Voltage drop seems excessive

[SlowPoke]

Just got off the phone with Emil regarding his voltage readings. The problem is; the sonars (Lowrance 520&525) are showing very low voltage when the motor is off. When he starts the motor, the 525 unit shuts off (low voltage) but the 520 stays on. He's never had a problem starting but it there seems to be more than usual voltage loss between the battery and the sonars. My 525&522 normally show 11.5+ after trolling on the kicker for a while. His get down into the 9's.

 

All readings with the motor off; freshly charged, new battery and no other accessories operating than listed.

12.4v at the battery

12.3v at the fuseblock

12.2v at both accessory switches (1&2) with all electronics OFF

11.1v at the sonar accessory switch(1) with sonar ON

11.6v at the trollmaster accessory switch(2) trollmaster ON

10.7v reading according to the sonar volt gauge

Drops into the 9v range with the key on.

 

Any ideas?

[smally21]

my humminbirds give me similar readings later in the day, just into the 10's. always assumed its loss in battery charge. lets send it back to the top

[cranks bait]

My bird has always been like this as well. I didn't feel comfortable using my sonar with the motor turned off. To ease my mind I added another battery. I just figured I had an old sonar and it was power hungry and normal?

[aplumma]

remove the unit and check the voltage with a multi meter to confirm the voltage. Remove switches and wire direct to see what the voltage drop is thru the switches and replace as needed (corroded contacts will increase resistance and lower the reading).Remove and replace the fuse and check connections for corrosion. Check to make ssure it is still factory wire between the battery and the sonar unit. The batteries if fully charged should read 12.65 volts. While I use Lowrance products I am sure it is the same on power consumption due to the units being wired in 22 gauge wire it should be minimal and the fact you can run one on 2 6 volt batteries while you ice fish points to a wire issue.

 

 

Art

[scugpg]

Too small of wire will cause that on a long run. I have no issues with my Lowrance finder but I run 14 or 16 gauge wire to them from the batteries. Very minimal voltage drop.

[Fisherman]

Just got off the phone with Emil regarding his voltage readings. The problem is; the sonars (Lowrance 520&525) are showing very low voltage when the motor is off. When he starts the motor, the 525 unit shuts off (low voltage) but the 520 stays on. He's never had a problem starting but it there seems to be more than usual voltage loss between the battery and the sonars. My 525&522 normally show 11.5+ after trolling on the kicker for a while. His get down into the 9's.

 

All readings with the motor off; freshly charged, new battery and no other accessories operating than listed.

12.4v at the battery

12.3v at the fuseblock

12.2v at both accessory switches (1&2) with all electronics OFF

11.1v at the sonar accessory switch(1) with sonar ON

11.6v at the trollmaster accessory switch(2) trollmaster ON

10.7v reading according to the sonar volt gauge

Drops into the 9v range with the key on.

 

Any ideas?

 

#1. Take the battery and give it an 8 hour charge, disconnect and let it sit with nothing connected for 24 hours, then go and check the resting voltage, should be 12.65V, if it's any less than that, ie, 12.4, it's only at 60-70% of charge and on its way to the recycle shop.

#2. With the voltage drop you see, remove your conectors and give them a good cleaning with a pencil eraser, if there's any amount(I mean ANY amount) of corrosion at crimp on connectors, re-wire and solder on the connectors.

[dave524]

Too small of wire will cause that on a long run. I have no issues with my Lowrance finder but I run 14 or 16 gauge wire to them from the batteries. Very minimal voltage drop.

 

X2, up your wire gauge on long runs and make sure you use fine stranded stuff. Stereo shops that do mobile installations are a good source, heavy gauge speaker wire.

[Pigeontroller]

Thats what I was thinking...

[SlowPoke]

remove the unit and check the voltage with a multi meter to confirm the voltage. Remove switches and wire direct to see what the voltage drop is thru the switches and replace as needed (corroded contacts will increase resistance and lower the reading).Remove and replace the fuse and check connections for corrosion. Check to make ssure it is still factory wire between the battery and the sonar unit. The batteries if fully charged should read 12.65 volts. While I use Lowrance products I am sure it is the same on power consumption due to the units being wired in 22 gauge wire it should be minimal and the fact you can run one on 2 6 volt batteries while you ice fish points to a wire issue.

 

 

Art

 

I don't know if the test at the battery was to the cable or the post; maybe corrosion causing a .2v drop right there.

