Knowledgeable electrical folks?

**J White** · 06-13-2023, 09:13 AM

I’m upgrading the sonar on my boat.
Got everything hooked up, and looking at the voltage displayed on the depthfinders I got a little perturbed. I was showing over 2 volts lower at the bow than directly off the battery post. But before I started pulling bigger wire, I decided to actually check with a meter. Borrowed a nice fluke dvm, and checking at the pins in the depthfinder plug, I’m only down .2 volt from battery to bow unit. It’s a 22 foot boat, and the way it’s laid out, I’ve got about a 30 foot wire run.
Battery at stern, up to center console, then back to stern, then up the gunnel to the front. No good path to fish wire through directly from center console to bow. But my question,
2 tenths of a volt drop is within reason, yes? And are the voltages shown on the units possibly that far off from reality? New H’bird helixes.
Thank you.

Sent from my iPhone using Crappie.com

**DockShootinJack** · 06-13-2023, 10:52 AM

.2 volts is fine. 2 volts is not. How many amps does the unit pull.

**J White** · 06-13-2023, 10:55 AM

Originally Posted by DockShootinJack

.2 volts is fine. 2 volts is not. How many amps does the unit pull.

3.2 for the head unit, but I’ve got 2 other things on that same wire - one at 165 milliamps, the other 950 ma

Ive got a fuse block in the front fed from the back, so I do have individual fuses for each item

Sent from my iPhone using Crappie.com

**J White** · 06-13-2023, 11:03 AM

This is where my lack of electrical knowledge shows - (I’m a machinist by trade)
I’m getting .2 drop under a no load situation. Is it possible that under load it IS pulling the voltage down?
I think this evening I’ll check it at the fuse block up front with everything powered up.

Sent from my iPhone using Crappie.com

**DockShootinJack** · 06-13-2023, 01:52 PM

It certainly can happen. Test it under a load of possible and see what your results are

**J White** · 06-13-2023, 08:35 PM

Originally Posted by DockShootinJack

It certainly can happen. Test it under a load of possible and see what your results are

Well, the units ain’t lying. With everything powered up, I’m back to
-2.0v
But, I know what I’m gonna do to fix it.
Pull in some 12 gauge wire, and run directly from my main battery disconnect. From H’bird’s website, it says 12 gage is good for 24 feet. This will shorten my run by 8 foot or more as well, and eliminate several splices. Lesson learned.

Sent from my iPhone using Crappie.com

**rnvinc** · 06-13-2023, 08:38 PM

We should remember that the voltage shown on an electronics screen is not direct voltage from the battery (like a Fluke meter reads).

The voltage on the screen is after the load to power the unit ... which is why your test at the pins was only down .2v ...

In a nutshell - the electronics unit is not a voltage meter ... and the voltage shown on the screen should only be noted as a general voltage of the battery itself ...

A better way to monitor actual battery voltage would be to install a battery meter ...

Rickie

**justinp61** · 06-13-2023, 08:45 PM

If you have Lowrance units, some models are known read the voltage low. My 9 Live at the bow does.

**J White** · 06-13-2023, 08:52 PM

Originally Posted by rnvinc

We should remember that the voltage shown on an electronics screen is not direct voltage from the battery (like a Fluke meter reads).

The voltage on the screen is after the load to power the unit ... which is why your test at the pins was only down .2v ...

In a nutshell - the electronics unit is not a voltage meter ... and the voltage shown on the screen should only be noted as a general voltage of the battery itself ...

Rickie

I’m known to overkill stuff, was going to go 10 gage. But I rummaged around in the shop and found a roll with a 100 feet or so of 12. It’s paid for, think it’s worth a go. Heck, as much as I have, may pull in 2 runs of it and divide the load up. For the record, what I was using was in the boat from previous owner. It’s 14 at best, may be smaller.

Sent from my iPhone using Crappie.com

**DockShootinJack** · 06-14-2023, 03:12 AM

Within reason nothing wrong with oversizing wiring. Never hurts to have extra capacity in place if you wish to add things in the future.

Thread: Knowledgeable electrical folks?

Thread Tools

Display