GPS? Blink Out

Islandtrader · #1 10-26-2013, 09:08 AM

Installed my garmin for a trial run (check out build thread to see mods) and the short answer is I like it.

Now the problem (I think I know one solution but seeing if there is something else I can do) the gps is hooked up to the house battery. I have a starting battery on its own. GPS is on and when I start the boat everything is fine no blink out. However when running I went to use the mercruiser power trim and NYC black out on the GPS(trim is on house battery). Had to hard start GPS.

Any ideas? Fixes or suggestions....thanks in advance.

Blue_Heron · #2 10-26-2013, 09:23 AM

Hmmm. Could be as simple as a loose battery connection, but I suspect you've checked for that.

Do you have the house battery wired to a fuse block and then the GPS and power trim fed from the fuse block? Wire sizes and lengths?

Low voltage systems are much more sensitive to voltage drop from wire resistance. I was surprised at how big the recommended wire sizes were for pumps and such. I wired most of my circuits with 12 gauge, or 10 gauge wire.

FishStretcher · #3 10-26-2013, 10:33 AM

You can prop it up with a capacitor. Much like the kiddies do with "bang caps" for their crazy car stereos, you can use something much smaller. A diode in the supply wire, followed by a small resistor, like 1 ohm, followed by a big capacitor would help with this. The diode is a one way valve that means the capacitor only props up the voltage on the GPS, not everything else.

It will keep the GPS alive for the time when the trim motor starts and hogs all the current, browning out the GPS. I can elaborate with a sketch and part numbers if you want.

erebus · #4 10-26-2013, 10:56 AM

Heh... NYC blackout.
Nice.

Islandtrader · #5 10-26-2013, 01:16 PM

Quote:

Originally Posted by FishStretcher

It will keep the GPS alive for the time when the trim motor starts and hogs all the current, browning out the GPS. I can elaborate with a sketch and part numbers if you want.

Please do...I need to get this done by Wed.

FishStretcher · #6 10-26-2013, 06:05 PM

A shopping list from digikey. Skip the first capacitor- it is too small. Actually skip them both and get a car audio capacitor from Wal-Mart.

Most anything should work. 0.5-5F (Farad) would be fine. The 100,000 uF cap from digikey is a 0.1Farad cap. The Walmart ones are ~10x the size for the same $25.

The (big, metal can) resistor is to limit current when you reconnect the battery (or else BANG). You want it low resistance, like 0.33 ohm so the GPS doesn't lose voltage thru the resistor. But enough that when you connect the cap (or turn the switch on the house battery), the rush of current into the capacitor doesn't blow it up, or the fuse. It is a balancing act. You might need a 10A fuse to the cap, or a 15. And then a 3A fuse after the cap(acitor) inline to the GPS.

The diode keeps the capacitor from feeding anything but the GPS unit. Which limits you to a 10A fuse. The diode is the check valve for electricity. The silver band is the output (GPS) side. You will have to do some soldering.

Equivalent parts might be available from digikey.

Schematic to follow.

I am figuring your GPS doesn't draw more than 24 Watts. I think mine uses 8 or 9?

FishStretcher · #7 10-26-2013, 06:13 PM

I think the schematic is attached.

FishStretcher · #8 10-26-2013, 06:18 PM

This is readable as a PDF

strick · #9 10-26-2013, 07:15 PM

Why is the trim not on the starting battery? Am I missing something?

strick

Islandtrader · #10 10-28-2013, 09:20 AM

Quote:

Originally Posted by FishStretcher

This is readable as a PDF

Quote:

Originally Posted by strick

Why is the trim not on the starting battery? Am I missing something?

strick

You aren't missing something...I did

So I think the easiest thing to do is re-route the cable to a common post and then hook up a direct line to the starting battery.

I guess I did not think this whole thing out when installing...

FS thanks, but now I think moving it to S/B is the right thing to do...