Michael Ross wrote:
120°F is high for PbSO4 isn't it? I always heard to keep the temp during
charging below 100°F.
Hot is good for performance; but bad for life.
The EV racers deliberately heat up their batteries to maximize the power
they can get out of the. However, this shortens their life. But that
doesn't matter in racing.
I have been thinking about pipe tape for this...with a controller. You
could weave a length of pipe tape among the cells, or fix it to a plate of
aluminum.
You need to know what you're getting. Some "tape" or "strip" heaters use
actual resistance wire (like nichrome, or just plain steel when they
want to be cheap). The resistance of a metallic wire is (roughly)
constant; so the current is predicted by Ohm's law. If you apply a fixed
voltage, it dissipates a fixed wattage, which produces a fixed
temperature *rise*. The exact amount of temperature rise is determines
by the insulation and thermal conductivity of the materials around it.
You need a thermostat to get a fixed temperature with this type of wire.
Others types use a conductive rubberlike material, whose resistance
changes *drastically* with temperature, applied voltage, and other
factors. This type of wire is used to make it somewhat self-adjusting.
They can make its resistance increase with voltage, so it tends to
self-regulate its wattage. And, they can make its resistance go up as
the temperature increases, so roughly regulates temperature without a
thermostat.
The drawback of the latter type of heating element is that they aren't
very stable. Their characteristics drift over time. They are also easily
deformed by flexing or pressure (such as pinching them, bending around a
sharp corner, or piling heavy batteries on top of it).
--
Engineers like to solve problems. If there are no problems handily
available, they will create their own problems. -- Scott Adams
--
Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm
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