Author Topic: Battery flat after riding with lights on  (Read 982 times)

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Drummie

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Battery flat after riding with lights on
« on: 27 August, 2017, 20:38:36 »
Hi all,

Out on my bike today for a run.  Decided to use the lights.  Haven't needed to use them yet, so today was the first time.  Rode with them on for around 20 minutes.  Stopped bike and switched it off.  Went to start it again after 5 minutes and it wouldn't start.  Checked the lights and they were almost non existent (a slight glow).   Jumped it with another battery it fired up straightaway and the lights were fine.  Connected multi meter to it while it was running but readings were jumping all over the place so couldn't get any kind of reading from it.

I got the same problem using the multi meter when I got the bike a few months ago.  I've done decent trips on it and it has always been fine until today when I used the lights for the first time.
I've had charging problems with other bikes before but always got a reading to show its not charging
Any idea what the problem could be?

Thanks in advance.  Any help much appreciated.


JulianS

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Re: Battery flat after riding with lights on
« Reply #1 on: 27 August, 2017, 20:41:31 »
Which bike do you have?

Drummie

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Re: Battery flat after riding with lights on
« Reply #2 on: 27 August, 2017, 20:44:38 »
sorry forgot that bit. its a a50 royal star.

om15

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Re: Battery flat after riding with lights on
« Reply #3 on: 27 August, 2017, 20:57:51 »
Go for the easy fixes first, change the battery and see how you go

JulianS

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Re: Battery flat after riding with lights on
« Reply #4 on: 27 August, 2017, 21:51:51 »
With engine going does the headlight intensity increase with revs?


Drummie

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Re: Battery flat after riding with lights on
« Reply #5 on: 27 August, 2017, 22:24:10 »
I've not noticed JulianS, but will check that tomorrow and let you know.

om15 the battery will need replacing. Put it on charge tonight and read fully charged after around an hour. So something definitely wrong there.

Any idea why I cant get a reading from the multi meter. as it fluctuates wildly.
« Last Edit: 27 August, 2017, 22:48:44 by Drummie »

STAR TWIN

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Re: Battery flat after riding with lights on
« Reply #6 on: 28 August, 2017, 07:02:29 »
If your multimeter if fluctuating, it's either your rectifier/zener diode/powerbox failing on the charging side or an intermittent short circuit somewhere. Your charging side should more than match riding with headlights on so there is something amiss. I would be surprised if it's just a battery problem. 

Drummie

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Re: Battery flat after riding with lights on
« Reply #7 on: 28 August, 2017, 12:36:00 »
I have checked this morning and the headlight does get brighter when I increase the revs, not to the point bulbs will blow but definitely an increase.
Also noticed a fuse on the lead/wire to the negative terminal on the battery. with the engine off and battery connected i'm getting 12volts from it, but 0volts from positive side. sorry if this is obvious but electrics are not my strong point.

Its a 1966 a50.

Like you said Star Twin I don't think its just the battery, I'm not that lucky.
« Last Edit: 28 August, 2017, 12:42:07 by Drummie »

Greybeard

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Re: Battery flat after riding with lights on
« Reply #8 on: 28 August, 2017, 13:57:46 »
Whilst I'm happy enough to recreate practically anything mechanical on the lathe or milling machine, electrical stuff leaves me cold. Following a wiring diagram was about the limit  :-[  I bought a copy of Classic Motorcycle Electrics Manual by James Smith. Its a superbly produced book that goes right to the basics and works through from there, basically assuming that the reader knows very little from the outset - unlike many other books on the subject.
It gave me an understanding of how dynamos, alternators and rectifiers etc work, and more importantly, how to test them. It's well worth tracking down a copy. Published price is 35 quid but it can be found for much less than that.

Steve
Steve from East Yorkshire - Not the Greybeard of the A7/A10 forum who was not actually registered on this one when I signed up ;-)

Mike Farmer

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Re: Battery flat after riding with lights on
« Reply #9 on: 28 August, 2017, 16:23:59 »
Hi :)

Classic Motorcycle Electrics on Ebay. Item No252989884779. 23.99 +postage.

Mike

Greybeard

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Re: Battery flat after riding with lights on
« Reply #10 on: 28 August, 2017, 18:46:46 »
That's the one, Mike. Worth every penny. A tad cheaper on Amazon too
https://www.amazon.co.uk/Classic-Motorcycle-Electrics-Manual-James/dp/1847979955/ref=sr_1_1?s=books&ie=UTF8&qid=1503942211&sr=1-1
I couldn't post a link to it earlier as I was using my tablet - there are some things that I've never bothered to find out how to do with it   :-[

Steve
Steve from East Yorkshire - Not the Greybeard of the A7/A10 forum who was not actually registered on this one when I signed up ;-)

JulianS

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Re: Battery flat after riding with lights on
« Reply #11 on: 29 August, 2017, 10:29:09 »
It is always worth checking the basics - check all connections are clean and bright, check for frayed or squashed wires, check that all is connected as per the wiring diagram and be suspicious of any bits of wiring which seem to have be crudely added in.

If fitted with zener diode check that the seat of it and heat sink is not corroded, clean if necesary.

The headlamp mounted ammeter can tell you a lot - the charging syatem should easily balance both ignition and headlamp load.

There are some basic checks on the charging system shown in the workshop manual - from the alternator before the rectifier and zener diode - after the rectifier and zener.

If you have a modern solid state regulator/rectifier the makers instructions should tell you how to check the out put from it.

If bike still fitted with the orignal open coil 3 wire alternator stator it could be past its best after over  50 years.

Drummie

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Re: Battery flat after riding with lights on
« Reply #12 on: 29 August, 2017, 22:07:18 »
Thanks for all your help. I'll have look at it over the weekend. That book does look like a worthwhile buy.

EDDIE SIMPSON

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Re: Battery flat after riding with lights on
« Reply #13 on: 29 August, 2017, 22:31:03 »
hello drummie,
the quick way i would check your system is with a multimeter on 20volts range dc across the 12.5 volt battery.
14 volts on tickover means its charging. 16 volts overcharging.
12 .5 volts and above at tickover with lights on fairly normal with an old alternator.
play around with lights on / off and if the volts show discharge means short circuit. wire touching frame?
as julian says , zeners can short circuit . cause poor charge or overcharge and boil batterys

Drummie

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Re: Battery flat after riding with lights on
« Reply #14 on: 30 August, 2017, 14:24:06 »
Hi Eddie Simpson, I have done some tests this morning and first of all found that my first multi-meter was faulty (now changed). When the bike is running at idle it reads 0 on the ammeter. when revved up it increases to just above 0. with the lights on, it drops just below 0 and back to around 0 when revved (headlight gets brighter when revved up).

With the engine switched off I got a reading of 12.25 volts across the battery terminals. when I switched the lights on for around 20 secs the voltage dropped to around 11.25 volts. When I started and ran the engine for a couple of mins then switch it off, it jumps up to around 12.80v.

I also found that when running i'm getting 14.30v at idle which increases to 16v at 3000 rpm, when connected across the battery terminals.

I was thinking rectifier, but then thought it would of blown the bulbs by now.