Asked
— Edited
Something I've been looking at since I undervoltaged one of my LiPo batteries is an auto cut off circuit when it get's below around 6.2v
I think this will do it but could do with some confirmation since this is not my area of expertise so am always concerned. Any comments and suggestions would be extremely appreciated.
If it is OK you can expect to see this replaced with a tutorial
Zener Diode is rated for 6.2V Mosfet is rated at 85A
I realise a small load may pass through R1 when shut off but I assume it will be so small it will not matter (unless left for a very long period)
If you'd like, I could test the circuit this saturday at our local hackerspace
That would be great if you could, I've not had chance to finish this one yet.
Hi Rich,
Sadly, your circuit did not work. In stead of 'snapping' off, the current just went down slightly with the voltage, I had a little talk with Ite, a very experienced EE and he recommended either a comparator or a specialized IC.
I'd also found this circuit, which I will be testing next:
-OFF-635062570995625000.png)
(more info)I just need to adjust the voltage divider for it to work with 2S Lipo's in stead of 3S.
Edit: we don't currently have the TL431 in stock and a simple cutoff IC would be cheaper
Thanks for testing it. I guess my theory is slightly off
I had assumed that if the voltage was above the rating of the diode it would allow it to pass therefore energising the transistor/mosfet base that allowed current to pass to ground, completing the circuit...
Hopefully we can find a solution, with LiPo batteries becoming more and more popular I'm sure it'll be something a lot of people will want - especially if they do what I did and leave their bot on.
This might be easier/cheaper for most people.
Its OK , it will get figured out soon enough. I will need a voltage cutoff on mine even when I'm still using lead acid so it doesn't get so far drained it takes a long time to charge back up.
@Rich.
Where did you get with this topic, with your own projects to incorperate a power cut-off circuit/off shelve solution? Was it something you followed up on?
No, this one never went anywhere. By the time I had time to get back on it the V4 was out which has it's built in low batter monitor which does the job just fine.