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--- ideas:power_supply [2006/07/08 10:36] – rocketboy
+++ ideas:power_supply [2011/10/20 08:24] (current) – rocketboy
@@ Line 1: / Line 1: @@
 ====== Power Supply ======
-For balloon power supplies think - compact, lightweight and able to withstand cold – the obvious choice is some form of lithium battery pack – but which?
+For balloon payload power supplies think - compact, lightweight and able to withstand cold – the obvious choice is some form of lithium battery pack – but which?
   * **Lithium Thionyl Chloride**  (Li-SOCl2) - these typically have a voltage of 3.6V per cell – very good operating temperature range (some to –60degC)  however they a poor current capability (with an  AA sized battery typically not able to sustain more than a few 10s of milliamps)
@@ Line 9: / Line 9: @@
 {{:ideas:2cr5.jpg|:ideas:2cr5.jpg}}
-  * **Lithium Iron DiSulfide** (Li/FeS2) - e.g. Energizer E2 L91 or L92 - These are 1.5V batteries which can be used as a direct replacement for ordinary Alkalines. They have Good temperature characteristics  (down to -40 deg C).  As good if not better current handling characteristics to the Photo Lithiums. Similar (possibly better) energy density to Lithium Thionyl Chloride/Photo Lithiums.
+  * **Lithium Iron DiSulfide** (Li/FeS2) - e.g. Energizer E2 L91 or L92 - These are 1.5V batteries which can be used as a direct replacement for ordinary Alkalines. They have Good temperature characteristics  (down to -40 deg C).  As good if not better current handling characteristics to the Photo Lithiums. Similar (possibly better) energy density to Lithium Thionyl Chloride/Photo Lithiums. Energizer publish a comprehensive datasheet including temperature performance profiles for their cells [[http://data.energizer.com/PDFs/lithiuml91l92_appman.pdf|here]].
 {{:ideas:l92.jpg|:ideas:l92.jpg}}
-  * **Lithium Polymer** (Li-Poly) – normal voltage 3.7V – fair operating temperature range (down to –20 deg C) – excellent current handling characteristics – with AA sized cells (not that Li-Po cells are normally that shape)  Capable of sustained loads of several 100s of milliamps and peak loads into amps.  The big advantage of these cells is that they are re-chargeable (with the right charger). These have about half the energy density per unit weight of Lithium Thionyl chloride/Photo Lithium/Lithium Iron DiSulfide.
+  * **Lithium Polymer** (Li-Poly) – normal voltage 3.7V – fair operating temperature range (down to –20 deg C see [[http://www.ibt-power.com/Battery_packs/Li_Polymer/Lithium_polymer_tech.html]]) – excellent current handling characteristics. The big advantage of these cells is that they are re-chargeable (with the right charger). These have about half the energy density per unit weight of Lithium Thionyl chloride/Photo Lithium/Lithium Iron DiSulfide. Li-pos are well known for how easily they combust. Charging and discharging too fast, discharging too much and puncturing can all cause fire or explosions.
+{{:ideas:lipo.jpg|:ideas:lipo.jpg}}
+  * **Lithium Ion** (Li-ion) - similar in most respects to Lithium polymer, see [[http://www.ibt-power.com/Battery_packs/Li_Ion/Lithium_ion_tech.html]]
-  * **Lithium Ion** (Li-ion) - similar in most respects to Lithium polmer, but can operate at lower temperatures - down to -30 deg C
+**Solar Cells** are a possible alternative to batteries – there is plenty of sunlight above the clouds – or what about a combination of Li-Poly/Li-Ion with a solar cell charger (but be aware that incorrect charging of these batteries can cause a fire). These solar cells are on sale at Maplins [[http://www.maplin.co.uk/Module.aspx?ModuleNo=2310&criteria=solar%20cell&doy=7m7|BZ48C]] - they put out 0.45V at 400mA in bright sunlight - strip them out of their plastic case and they weigh just 8g each - size 57mm x 88mm x 2mm. (As of 14/11/09, BZ48C has been discontinued by Maplin, [[http://www.maplin.co.uk/Module.aspx?ModuleNo=97350|Order Code: N80CH]] seems to be the nearest replacement.)
-**Solar Cells** are a possible alternative to batteries – there is plenty of sunlight above the clouds – or what about a combination of Li-Poly/Li-Ion with a solar cell charger (but be aware that incorrect charging of Li-Poly batteries can cause a fire). These solar cells are on sale at Maplins [[http://www.maplin.co.uk/Module.aspx?ModuleNo=2310&criteria=solar%20cell&doy=7m7|BZ48C]] - they put out 0.45V at 400mA in bright sunlight - strip them out of their plasic case and they weigh just 8g each - size 57mm x 88mm x 2mm.
 {{:ideas:solar.jpg|:ideas:solar.jpg}}
+You can also find small-size solar panels suitable for airborne purposes on: [[http://www.solarbotics.com/]]