Emergency starting link

[ghostlymoron]

Explosion proof switches are unnecessary as they are not installed close to the batteries.

Paul are the switches you fit explosion proof switches. If not you may still have the same event.

The other point is the the hydrogen produced is lighter than air so would tend to disperse anyway.

 

[PaulRainbow]

Paul are the switches you fit explosion proof switches. If not you may still have the same event.

The other point is the the hydrogen produced is lighter than air so would tend to disperse anyway.

Yes, the switches i fit are ignition protected, but even if they were not and an explosion occurred you would not have your face in the battery compartment connecting jump leads.

Hydrogen is lighter than air, but if it is being produced it will still be present. We've got a thread running on here about Co alarms being set off under normal charging regimes with some batteries, i wouldn't want to risk a spark around those.

A proper switch costs just £20, how much for a decent set of jump leads ?

If the engine battery has actually failed, how do you easily isolate it and use the domestic batteries to complete the passage with just a set of jump leads ?

 

[lw395]

So, we've opted for jump leads.

We've just arrived at the marina and want to go sailing. The batteries should be nicely charged, been on charge since the last time we used the boat. Damn, the engine won't start ! No problemo, out with the jump leads and up with the sofa cushion, beneath which the batteries live. Connect the jump leads and discover just why the engine battery won't start the engine, BOOM ! The battery has a shorted cell and has been boiling away for some time, lots of luverly explosive gas in the battery compartment (or at least there was a couple of seconds ago). I'm sure most of the burns will heal in time and with luck one of my eyes will be at least a little bit useable.

Wish we'd have gone with a 3rd switch. Could have just isolated the dead battery by turning the switch off and turned the emergency one on.

Of course everyone will think carefully and carry out proper diagnostics before just turning the emergency start knob won't they?

 

[rogerthebodger]

Yes, the switches i fit are ignition protected, but even if they were not and an explosion occurred you would have your face in the battery compartment connecting jump leads.

Hydrogen is lighter than air, but if it is being produced it will still be present. We've got a thread running on here about Co alarms being set off under normal charging regimes with some batteries, i wouldn't want to risk a spark around those.

A proper switch costs just £20, how much for a decent set of jump leads ?

If the engine battery has actually failed, how do you easily isolate it and use the domestic batteries to complete the passage with just a set of jump leads ?

The explosive limits of hydrogen in air range from about 18 -- 60 % and as hydrogen is lighter than air would you get that 18 % concentration in and opened battery box.

The position of the CO sensor and then sensitivity to hydrogen would be a factor. I would think the sensitivity would be much less than 18 % the minimum level in air. In oxygen would be a very different matter.

 

[PaulRainbow]

The explosive limits of hydrogen in air range from about 18 -- 60 % and as hydrogen is lighter than air would you get that 18 % concentration in and opened battery box.

The position of the CO sensor and then sensitivity to hydrogen would be a factor. I would think the sensitivity would be much less than 18 % the minimum level in air. In oxygen would be a very different matter.

I've seen batteries that have been on charge in an open workshop explode because of a spark.

I've seen vehicle batteries that have exploded under the bonnet.

I've seen vehicle batteries that have exploded beneath the seat in a Transit van, while the van was travelling along the road. The driver almost lost the sight in both eyes and suffered serious burns.

 

[PaulRainbow]

Of course everyone will think carefully and carry out proper diagnostics before just turning the emergency start knob won't they?

I doubt it. I imagine most people would turn the switch on, start the engine and turn it off again. Same as someone would likely do with jump leads. Difference is, if a battery is excessively gassing, the switch won't cause an explosion, the jump leads almost certainly will.

There are several other reasons why a switch makes more sense and the total cost of fitting a switch is about £25. Jump leads would probably be £15 for a half decent set, a good set would be more like £35. Seems like a no-brainer to me, but if people want to use jump leads they can please themselves.

 

[awol]

It's rare to find an engine now with a non pre-engaged starter. A pre-engaged solenoid cannot be bypassed if it fails to energise and engage the drive pinion. If you short the terminals as you used to do with the older style starter motors the motor will spin but will not be engaged with the ring gear. So if the solenoid fails you are screwed.

Strange! Shorting the 2 large terminals on my old 2GM starter solenoid worked just fine.

 

[PaulRainbow]

Strange! Shorting the 2 large terminals on my old 2GM starter solenoid worked just fine.

Was it pre-engaged ?

 

[lw395]

Strange! Shorting the 2 large terminals on my old 2GM starter solenoid worked just fine.

Most pre-engage starters will work like a Bendix type.
The pinion usually moves along a helical scroll much like a bendix starter. This helps keep the pimion engaged as the surge current of the motor depowers the solenoid. It also helps break the solenoid when the engine starts.
It's useful to know, when the solenoid contacts are worn or corroded.
On some starter motors there is apparently another winding in the solenoid which is in series with the motor current, so this helps hold the solenoid 'on' until the current is reversed as the engine starts, when it throws the solenoid 'out'.

There is often more subtlety to these things than first meets the eye!

Moto Guzzi owners often had 50p coins with burn marks from starting bikes this way!