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Info From A Lead Acid Battery On An Engine?

Started by eeboarder August 17, 2009
I am developing a system that is powered from a 12V or 24V lead acid
battery configuration on an industrial engine. These are the same lead acid
batteries used in vehicles. The batteries or battery will always be charged
by an alternator running off of the engine.

Is it possible to get a run signal just from the battery? The PIC24F
microcontroller being used needs to be able to tell if the engine is on or
off. If could monitor the engine operation(on or off) from the power
source, I wouldn't need an additional device to monitor this(oil pressure
switch).
eeboarder wrote:
> I am developing a system that is powered from a 12V or 24V lead acid > battery configuration on an industrial engine. These are the same > lead acid batteries used in vehicles. The batteries or battery will > always be charged by an alternator running off of the engine. > > Is it possible to get a run signal just from the battery? The PIC24F > microcontroller being used needs to be able to tell if the engine is > on or off. If could monitor the engine operation(on or off) from the > power source, I wouldn't need an additional device to monitor > this(oil pressure switch).
You should be able to base it on the voltage. During charging the voltage should be in the 14 (28) volt range. When the engine is not running the voltage should be no more than the max charged voltage. I can not remember the full charge voltage off the top of my head, but it should be easy to find. The only way to charge the battery to full is to exceed that voltage. Scott
On Mon, 17 Aug 2009 09:50:43 -0600, Not Really Me wrote:

> eeboarder wrote: >> I am developing a system that is powered from a 12V or 24V lead acid >> battery configuration on an industrial engine. These are the same lead >> acid batteries used in vehicles. The batteries or battery will always >> be charged by an alternator running off of the engine. >> >> Is it possible to get a run signal just from the battery? The PIC24F >> microcontroller being used needs to be able to tell if the engine is on >> or off. If could monitor the engine operation(on or off) from the power >> source, I wouldn't need an additional device to monitor this(oil >> pressure switch). > > You should be able to base it on the voltage. During charging the > voltage should be in the 14 (28) volt range. When the engine is not > running the voltage should be no more than the max charged voltage. I > can not remember the full charge voltage off the top of my head, but it > should be easy to find. The only way to charge the battery to full is > to exceed that voltage. > > Scott
--- and expect the indication to be a lot less reliable than a spark signal, oil pressure, crankshaft once-around signal, or other signal that happens as a direct consequence of the crankshaft turning. -- www.wescottdesign.com
On 2009-08-17, Not Really Me <scott@validatedQWERTYsoftware.XYZZY.com> wrote:
> eeboarder wrote: > >> I am developing a system that is powered from a 12V or 24V >> lead acid battery configuration on an industrial engine. These >> are the same lead acid batteries used in vehicles. The >> batteries or battery will always be charged by an alternator >> running off of the engine. >> >> Is it possible to get a run signal just from the battery? The >> PIC24F microcontroller being used needs to be able to tell if >> the engine is on or off. If could monitor the engine >> operation(on or off) from the power source, I wouldn't need an >> additional device to monitor this (oil pressure switch). > > You should be able to base it on the voltage. During charging > the voltage should be in the 14 (28) volt range.
I think they usually design for a 13.8V charching voltage once the battery is fully charged. If the battery has been run down a ways, it might be lower.
> When the engine is not running the voltage should be no more > than the max charged voltage. I can not remember the full > charge voltage off the top of my head, but it should be easy > to find.
It's around 12.6-12.8V.
> The only way to charge the battery to full is to exceed that > voltage.
He'd probably be better off measuring the direction of current flow in the cable to the battery terminal, but sensing it without a shunt resistor will require some sort of inductive sensor. -- Grant Edwards grante Yow! BARBARA STANWYCK makes at me nervous!! visi.com
On Mon, 17 Aug 2009 10:55:26 -0500, Tim Wescott <tim@seemywebsite.com>
wrote:

