# Temperature Coefficient Conversion %/C to %/K

sun_day
Registered Users Posts:

**23**✭✭
Hey all! I am using a software that only allow me to input %/K for the temperature coefficient. The solar module datasheet provided me a Voc temperature coefficient of -0.31%/C.

How can I convert %/C to %/K?

Thanks!

How can I convert %/C to %/K?

Thanks!

## Comments

5,183✭✭✭✭kel·vin(kĕl′vĭn)n. pl.kelvinAbbr.K1.A unit of absolute temperature equal to 1/273.16 of the absolute temperature of the triple point of water. One kelvin degree is equal to one Celsius degree. See Table atmeasurement.2.KelvinA temperature scale in which zero occurs at absolute zero and each degree equals one kelvin. Water freezes at 273.15 K and boils at 373.15 K.KID #51B 4s 140W to 24V 900Ah C&D AGM

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23✭✭3,738✭✭✭✭compensationis millivolts per degree K then it is also per degree C (no conversion necessary).Unfortunately the temp coefficient is not linear with temperature... That's why the coefficient for your batteries is given as a percent per degree Kelvin. In other words, the number of millivolts of

compensationper degree depends on the temperature.This is important because 30° C is 150% of 20° C, but 303° K (which is 30° C) is only 103% of 293° K (which is 20° C). As a practical matter, the temperatures at which we operate our batteries is fairly narrow on the Kelvin scale and the temp

compensationin millivolts per cell varies little over those temperatures.Thus if the temp

compensationwere 4 millivolts per cell at 20 ° C, then it would be reduced by 3.1% (10 degrees X -.31% per degree) to 3.9 millivolts per cell at 30° C.--vtMaps

23✭✭3,738✭✭✭✭I would prefer to set a temperature compensation of millivolts per degree. In the temperature range we run our batteries, that approach is good enough. Ultimately, what matters is the SG of your batteries.... if the batteries are cold and the SG is not up to spec, increase your absorb time and/or absorb voltage and/or your temp compensation. If the batteries are hot and the SG is up to spec, but you are using a lot of distilled water, then reduce your absorb time and/or absorb voltage and/or increase your temp compensation

--vtMaps

EDIT: I just reread this thread and realized you are asking about the temp coefficient of Voc of your modules. I have been writing about temp coefficient of battery charging. What sort of software are you using that needs the temp coefficient of Voc?

23✭✭Thanks for the reply. I am using Tritec TRI-KA software (it is an IV curve equipment and software). I need to input the temperature coefficient from the datasheet but the units they have in the software is only in %/K (or mV/K). However, the solar module datasheet provided the temperature coefficient only in %/C.

Therefore I don't think I can directly input -0.31%/C into the software as the unit in the software is %/K.

Really at a lost here... T_T

3,738✭✭✭✭However a K degree and a C degree are the same size, therefore mV/K is the same as mV/C.

--vtMaps

31,688adminIf mVolts/C -- The value will change based on Voc of cell/panel. (mV/C will be different when Voc is different between test subjects).

- Voc * %/C = mV/C

-Bill23✭✭@Bill - I don't think the formula finds the %/C to %/K as I think you are trying to show how to convert %/C to mV/C.

Does anyone else still have any idea on the unit change from %/C to %/K? @[email protected]

31,688adminIf you are doing differences in temperatures.

Absolute temperature conversion:

°C = K - 273

-Bill

3,738✭✭✭✭--vtMaps

23✭✭31,688admin-Bill

23✭✭Thanks lot for the help and teaching. I have understood it now.

2✭Hello,

A module I am working with shows the Temp Coeff for Voc as -(80±10)mV/°C How do I convert this to %/C?

Thank you,

Ed

31,688adminHere is an example for a Voc~21 volts ("12 volt" solar panel)

Note we are missing one variable, the per "what" device ... I am guessing this is per solar panel (i.e., per 21 Voc at standard temperature).

-Bill