Elevation

[TravlinMan]

Was makin my coffee this mornin and got thinkin about elevation changin up the boilin point and then I started thinkin what good is my battery temp sensor if it don't know my elevation? If I'm at 10,000' ain't my converter gonna boil the batteries if it uses the same voltage as it does at 0'? Am I overthinkin this?

[OTRA15]

Won't the temp sensor take care of this, at least indirectly? I forget do you have AGM's or lead cell flooded? The dual use of the word "boil" may result in some over-thinking IMO. Is the chemistry of water boiling at 212F similar to batteries boiling due to overcharging?



Beyond my knowledge, but a good question!

Peter

[TravlinMan]

I still got the interstate wet batteries.

The thing is that the temp sensor only measures the surrounding area of the battery. So its never gonna sense 195 degrees or more. It don't know the temp of the water, just the environment. Also, even if it knew the temp of the water, if it thinks the boilin point is 211 but it's actually 195 cause of elevation... How does it account for that? Im just tryin to uderstand the science here....

[OTRA15]

The thing is -- it is no longer "water" IMO. It is a new chemical that started with H2O as a main ingredient. The question would be what is the boiling point of that new liquid, and is it affected by changes in barometric pressure?

Sometimes during really low pressure weather events [hurricanes etc.], the atmospheric pressure probably gets as low as it does at high elevations, yet we have never seen warnings not to charge batteries during a hurricane, for instance.

Guessing a non-issue . . . think I will stop thinking about it . . .

[rmkrum]

Batteries don't actually "boil" in the sense of heating a kettle of water to the boiling point. What is described as "boiling batteries" is water loss due to overcharging. It's not heating the battery to the vaporization point of water...

[TravlinMan]

Ok thank you. That was just what I was wonderin.

[Burnside Bob]

Battery "boiling" from over charging and water boiling are two different processes. In the first, the gasses "boiling" out of the battery fluid are hydrogen and oxygen. In the second, the gas boiling is water vapor.

The first process is driven by electric potential and is not significantly affected by altitude. The second process is driven by heat and atmospheric pressure determines the boiling temperature.

There is a good discussion of gas generation in lead acid batteries in this article (among other topics):

http://www.battcon.com/papersfinal20...008proof_6.pdf

And there is a graph of water's boiling temperature by altitude here:

http://www.engineeringtoolbox.com/bo...de-d_1344.html

And that's probably info overload!!

[Jammer]

Originally Posted by TravlinMan

Was makin my coffee this mornin and got thinkin about elevation changin up the boilin point and then I started thinkin what good is my battery temp sensor if it don't know my elevation? If I'm at 10,000' ain't my converter gonna boil the batteries if it uses the same voltage as it does at 0'?

nope

Am I overthinkin this?

Yup

Batteries don't reach a temperature where the electrolyte actually "boils." What's going on here is that the voltage at which they are fully charged is lower when temperature is higher. So in order for the converter to know when to stop charging it has to know voltage and temperature. Altitude does not affect the battery to any material degree.

[rmkrum]

Well, actually you can overcurrent a battery to the point that the electrolyte does boil, but it take a lot of current to do that. I've had it happen in a series string of batteries that added up to 120 volts D.C. When one battery shorted out (AGM type) the case ruptured and stared spewing steam (plus acid vapor). Was no fun getting that under control.

It was part of a big UPS system and we think a couple cells shorted out. The battery charge circuit went full current trying to bring the voltage up fast.

[TravlinMan]

Thank you it is helpful for me to try and understand this stuff. I appreciate it.