Interesting battery isolator

[GlutealCleft]

While surfing around wasting time, I came across this idea for a battery isolator:

http://www.discovercircuits.com/H-Corner/bat-iso.htm

It looks pretty interesting.  Using a switching FET instead of a diode means that you don't have the forward voltage drop to keep your batteries from reaching full capacity.  At about $3 per chip, you could make a board with as many "channels" as you needed for between $5-$9 per channel, depending on how large (and how many) FETs you needed.

I know that there are some serious electronics wizards here, has anyone fiddled around with anything like this?

[Nando]

I have designed the equivalent with N MosFet devices in dual ( series ) form for

full bi-directional control.

This controller is geared to be used with P MosFet devices that are more expensive and limited voltage range for those that have high current capability.

The controller comes in the sot size only, for power control in boxes like the cellular phones.

The ones I have designed were capable of handling 100 to 150 amps or even higher with a greater number of Fets in parallel.

Nando

[dinges]

I am sure quite a few people in this board are interested in your design. I know I am.

A schematic to have a peek at would be very nice; could you post it here? I assume the original poster would like to see it too.

Regards,

[wooferhound]

The schematic is in the link that the original poster listed . . .

[wooferhound]

Oops he was talking about Nando's design

[Nando]

PETER:

I can only present a basic idea, since the design, I did, was for a commercial entity and I have to respect the contract.

The isolated supply is to drive the power Mosfets and the isolation could be just above the controller positive supply rail if the voltage of the isolated is just at their supply level, like two 12 batteries that need isolation when a vehicle is OFF and when it is ON and battery charging to be able to charge the isolated battery with the same voltage level of the other battery.

Full isolation, if the voltage of the controller is different from the batteries being switched.

The Controller can be a simple circuit like an optocoupler driving the small P & N Mosfet gate drivers or a regular gate driver used with the power Mosfets.

The power Mosfets in parallel must have very low Rdson to insure very low losses when ON, like a number of Mosfet that all of them in parallel-series produce 0.001 Ohms Rdson, this implies that with this low value , 100 amps can be switched, since the voltage dropped across the Fets is just 100 millivolts, representing 10 watts dissipation across the Fets.

Temperature behavior has to be analyzed to insure proper low saturation voltages.

Nando