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astra_conv:conversion:dcdc_converter:dcdc_converter [2014/03/17 21:07] 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] |
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Requirements are e.g. | Requirements are e.g. | ||
- | * Water-Proofness: A device with air cooling and a nervous blower wont go anywhere easily - it is too noisy for the interior, and too sensitive for the engine bay. | + | * Humidity protection: A device with forced air cooling and a nervous blower wont go anywhere easily - it is too noisy for the interior, and too sensitive for the engine bay. |
* Output voltage: The output voltage must be 13.8V to 14V (under load as well) so that the 12V battery can be charged and is not depleted during driving. A grid voltage near 14V is also expected by the headlights, which will otherwise not appear "bright". | * Output voltage: The output voltage must be 13.8V to 14V (under load as well) so that the 12V battery can be charged and is not depleted during driving. A grid voltage near 14V is also expected by the headlights, which will otherwise not appear "bright". | ||
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The sealed converter (the light grey box at the left edge of the first picture) mounted onto the [[astra_conv:conversion:auxiliary_frame:auxiliary_frame#controller_frame|"controller" auxiliary frame]]. The mounting position is close to the radiator grill to ensure good ventilation. This device has an output voltage of 13,8V and delivers up to 36Amps. | The sealed converter (the light grey box at the left edge of the first picture) mounted onto the [[astra_conv:conversion:auxiliary_frame:auxiliary_frame#controller_frame|"controller" auxiliary frame]]. The mounting position is close to the radiator grill to ensure good ventilation. This device has an output voltage of 13,8V and delivers up to 36Amps. | ||
- | {{:astra_conv:conversion:dcdc_converter:p1090919.jpg?700 |}} {{:astra_conv:conversion:dcdc_converter:p1100610.jpg?700|}} | + | {{:astra_conv:conversion:dcdc_converter:p1090919.jpg?600|}} {{:astra_conv:conversion:dcdc_converter:p1100610.jpg?600|}} |
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+ | The second device has forced air cooling, so it required a protective shroud. | ||
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+ | A short "making - of": | ||
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+ | {{:astra_conv:conversion:dcdc_converter:p1110486.jpg?300|}} {{:astra_conv:conversion:dcdc_converter:p1110487.jpg?300|}} | ||
+ | {{:astra_conv:conversion:dcdc_converter:p1110489.jpg?300|}} | ||
+ | {{:astra_conv:conversion:dcdc_converter:p1110490.jpg?300|}} | ||
+ | {{:astra_conv:conversion:dcdc_converter:p1110492.jpg?600|}} | ||
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+ | The current limiter utilizes the shroud as a heat sink (with additional cooling by the converter's air flow). | ||
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+ | {{:astra_conv:conversion:dcdc_converter:p1110591.jpg?600|}} | ||
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+ | 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. | ||
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+ | {{:astra_conv:conversion:dcdc_converter:p1110595.jpg?600|}} | ||
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+ | 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. | ||
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+ | {{:astra_conv:conversion:dcdc_converter:p1110482.jpg?600|}} | ||
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+ | \\ | ||
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+ | ==== how to spare the weight of the 12V lead-acid battery ==== | ||
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+ | 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. | ||
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+ | 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. | ||
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+ | 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. | ||
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+ | 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. | ||
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+ | 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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