Electrical Problem

[LONG_KEELER]

I have a Navman chart plotter.

It has a voltage alarm that the user can set.

I have about 12.8 v at the house battery but the alarm beeps at a setting of 12.2 v.

I have a voltmeter but am unsure how to measure the voltage at the switch panel for the appliance.

Also, could the nature of the wiring at the switch cause a voltage drop ?

Any help would be gratefully received.

Regards,

 

[noelex]

There may be excessive voltage drop in the wiring and conections. It is certainly worth measuring.
Se the voltmeter to volts at an appropriate scale (usually 20v) and put the probes on the nearest conection to plotter that you can get. Make sure the plotter is on. Compare this reading to the voltage measured a the battery terminals. It should be within 3% or 5% at worst.

The voltage reading of plotters tends to be very inacurate. (I don't know why they cannot calibrate the voltmeter) so its possible the voltage reading at the chartplotter is wrong.
My Simrad is 0.3 v wrong, my Furuno is 0.1 v wrong. The B&G has the best system, adjustable calibration so it's spot on.

 

[nigelmercier]

I have about 12.8 v at the house battery but the alarm beeps at a setting of 12.2 v.

Do you mean it is set at 12.2V, but beeps when the battery is 12.8V?

 

[LONG_KEELER]

Do you mean it is set at 12.2V, but beeps when the battery is 12.8V?

Sorry Nigel. Did not make that bit very clear.

The plotter is effectively saying that it there is only 12.1 v passing through it's voltage checker when there is 12.8 at the battery. I had to keep setting it back to see what it was registering.

I tend to leave the plotter on during the night for the anchor watch. I anchor quite a lot.

For the last few month's I have had it set at 12.4 v and things have been fine. It started to beep last week and found that I had been leaving the radar on standby without knowing. Hence the voltage drop. This has been a very nice feature as I have no fixed volt gauge.

I recharged the 110ah house battery which is quite old. Showing 12.7 v the plotter, still beeped as above. Decided to renew the battery and it has made no difference. I am wondering if the switch panel connections are dirty/pitted .

Many thanks, and thanks to Nolex . I will definitely follow your suggestions and report back.

 

[oldsaltoz]

Some electronic devices come with a combination of long and somtimes very thin cable, this alone can cause a voltage drop/use extra battery power.

Because the make has no clue as to the distance between the supply and final location of the device the cable is just thick enough to supply required voltage, any dodgy termination may cause problems.

If you find a section a section of long cable hidden along it's length, pull it through to the supply terminal and shorten it.

Good luck and fair winds.

 

[William_H]

Measuring voltage drop

A more sensitive or accurate way to measure volt drop is to connect the positive probe of your digital volt meter to the battery +ve terminal. With the plotter and any other equipment drawing current connect the negative probe to the positive wire nearest to the plotter. Use a 2v scale on the meter and actual loss will be measured ie difference between the battery terminal and the plotter. good luck olewill

 

[noelex]

A more sensitive or accurate way to measure volt drop is to connect the positive probe of your digital volt meter to the battery +ve terminal. With the plotter and any other equipment drawing current connect the negative probe to the positive wire nearest to the plotter. Use a 2v scale on the meter and actual loss will be measured ie difference between the battery terminal and the plotter. good luck olewill

As William says this is a good method to measure voltage drop. Note however the above only measures the voltage drop on the + side of the circuit. You have to do the same for the negative side of the circuit and add the two up to get the total voltage drop.
If you have excessive voltage drop by measuring the drop in various parts of the circuit you can narrow down where the problem is.

 

[john_morris_uk]

A more sensitive or accurate way to measure volt drop is to connect the positive probe of your digital volt meter to the battery +ve terminal. With the plotter and any other equipment drawing current connect the negative probe to the positive wire nearest to the plotter. Use a 2v scale on the meter and actual loss will be measured ie difference between the battery terminal and the plotter. good luck olewill

That's a good way of doing things and it certainly appears that there may be a problem with the cables and connections somewhere.

I am slightly anxious about the set up though. The OP said he has one 110 Ah domestic battery. That's 55 Ah useable capacity. Lots of plotters use a couple of amps and over 12 hours thats 24 Ah of energy which is HALF of your available. This ignores fridges, lighting etc etc. If the domestic battery has been frequently discharged more than 50% then it will lose capacity and one is into a downward spiral of disappearing battery resource.

So check the wiring, but I would humbly suggest having a good hard think about the battery bank and it's charge discharge regime.

 

[Tintin]

Try cleaning any fuse contacts and fuse ends.

 

[LONG_KEELER]

Many thanks to all for contributing .

Just as a follow up I took some measurements as suggested.

12.76 v at battery before test.

12.52 v at Plotter on switch panel with power to plotter.

12.32 v " " " " " with plotter, vhf, log , sounder on.

I will try olewill's better test also and other items suggested.

For info, the plotter only draws 500 mA and I don't run a fridge .

AS Oldsaltoz mentioned , the wire from the plotter is very whispy and has to travel about 6' to the switch panel.