Author Topic: Overcharging on a BSA?? You better believe it!!  (Read 5364 times)

Offline Beezageezauk

  • N.E. England
  • Resident Legend
  • *****
  • Join Date: Mar 2006
  • Posts: 669
  • Karma: 20
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.



Offline warmshed

  • A's Best Friend
  • ***
  • Join Date: Jul 2012
  • Posts: 161
  • Karma: 5
Re: Overcharging on a BSA?? You better believe it!!
« Reply #1 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.

Online bsa-bill

  • Wise & Enlightened
  • *
  • Join Date: Mar 2006
  • Posts: 5473
  • Karma: 64
Re: Overcharging on a BSA?? You better believe it!!
« Reply #2 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
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline beezermacc

  • Wise & Enlightened
  • *
  • Join Date: Dec 2011
  • Posts: 1010
  • Karma: 39
  • Not for the purist!
    • Priory Magnetos Ltd.
Re: Overcharging on a BSA?? You better believe it!!
« Reply #3 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.
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

Offline wilko

  • Resident Legend
  • *****
  • Join Date: Mar 2010
  • Posts: 681
  • Karma: 4
Re: Overcharging on a BSA?? You better believe it!!
« Reply #4 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.

Offline warmshed

  • A's Best Friend
  • ***
  • Join Date: Jul 2012
  • Posts: 161
  • Karma: 5
Re: Overcharging on a BSA?? You better believe it!!
« Reply #5 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.

Offline beezermacc

  • Wise & Enlightened
  • *
  • Join Date: Dec 2011
  • Posts: 1010
  • Karma: 39
  • Not for the purist!
    • Priory Magnetos Ltd.
Re: Overcharging on a BSA?? You better believe it!!
« Reply #6 on: 09.07. 2012 00:53 »
Service sheet 805 specifies 13 amp / 6v. Beezageezauk is on 6v, not 12v


....time for bed says Zebedee...........
Priory Magnetos Ltd - A10 spares, magneto and dynamo refurbs. www.priorymagnetos.co.uk

Offline warmshed

  • A's Best Friend
  • ***
  • Join Date: Jul 2012
  • Posts: 161
  • Karma: 5
Re: Overcharging on a BSA?? You better believe it!!
« Reply #7 on: 09.07. 2012 00:56 »
oops, sorry cant read, but will try harder.

Online KiwiGF

  • Last had an A10 in 1976, in 2011 it was time for my 2nd one. It was the project from HELL (but I learned a lot....)
  • Wise & Enlightened
  • *
  • Join Date: Feb 2011
  • Posts: 1469
  • Karma: 12
Re: Overcharging on a BSA?? You better believe it!!
« Reply #8 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!
New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife)

Offline warmshed

  • A's Best Friend
  • ***
  • Join Date: Jul 2012
  • Posts: 161
  • Karma: 5
Re: Overcharging on a BSA?? You better believe it!!
« Reply #9 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.

Offline BSA_54A10

  • Wise & Enlightened
  • *
  • Join Date: May 2008
  • Posts: 2025
  • Karma: 32
    • BSA National
Re: Overcharging on a BSA?? You better believe it!!
« Reply #10 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.
Bike Beesa
Trevor

Offline Beezageezauk

  • N.E. England
  • Resident Legend
  • *****
  • Join Date: Mar 2006
  • Posts: 669
  • Karma: 20
Re: Overcharging on a BSA?? You better believe it!!
« Reply #11 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.


Offline warmshed

  • A's Best Friend
  • ***
  • Join Date: Jul 2012
  • Posts: 161
  • Karma: 5
Re: Overcharging on a BSA?? You better believe it!!
« Reply #12 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.

Online KiwiGF

  • Last had an A10 in 1976, in 2011 it was time for my 2nd one. It was the project from HELL (but I learned a lot....)
  • Wise & Enlightened
  • *
  • Join Date: Feb 2011
  • Posts: 1469
  • Karma: 12
Re: Overcharging on a BSA?? You better believe it!!
« Reply #13 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! 
New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife)

Offline wilko

  • Resident Legend
  • *****
  • Join Date: Mar 2010
  • Posts: 681
  • Karma: 4
Re: Overcharging on a BSA?? You better believe it!!
« Reply #14 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.