Apologies if this has been done before, I couldn’t find it though. Actually my wife’s bike, a Kawasaki 250sl. It doesn’t get used that much, especially over winter. I have been connecting it to the optimate every few weeks, and leaving it until charged (green light). Charged it yesterday and got it out to start it today. Initially turns over as normal but doesn’t fire up. Within a few seconds it’s as if the battery is dead. Back on the optimate and green light within 5 minutes. Try again, same thing. Had a similar thing with my Ducati, ended up needing a new battery and guess it’s the same for my wife’s bike. What am I doing wrong, as I seem to be killing batteries ?
12.44v with bike switched off Drops to 11.88v when switched on (lights are on permanently on this bike)
If we assume you meter is accurate to within 0.2V then it appears "aged". Straight off an Optimate I'd expect it to be nearly 13V. It is acting like a battery with a massively reduced capacity. Has it ever been allowed to drop below 10.8V? Again assuming that it is 10V or so after the attempted start. If it is not and it is still up at +12.3 then perhaps high resistance somewhere in the battery leads or start circuit.
I don’t think it’s ever dropped that low, but must confess I’ve not measured it. I have just been connecting to the optimate every 4/5 weeks.
We need to know the voltage when cranking. Sprinter Van, 2150cc with a brand new battery... F.cking Huge one.... when cranking 11.2V, off load after 3 days 12.88V... ignition on (Fuel pump, glow plugs and running lights) 12.7V.... When driving 14V down to 12.88V... intelligent alternator.
Yes, guessed it would be. Bit of a pain to leave it on all the time. I don’t think the optimate model I have is very good at charging a flat battery, I say this based on my Ducati, which I left too long, the optimate showed a green light after about an hour, but the battery wasn’t charged. Putting it on a cheap basic charger got it going - didn’t last more than a few months though.
You may find that the Optimate is failing. I had one exactly the same, about 8 years old. It kept telling me the bike was charged but the battery was lower on voltage than I would expect. I went and bought a new Optimate 1, plugged it in and found it spent the next 4 hours sat with the amber light on until the battery was actually charged. I was uncertain when the dealer told me they failed over time, but this certainly seemed the case.
@Alan williams Alan modern bike battery tenders, tbh all modern tenders do not like discharged batteries. I have a classic Fiat that has a power drain somewhere, probably the alarm/immobiliser system, so if I forget to connect tender in good time, battery discharges and said will not have anything to do with it. I used to connect up a spare and force some electrons in 'til the tender would take up again. Like you only lasted 6 months or so. I now disconnect battery until the old girl is required. Modern tenders are fine to leave on until you need the bike.
Think I will try, for the hell of it, taking battery off and putting on a standard charger tomorrow. See if that helps.
