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5v 2amps from a 12v 110amp leisure battery? Answered

whats the best way to get a power supply to my raspberry pi b+ which is 5 volts 2 amps from a 12 volt 110 amp leisure battery?

the method ive thought of so far is to connect a 12v cigarette lighter socket straight to the battery and put a 2amp usb charger in there, i cant see why this wouldn't work but is there a better way of doing this as i intend on using the Pi for playing music and if i don't get a good power supply it could interfere with sound quality.

thanks

Discussions

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AbleArcher83

3 years ago

they turned up today, thank you for you help.

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verence

3 years ago

Using a 2A USB charger sounds like a solid idea. Just to be safe, put a fuse (1A, slow) between the charger and the battery. 110A x 12V are A LOT of energy in the short circuit case. Put a low ESR capacity between 5V and ground to filter out any switching noise.

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AbleArcher83verence

Reply 3 years ago

sounds good verence, what does 'slow' mean in the 1A, slow that you mention

and what size low esr capacitor would you suggest?


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verenceAbleArcher83

Reply 3 years ago

A 1A fuse will not trip in the first instant the current goes over / reaches 1A. There is a little wire that needs to be heated up and melt. Depending on how much thermal mass the fuse has this may take a longer or shorter time.

A fast fuse will blow (almost) immediately while a slow fuse will tolerate a short period with a higher current. This is useful, when a circuit has a high in rush current when switched on. See here.

The capacitor is not critical. Something 1,000µF and up. 

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AbleArcher83AbleArcher83

Reply 3 years ago

sorry just to make sure ive understood i need to solder the capacitor to the 5v and ground of the usb charger?

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verenceAbleArcher83

Reply 3 years ago

Yep. Most likely, the capacitor's negative pole will be marked with a band of "-". This goes to the 0V/Gnd/Minus output of the charger, the other side goes to 5V of the output. Put the capacitor close to the charger if you have long cables between charger and Raspi.

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AbleArcher83verence

Reply 3 years ago

im just looking at getting a capacitor from ebay now verence does it matter what the voltage is? they seem to vary quite a lot

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verenceAbleArcher83

Reply 3 years ago

At least the voltage it is used at. As the USB output is regulated to 5V, a 5V capacitor is just okay, 10V are better. Anything higher is okay but will not be better. If you order more than one piece to get a better price, Downunder35m's 16V are a good value, you can use the leftovers in 12V circuits as well.

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Downunder35mAbleArcher83

Reply 3 years ago

16V electrolytic will do, anythin up to 50V is fine too, above that they just get beigger in size with no benefit to you.