st st st stuttering Bonnie

[henry_norton]

My 65 Bonneville (with a Boyer electronic ignition) has developed a strange electrical fault. It starts and runs fine but it stutters and conks out whenever any of the electrics are used (lights, brake light or even the horn). I'm pretty sure it's a problem with the battery but I always thought (maybe naively) that a bike would run independently of the battery once it was started.

Any thoughts?

[L.A.B.]

I'm pretty sure it's a problem with the battery but I always thought (maybe naively) that a bike would run independently of the battery once it was started.

Depends on the amount of alternator output - especially at low RPM?
The Boyer needs a good voltage supply to work at all, and if the battery isn't charging properly it won't be helping matters, especially if you have an older version alternator as they don't exactly make an awful lot of power, so the first thing I'd do is change the battery?    

[henry_norton]

Thanx for the reply L.A.B. Funnily enough when it first started playing up it would start just fine (as it always has), but would not rev past tickover. I've charged the battery now and it revs OK but still doesn't like sharing the battery with any other electrical parts - lights and horn etc. Busted batteries are hardly uncommon on brit twins but I'm still puzzling over why it causes problems when the bike's running  :-?

I'll check the alternator the morrow. HN

[Rex]

 so the first thing I'd do is change the battery?    


First thing I'd do is check the charging rate.
As a simple check, do the lights get brighter when you rev it? Stick a meter across the battery and check the charging voltage at tickover and 3-4000 rpm; you should see it rise.

[henry_norton]

Thanx Rex - unfortunately the lights don't get brighter when I rev it up as it konks out every time I turn them on. I'm only reading 10.5 volts across the battery terminals (over 11 when it's running) so it looks like another battery in the electronics graveyard. Has anyone tried one of these new fangled, super duper gel type batteries I've read about in OBM? I'm averaging one battery per year at the moment....  

[Searchguru]

Hi,
I have three bikes, two cars and not enough time therefore I was consuming bike batteries like you.
With your new battery, acid or gel, get a trickle charger. I got a couple of them from motorbikebatteries.com, or similar, a couple of years ago. They were about a tenner each. I also bought a 24 hrs timer plug. I have both bikes attached to their trickle chargers on the same extension lead which is then timed to switch on for one hour each night. No more flat batteries!
The only real difference with a gel battery is it is maintenance free i.e you can't top it up as it shouldn't need it so they can be used in jetskis and such like. If you can get one which matches your current 'wet' battery in performance it is likely to be more expensive. It will need modifications to you battery box to retain it as it will probably be smaller. Best of luck

[henry_norton]

Thanks for the tip searchguru. As it happens I do have a trickle charger - or should I say a trickle switch on my charger. I'll give it a go. Cheers!

[Searchguru]

Henry,

Please be aware, if you weren't already, that you should never use a 'car' battery charger as they pump too much into a bike battery and will cause damage. It may not appear damaged but if this is the type of charger you are using it could be the explanation for your frequent 'deaths'. The trickle chargers I use are the same as this one:

http://cgi.ebay.co.uk/BATTERY-TRICKLE-CHARGER-6V-12V-SCOOTERS-MOTORCYCLES_W0QQitemZ260285644730QQihZ016QQcategoryZ25643QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

It has wiring which stays attached to the bike and you just connect it up and plug it in when you park next to a power socket.
The best of both worlds is something like an Optimate 4, which is about 40 squid, which will charge your battery then trickle charge it whenever you plug it in. It will easily pay for itself in a couple of years.

[Rex]

Those Optimates have been taking a beating on various Net forums recently. Things like the batteries being just as flat and short-lived and furred-up as not using the Optimate.
I guess you can't please everyone.

[G1ULZ]

Thanx for the reply L.A.B. Funnily enough when it first started playing up it would start just fine (as it always has), but would not rev past tickover. I've charged the battery now and it revs OK but still doesn't like sharing the battery with any other electrical parts - lights and horn etc. Busted batteries are hardly uncommon on brit twins but I'm still puzzling over why it causes problems when the bike's running  :-?

