Voltage drop at panel

[redunculous]

So I've noticed that my batteries haven't been performing too well which I honestly struggled to believe as they are reasonably new Trojan 105's.

On my electrical panel in my cabin the voltmeter shows 11.5v yet direct on my batteries I am seeing 12.5. It looks like when I add to the load it will drop the voltage further (will play with loads on it tomorrow to verify)

I have checked connections at both ends and no corrosion is visible - the connections at the battery switch that are exposed to the elements in one of the cockpit lockers that houses my batteries shows 12.5.

I would say it's about 15ft +- a ft from the batteries to the panel and the gauge looks to be about 8 - 10.

Is the gauge too small for this and that's why I am seeing a voltage drop or is there more too it? I am generally pulling 8amps with a 1v loss between the panel and the batteries.

 

[justsomeguy]

Is the gauge too small for this and that's why I am seeing a voltage drop or is there more too it?

No. I think there's more to it.

How old is "reasonably new"?

 

[redunculous]

I would hazard 2 years if memory serves me correct. Good charger on them when I'm not sailing which is a lot more often then when I am

I can't understand why I would see 12.5 at the batteries but 11.5 down below unless it was corrosion or incorrect gauge? It's driving me batty

 

[Brian D]

Not only do you have to check the positive side, you must also check all the connections on the negative side. I know you knew this but just saying. Don't forget that if you calculate 15-so-feet of wire you actually have twice that. Both side need to be accounted for. And, again, I knew you knew this.

You can try this. Take any length of wire and connect one side to the battery negative terminal. This will be connected to your Digital Volt Meter. There will be next to zero current flowing in this wire since the only load will be the meter. Check at all exposed points along the path to the panel. But first check at the pos terminal for your reference point. This might tell you if there is a voltage drop and where it is.

 

[justsomeguy]

Two years old, even for Florida...likely not age. As you'll be playing with it tomorrow, try new wires to the meter?

 

[redunculous]

justsomeguy - Sat in the middle of the berry islands at the moment at a little cay - sadly no wire that gauge onboard and none near by. Will be pulling out the voltmeter again in the morning and seeing what I can find.

Brian - I did know that but did I do it? No I concentrated on the positive! Will be testing the negatives in the morning when I've had coffee and my brains functioning properly ha! Thank you for the gentle reminder !

 

[Brian D]

One other thing @redunculous, many years ago as an active musician playing rock music, sometimes the amps would start acting up. This was also true with my amateur radio equipment. The gentle fix was to loosen the ground connection or screws on the PCB and then refasten them. So after you do your checks, it wouldn't hurt to loosen the screws and nuts, wiggle the wire, then refasten the hardware. Just saying.

 

[Johnb]

Have you clarified in your own mind whether this is a new problem or if it has always been that way.
If it once was good and now is not, and the voltage right on the battery is good then some connection has deteriorated. Don't just look at them, take them apart and clean them.

 

[justsomeguy]

sadly no wire that gauge onboard

I never said what gauge.

 

[Rich Stidger]

The voltmeter on my panel has always read low. About a volt. I wrote it off to poor calibration. None of my equipment running from the panel seems to be suffering. My h40.5 is a 1997 model.

 

[Maine Sail]

#1 30+/- feet of 8-10GA wire is simply too small for a 40' vessels DC panel feed. Items such as navigation lights, nav equipment etc. require no more than a 3% voltage drop from battery voltage. Even at just 8A your losing 2%, and this is just to the panel not all the way to the nav lights, and this is under your "average" house load of just 8A. Kick on a few more items and your nav lights and other critical circuits are now out of compliance with the safety standards maximum 3% voltage drop.

#2 I know the builders do it, because it's easy, but volt meters should not be measuring voltage at the panel end of a circuit. They should always be a direct feed to the positive bus or direct to the battery + & - terminals before any voltage drop has occurred.

#3 Analog voltmeters can not be trusted for accuracy in the marine environment. I can count on one hand the number of accurate analog volt meters I have come across over the years. A better choice would be a digital meter that reads to the hundredths, not just the tenths of a volt. Adding the hundredths position helps you understand "trending directions"... A meter such as the Blue Sea 1733 is a reasonable price and good choice...

Rx -

-Install real wires for your DC positive & negative wire feed as opposed to kite string.

-Wire your volt meter positive (with fusing) & negative directly to the battery bank or its very close proximity bus (within 5" - 7" of battery)

-Ensure your volt meter is accurate when directly sensing voltage at the battery bank.

