LocoBRD
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| posted on 21/5/09 at 08:15 AM |
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Voltage Drop
Hi there,
I'm a newbie to this site for posting but have used it many a time to answers queries I've had over the last few months. This time though,
I felt the need to post 
I have an ETB DigiDash 2 installed and have found that the battery warning light keeps coming on when switching on the lights to dipped. It seemed
that the voltage reading was showing 11.5V on the ETB.
The battery itself reads 12.2 at this point which I understand is usual. I have also checked the ignition as this is where the ETB is wired into and
it also shows 11.5V.
Things I have also checked are the switch (replaced this) cables to the lights, relays etc and all are clean, no nicks, connections all solid etc. I
have also disconnected the lights and still get this reading.
Has anyone got any idea why I get such a voltage drop at the ignition and any suggestions as to how I can solve this please?
I know the value of the battery minimum reading on the ETB can be lowered but I'm worried that as it reads differently to the actual battery
voltage I won't be getting a true reading as such.
Sorry for the essay on my first post.
Thank for any help received
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Guinness
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| posted on 21/5/09 at 08:17 AM |
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Hi
Do you have a resistor in the ignition circuit? Lots of bike engined cars need one.
Mike
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sickbag
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| posted on 21/5/09 at 08:28 AM |
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Sounds like you've got a bad connection or two. Start from the battery and make sure all connections are tight and secure by disconnecting then
reconnecting them.
Maybe a smear of Vaseline on some of the more exposed connectors too - just to help keep corrosion at bay.
Finally back on the job!
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scotlad
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| posted on 21/5/09 at 08:38 AM |
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12.2 volts sounds a bit on the low side to me- it should be at least 13volts i would have thought. I'm happy to be corrected though
Wonderous is our great blue ship that sails around the mighty sun, and joy to everyone that rides along!
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02GF74
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| posted on 21/5/09 at 08:45 AM |
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we can assume that you battery is not being drained? i.e. you need to use a mains powered charger on it..
13.5 V is what you should see wehn engine is running at about 2,000 rpm, measured across the battery terminals.
I note that you have a bike engine - but are using it to power two sets of headlamps and rear lamps so it may be that the alternator/generator is not
able to cope with the load; most modern bikes have twin headlamps but I do not know wattage of bulbs for comparison.
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BenB
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| posted on 21/5/09 at 09:33 AM |
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Some alternators don't put out enough juice at idle to supply the demand of a car so you might find the voltage dropping if you're idling
and you put the headlights on (I flattened my battery once doing this, leaving me stranded!!!).
As said you really want to be seeing 13.5-14v across the battery terminals when the engine is running.
12.2 / 11.5v isn't a major difference. The worry is why you're only seeing 12.2v.... It would suggest either the battery is extremely flat
(but then how do it start the engine) or the alternator is suspect.
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LocoBRD
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| posted on 21/5/09 at 09:38 AM |
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Guinness - nope no resistor. We bought the car already built and installed the ETB afterwards but no existing resistor at all. What size resistor
would I need and where would it sit in the wiring circuit?
02GF74 - It is a new battery and is charged with an Optimate Charger. Voltage readings are also fine when at higher revs. And it's one pair of
headlamps incorporating side, dipped and full beam each with separate feeds and fuses via relays. (except side which is direct)
Thanks for the replies
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bigfoot4616
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| posted on 21/5/09 at 10:49 AM |
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the only resistor i have fitted on mine(919 blade) is the one to sort out the immobiliser on the pink wire to the CDI. as yours runs forget about
that.
i would guess at alternator or associated wiring, possibly regulator although i'm not sure what they normally do when they're faulty
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mad4x4
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| posted on 21/5/09 at 12:12 PM |
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Could be an earth Problem ??
Scot's do it better in Kilts.
MK INDY's Don't Self Centre Regardless of MK Setting !
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nike5
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| posted on 21/5/09 at 09:25 PM |
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Where is the battery fitted? under bonnet or at rear of car.
At the moment thinking where to fit my battery. Have been warned if I fit battery cables too long (or of a low quality) would create a voltage drop.
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LocoBRD
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| posted on 22/5/09 at 01:45 PM |
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nike5 - The battery is under the bonnet. It is secured to the scuttle and within close distance to the charging circuit and ignition
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