 

We didn't get into taking things apart but that is the next step. The fuse block was behind a panel so we couldn't test or check the inout voltage/wire on the lug. I suspect it's the factory wire but it's worth checking for the sake of a few screws. The block test was at the fuse connection.

 

I suggested it might be a bad switch; it's the most vulnerable link in the chain. This where it gets a little fuzzy because I was diagnosing over the phone. I was asking him to check input at the switch and comparing it to output at the switch, with the switch on. Perhaps bypassing the switch temporarily is the best test.

 

(Emil: if the switch is a problem it must be replaced otherwise wiring direct will drain your battery. The external switch is the only thing to control on/off power to the network bus)

 

I suspect he's using the Lowrance harness without small gauge extensions.

 

To me, everything points to the switch.

 

 

Too small of wire will cause that on a long run. I have no issues with my Lowrance finder but I run 14 or 16 gauge wire to them from the batteries. Very minimal voltage drop.

 

Good advice but I don't think that is an issue here and I will confirm.

 

 

#1. Take the battery and give it an 8 hour charge, disconnect and let it sit with nothing connected for 24 hours, then go and check the resting voltage, should be 12.65V, if it's any less than that, ie, 12.4, it's only at 60-70% of charge and on its way to the recycle shop.

#2. With the voltage drop you see, remove your conectors and give them a good cleaning with a pencil eraser, if there's any amount(I mean ANY amount) of corrosion at crimp on connectors, re-wire and solder on the connectors.

 

#1 It's a new battery on a fresh charge. His reading are higher with the new battery and the 525 doesn't shut down so we've eliminated part of the problem by removing the 5yr old battery.

#2 Agreed, connections are a killer. I've witnessed voltage swings at a battery just by applying pressure to the connector.

[Vanselena]

I run solid 14 gauge copper from the battery to the fuse box and make sure all connections are soldered for minimum loss as well as cover connections with silicon,

[icefisherman]

Yes battery is brand new and fully charged.

All cabling is the original Lund and Lawrance cables.

 

Went fishing yesterday and after having the main motor off for 5 hours and using both 520 and 525 during that time, when it was time to go back and started the main motor....bammmm....the 525 shut off ....520 stayed on....

 

I was hoping it is a battery issue and with the new battery the 525 will not shut off but it did....

 

Not sure why it is doing it....

 

Today I tested the voltage at the switch 1 (controls both fishfinders and few other things) and switch 2 (controls Troll Master and few other things).

 

1) With the fishfinders off and the switch 1 in OFF position I measured 12.25 V at the switch prongs.

 

2) With the fishfinders off but switch 1 in ON position I measured 12.15 V at the switch prongs.

 

3) With both fishfinders ON and switch 1 in ON position I measured 11.1 V at the switch prongs.

 

4) Battery measured 12.3 V at the battery terminals while taking the above measurements

 

All measurements taken with digital volt meter.

 

Both switches are at the dash board so cables from switches to fishfinders are very short.

 

Loosing 1 V the moment the fishfinders are switched ON.

Switch 1 "eats" only about 0.1 V so I am not sure it is a switch problem...if it is I'd be glad as it'll be easy/cheap replacement.

Cables from battery to switch (via the fuse panel) "eat" all together 0.05 V so they are not the problem.

 

I guess logically it is either the cables between the switch 1 and fishfinfers or the 525 itself?!?

 

Any comments?

[DRIFTER_016]

Ok, here's my take on this issue.

First of all your battery is not fully charged.

At 12.3V you are only at about 55% of full charge.

Take the battery out and get a full charge into it on a charger.

Next take the battery to a local garage or Canadian Tire and have it load tested.

I think you will find it has a weak cell and needs replacement.

[icefisherman]

Ok, here's my take on this issue.

First of all your battery is not fully charged.

At 12.3V you are only at about 55% of full charge.

Take the battery out and get a full charge into it on a charger.

Next take the battery to a local garage or Canadian Tire and have it load tested.

I think you will find it has a weak cell and needs replacement.

 

 

I've changed my "old" battery with this brand new one couple days ago....

The new one "was" fully charged before my trip yesterday....I guess it is not now after the trip since it was only charging from the main motor on the way out and the way in (5 min each way) and was been drained for 5 hours of perch fishing....

