Hello,

I have a high-drain device that uses 2 NiMh (or 2 NiZn) AA batteries.
(Of course, the voltages would be slightly different for NiZn)

What I would like to do is find a schematic for a relatively simple circuit that would protect the batteries from excessive discharge by opening the circuit at 1.6v thereby stopping the flow of current and preventing the batteries from discharging any further.

For 12v batteries you can get them for next to nothing all day on ebay.
https://www.ebay.com/itm/Automatic-...810313&hash=item2a8a402a22:g:x0YAAOSwiiRZiVCD

I want something just like this but for the range of 1v to 3v.....
Is there such a circuit (or device) readily available?

 

Here's a circuit that uses a LED.....but it wont cut off the current

 

You may need to make it yourself.

Unfortunately, the TL431 doesn't go low enough but there are others voltage refs that will work. Use a comparator like the LM339 and a shunt voltage reference like the ZXRE060. Set up the ref to something like .6V as one input to the comparator and use a voltage divider from the battery so the cutoff voltage causes .6V on the other input to the comparator. It's got an open collector output that can sink up to 16 mA. Use that to control a transistor which would then control a relay or mosfet.

 

Hello,

I have a high-drain device that uses 2 NiMh (or 2 NiZn) AA batteries.
(Of course, the voltages would be slightly different for NiZn)

What I would like to do is find a schematic for a relatively simple circuit that would protect the batteries from excessive discharge by opening the circuit at 1.6v thereby stopping the flow of current and preventing the batteries from discharging any further.

For 12v batteries you can get them for next to nothing all day on ebay.
https://www.ebay.com/itm/Automatic-...810313&hash=item2a8a402a22:g:x0YAAOSwiiRZiVCD

I want something just like this but for the range of 1v to 3v.....
Is there such a circuit (or device) readily available?

Hi, what is ''high drain'' one Amp 100 Amp or 100mA?
Do you want to feed the protecting logic using the same cell's 3V?
This information is needed to define components.
(but difficult hence should be activated while >1.6V and therefore using current. And when switch off never goes on without human intervention )

Picbuster

 

High drain....yeah, that was a little too exact wasn't it? lol

I think I meant "High Drain" for 2 AA batteries.....so about 2-3Amps? (I'm gussing)
It's a battery powered vacuum so I just assumed it would draw a lot of amps for AA batteries.

Hi, what is ''high drain'' one Amp 100 Amp or 100mA?
Do you want to feed the protecting logic using the same cell's 3V?
This information is needed to define components.
(but difficult hence should be activated while >1.6V and therefore using current. And when switch off never goes on without human intervention )

Picbuster

Please accept my apology for the ambiguity.
I don't really know the amps drawn by the device but I made an assumption that it would be considered "high drain" (for this application) since it is a vacuum powered by 2 AA batteries. But you are right....I don't really know. I can measure the current with a VOM and I will post it once I do.

I think the protection circuit would have to be powered by the same to AA's

Thanks for you help.

 

a P mosfet, resistor and zener might do the trick.
Keep the gate low till power reached the wanted voltage. (Current will flow)
However; as a real pic buster will use the pic12lfxxx series 1.8V=> 3.6V. (no power supply chip needed)
use the analogue input measure keep the mosfet on. pulling it low with a N mosfet.
When voltage is bad set the pic in a endless loop.
like ; while (1) {Current=Off;}
Only a restart will recover from this situation.
When it goes to bad pic stops the N fet gate is low ( resistor) so P channel fet will not conduct.

If you want I can provide you with schematic.

Picbuster

 

A microcontroller wouldn't be a bad solution though instead of keeping powered, I'd suggest powering the PIC or Tiny from the controlled side of the mosfet so it doesn't continue to drain the battery, no matter how small that is.