I'll check the alternator the morrow. HN

When  you  take  your  battery  off  charge  be  aware  that  the  reading  on  the  meter  may  show  around  12 volts,  this  maybe  a  surface  charge  reading,  You  need  to  attach  a  load  like  a  bulb  and  observe  the  voltage  drop,  If  it  is  excessive  then  the  battery  is  faulty.  If  the  battery  is  satisfactory  fit  it  to  the  bike  and  start  it  with  no  other  load,  check  the  meter  reading  which  should  now  be  13.8  volts  or  above,  now  add  the  load  one  by  one  and  again  look  for  a  voltage  drop,  If  this  is  excessive  - 12 volts  there  is  a  good  chance  the  engine  will  stop  and  the  charging  system  is  suspect.  You  should  never  run  a  AC  to  DC  charging  system  with  the  battery  disconnected  and  if  its  faulty  it  forms  a  resistance  to  the  charging  rate  which  drops.  Good  Luck,  Lou Dalby  Ex  T & I  BSA.

[henry_norton]

Please be aware, if you weren't already, that you should never use a 'car' battery charger as they pump too much into a bike battery and will cause damage. It may not appear damaged but if this is the type of charger you are using it could be the explanation for your frequent 'deaths'.

Thanks searchguru, that could be the reason. When I bought the charger 15 years ago it said 'car and motorcycle battery charger' on the box but I guess we can't trust anything these manufacturers tell us. Thanks for all the responses. HN

[L.A.B.]

When I bought the charger 15 years ago it said 'car and motorcycle battery charger' on the box but I guess we can't trust anything these manufacturers tell us.

Standard lead-acid batteries should be charged at an Amp rate of up to 10% of their Amp-hour rating, so a charger meant for cars and motorcycles could possibly charge at too high an Amp rate for a small motorcycle battery? So maybe a charger meant for smaller motorcycle batteries would be better? Cheap Chinese/Taiwanese  batteries don't seem to last long. A good quality Yuasa, Varta etc. battery should last a few years, at least, if it's charged correctly and the electrolyte level isn't allowed to drop below the "minimum" mark?      

[henry_norton]

Yeah, there can be that mentality of 'if it's going to be shaken to bits anyway there's no point in spending any more than the absolute minimum.' It applies to alot of things in life these days.

I'll try a higher quality battery and see how it goes - if it doesn't work out I'll let everyone know.  

[lxmlvll]

Hi,

Buy a multimeter, cheap one <£10 'll do.

Borrow book on bike electrics(library).

Clean all connections.

Charge battery, fit to bike, leave one terminal disconnected.

Measure voltage before connecting other terminal - should read 13.2v DC if batt in good order + fully charged. Connect other terminal, measure again with ignition off(no load), should show same voltage. Less means drain somewhere, possibly through rectifier or zener diode, so disconnect each in turn to isolate faulty part.

Turn ignition on, measure again. There should be small drop in voltage compared to previous measurement(1/2v to 1v). Even with faulty or discharged batt, when engine starts a rise in voltage should be evident at just over idle.

If there is drop in voltage as engine revs, charging system isn't working. If so, disconnect leads coming from alternator to rectifier and with engine running, measure voltage(AC) across any two of the three leads. I'm not sure offhand what these Vs should be, but they should be within 1v of each other. If no or very low voltage seen across any pair, that phase is open circuit or high resistance. If this is the case (low or no V across 1 or more pairs), measure resistance across all three pairs. They should be within + or - 1/2 ohm of each other. If not, fault may lie with alternator.

If alternator checks OK for voltage and continuity, rectifier may be faulty. Disconnect all wires, check resistance across the three terminals on rect in turn, swaping probes over each time - should be high resistance one way (meg or millions of ohms), low the other (as much as kilo or thousands of ohms). If there's not a BIG difference, rectifier is faulty.

Check resistance both ways across terminal which feeds battery and earth, - should be very high (meg ohms), if low, part is faulty.

If all components check out OK and if there is enough juice to start bike, it should run OK even with flat batt.

Hope this helps.

Regards.

A.

[henry_norton]

Thanks lxmlvll

Thanks for the post - very helpful - although my mulitmeter reads less than eleven volts across my battery I'm sure that's the problem. However, I'll go through the procedure you described just to see if there might be more issues with my old bikes electrics (that might explain its apetite for batteries).