So yes I'll fully charge it again...with the charger (just bought the CTEK one) (supposedly the best thing since sliced cheese;-)

I doubt it is bad battery though...if it is I have another battery I can use for the test....so battery problems are the easiest to eliminate in this case.

 

The significant voltage drop (which is my main problem) I am afraid will remain at the same level even with another battery.

[Vanselena]

I could be that the new battery has a bad cell or the cranking amps are not high enough.

 

Every fish finder has different tolerance as to minimum voltage, it sounds like starting your engine is drawing enough power to push one of your fish finders past the tolerance level. I would try another battery with greater cranking amps.

 

 

 

I've changed my "old" battery with this brand new one couple days ago....

The new one "was" fully charged before my trip yesterday....I guess it is not now after the trip since it was only charging from the main motor on the way out and the way in (5 min each way) and was been drained for 5 hours of perch fishing....

So yes I'll fully charge it again...with the charger (just bought the CTEK one) (supposedly the best thing since sliced cheese;-)

I doubt it is bad battery though...if it is I have another battery I can use for the test....so battery problems are the easiest to eliminate in this case.

 

The significant voltage drop (which is my main problem) I am afraid will remain at the same level even with another battery.

[Rattletrap2]

I'm a little confused, but it ain't the first or last time for this!LOL

Regardless if your battery is new or not, it has to read 12.6 volts or better to be fully charged. 12.3 volts is dead as far as I am concerned. If you take the readings at the battery, then line loss through wiring is irrelevant. Electronics such as graphs and such only draw milliamps. I can see them shutting down when you crank over your big engine if the battery is weak. You need to perform a proper load test. Any parts store, garage or CTC can do this for you. Having 12.6 volts at rest and then seeing it drop under load is common with a bad battery.

 

If your wiring to the big engine is undersized, you will drop voltage to it under load (when cranking it) if measured at the motor. If measuring at the battery, it should still show strong unless there is something wrong with your starter motor?

[scugpg]

Yup a fully charged battery should be around 12.6 or a bit more. Try hooking that 525 up to the battery directly and see what it reads.

 

Still think its a wiring issue in the circuit.

 

Keep in mind - If you have the display on the 525 on full brightness, it will read less that the actual battery charge. Try dimming the brightness on the 525 and see what it reads for Voltage.

[icefisherman]

OK Guys,

 

just charged overnight the battery fully ....with all cables connected but nothing ON - it read 12.75V

Same range of reading after that but somewhat higher than yesterday as a result of charging the battery...proportions remain the same though and this is my main concern:

 

1) With just the switch 1 ON - 12.65V

2) With both fishfinders ON and both of them at full brightness - 11.5V

3) With both fishfinders ON and both of them at one level dimmer - 12V

4) With both fishfinders ON and both of them at two levels dimmer (hard to see much during the day)- 12.1V

 

Again all reading measured at the prongs of Switch 1.

 

As you can see despite battery been fully charged or not, the proportion of voltage loss remains about the same...basically loosing more than 1V the moment I turn the fishfinders ON.

 

This is where the largest voltage drain is and I'd like to know how "normal" this is?!?

 

Haven't tested the battery at CT yet but to eliminate the possibility of battery been bad, I've connected yet another brand new/fully charged battery - and got same readings....so it is NOT a battery issue - guaranteed!!!

[scugpg]

How long of a wire run is it and what gauge wire are you using?

 

Connections look good at the switch?

 

You could start by-passing things and testing the 525 out at different sections in the circuit.

[icefisherman]

12 gauge from battery to fuse panel

16/18 gauge from there to and from switch

Then the Lawrance original cables are smaller gauge maybe 20 or so...

 

Boat is Lund 1700 Pro Sport so total cable run should be 15 feet or so from battery to fishfinders.

 

After 3 more hours of testing this morning I think I'll just connect the Switch 1 to my second battery (under the dash powering my downriggers and trolling motor and few smaller things) and power the fishfinders that way...tested it and voltage with both of them ON is about 12.2-12.3V

 

This way the big motor will not be involved at all and no issues with shutting down my 525.

[Tybo]

Emil. Check the battery again. I suspect that you have a bad terminal.

With your meter. Place the leads on just the lead posts,Take reading.

Then place just on connectors. Take reading. If there is any change theres the problem.

