greatest invention i am tyrying to build

The voltage to set depends on the battery and its drain. EG - battery varies from ~11.3V to 12.7V (fully discharged to fully charged; Open Circuit voltage). Cranking batteries normally should not be discharged more than 30% (& deep cycle no more than 50% for good life). Hence - using my conservative rule of 0.1V per 10% discharge, 30% discharged is 12.7 - 0.3V = 12.4V. So you want to set the voltage to an open-circuit voltage of 12.3V to 12.4V. But that might be 11.5V or 11.0V depending on the load (and battery internal resistance - which increases as the battery discharges). 10V is too low. (Even under very high discharge rates - even UPS batteries at a 10 minute discharge rate are rarely taken as low as 10V, though they are AGM batteries....) As to what is enough to crank the vehicle - you will simple have to trial and error. Calculations could be done for a known battery and vehicle assuming reasonable staring time, but as the battery ages or temperatures drop or.... And you don't want a COx sensor in the box, nor car - you want it wherever living things are likely to be effected. But hopefully the bbq'er will notice people passing out and be able to stop the vehicle - unless they too have passed out, or the vehicle is locked etc.

oldspark wrote: The voltage to set depends on the battery and its drain. EG - battery varies from ~11.3V to 12.7V (fully discharged to fully charged; Open Circuit voltage). Cranking batteries normally should not be discharged more than 30% (& deep cycle no more than 50% for good life). Hence - using my conservative rule of 0.1V per 10% discharge, 30% discharged is 12.7 - 0.3V = 12.4V. So you want to set the voltage to an open-circuit voltage of 12.3V to 12.4V. But that might be 11.5V or 11.0V depending on the load (and battery internal resistance - which increases as the battery discharges). 10V is too low. (Even under very high discharge rates - even UPS batteries at a 10 minute discharge rate are rarely taken as low as 10V, though they are AGM batteries....) As to what is enough to crank the vehicle - you will simple have to trial and error. Calculations could be done for a known battery and vehicle assuming reasonable staring time, but as the battery ages or temperatures drop or.... And you don't want a COx sensor in the box, nor car - you want it wherever living things are likely to be effected. But hopefully the bbq'er will notice people passing out and be able to stop the vehicle - unless they too have passed out, or the vehicle is locked etc.

But hopefully the bbq'er will notice people passing out and be able to stop the vehicle - unless they too have passed out, or the vehicle is locked etc Thanks again,i am beginning to understand more about car batteries. I think the comment in bold is very funny and i burst put laughing just nowthe only interesting answers are the one that destroys the question.

I think a CO detector exposed in the vehicle would be better then nothing.  Like other things, you would have to trial it out.  I would think if you detect even low amounts of CO inside the car that would indicate that it isn't outside.  There would be quite a bit of lag on it, but it is better then nothing at all.

The sensor looks pretty straight forward - you would just need to determine where you would want the cut off and run it through an adc.  I think, in this case, it really could be that easy!

Kevin Pierson

And frankly Peter and I were taking the wiz, Kevin was tying to shut the poster up with knowledge! Look at his profile, I think he also mentions his company in one of these posts, Google it.

Yeah - I googled... Some links don't work but you will find stuff... I think I said something akin to "it's a good idea, but stupid" - ie, it seems like a good idea until you really think about it. (In tis case though, it may may need a bit of expertise - like the auto-starters that you guys know about, and battery behavior that I know about, and safety that most experienced know about. (Maybe a cat-converter to convert CO2 to CO since CO doesn't kill...?) [That's a joke - a medical student once wrote that...] Anyone seen my wheel? I don't want to have to invent it again!

My project is not complete yet due to a voice activated project for a mark3 golf.i will post a video of the finished project in 3 weeks timethe only interesting answers are the one that destroys the question.

tic tok tik toc....

Oh no please Peter do I need this tosh at 6:26 a.m.?

Yeah - sorry. But this post just appeared in front of me (keys ahead of the buffer again?). I read and just had to... Blame it on too much grass. (See my other "sweat" reply!) BTW - England nil. The other team will win.