 

[agprice22]

Just because you cannot see corrosion does not mean it is not there. Just last week, the power trim on my outboard stopped working. Turns out a butt connector sealed in heat shrink was corroded. I diagnosed it with the volt meter, but it showed 12.7 at both ends, so I grabbed a battery, brought it right to the motor and connected short leads right to the motor. The problem was solved. I knew then that it was wiring. The only junction I could not see was the one with heat shrink. I peeled back the heat shrink, and WAHLAH... about 1/2" of the leads, both ground and positive, had some green corrosion. I was surprised that so little corrosion could cause this, but it did.
I redid the connections, and everything worked fine. I also noted that my batteries lasted much longer the day I sailed after the fix!

Check your cables along the entire length. Look for bulges. Loosen and retighten all your connections. While your connections are loose, check the lug connectors. The wire should be stiff and solid feeling within the insulator for an inch away from the lug. If it is not, you may not have a good crimp. Pull back any tape or heat shrink and inspect the connections.

 

[DayDreamer41]

My vote goes with MS on the gauge accuracy, replace the gauge and your problem will disappear, or keep the gauge and add the difference to the reading from what you read at the bats and what you see at the gauge.

 

[shemandr]

Thanks again MS for the clarification with regard to where panel volt meters (Are likely to) measure voltage. I have wondered about that for years. Now I know it is likely that my analog voltmeter is nearly useless except maybe to tell me the alternator is putting something out. If I ever run the wires directly to the battery, and buy a digital meter, it would save me crawling into the battery area, which isn't all that easy. That would be an upgrade worth the trouble.

 

[dlochner]

Thanks again MS for the clarification with regard to where panel volt meters (Are likely to) measure voltage. I have wondered about that for years. Now I know it is likely that my analog voltmeter is nearly useless except maybe to tell me the alternator is putting something out. If I ever run the wires directly to the battery, and buy a digital meter, it would save me crawling into the battery area, which isn't all that easy. That would be an upgrade worth the trouble.

A better upgrade for the same amount of work would be installing a Balmar Smart Gauge. The SG will provide both the voltage at the battery and the state of charge. It can monitor 2 battery banks.

In an attempt to provide better information on my batteries and to reduce the miles of wiring in the boat, I disconnected the analog voltmeter from the batteries and connected one of three meter inputs to the panel. The analog meter gives a rough indication of battery voltage and the Smart Guage a more accurate reading. Since the analog meter is always on, it is easy to give it a quick check to see that things are most likely OK. The SG requires pushing a button to get a voltage reading.

 

[NYSail]

I had a similar problem..... turned out to be a bad neg wire from the battery PLUS corrosion on the engine ground that I could not see. I replace my neg wire and the hen undid the engine (on starter for me) ground bolt and cleaned all rust and corrosion. No problems no drop in voltage no flickering lights etc.... start simple. And follow ms advise!

 

[Brian D]

What I like about that Blue Sea Volt Meter is it draws .015 amps which means for a 40' run(20' pos and 20' neg) of AWG16 wire, one will see about .008 vdrop total. Not bad.

 

[redunculous]

Thanks for all the responses - I've been busy resistance checking everything on the negative side this morning - panel to motor to batteries. Voltmeter at panel is analogue but the issue is not the voltmeter - my handheld meter confirms the volt drop down at the panel as I mentioned I think?

Now perhaps I am cocking this up so please educate me but when I have my meter set to ohms the only time I see any resistance (all other resistance checks go to zero) is between a battery to battery cable at my house bank. I see a reading of 1.5.

I've cleaned all connectors and sprayed them with a corrosive blocker once reconnected and re terminated quite a few to be sure. Everything seemed to be fine except for this one battery to battery cable - is that resistance enough to cause this issue?

MS I will be installing a new wire of sufficient gauge when I have chance (Marsh harbor in the Abacos should have that and I'm there next week) - rather irritated that they used such a small gauge. I will also install that meter you recommended so thank you for that.

Rich - same boat and same issue since I had it but lately it's got to me so I finally opened it up and put the meter on the connections in there and it's not the analogue meter that's just not calibrated right for me - I've actually lost a volt and when sailing I watch my volts dive with my autopilot on etc (I've never checked my battery bank when sailing which is something I will check next to see if my volts are nice and high which I suspect will be the case)

Agprice22- wires are buried in the boat walls so physically checking this is not something I can do right now on the hook.

Thank you to all for the replies - always a pleasant surprise to log on and see all the good feedback I get / stay tuned for my not charging alternator post haha

 

[redunculous]

Just thought about my batt to batt neg cable that shows resistance

If I am still seeing the correct volts on the pos and neg of my bank then that can't be the problem as surely it would show what I am seeing at the panel.

I'm still on the gauge

Frustrating stuff as I'm in the middle of nowhere

 

[Brian D]

What is the gauge and length of that suspect cable? There should be 0Ω resistance. Unless the cable is really long. You might have issues with the connectors on that cable. When you measured the cable, it was not connected to anything at all? Of course you disconnected it, why am I even asking that silly question.