[dave524]

FWIW , dad taught me to turn off all accesories in the car when starting 40 sum years ago, like radio heater blower, lights etc., still do it in all vehicles. Of course batteries then weren't what they are today, fuel systems of that day were prone to flooding if it didn't start right away and today there is a lot of stuff that you can't power down. But it still makes sense.

[DanD]

Just so I understand what you are calling a voltage drop; you’re taking a voltmeter reading at the source (battery terminals positive and negative) and then at the device power terminal to ground? If so; what you are seeing is total voltage usage over the entire system not of a particular device or portion of its circuit.

Taking readings at a device with it turned on and the meters leads connected between pos & neg, will show you a lower voltage because the device is using voltage.

 

If you want to test a circuit to determine if (and where) there is high resistance; connect the voltmeter leads in parallel of battery positive and that section of the circuit or at the device in that circuit power (positive) input.

Turn the circuit on and take a reading of the circuit; anything above .2 of a volt “Voltage Drop” is considered high resistance and needs to be repaired or replaced.

Let me show you in the diagram below of how to perform an actual voltage drop test.

 

In diagram #1 shows how to connect the voltmeter to check the circuit’s entire positive side; which contains the connecting wiring, fuse, switch right up to where the positive lead going into the device.

With the switch closed (circuit turned on and device functioning) there should be less then .2V showing on the meter and that is the maximum voltage you would ever want to see, preferably less than.1V.

 

Diagram #2 shows that there’s a corroded section in the wiring (circled); causing some resistance to current flow. The meter connected same as in #1 (dotted line) shows a voltage of .28volt. Move the voltmeter lead to the out-side of the switch and it shows the same voltage drop. This tells us the problem is still closer towards the battery.

 

Diagram #3 the meter is reading .26V this tells us that there is some resistance across the switch but only.02V not our main problem.

 

Diagram #4 we’ve moved the voltmeter lead to the out-side of the fuse and the voltage reading now is .06V which is more then acceptable.

 

Now we know that the high resistance is in the wire between the fuse & the switch.

The negative side of a circuit can be tested in the same manner; which is just as important; especialy on boats, that should have the ground of all its electrics hard wired to the battery.

 

Like someone else here stated; the one fish finder might be turning off because the starting circuit might be dragging the voltage below the finders turn off point.

 

Any 12V DC circuit can be voltage drop tested the same way; including the starting circuit, the same values apply.

These tests must be performed with whatever device turned on or actuated. Testing the circuit like in #1 but with the switch open will (or should) give you source (battery) voltage readings within the .2V max. That’s because the circuit is incomplete, no current flow so no voltage is being used; that’s also if the ground side of the circuit does not have any issues.

 

Hopefully I didn’t confuse the issue even more.

I’ve been using voltage drop testing rather then ohmmeter tests for resistance checking for years. An ohmmeter testing a braided wire; that has all but one or two strands of wire not broken; could still give you a low resistance reading on the ohmmeter; but a voltage drop reading on an active (turned on) circuit will show you every time.

 

Dan.

[SlowPoke]

Hopefully I didn’t confuse the issue even more.

 

 

Excellent,EXCELLENT post Dan!

We were going to check it with the ohmmeter but Emil is in Georgetown and I'm in London trying to walk him through it over the phone. Not only will this be an easier test, it will in fact pinpoint where the issue is. So far, we've narrowed it down between the battery and the fuseblock BUT there seems to be a connector(s) in the harness between them.

Because we have the same model sonar units, we know his volt reading at the unit is lower than it should be. Now we have to find out why.

 

By the way, I might drop by for an explanation on how to test my voltage regulator on my boat motor! I'm getting some whacky readings.

[DanD]

Sure stop in Brian; not sure how much help I’ll be though?

Never had much to do with magnetos and charging coils; but if you can come up with a wiring diagram; we together might make sense of it?

I’ll do what I can to help; but not guaranteeing we won’t let the smoke out of the regulator. and that's not a good thing; because I've never been able to figure out how they got all that smoke into those little electronic boxes in the first place?

That’s if there is one; I know some outboard’s charging systems were self limiting; via the design of induction charging coils?

 

 

Dan.

[NANUK]

Are you using Lowrance supplied glass fuses? those fuse holders are known to get loose after a while,

if thats the case, change them to automotive(blade style) fuses.

also make sure all the spade connectors and the wires in those connectors are good and tight. you'll need a proper crimping tool.