>On Mon, 17 Aug 2009 09:50:43 -0600, Not Really Me wrote: > >> eeboarder wrote: >>> I am developing a system that is powered from a 12V or 24V lead acid >>> battery configuration on an industrial engine. These are the same lead >>> acid batteries used in vehicles. The batteries or battery will always >>> be charged by an alternator running off of the engine. >>> >>> Is it possible to get a run signal just from the battery? The PIC24F >>> microcontroller being used needs to be able to tell if the engine is on >>> or off. If could monitor the engine operation(on or off) from the power >>> source, I wouldn't need an additional device to monitor this(oil >>> pressure switch). >> >> You should be able to base it on the voltage. During charging the >> voltage should be in the 14 (28) volt range. When the engine is not >> running the voltage should be no more than the max charged voltage. I >> can not remember the full charge voltage off the top of my head, but it >> should be easy to find. The only way to charge the battery to full is >> to exceed that voltage. >> >> Scott > >--- and expect the indication to be a lot less reliable than a spark >signal, oil pressure, crankshaft once-around signal, or other signal that >happens as a direct consequence of the crankshaft turning.
Yes. There should also be a lot of RF noise coming from the alternator when it is running. IIRC: The nominal battery voltage SB 12.6. Float charge is something in the mid 13s. Charging voltage is usually 14+, all for a 12V system. IIRC :-) -- ArarghMail908 at [drop the 'http://www.' from ->] http://www.arargh.com BCET Basic Compiler Page: http://www.arargh.com/basic/index.html To reply by email, remove the extra stuff from the reply address.
>I am developing a system that is powered from a 12V or 24V lead acid > battery configuration on an industrial engine. These are the same lead > acid > batteries used in vehicles. The batteries or battery will always be > charged > by an alternator running off of the engine. > > Is it possible to get a run signal just from the battery? The PIC24F > microcontroller being used needs to be able to tell if the engine is on or > off. If could monitor the engine operation(on or off) from the power > source, I wouldn't need an additional device to monitor this(oil pressure > switch).
I'm certainly no expert but it seems to me that it should be possible to monitor the power supply voltage for the presence of some characteristic motor noise that would be absent when the motor isn't running. On the other hand, my proposal might lead you to an overblown and unreliable solution but it might be worth a look. JJS
"eeboarder" <jmeyer@emittechnologies.com> wrote in message 
news:x8idnQledMDB5BTXnZ2dnUVZ_gGdnZ2d@giganews.com...
>I am developing a system that is powered from a 12V or 24V lead acid > battery configuration on an industrial engine. These are the same lead > acid > batteries used in vehicles. The batteries or battery will always be > charged > by an alternator running off of the engine. > Is it possible to get a run signal just from the battery? The PIC24F > microcontroller being used needs to be able to tell if the engine is on or > off. If could monitor the engine operation(on or off) from the power > source, I wouldn't need an additional device to monitor this(oil pressure > switch).
Use the signals available on the CAN bus that describe the situation in which you are interested?
Tim Wescott wrote:
> On Mon, 17 Aug 2009 09:50:43 -0600, Not Really Me wrote: > >> eeboarder wrote: >>> I am developing a system that is powered from a 12V or 24V lead acid >>> battery configuration on an industrial engine. These are the same >>> lead acid batteries used in vehicles. The batteries or battery will >>> always be charged by an alternator running off of the engine. >>> >>> Is it possible to get a run signal just from the battery? The PIC24F >>> microcontroller being used needs to be able to tell if the engine >>> is on or off. If could monitor the engine operation(on or off) from >>> the power source, I wouldn't need an additional device to monitor >>> this(oil pressure switch). >> >> You should be able to base it on the voltage. During charging the >> voltage should be in the 14 (28) volt range. When the engine is not >> running the voltage should be no more than the max charged voltage. >> I can not remember the full charge voltage off the top of my head, >> but it should be easy to find. The only way to charge the battery >> to full is to exceed that voltage. >> >> Scott > > --- and expect the indication to be a lot less reliable than a spark > signal, oil pressure, crankshaft once-around signal, or other signal > that happens as a direct consequence of the crankshaft turning.
Very true, depends on what reliability you need and what connections you have or can make. The battery voltage has the advantage that you are already connected to it. Scott
In article <7evrdqF2hb6msU1@mid.individual.net>, 
scott@validatedQWERTYsoftware.XYZZY.com says...
> Tim Wescott wrote: > > On Mon, 17 Aug 2009 09:50:43 -0600, Not Really Me wrote: > > > >> eeboarder wrote: > >>> I am developing a system that is powered from a 12V or 24V lead acid > >>> battery configuration on an industrial engine. These are the same > >>> lead acid batteries used in vehicles. The batteries or battery will > >>> always be charged by an alternator running off of the engine. > >>> > >>> Is it possible to get a run signal just from the battery? The PIC24F > >>> microcontroller being used needs to be able to tell if the engine > >>> is on or off. If could monitor the engine operation(on or off) from > >>> the power source, I wouldn't need an additional device to monitor > >>> this(oil pressure switch). > >> > >> You should be able to base it on the voltage. During charging the > >> voltage should be in the 14 (28) volt range. When the engine is not > >> running the voltage should be no more than the max charged voltage. > >> I can not remember the full charge voltage off the top of my head, > >> but it should be easy to find. The only way to charge the battery > >> to full is to exceed that voltage. > >> > >> Scott > > > > --- and expect the indication to be a lot less reliable than a spark > > signal, oil pressure, crankshaft once-around signal, or other signal > > that happens as a direct consequence of the crankshaft turning. > > Very true, depends on what reliability you need and what connections you > have or can make. The battery voltage has the advantage that you are > already connected to it.
Assuming the feed you are getting is from a very close point to the battery or alternator, not via a 6ft or longer feed, via in line fuses. Some kindly sole may even put a suppression caps or line choke on your feed somewhere. At start or later modification as people have habits of cleaning DC supplies on motors over time in many places. All of which is just some of the many ways you may not be able to rely on it being what you think always. -- Paul Carpenter | paul@pcserviceselectronics.co.uk <http://www.pcserviceselectronics.co.uk/> PC Services <http://www.pcserviceselectronics.co.uk/fonts/> Timing Diagram Font <http://www.gnuh8.org.uk/> GNU H8 - compiler & Renesas H8/H8S/H8 Tiny <http://www.badweb.org.uk/> For those web sites you hate
eeboarder wrote:
> I am developing a system that is powered from a 12V or 24V lead acid > battery configuration on an industrial engine. These are the same lead acid > batteries used in vehicles. The batteries or battery will always be charged > by an alternator running off of the engine. > > Is it possible to get a run signal just from the battery? The PIC24F > microcontroller being used needs to be able to tell if the engine is on or > off. If could monitor the engine operation(on or off) from the power > source, I wouldn't need an additional device to monitor this(oil pressure > switch).
I would be concerned about the reliability of that approach. Will the alternator disconnect for an over-voltage condition? Someone else mentioned a low-voltage condition when charging a discharged battery. I measured the AC riding on my car battery with my Radio Shack meter. It indicated 6 to 11 mV during idle -- I thought there would be more, but there might be enough hash to detect. Would the sampling be shielded enough from other, non-motor, noises to work reliably? -- Thad