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CrappiesNeyes

Isolating depthfinders from starting battery?

9 posts in this topic

Is there any way to isolate the depthfinder circuits from the amp draw when starting the big motor? Sometimes when I start the big motor it turns the depthfinders / GPS's off and I have to restart them.

Thanks in advance. CNE

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Well, here is where I can help.

We create a fused, diode protected with Capacitor circuit.

Essentially you put a 5 amp fuse inline with a 6 amp diode, then use a pair of 6800uF capacitors in parallel with ground (or do 4 if you want a larger reserve) and then put a 3 amp fuse in series with the output.

The first fuse is to protect from short circuit, and to protect the diode from thermal failure.

The diode protects from power backflow, such as the temporary voltage drop that occurs when the starter engages.

The capacitors hold a small charge to keep the output voltage stable. They also help provide noise filtering on a basic level.

The last fuse is to protect the GPS unit that is connected.

I have also used this circuit before to remedy problems when a motor circuit (such as a trolling motor) or fans, causinf interference.

I can throw together a schematic later if needed.

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Have had the same problem with my depth finder.

Electronically challenged where do you get the parts to make it?

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Sounds like you have a million dollar idea. Package it and sell it.

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Radio Shack probably has all that stuff.

If not there then DigiKey, Mouser, et al.

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Don't forget the hash filter caps in parallel with those big boys, and the inductor inline with the output to clamp the spikes.

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hey GBPacker-

A schematic would be good. I have the same problem with my graph shutting off. As long as this set-up would be safe to use, I would be willing to try it.

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Talked to a guy at Capras very helpful.

Told me to run it directly off the battery. Kept the fuses on it of course.

Wired it directly to the battery and no more shutting off.

Man is that nice not to have to screw around with!

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One question do they recommend putting a fuse on the ground wire also? On all of my applications, if i am running a paired wire i will twist them and ground both leads. Just in case you do short it will blow hot or ground rather than melting wires. I am sold on battery isolater for multipurpose batteries. Good luck.

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