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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?
Yes and No. It depends on the particular engine assembly.
> 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).
The alternator generates the AC ripples which can be seen at the battery terminals. You can even get the engine RPM by that ripples. However this behaviour is stongly dependent on the particular engine and the associated electrics, and this method won't work at all for some engines. So, if your goal is a mass production device, I won't count on it. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com
On Aug 17, 12:18=A0pm, Vladimir Vassilevsky <nos...@nowhere.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 cha=
rged
> > by an alternator running off of the engine. > > > Is it possible to get a run signal just from the battery? > > Yes and No. It depends on the particular engine assembly. > > > 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 pressu=
re
> > switch). > > The alternator generates the AC ripples which can be seen at the battery > terminals. You can even get the engine RPM by that ripples. However this > behaviour is stongly dependent on the particular engine and the > associated electrics, and this method won't work at all for some > engines. So, if your goal is a mass production device, I won't count on i=
t.
> > Vladimir Vassilevsky > DSP and Mixed Signal Design Consultanthttp://www.abvolt.com
Hmmm....maybe use the exciter circuit thru a bridge on-board and detect when the voltage is equalized or , as someone said, perhaps detect the change in current flow to/from the battery. have to create a rectifier circuit that indicates the change in current flow, but it could be built into your on-board power supply I guess. I dunno if I made myself clear! hah! Carl

1 Lucky Texan wrote:

> On Aug 17, 12:18 pm, Vladimir Vassilevsky <nos...@nowhere.com> wrote: > >>eeboarder wrote: >>
>>>Is it possible to get a run signal just from the battery?
>>Yes and No. It depends on the particular engine assembly. >>The alternator generates the AC ripples which can be seen at the battery >>terminals. You can even get the engine RPM by that ripples. However this >>behaviour is stongly dependent on the particular engine and the >>associated electrics, and this method won't work at all for some >>engines.
> Hmmm....maybe use the exciter circuit thru a bridge on-board and > detect when the voltage is equalized or , as someone said, perhaps > detect the change in current flow to/from the battery. have to create > a rectifier circuit that indicates the change in current flow, but it > could be built into your on-board power supply I guess.
This isn't 100% reliable either since the current flow depends on the engine RPM, the amount of electric load, the temperature and the charging state of the battery. In our days it is all controlled by the MCUs, so you can't take anything for granted. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com