Lithium battery question

[Kevin22]

Resistance from wiring in the run can cost you several tenths of a volt. Resistance from connections, including at the battery, at the unit, at the unit’s cable and the fuse can cost a bunch too. When you only have about 1.5-2V to spare above the minimum operating voltage of the equipment, it’s important to save everywhere you can, especially if the battery is used for engine cranking.

About 5-8% loss is okay, any more that and you have some bad connections somewhere or need to go to larger wire.

14 gauge marine wire running 20 feet on a 3amp load (twice that of livescope) should drop about 0.3v off 12v, so 3%. Having resistance and voltage loss is normal, you just do not want it to be excessive. There is zero reason to use 8, 6, or 4ga wire for a 1.75A draw just to reduce a 3% voltage loss to <1%. Sounds good, but makes no real world impact other than you are spending 5 times more on wire.



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[CatFan]

About 5-8% loss is okay, any more that and you have some bad connections somewhere or need to go to larger wire.

14 gauge marine wire running 20 feet on a 3amp load (twice that of livescope) should drop about 0.3v off 12v, so 3%. Having resistance and voltage loss is normal, you just do not want it to be excessive. There is zero reason to use 8, 6, or 4ga wire for a 1.75A draw just to reduce a 3% voltage loss to <1%. Sounds good, but makes no real world impact other than you are spending 5 times more on wire.



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Until you crank the outboard and see a large voltage sag. Then, any reduction in loss to the units is critical. Voltage loss happens on both the positive and negative wire.

[Kevin22]

Until you crank the outboard and see a large voltage sag. Then, any reduction in loss to the units is critical. Voltage loss happens on both the positive and negative wire.

This post is not about running livescope on a starting battery, it is about running on a dedicated lithium battery.

And even then, a voltage sag when starting the motor is a weak or too small of a battery. You can have 0 gauge wiring to your fishfinder and it will still sag to whatever the battery goes to when your 30A starter is engaged... Having thinner wire to your fishfinder does not make your voltage drop when you start the engine.

On top of all of that, why do you care if your livescope transducer voltage is dropping when you start the outboard? I dont know if I have ever been watching sonar while starting the motor.

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[CatFan]

This post is not about running livescope on a starting battery, it is about running on a dedicated lithium battery.

And even then, a voltage sag when starting the motor is a weak or too small of a battery. You can have 0 gauge wiring to your fishfinder and it will still sag to whatever the battery goes to when your 30A starter is engaged... Having thinner wire to your fishfinder does not make your voltage drop when you start the engine.

On top of all of that, why do you care if your livescope transducer voltage is dropping when you start the outboard? I dont know if I have ever been watching sonar while starting the motor.

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You are clearly an amazing expert. No sense correcting your misunderstanding.

[Soonerdg65]

The long and the short of it is, especially with modern sonar and FFS, is that the more voltage to the unit the better the picture. So running 10 ga wire will get you significantly more voltage to your unit than 16 ga wire over a 17-20 foot run. The foot or so of smaller gauge wire at the unit doesn't affect the voltage nearly as much as the long run.

[Kevin22]

The long and the short of it is, especially with modern sonar and FFS, is that the more voltage to the unit the better the picture. So running 10 ga wire will get you significantly more voltage to your unit than 16 ga wire over a 17-20 foot run. The foot or so of smaller gauge wire at the unit doesn't affect the voltage nearly as much as the long run.

Negative. Livescope is internally regulated to 12v, so any voltage over 12v will not improve picture. Under 12v is not noticeable until you get around 11v. Lithium batteries are dead at 12v, running volts is 13-13.5v for 90% of capacity. so even if you have tiny wiring, you are going to be just fine as long as your transducer is getting the appropriate AMPS without heating up your wiring. You cannot drop enough voltage in a 20ft run to hurt livescope, with a lithium battery. You will run a fire risk if you go too small.

16ga is actually appropriate if you are just running your livescope off the wire run, on a 20' run. Livescope draws 3A at start up for 3 seconds, then draws 1.75 while running. I personally would not use 16, because the price difference isnt that much to go ahead and use 14 or 12 marine wiring.

Likely your running lights draw more power than livescope, that is what most guys do not understand. Your actual head unit is what is drawing the most power.

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