Introduction: Make a Battery Protection Circuit (low Voltage Cut-off)

In this video I will show you how to build a simple lithium battery protection circuit, so you can power your homemade projects without ever worrying about over discharging your battery.

How to use lithium batteries safely:

More info on battery measurements:

Items you'll need:

Alarm circuit:

Relay: DSP1a-L2-DC5V (select one of the distributors - price is around $5)

Music by Kevin McLeod and Löhstana David


dhyde79 (author)2017-11-14

I'm hoping to make something like this, could you help me with it? I need a circuit that'll monitor voltage of a battery (3S LiPo, "normal voltage" of 11.1V, minimum voltage of 9V) but, instead of a digital readout, I only need 3 LED's, (red/yellow/green) for "full" (11.1V+) "medium" (11.0V-10V) and "low" (less than 10V), and, since it's for an airsoft gun, I need it as compact as possible, and preferably without the LEDs having to be soldered directly to a board, but rather run on a lead so that I can run them through the gun back to where I want it to be (and be visible). Could you possibly assist with this?

dtawom made it! (author)2017-08-31

Help me DIY-Wan Kenobi ... you're my only hope. I've built a variation of this with the intention
of using it to drain cell phone batteries for their three initial training
cycles. I've only made one change to
your original circuit design to accommodate a single cell instead of two, but
it's not working as it should. I've
attached a picture with a modification to your original diagram that shows the
only change I made.

Here is the problem: The alarm appears to be working fine,
but when the battery reaches the predefined voltage the relay never trips and
the power draw device stays on (in my case an LED flashlight). I've removed and
tested the relay independently and it is working, I've also tried another alarm
circuit in case the first one was defective.
I've narrowed it down to the speaker connections, when the alarm trips,
no power is provided to the speaker positive and negative connections, nor does
the red LED start flashing. If I manually
apply power to the positive and negative speaker connections the relay trips,
the red led starts flashing, and my power draw device turns off.

Am I missing something simple here, did I just get two
defective alarm circuits, did my design change have an impact I don't
understand? Any help from anybody would
be greatly appreciated.


FreekC1 made it! (author)2017-07-26

Hi Matt, I made your circuit, used a DE1a-L2-5V because this one is 10A rated :) The only change needed was to connect the switch to the first coil and the alarm system to the second. Thank you for the great circuit!

RedBul Fuel (author)2017-02-21

Am I able to use this DSP1A-L2-DC9v instead of the DSP1A-L2-DC5v and just tap into the 3s balance wire? I am unable to get a hold of the 5v in Canada without crazy shipping cost or is there another brand I can substitute. hope you or someone can help

ArlingtonH made it! (author)2017-02-17

Based on the original, this is a version of the
“Battery Protection Circuit (low voltage
cut-off)” that I recreated.

I am using two combined latching switch to create a nine (9) pole-latching switch, which can be
connected and successfully operate any 2 to 8 cell lipo battery.

The latching switch turns on/off the unit as

Two protection circuits will be use as part of a lipo battery 2000 watt 1 ohm resistors discharger
system for medium to large capacity batteries
used in RC vehicle.

The prototype works well.

DanielJ245 made it! (author)2017-01-14

I have slightly altered the design to fit my needs, but it is basically the simpler version of the two

barrymossel (author)2016-01-16

Wow, really great, just what I needed. Could you maybe link to all products used?

Is it necessary to use a 82 Ohm resistor or could I use a 100 Ohm one?

And what kind of push button do you use, as I guess it should be a momentary switch, but it looks like a latching switch?

seamster (author)2014-11-05

Very nice! This is a handy item to have.

I've wanted a low voltage alarm for my rc planes, but never sprung to buy one. I'm guessing this could be modified fairly simply to trip a loud buzzer, rather than simply cut off power?

ffink (author)seamster2015-09-14

the lipo alarm which is modified in this instructable beeps loudly when the trigger voltage is being reached. this instructable shows how to modify it so it doesn't beep anymore but instead cuts thr circuit. if you simply want an alarm but no circuit cut, just use the alarm behind the link.

MarcR6 (author)2015-07-23

To turn the circuit off, wouldn't it be more simple to add a toggle switch between one of the balanced connectors and the monitor, so that when off, it would read 0v and trigger the "alarm" which in turn triggers the relay?

About This Instructable




Bio: Hello! I'm Matt and I love making things. I'm always thinking of new ideas and how to make them as awesome as possible ... More »
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