Forewarning of failing reg/rec?

My 01 SVS is suddenly refusing to start despite working fine on my long commute this morning. Everything powers on nicely - lights, indicators, dash display etc. - but when I try to start the bike, there's a big clunk from the starter motor before the entire dash display dims significantly and the bike dies.

I've never experienced a reg/rec failure before but everything I've read on here makes it sound like you won't know it's failing until the bike just dies on you. The battery's obviously still holding a charge because it powers the electrics until I try to start the bike so I'm wondering if this is a forewarning that the reg/rec's had it?

The battery's on charge right now and I'm hoping to god it'll work tomorrow because I badly need it to get to work.

[yorkie_chris]

Battery lighting lights up does not indicate it's charged. The fact that the bike doesn't work suggests it isn't.

Think about it, lights are tiny 5w affairs, the starter motor demands a huge belt of current, so a duff battery can power everything fine, or appear to, just not start the engine.

Sounds to me like the battery's been hit by this cold weather; I wouldn't worry too much about it.

Recharge the battery, keep it on a battery tender (optimate etc) during this cold weather, and might as well check all the battery connections are tight and clean.

[yorkie_chris]

How long is a long commute? Do you have lots of extra electrics?

Battery should be easily happy if you've just ridden for 40 minutes or so. Unless it was at very low rpm the whole way and you have heated grips/clothing, lights on etc.

I'm just a little sceptical of it being the cold because the bike's happily survived the holiday period in South Bedfordshire, where it's been a lot colder than east London, which is where the battery died today.

This morning's commute was 70 miles, took about 90 minutes and the battery was just powering the bike plus a heated jacket. The bike's almost completely stock, not running anything that draws more power than normal.

Battery's still charging, got a multimeter waiting to test it once it's done. I'll pop it back in the bike tomorrow morning and check the voltage across it with the engine running just to rule out the reg/rec. If everything's okay then I'll put it down to the cold and just get in the habit of taking the battery indoors at night (park on street, can't use a trickle charger) till the weather improves.

[yorkie_chris]

I'd say without a doubt that you have a problem then.

See what the battery voltage is after taking it off charge and leaving it for an hour, then put it back on and check the charging voltage.

The battery's been on charge for 14 hours now and the charger's telling me it's still not finished. Disconnected it anyway, waited an hour and the voltage across the battery is 12.92, which is close enough to 13 to be okay I think? Charging voltage is 13.94.

Going to pop it back in the bike tonight and check the voltage with the engine running to see what happens.

[Taipan]

Originally Posted by ranathari

The battery's been on charge for 14 hours now and the charger's telling me it's still not finished. Disconnected it anyway, waited an hour and the voltage across the battery is 12.92, which is close enough to 13 to be okay I think? Charging voltage is 13.94.

Going to pop it back in the bike tonight and check the voltage with the engine running to see what happens.

Sounds perfect. CHeck your voltage is the same across the battery when running with lights on and off though.

I've had a similar problem to yours (not SV though) with a power drop when hitting the starter and it was a loose connection on the frame earth.

[embee]

Originally Posted by ranathari

.....the battery was just powering the bike plus a heated jacket. The bike's almost completely stock, not running anything that draws more power than normal. (..apart from a heated jacket!!)

I think there might be a clue here.

Do you know what power the jacket is rated at?

With lights on, you need to be doing a few thousand rpm to break even on the charging, any idling will be discharging and it takes several times longer to regain the charge than to lose it.

Do you have the jacket supplied through any sort of voltage sensing device so it cuts off if the voltage drops below a certain level? Something like this for example.

Batteries do just die sometimes, and it's difficult to over-emphasise how much harder it is on batteries at these sort of temperatures. Not only does the cranking current increase dramatically but the chemistry just slows right down when cold, so a battery which would deliver quite happily at 20degC simply can't do it at zero.

Obviously first thing is exactly what you are doing, checking battery and charging volts while the engine's running and various things are switched on. Sounds like you'll need a top quality battery for your use, a Yuasa YTZ-14S or equivalent (it does mean losing the fuse tray on top of the battery on a curvey, but it's perfectly do-able). Not all batteries are made equal, some are more equal than others.

(PS - clean all the terminals and all the fuse blades too, any voltage drop here won't be recovered)

I'm pretty sure it's not the jacket as I've had that wired into the bike since November and it's not caused any problems. There's an inline fuse for it as well.

Battery is a Yuasa and it's less than a year old. It's still holding a charge but the dreadful snow here (visibility's down to 20 yards) means I can't put it back in the bike and test the reg/rec. Will have to hope the snow settles tomorrow and then just pull a sickie so I can try and get the bike working again, including checking the terminals and the fuses.