Schottky diodes instead of battery Isolator?

[fishrdan]

Has anyone used a bunch of Schottky diodes to isolate and charge their batteries? Voltage drop shouldn't be too bad as the Shottky's only drop .15-.45V, better than the batteries not getting any charge at all if I forget to flip the switch while running.

I'm not looking to add an isolator ($), but wouldn't mind connecting 5-10, 5 or 8 amp Schottky diodes to keep the "non-engine" batteries charged. Cost about $10.

 

[Silvertip]

Re: Schottky diodes instead of battery Isolator?

Remember that those diodes not only pass current TO the house batteries but they must also BLOCK current going from the house batteries to the starting battery. Since starting current draw is very high, the reverse current value of those diodes needs to be very high.

 

[t4kne]

Re: Schottky diodes instead of battery Isolator?

Actually, the only worry is that the diodes have a reverse voltage rating. There is no current flow until you have exceeded the reverse voltage rating. If you have not approached the reverse voltage rating, nothing to worry about.

 

[flargin]

Re: Schottky diodes instead of battery Isolator?

I think there are some commercial isolators made with them. I think the key is the heat dissipation.

 

[fishrdan]

Re: Schottky diodes instead of battery Isolator?

The reverse voltage is 45-60V so I should be OK there.

I was wondering how hot they would run and planning to build it so they were running at 1/2 their rating. Also planning to spread them apart so they have air flow in between, though I don't know who well it would work seeing that the underside of the battery switch is pretty much sealed up, little to no air flow. I might have to fab up an aluminum heatsink and use 1 high current 40-50 amp diode....

Thinking of how it's all going to work, the house batteries will charge fine through the diodes while the engine is running. But after then engine is shut down, the engine battery will discharge through the diodes to the house battery as the house battery voltage drops. Guess I'll have to throw in a relay or a couple high current transistors to close the circuit while the engine is running and open it when the engine is off.

Starting to sound like I'm reinventing the wheel and building an isolator,,, and it would be easier to buy an isolator....