ER-5 Won't start unless the lights are off?

[ncrn]

Hey, I'm having some trouble with my ER-5 at the moment. For the past week it has had some trouble starting, as in I needed to hold the starter button down for roughly 2-3 seconds before the starter would turn, but when it did the bike would jump to life happily and run fine. Now I've found that if I switch the lights off it starts up first time no bother.

I've tried re-charging the battery overnight with my maximiser but the problem still persists. I have a suspicion that the battery may be gone, as I'm 90% sure its the original which would make it over 13 years old now! However I'm not sure how to check if the battery is actually dying, or is there something else potentially wrong like the starter relay?

Any advice on what to check would be appreciated

James
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Past: 55 Sym Jet, 91 ZZR250, 03 NSR125R. Present: 97 ER-5.
https://www.nsr125.co.uk - NSR Owners forum.

[temeluchus]

You may have a duff battery, parts of the plates can sulphate, leading to a drop in the amount of charge the battery can hold. So when you take the additional load off the battery it just has enough current to start the bike.

charge it with your charger, wait overnight and check the voltage in the morning with a meter. If it discharges significantly overnight, it needs to be changed. 12.6v is fully charged, 12.2 is half discharged and anything below 12v is pretty much discharged.

Batterys are cheap enough for a reputable quality make that its worth changing if the age of the old one is unknown.
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Some shite cruiser. Now with guns and FREEDOM!

[ncrn]

Cheers, I went to check the voltage of my battery but it seems that the harsh winter in my garage has killed my voltmeter so I need to go buy a new one tomorrow to check it out . If it looks off I'll probably just swap it out, I need the bike to survive another 8k miles over the next 4 months so I figure its a minor cost to keep it going if needs be. If the voltage looks ok is there anything else I should look for?
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Past: 55 Sym Jet, 91 ZZR250, 03 NSR125R. Present: 97 ER-5.
https://www.nsr125.co.uk - NSR Owners forum.