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Running without a battery


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#1 Joey55 OFFLINE  

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Posted April 24, 2017 - 06:11 PM

I have a Kubota T1770 lawn tractor.  Started it up this spring for first time and found that the battery had lost its charge over the winter.  Boosted the engine off another battery to get started, but engine would stop immediate upon removing booster cables (old battery had been removed prior to boosting).  Wondering why the engine would not continue to run after successful starting.  Someone told me that I had to have a battery (regardless of its condition) in the electrical loop in order for the engine to remain running.  Is this correct, and if so why, if the battery has little or no charge left?  


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#2 637Yeoman OFFLINE  

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Posted April 24, 2017 - 07:13 PM

It is correct. Its making a complete circuit


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#3 chieffan OFFLINE  

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Posted April 24, 2017 - 07:15 PM

Go buy a good battery before you burn something else up. 367 Yeoman is right on.


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#4 MiCarl OFFLINE  

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Posted April 24, 2017 - 07:17 PM

Basically there are two forms of ignition systems:

 

The first uses electricity generated by the flywheel to power the ignition system.  These are the ignition systems used in devices without batteries (push mowers, chainsaws, leaf blowers etc.).  They can also be used in some electric start engines because the charging system is completely separate from the ignition system.

 

The second uses electricity from the battery.  These are typically more advanced systems like you find in automobiles etc.  These systems run off the battery.  They can be points type ignitions, electronic ignitions or computerized ignitions.

 

Now the question you're asking yourself is why the electricity from the charging system won't run the ignition after you disconnect the boost.  The reason is that the charging system doesn't output a constant supply of electricity, it comes in little spurts.  It needs a battery (even a really poor one often will do) to store enough juice to keep things going between spurts.  Unless the generator or alternator uses permanent magnets it will need that juice from the battery to keep the field coils magnetized.

Also, without the battery to act as a sort of shock absorber the voltage regulator won't do it's job properly.  Voltage can potentially go quite high on the spurts which the ignition system might not like and might even damage the electronics.


Edited by MiCarl, April 24, 2017 - 07:20 PM.

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#5 rustyoldjunk OFFLINE  

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Posted April 24, 2017 - 10:11 PM

What MiCarl said.

Long story short a battery ignition such as used by most Kohler K series needs a battery.

Most mag style coils and SSI style coils,most Briggs cast iron and aluminum and most Tecumseh engines will run without a battery.

Recoil start engines use magneto or solid state ignitions.


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#6 Joey55 OFFLINE  

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Posted April 26, 2017 - 08:28 AM

Thank you all for your input and a particular thank you to MiCarl.  Your explanation is exactly what I was hoping for as I recall doing the same thing with older engines and had no trouble with them stalling, but I didn't know what had changed.  Now that you mention it I do remember changing points and condenser in the older ones during tune ups. 

I have installed a new battery already as Chieffan suggested so should be good for the summer so bring on the grass! :pushmower:


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