Difference between revisions of "battery power storage"
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[[Category:Engineering]] | [[Category:Engineering]] | ||
+ | == Lithium == | ||
+ | |||
+ | It requires about 0.3 grams of lithium to store 1 Ampere hour of power. | ||
+ | |||
+ | == battery pack thermal protection == | ||
A custom battery pack should have thermal protection to prevent cell damage or rupture during charging or discharging. | A custom battery pack should have thermal protection to prevent cell damage or rupture during charging or discharging. | ||
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An NTC thermistor can also be used for surge protection. It gives a soft start when equipment is first powered up. When powering up the NTC is cold and resistance is high thus limiting current. As the current flows the NTC thermistor will get warmer. This causes resistance to drop which removes the current limiting factor from the circuit. | An NTC thermistor can also be used for surge protection. It gives a soft start when equipment is first powered up. When powering up the NTC is cold and resistance is high thus limiting current. As the current flows the NTC thermistor will get warmer. This causes resistance to drop which removes the current limiting factor from the circuit. | ||
− | == Measure R<sub>T</sub> == | + | === Measure R<sub>T</sub> === |
Put the NTC thermistor in series with a fixed value resistor to create a voltage divider. V<sub>cc</sub> will typically be 5V or 3.3V for a microcontroller. In this example I use a 10kΩ resistor. Measure the voltage drop across the NTC thermistor, '''V<sub>drop</sub> = R<sub>T</sub> / (R<sub>T</sub> + 10000) * V<sub>cc</sub>'''. So this gives us, '''R<sub>T</sub> = 10000 / (V<sub>cc</sub> / V<sub>drop</sub> - 1)'''. | Put the NTC thermistor in series with a fixed value resistor to create a voltage divider. V<sub>cc</sub> will typically be 5V or 3.3V for a microcontroller. In this example I use a 10kΩ resistor. Measure the voltage drop across the NTC thermistor, '''V<sub>drop</sub> = R<sub>T</sub> / (R<sub>T</sub> + 10000) * V<sub>cc</sub>'''. So this gives us, '''R<sub>T</sub> = 10000 / (V<sub>cc</sub> / V<sub>drop</sub> - 1)'''. | ||
− | == PTC Fuse == | + | === PTC Fuse === |
A '''PTC''' resistor may also be used as a thermal fuse to temporarily cut power to or from the cell. | A '''PTC''' resistor may also be used as a thermal fuse to temporarily cut power to or from the cell. | ||
− | == Table of Resistance versus Temperature for M 3950 == | + | === Table of Resistance versus Temperature for M 3950 === |
− | T(°C) | + | R<sub>T</sub>(Ω} T(°C) R<sub>T</sub>/R<sub>25</sub> TF(%) α(%/°C) |
<pre> | <pre> | ||
− | -55 99.56 23.2 -7.71 | + | 995600.0 -55 99.56 23.2 -7.71 |
− | -50 68.95 20.1 -7.42 | + | 689500.0 -50 68.95 20.1 -7.42 |
− | -45 48.38 17.3 -7.15 | + | 483800.0 -45 48.38 17.3 -7.15 |
− | -40 34.37 14.8 -6.89 | + | 343700.0 -40 34.37 14.8 -6.89 |
− | -35 24.71 12.5 -6.64 | + | 247100.0 -35 24.71 12.5 -6.64 |
− | -30 17.96 10.6 -6.41 | + | 179600.0 -30 17.96 10.6 -6.41 |
− | -25 13.20 8.8 -6.18 | + | 132000.0 -25 13.20 8.8 -6.18 |
− | -20 9.803 7.3 -5.97 | + | 98030.0 -20 9.803 7.3 -5.97 |
− | -15 7.351 5.9 -5.77 | + | 73510.0 -15 7.351 5.9 -5.77 |
− | -10 5.585 4.7 -5.57 | + | 55850.0 -10 5.585 4.7 -5.57 |
− | -5 4.251 3.7 -5.39 | + | 42510.0 -5 4.251 3.7 -5.39 |
− | + | 32750.0 0 3.275 2.8 -5.21 | |
− | + | 25440.0 5 2.544 2.0 -5.04 | |
− | 10 1.992 1.4 -4.88 | + | 19920.0 10 1.992 1.4 -4.88 |
− | 15 1.572 0.8 -4.73 | + | 15720.0 15 1.572 0.8 -4.73 |
− | 20 1.249 0.4 -4.58 | + | 12490.0 20 1.249 0.4 -4.58 |
− | 25 1.0000 0.0 -4.44 | + | 10000.0 25 1.0000 0.0 -4.44 |
− | + | 8057.0 30 0.8057 0.4 -4.30 | |
