Power control with tank

**4u2n** · 10-22-2004, 11:59 AM

My boss donate an DC-DC power converter type NVD-12SC12, 8-16 in 12volt out at 7.5 amp

I have look in the forum an find some tips an put it together

In my car there is not power on the cigarette plug when there is not key in, then I think it can be a good idea to have a tank battery for to reason

1. If the car crash

2. when I remove the IGN Signal and take the key out, and go from the car, it have power to make a power down sequence

I use a double relay to make a total disconnect from car electric system

When it come power in the cigarette plug it automatic flip the relay and charge the tank battery

**justICE** · 10-22-2004, 02:26 PM

Yay something to do.

1) diode D1 and D3 will always be in reverse bias because the node that is connected to the cathodes does not allow a voltage drop. It is connected through that relay.

2) what did you edit this with. I would like to redraw it with a reply so that I am more clear.

*edit* I guess I am unclear of the use of D3.

**justICE** · 10-22-2004, 02:27 PM

One more thing before I go back to looking at it. You should check the fuse value for that cigarette lighter. I may be wrong but it seems like ~8amps is a decent load for that thing.

**4u2n** · 10-23-2004, 02:01 AM

Originally Posted by justICE

Yay something to do.

1) diode D1 and D3 will always be in reverse bias because the node that is connected to the cathodes does not allow a voltage drop. It is connected through that relay.

2) what did you edit this with. I would like to redraw it with a reply so that I am more clear.

*edit* I guess I am unclear of the use of D3.

D1 and D2 it use is uset to lead the power when the relay switch from the main power to tank battery and back again.

I use Circad to draw this Schematic and it can also draw PCB

**Arathranar** · 10-23-2004, 01:24 PM

What's the point of R1?

**Arathranar** · 10-23-2004, 01:27 PM

In my car, the cigarette unexpectedly gets connected to ground when it gets switched off.

**Arathranar** · 10-23-2004, 01:32 PM

How big a tank battery are you going to use? 7.5A is a lot of current and will cause a voltage drop from the tank battery.

**Arathranar** · 10-23-2004, 01:33 PM

Can you explain all the bottom right of the circuit?

**justICE** · 10-23-2004, 02:03 PM

R1 is to limit the current into the tank. I understand D1 and D2 but D3 still doesn't make sense to me=).

**4u2n** · 10-23-2004, 03:08 PM

Originally Posted by Arathranar

In my car, the cigarette unexpectedly gets connected to ground when it gets switched off.

It is no problem because the relay, switch to tank battery and the only thing you put to ground is the coil of the relay and the catode of D2, and the only thing connected to the circuit is ground in that situation