Reversable battery circuit

[Jester]

I'm looking for a circuit that will allow a circuit to operate with the battery connected with correct or incorrect polarity.

The circuit below seems like an efficient and elegant solution except it will only work for circuits in the mA range.

Is anyone aware of a solution for higher currents (say 2A) that relies on low Rds FET's?

The bridge rectifier solution is a non starter because of the diode drops. I'm not looking for circuit that simply protects the circuit from a reverse battery, but one that allows operation with reverse battery.

 

[FvM]

I believe, two pairs of logic level NMOS and PMOS FETs should do. Simply an extension of the usual reversal protection circuit.

 

[Jester]

I believe, two pairs of logic level NMOS and PMOS FETs should do. Simply an extension of the usual reversal protection circuit.

This will be used between a 1A charger and a 3.6V Lithium battery based circuit, do this look like a reasonable FET to use?
https://www.digikey.ca/product-detail/en/DMHC3025LSD-13/DMHC3025LSD-13DICT-ND/3677986

 

[D.A.(Tony)Stewart]

Nice try, but that would need a separate supply.
2A currents are pretty large for a 1.5V battery,
Maybe this will work https://www.digikey.com/product-detail/en/SM74611KTTR/296-35688-2-ND/3906419 $3.78 (1)

 

[Jester]

Nice try, but that would need a separate supply.
2A currents are pretty large for a 1.5V battery,
Maybe this will work https://www.digikey.com/product-detail/en/SM74611KTTR/296-35688-2-ND/3906419 $3.78 (1)

I don't follow the part about a separate supply?

Vgs(th) = 2V

2A is the maximum current available from the charger, actual current would likely be about 100mA

Circuit:

 

[D.A.(Tony)Stewart]

How do you bias Vgs when it is larger than Vbat.

 

[FvM]

MOSFETs can connected as synchronous rectifier, they don't need an external supply



For 3.6V battery operation, you'll prefer MOSFETs with specified Rdson at 2.5V Vgs.

- - - Updated - - -

I see you ended up with the same circuit.

 

[D.A.(Tony)Stewart]

I'm looking for a circuit that will allow a circuit to operate with the battery connected with correct or incorrect polarity.

The circuit below seems like an efficient and elegant solution except it will only work for circuits in the mA range.

Is anyone aware of a solution for higher currents (say 2A) that relies on low Rds FET's?

The bridge rectifier solution is a non starter because of the diode drops. I'm not looking for circuit that simply protects the circuit from a reverse battery, but one that allows operation with reverse battery.
View attachment 119520

Your requirements shows Vbat 1.5 to 5.5 but the bridge you chose shows Vgs=2.5 as a threshold, thus Vbat is compromised.

 

[Jester]

MOSFETs can connected as synchronous rectifier, they don't need an external supply



For 3.6V battery operation, you'll prefer MOSFETs with specified Rdson at 2.5V Vgs.

- - - Updated - - -

I see you ended up with the same circuit.

Yes, full turn on may be a bit marginal with this voltage and obviously no good for single or double cell applications. I will keep looking for a better array, thanks again:smile:

 

[FvM]

I think, 1.5 to 5.5 is a Maxim application note specification. But 2.5. or 1.8 V logic level FETs would be better than the Diodes 4.5 V type.