Jump starting

[docc]

Having ignored the obvious signs of a charging failure (no "battery" light key on/pre-start), the Sport left me stranded on the byway.  The battery tested flat (10.5 volts) and would only click the solenoid briefly.

 

My son was kind enough to bring some cables and I disconnected the negative lead and let his 325i juice up the dead Hawker for a few minutes bringing it to 11.9 which got me home-(ish).

 

So, I got some cables to carry on the bike, but I'm vague on the warnings about jump starting the V11. What's the real deal?

[docc]

Once home and seeing no charge light and no charge, I thought for sure I was in for a regulator. While my 30 amp MAXI fuse "looked" ok when I "inspected" it on the roadside, it was open without looking burned. I found the positive lead to my terminal block had loosened up. After tightening the connection and replacing the fuse, she was, once again, Running GREAT!

 

I'm thinking some arcing on the loose connection blew the fuse over the last thousand miles since I had that all apart. I feel stupid I missed the blown fuse on the roadside, so I got one of those "Smart Fuses" that light an LED when they blow.

 

With the battery so flat, I don't think it would have jumped off anyway, but I'd like to learn what the big deal is jumping off motorcycles - why is it so taboo? Or is that just Bad Forum Science?

 

(left:SmartFuse/right:bad fuse)

[czakky]

No idea why its supposedly bad. But why not bump/push start?

 

Glad to hear its something simple BTW.

[docc]

Still riding on high hopes that the simple discovery is the Real Solution!

 

Once we gave the battery a little charge we did push it off. I was actually surprised it went as far as it did on the brief charge. I'm thinking just jumping it wouldn't have given the battery anything unless I had found/replaced the bad fuse at the time.

[czakky]

Dont think mine cranks below 12.3 or so.

[docc]

Thinking about it rationally (now that I'm not marooned), it seems we could have put the cables on from the car for the charging session and with the ignition and Run Switch off, the ECU would never know what we were up to.

 

It was probably unnecessary to disconnect the battery ground.

 

Yet, is there some electro-ugliness that might have wreaked some sort of havoc on the regulator or stator?

[GuzziMoto]

I have bump started the wifes V11 a few times. But that only works if you have a minimum charge in the battery to run the ECU and you also have to have a working charging system to keep it running. Or it will not run for long.

I have also used jumper cables to jump start her V11 along with many other bikes. My main recommendation if you are doing that is to not start the engine of the vehicle supplying the jump start. That limits the amount of charge provided so as to not overwhelm the bikes electrical system. I also prefer to attach the cables to the positive lug of the battery and to a good ground, leaving the ground cable for the battery hooked up.

[luhbo]

It's dangerous only in case you have a dead battery. Dead does not mean flat. Even a flat battery can buffer the dangerous voltage spikes that can occure when you remove the jump cables or in case one of them just falls off. Not so a dead one (broken internals or other effects that push its internal resistance through the roof).

So removing the ground of the bikes battery is a real risky thing (your battery's acting dead in this case) and on the other hand taking the engine, a footpeg or other well grounded metal parts as the negative pole is a good idea, because such parts usually offer much better and safer grip for the clamp as the small battery pole can do.

 

Nonetheless a lot of 16M units gave up their ghosts during jump starting, but as so often, who knows what the owners really did to them.

 

Hubert

[moto fugazzi]

I also heard not to jump or bump start bikes with ECUs because the sudden voltage spike could fry the ECU. I do agree with what Hubert said.

IIRC, there's also some kind of warning in my newer cars manual about jump starting as well. Being automatic, I don't think bump starting is an option. 

Ken