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When Optima or Exide talk about "stopping when the battery reaches
120degrees F", How do they measure temperature.

On an AGM, which would be better, measure the case temperature, the
positive post or the negative post?

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Jeff Shanab writes:
>
> When Optima or Exide talk about "stopping when the battery reaches
> 120degrees F", How do they measure temperature.

Optima recommends putting the temperature sensor about an inch down
from the top of one of the inner cavities (reaching up from the bottom,
attached to the side of one of the inner cells).

I don't have Exide information.


> On an AGM, which would be better, measure the case temperature, the
> positive post or the negative post?

How about: None of the above? Optima specifically states that the
battery posts are not good places to measure temperature, especially
if cables are attached to the posts.

Ralph

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Jeff Shanab wrote:
> When Optima or Exide talk about "stopping when the battery reaches
> 120degrees F", How do they measure temperature.
>
> On an AGM, which would be better, measure the case temperature, the
> positive post or the negative post?

I'd measure the post temperature if you want a fast response. If a slow
response is adequate, somewhere on the sides or bottom of the plastic
case may be adequate if you put a piece of insulation over the sensor so
it is not affected by surrounding air temperature.

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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From: Morgan LaMoore
> If you measure post temperature, you're measuring an average between
> battery temperature and air temperature. All the (thermally
> conductive) battery wiring will mess with your temperature reading.

Yes, the post and associated wiring is air cooled. However, the internal heat from the battery is being conducted to the post by solid thick metal and direct contact with the electrolyte. Heat conduction through the metal and liquid generally "beats" the heat radiated by the air.

It actually works fairly well; better than trying to measure internal temperature through a thick plastic case.

> Besides, you shouldn't need a very fast response for battery
> temperature.

It depends on what you're doing. At low currents, battery temperature changes very slowly. But at high currents, it can change quickly; especially if something goes wrong.

Having the temperature sensor on the battery terminal also detects loose or corroded battery terminals!


--
"Excellence does not require perfection." -- Henry James
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart-at-earthlink.net

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The fact that when not charging, measuring the post temp can detect
loose connections is one of the considerations.

When chargeing I won't be putting in enough amps for a bad connection to
show up.(some people may but not me)


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