at present being checked out.  If it's ok I'll fit it towards the weekend and then have the suspect dynamo checked.  This way I won't be without the bike.

I have been using the bike for regular short distances but riding with the headlight on and trying to keep the rate of charge below 4 amps.  Hopefully this wouldn't cause damage to any of the components.

I'll add more updates as and when I get the information.

Cheers,

Beezageezauk.

Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: warmshed on 09.07. 2012 22:48
"bought myself a 6volt 35/35watt QH bulb in an attempt to put more of a resistance across the circuit, giving me a brighter light and hopefully reduce the reading at the ammeter.....it didn't work.  The readings were about the same with the original bulb fitted."

A higher wattage gives a lower resistance not a higher one, thats how you get more watts. It will increase the load on the dynamo. The higher the wattage the lower  the resistance and the higher the current(amps)
 
"at present your suggestions seem to be pointing to a fault with the dynamo and I will be having it checked out at the weekend".

See my last post, the dynamo seems to be working fine, worth checking the ammeter wiring.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: KiwiGF on 10.07. 2012 00:29
Hi Beezageezauk, I also think your dynamo is fine (maybe better than fine, as it can generate so much power!).

The discharge of 6amps with motor stopped and charge of 8 amps when engine running probably means the ammeter is wired correctly (but it's worth checking anyway). It might also be worth checking the various load/amp readings with a multi meter however, in case the lucas ammeter is not accurate.

That will probably still leave you with the problem that the ammeter is telling you the dynamo is overloaded, and with a 35 watt headlight bulb it almost certainly is being overloaded.

A 60 watt dynamo will help. 60 watts equates to 10 amps, but that's still not enough to supply the load you are seeing of around 16 amps, so the 60 watt dynamo will also be overloaded (this assumes the regulator maintains the same voltage for both dynamos).

Dropping the bulb wattages will obviously reduce the load.

Changing the battery to one that draws less charging current will reduce the load as well, a smaller battery will probably draw less current when charging (depending on type/brand etc), but of course will discharge quicker as well.

A regulator that limits the current drawn from the dynamo to circa 7 amps (40 watt dynamo) or 10 amps (60 watt dynamo) will be the best solution, but I do not know if those are available.

I've not yet run my bike, but have bought a DVR2 and a 6ah "AGM" battery that fits inside the OEM rubber case, I have both a 40 watt and 60 watt dynamo but will fit the 60 watt.

A few months ago, using multimeters, test bulbs and a drill to spin the dynamo I adjusted my mechanical regulator "on the bench" before deciding to go the DVR2 route. The main reason for going to the DVR2 was that I found that a "feature" of the mechanical regulator is to let the battery discharge several amps through the dynamo at tickover (when the dynamo is generating less than 6 volts),

To me discharging through the dynamo seemed a "waste" of valuable battery charge that I could not afford given the smaller battery I had fitted. I think the discharge occurs to avoid the regulator constantly switching the dynamo from "engine stopped mode" to "engine running mode" - with consequent wear/tear to the switch contacts, but I could be wrong.

The DVR2 claims not to "waste" battery charge at tickover like the mechanical one, but I have not tested it doesn't! 
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: wilko on 10.07. 2012 01:38
If you increase the tension on the cutout points it will cut out sooner. That's why they're adjustable.Mine has been impeccable for 8 years.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: beezermacc on 10.07. 2012 07:47
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.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: warmshed on 10.07. 2012 16:09
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.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: KiwiGF on 11.07. 2012 00:53
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".
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: warmshed on 11.07. 2012 07:27
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.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: KiwiGF on 11.07. 2012 07:38
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
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: BSA_54A10 on 11.07. 2012 08:58
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.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: Beezageezauk on 11.07. 2012 09:55
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.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: chaterlea25 on 11.07. 2012 12:21
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
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: beezermacc on 11.07. 2012 16:31
Desperate to know how you get on with the new(ish) dynamo...... the suspense is agonising!
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: warmshed on 11.07. 2012 16:59
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.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: KiwiGF on 12.07. 2012 00:00
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?
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: warmshed on 12.07. 2012 07:44
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.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: Beezageezauk on 12.07. 2012 09:19
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.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: beezermacc on 12.07. 2012 15:17
All is well with the world...!
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: Beezageezauk on 13.07. 2012 20:59
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.
Title: Re: Overcharging on a BSA?? You better believe it!!
Post by: Guy Wilson on 27.08. 2012 16:01
is your regulator 12 volt by mistake? Sounds simple but would explain the over enthusiasm...?