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--- astra_conv:conversion:dcdc_converter:dcdc_converter [2014/03/17 21:30]
richard
+++ astra_conv:conversion:dcdc_converter:dcdc_converter [2014/03/17 22:37]
richard [how to spare the weight of the 12V lead-acid battery]
@@ Line 72: / Line 72: @@
 A short "making - of":
 {{:astra_conv:conversion:dcdc_converter:p1110486.jpg?300|}} {{:astra_conv:conversion:dcdc_converter:p1110487.jpg?300|}}
 {{:astra_conv:conversion:dcdc_converter:p1110489.jpg?300|}}
@@ Line 77: / Line 78: @@
 {{:astra_conv:conversion:dcdc_converter:p1110492.jpg?600|}}
-The current limiter is using the shroud as a heat sink (with additional cooling by the converter's air flow).
+The current limiter utilizes the shroud as a heat sink (with additional cooling by the converter's air flow).
-{{:astra_conv:conversion:dcdc_converter:p1110591.jpg?300|}}
+{{:astra_conv:conversion:dcdc_converter:p1110591.jpg?600|}}
 On the right, the opened 100V distribution box can be seen, with primary side fuse and the terminal area of the DC/DC converter primary driver. The output relay is hidden below in the front 12V distribution box.
-One device had failed at low temperature. Now, my DC/DC converters have to undergo the harsh and very professional "deep freeze" test.
+{{:astra_conv:conversion:dcdc_converter:p1110595.jpg?600|}}
+One device had failed at low temperature. Now, my DC/DC converters have to undergo a harsh and highly professional "deep freeze" test, to prove that they do start up at -18 degrees Celsius.
 {{:astra_conv:conversion:dcdc_converter:p1110482.jpg?600|}}
+\\
+==== how to spare the weight of the 12V lead-acid battery ====
+In principle, it would be possible to keep the DC/DC converter on permanently, or to add a second, smaller device that feeds the 12V grid while the car is idle.
+An additional, small DC/DC converter could be optimized for prolonging the battery life by doing all that ctek rituals of switching between different charging phases at different voltages. I am imagining to use a small 15V output DC/DC converter module as a power supply, followed by a microcontroller circuit that fine tunes the output voltage.
+With a permanent power supply, the battery is not drained any more while the car is idle, and it's size can be substantially reduced.
+The extreme case would be to omit the 12V battery at all. Of course, without a battery, it must be ensured that at any time that the DC/DC converter can deliver sufficient current to feed all 12V consumers. Especially for the anti-lock brakes, I am however not so sure about their peak current drain. A 12V battery will also come in handy as a back-up supply when the traction circuit is interrupted (maintenance) or when the DC/DC converter is broken.
+So, it is probably the best option to keep the 12V battery, and only make it smaller. Unfortunately, batteries below some 40Ah dont have proper sockets, so a mechanical adapter bracket will be required.
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