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I'm looking for a device that breaks a circuit once the voltage of my battery gets too low. This to protect the battery.

Example: I have a 12V battery, once it reaches ~11V the huge voltage drop begins, but the device that is connected to the battery still runs and draws current. I need another device that can detect the voltage goes below 11V and then automatically breaks the circuit, preventing the circuit to draw more current from the battery. Basically, it shuts down the whole circuit.

Since English is not my native language and I'm not aware of any kinds of systems in my own language, I'm having a hard time finding something like this. Thanks in advance.

EDIT: or can I make my own?

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  • $\begingroup$ Zeners, FETs, op-amps,... there are dozens of simple voltage-sensitive control circuits. Find a "Electronics for Dummies" equivalent book or web page in your choice of languages. $\endgroup$ – Carl Witthoft Jul 27 '16 at 12:26
  • $\begingroup$ Thanks for the advice, but I don't really have the time to sift through a book of 400+ pages. Can you give me a specific example or website covering this? $\endgroup$ – Len Jul 27 '16 at 13:21
  • $\begingroup$ Better yet, buy a regulator, e.g. pololu.com/product/2577 or cdn.sparkfun.com/datasheets/Components/General/TO-220.pdf $\endgroup$ – Carl Witthoft Jul 27 '16 at 15:19
  • $\begingroup$ I don't need a regulator. I already have a buck converter to get my desired voltage, but I just need to protect my battery. Chris Johns has given a good answer below. $\endgroup$ – Len Jul 28 '16 at 7:27
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The simple answer is that you can get off the shelf modules which does exactly what you want.

They are often called 'split charge modules' and are designed for installations like boats and motor-homes which have batteries charged off an engine alternator but prevent the starter battery form being fully discharged.

This is one example http://www.12voltplanet.co.uk/voltage-sensitive-relay-12v-140a.html

They are not expensive and are easy to fit with basic knowledge of electronic systems.

There are also more sophisticated systems which allow for conditioning and management of auxiliary batteries

I have used this brand before : enter image description here

I can't remember the exact specification but they would certainly be in the 1A sort of range for a 12V system. I suggest this one in particular as it is easy to disassemble so you could discard the case and screw terminals to make it a lot more compact to package with the rest of your circuit.

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  • $\begingroup$ Thank you. It's a bit big for my own circuit (only have a low amperage system, but it runs for several days/weeks). I'm going to investigate further on this, but do you know anything smaller scale? As in: 12V 1A? $\endgroup$ – Len Jul 28 '16 at 7:36
  • $\begingroup$ if you buy a device like that check out the specs, I would bet that automotive device has some off-state current draw, so that it will reconnect when you charge the battery. For your application you ideally want a circuit that latches completely off. $\endgroup$ – agentp Jul 31 '16 at 15:03

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