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




About: 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, always with a mind to share the process online. Take a look at my profile and see if th...

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


4 People Made This Project!


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8 Discussions


Question 8 months ago

will this work as is on a 4s pack or will it need to be modified in any way?


Question 1 year ago on Introduction

That relay only handles 8A. Would this circuit still be suitable for RC projects (such as drones) that can routinely spike to hundreds of Amps current?


1 year ago

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?

RedBul Fuel

2 years ago

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


3 years ago

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?


4 years ago on Introduction

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?

1 reply

Reply 3 years ago

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.


3 years ago on Introduction

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?