Mega 360 Screws rusting

[Beallright]

The Mega 360 power along with all my electronics are on a dedicated separate 125 Lithium battery. Then drain and ground are attached. Verified with an ohm meter the integrity of all wires back to ground and power. I had a previous Mega 360 mounted that the screws did not rust but I pinched the wires on the transducer cable, so the original was replaced, and now the new Mega 360 is rusting the screws. Just for the sake of making sure I re did the connection to the ground and the drains and power.

I have been running a dedicated battery setup for several years and this is the first issue with rusting screws.

Anything else I can check or do

[SLYDoggie]

Are you sure both your negative and drain/shield wires are connected to negative/ground? Sounds like the drain/shield may not be connected.

[Beallright]

Everything is connected and verified. If I go to drain/ground and the screws I get 11 ohms on a fluke doom

[Wayne P.]

Everything is connected and verified. If I go to drain/ground and the screws I get 11 ohms on a fluke doom

Edited, the dedicated battery needs a water ground. When a starting battery is used, the negative is connected to the outboard's block so it has ground to water. You have to duplicate that by connecting the dedicated battery's negative to the outboard or starting battery negative.

That's the drain wire to chassis ground stated in the installation instructions.

[SLYDoggie]

Edited, the dedicated battery needs a water ground. When a starting battery is used, the negative is connected to the outboard's block so it has ground to water. You have to duplicate that by connecting the dedicated battery's negative to the outboard or starting battery negative.

That's the drain wire to chassis ground stated in the installation instructions.

Oh, wow. I wouldn't have thought of this. Great information!

My Mega Live and Mega 360 are both connected to the starting battery so I'm covered but wouldn't have guessed this for a dedicated battery.

[Fishshooter]

Edited, the dedicated battery needs a water ground. When a starting battery is used, the negative is connected to the outboard's block so it has ground to water. You have to duplicate that by connecting the dedicated battery's negative to the outboard or starting battery negative.

That's the drain wire to chassis ground stated in the installation instructions.

So to achieve a water ground, should you connect drain wires to cranking battery instead of stand-alone electronics battery or could doing it that way cause interference issues ? I'm not sure how to achieve a water ground with a stand-alone electronics battery. Maybe a separate wire from stand-alone electronics battery negative to either cranking battery negative or to engine block/ground ?

[G48]

I paralleled my lithium cranker to my lithium house battery but not for the reason Wayne mentioned above... so 2 birds with 1 stone I guess.

[78Staff]

Edited, the dedicated battery needs a water ground. When a starting battery is used, the negative is connected to the outboard's block so it has ground to water. You have to duplicate that by connecting the dedicated battery's negative to the outboard or starting battery negative.

That's the drain wire to chassis ground stated in the installation instructions.

So to achieve a water ground, should you connect drain wires to cranking battery instead of stand-alone electronics battery or could doing it that way cause interference issues ? I'm not sure how to achieve a water ground with a stand-alone electronics battery. Maybe a separate wire from stand-alone electronics battery negative to either cranking battery negative or to engine block/ground ?

Older thread, but figured I would post here instead of creating new/duplicate thread... I also am planning on running stand-alone lithium 125ah for electronics only. The manual shows connecting the drain to the terminal block along with the primary ground - I suspect the assumption in that example is that the fuse block is connected to the starting battery.

So for the stand alone battery setup - is there any issue running a negative jump cable from the stand alone battery to the starting battery? In my case electronics is lithium, starting is AGM, not sure if that matters? What about chargers/charging, does the cable from neg to neg cause any issues or confuse the charger, etc. Just not that familiar with this type of setup - have always ran single battery for everything in the past.

Would it cause issue for the standard ground being connected to lithium electroncs battery (via fuse block) and the drain wire connected to the starting battery - I have dedicated ground wire back to starting battery from my previous AT install I could re-purpose.

The drain wire being bare also kind of freaked me out lol, but I assume you just crimp on a connector like normal?

[78Staff]

Well she's mostly mounted up - still tidying up some wiring at the bow due to multiple units, but have the 360 power run back to a Blue Sea Fuse panel in the starboard rod locker.

Still a bit confused on the drain wire ground. If I also ground it at the Blue Sea fuse block, it will be grounded to a stand alone lithium for electronics, which appears to not be correct. I do have a dedicated ground wire running back to the starting battery available I could tie it into, but not sure if having ground & drain connected to two different batteries is proper.

Then there's the other option mentioned in thread above to just connect neg lead from the starting battery (AGM) to Electronics Battery (Lithium), but I don't know enough about wiring to know if that would cause other issues, ie with charging or BMS, etc?

[woppercatcher]

I had my Mega Live and Mega 360 connected to a dedicated battery for over a year without any rusting and now on my new boat I have a house battery running all my boat power. The house battery might be grounded but I have no idea since the dealer did all the wiring. So far no rusting and I don't expect any but I do plan on changing the house battery and cranking to run in parallel soon.

[Wayne P.]

The original 360 stated to "tape the drain wire". When the MEGA 360 was first released, it had the same instrucitions. A couple of months later the instructions were changed to connect the drain wire with the negative wire. This is why---

[78Staff]

The original 360 stated to "tape the drain wire". When the MEGA 360 was first released, it had the same instrucitions. A couple of months later the instructions were changed to connect the drain wire with the negative wire. This is why---

Wayne's probaly like "not this guy again..." lol

Yeah I understand the why, I just am unsure of where to connect it since I have stand-along battery setup. Confused about the options:

* Just wire it to stand alone along with primary ground per the included instructions.

* Wire it to stand alone, add jumper cable from stand along batt neg to starting batt neg. I don't know what if any issues this would cause with running, charging, etc. They are different chemisries as well, not sure if that makes a difference. I assume since only a few inches a 10ga cable with ring terminals would suffice?

* Split the ground - primary to stand alone batt, drain wire to starting batt neg. This seems like it would create interferance and all sorts of issues, tbh.

But I just don't know enough about wiring. I know things like Perko switches and Yandina Combiners etc have you connecting the neg terminals of two batteries together, so it must be a common thing?

[78Staff]

I guess the jumper wire between house Lithium neg and starting AGM neg (common ground I guess this is callled?) is the way to go - seems like making that connection doesn't cause any issues, since most battery switching/combining devices require that as well.

[bobcoy]

It is the only source of earth ground on a boat. Should be the ultimate destination of every ground wire. Not necessary to run them all to the water/earth ground, but the connection to the Motor/earth/water ground.

[Beallright]

So as the OP, I run a dedicated electronics battery. After wiring my drain to the negative block of the house battery the corrosion of the screws has appeared to stop. I did not run the wire direct to battery. I have an accessory block that has a ground block and that is where I landed the wire. I used uninsulated connectors to connect the drain to a #12, and soldered the connection.

[woody135]

All the negatives on the 12 Volt side need to be connected. Period. The Engine ground and the engine gauges need to talk. Once you add a battery for electronics only, there has to be a path back for electrons to the motor and all its grounding points. How do I know? I know. Usually its the fuel gauge that gives it away. And the rust.

[78Staff]

I guess the jumper wire between house Lithium neg and starting AGM neg (common ground I guess this is callled?) is the way to go - seems like making that connection doesn't cause any issues, since most battery switching/combining devices require that as well.

So got my batteries/charger/wiring all completed today, and went ahead and put a short jump cable from the neg of the Northstar AGM starting battery to the neg of the Ionic 125ah standalone electronics battery - so should be all set I think.