I am trying to power up a Raspberry Pi outdoors. So I got a lead cell battery and a car cigarette lighter to USB converter (12v-to-5v step down converter). Unfortunately, before even connecting the raspberry, the converters broke down.

I have the following lead acid cell battery is 12v and 7Ah, 28w/cell/15min

Now I connected this battery with a car battery cigarette lighter hub and usb output :


buit it burnt right away.

Then I tried another cigarette lighter to USB converter but it was also destroyed.


The question would be, what am I doing wrong? what additional elements needed to make this thing work.

Would this device work? http://www.ebay.com/itm/DC-Converter-Buck-Module-12V-convert-to-5V-usb-output-power-adapter-/251195111986


closed as not a real question by Leon Heller, Phil Frost, Anindo Ghosh, Olin Lathrop, Brian Carlton Feb 11 '13 at 18:08

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ Please edit your post to state what your question is. As it stands, it does not state what answer you seek. \$\endgroup\$ – Anindo Ghosh Feb 11 '13 at 13:58
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    \$\begingroup\$ Another insightful question might be: "What engineering tradeoffs were made to make this device profitable at $1.70?" \$\endgroup\$ – Phil Frost Feb 11 '13 at 15:23
  • \$\begingroup\$ @PhilFrost - +1 for your excellent point. \$\endgroup\$ – Michael Karas Feb 11 '13 at 16:02
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    \$\begingroup\$ I do not understand why being so sarcastic. If you have knowledge either share it or ignore this thread. \$\endgroup\$ – user18882 Feb 11 '13 at 16:11
  • \$\begingroup\$ @AnindoGhosh I have rewritten my question, thanks. \$\endgroup\$ – user18882 Feb 11 '13 at 16:11

Given the unknown pedigree of the DC-DC switching regulator module specified in the question, it is difficult to speculate on whether the device would work well, work for a while, or fail outright. You won't know till you try.

The product description in the listing does specify a 3 Ampere capacity, so it should be good for at least a third of that, if it doesn't suffer from infant mortality, i.e. product failure at first power-on, as some poorly engineered or constructed devices, or even excellent and normally reliable products, do.

Also, as the question does not specify which model of the Raspberry Pi is involved, the following information from the Pi site might be useful:

Model B owners using networking and high-current USB peripherals will require a supply which can source 700 mA (many phone chargers meet this requirement).

Model A owners with powered USB devices will be able to get away with a much lower current capacity (300 mA feels like a reasonable safety margin).

Please note that, as with much of the "technical" information made available by the foundation, there is no specified maximum limit of power consumption, just a somewhat vague "feels like a reasonable safety margin".

A phrase like that should be grounds for worry.


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