− | + | 6534.0 35 0.6534 0.8 -4.17 | |
− | + | 5331.0 40 0.5331 1.2 -4.05 | |
− | + | 4376.0 45 0.4376 1.7 -3.93 | |
− | + | 3612.0 50 0.3612 2.2 -3.81 | |
− | + | 2998.0 55 0.2998 2.8 -3.71 | |
− | + | 2501.0 60 0.2501 3.4 -3.60 | |
− | + | 2097.0 65 0.2097 4.0 -3.50 | |
− | + | 1767.0 70 0.1767 4.6 -3.40 | |
− | + | 1496.0 75 0.1496 5.3 -3.31 | |
− | + | 1272.0 80 0.1272 6.0 -3.22 | |
− | + | 1087.0 85 0.1087 6.7 -3.13 | |
− | + | 932.1 90 0.09321 7.4 -3.05 | |
− | + | 802.7 95 0.08027 8.1 -2.97 | |
− | 100 0.06939 8.8 -2.89 | + | 693.9 100 0.06939 8.8 -2.89 |
− | 105 0.06020 9.5 -2.82 | + | 602.0 105 0.06020 9.5 -2.82 |
− | 110 0.05243 10.2 -2.75 | + | 524.3 110 0.05243 10.2 -2.75 |
− | 115 0.04581 11.0 -2.68 | + | 458.1 115 0.04581 11.0 -2.68 |
− | 120 0.04017 11.7 -2.61 | + | 401.7 120 0.04017 11.7 -2.61 |
− | 125 0.03533 12.5 -2.55 | + | 353.3 125 0.03533 12.5 -2.55 |
− | 130 0.03117 13.2 -2.48 | + | 311.7 130 0.03117 13.2 -2.48 |
− | 135 0.02759 14.0 -2.42 | + | 275.9 135 0.02759 14.0 -2.42 |
− | 140 0.02449 14.7 -2.37 | + | 244.9 140 0.02449 14.7 -2.37 |
− | 145 0.02180 15.5 -2.31 | + | 218.0 145 0.02180 15.5 -2.31 |
− | 150 0.01945 16.2 -2.26 | + | 194.5 150 0.01945 16.2 -2.26 |
</pre> | </pre> |
Latest revision as of 05:51, 27 June 2017
Contents
Lithium
It requires about 0.3 grams of lithium to store 1 Ampere hour of power.
battery pack thermal protection
A custom battery pack should have thermal protection to prevent cell damage or rupture during charging or discharging. The standard is to use an NTC thermistor 10k 3950. That is, R25°C=10kΩ, and B=3950. B is the sensitivity index constant. Note that 25°C=298.15°K. To calculate temperature from resistance, T = B / (ln(R/r∞)).
An NTC thermistor can also be used for surge protection. It gives a soft start when equipment is first powered up. When powering up the NTC is cold and resistance is high thus limiting current. As the current flows the NTC thermistor will get warmer. This causes resistance to drop which removes the current limiting factor from the circuit.
Measure RT
Put the NTC thermistor in series with a fixed value resistor to create a voltage divider. Vcc will typically be 5V or 3.3V for a microcontroller. In this example I use a 10kΩ resistor. Measure the voltage drop across the NTC thermistor, Vdrop = RT / (RT + 10000) * Vcc. So this gives us, RT = 10000 / (Vcc / Vdrop - 1).
PTC Fuse
A PTC resistor may also be used as a thermal fuse to temporarily cut power to or from the cell.
Table of Resistance versus Temperature for M 3950
RT(Ω} T(°C) RT/R25 TF(%) α(%/°C)
995600.0 -55 99.56 23.2 -7.71 689500.0 -50 68.95 20.1 -7.42 483800.0 -45 48.38 17.3 -7.15 343700.0 -40 34.37 14.8 -6.89 247100.0 -35 24.71 12.5 -6.64 179600.0 -30 17.96 10.6 -6.41 132000.0 -25 13.20 8.8 -6.18 98030.0 -20 9.803 7.3 -5.97 73510.0 -15 7.351 5.9 -5.77 55850.0 -10 5.585 4.7 -5.57 42510.0 -5 4.251 3.7 -5.39 32750.0 0 3.275 2.8 -5.21 25440.0 5 2.544 2.0 -5.04 19920.0 10 1.992 1.4 -4.88 15720.0 15 1.572 0.8 -4.73 12490.0 20 1.249 0.4 -4.58 10000.0 25 1.0000 0.0 -4.44 8057.0 30 0.8057 0.4 -4.30 6534.0 35 0.6534 0.8 -4.17 5331.0 40 0.5331 1.2 -4.05 4376.0 45 0.4376 1.7 -3.93 3612.0 50 0.3612 2.2 -3.81 2998.0 55 0.2998 2.8 -3.71 2501.0 60 0.2501 3.4 -3.60 2097.0 65 0.2097 4.0 -3.50 1767.0 70 0.1767 4.6 -3.40 1496.0 75 0.1496 5.3 -3.31 1272.0 80 0.1272 6.0 -3.22 1087.0 85 0.1087 6.7 -3.13 932.1 90 0.09321 7.4 -3.05 802.7 95 0.08027 8.1 -2.97 693.9 100 0.06939 8.8 -2.89 602.0 105 0.06020 9.5 -2.82 524.3 110 0.05243 10.2 -2.75 458.1 115 0.04581 11.0 -2.68 401.7 120 0.04017 11.7 -2.61 353.3 125 0.03533 12.5 -2.55 311.7 130 0.03117 13.2 -2.48 275.9 135 0.02759 14.0 -2.42 244.9 140 0.02449 14.7 -2.37 218.0 145 0.02180 15.5 -2.31 194.5 150 0.01945 16.2 -2.26