Added a Voltmeter onto the Battery

[Jeff T]

Our 2017 Scamp came with the on-board "charge wizard" so I plan to keep the shoreline plugged in for winter storage. The larger question was how to know the charger was working. Just plugging in the trailer and walking away didn't seem the best idea. I decided to add an exterior waterproof voltmeter at the battery. I located one on the web and mounted it onto the battery box cover. (It is wired directly onto the battery, fused for safety and enough extra wire I can set the cover aside to add water and check the battery cells.) I did add a momentary contact button (switch) onto the side of the voltmeter housing so with a push of a button I can see the current reading. So now I know if the converter is delivering a charge or if not the actual voltage of the battery at rest.

[Buggeee]

Cool.

[BatDude]

Can you please share where you found this?

Sounds like an item I should add.
We are on countdown - 20 Days before we head south for the winter.

[k0wtz]

I found my 12v stuff on ebay and amazon!


bob

[Jeff T]

Amazon has many choices for "waterproof voltmeters". I took a shot and thought this one might offer the best mounting option but they have many others to choose from. There were two thing I didn't really like about this one. How difficult it was to see in the daylight and the fancy graphic displayed around the dial maxed out at 13 volts. The numbers work OK so seeing "13.8" volts works great but that fancy display is maxed in the green. Not a big deal as it works as intended for keeping an eye on the battery and charging system.

amazon.com/gp/product/B01MA3UZC9

p.s. I added the momentary contact push button (drilled a hole to mount it into the plastic voltmeter housing) so the voltmeter would not become a parasitic draw on the battery. Amazon had lots to choose from that were waterproof as well. The wire, in-line fuse, and extra stuff I had or purchased at the local box store.

[Glenn Baglo]

Why not just install a 12V outlet inside the trailer? You can plug a voltmeter into it to get a reading, and use it for other 12V electronics.

[rick in arvada]

In my experience the voltmeter inside the trailer will give readings of .2 or more less than the voltmeter at the battery. For an accurate reading, the closer to the battery, the better.

[Glenn Baglo]

Originally Posted by rick in arvada

In my experience the voltmeter inside the trailer will give readings of .2 or more less than the voltmeter at the battery. For an accurate reading, the closer to the battery, the better.

Once you know that...

[Jeff T]

I gave consideration for a plug in voltmeter. I do have a 12 volt outlet but it is under the table near the floor. It was extra work to add this onto the battery box but I wanted to see what (charge) the battery was seeing. Besides, I can keep the trailer locked and do a quick check just walking up to the trailer on a cold winters day. I guess that makes me lazy.

[Buggeee]

eBay is a good source for these kinds of 12v doodads as well. You'll pick up search terms along the way from the item descriptions that will lead you more, etc. Lots of fun

[k corbin]

Interesting conversation and it looks to be a convenience that perfectly suits the needs of the installer.

I did install a 12v exterior outlet as part of my renovation but it is at the opposite end of the trailer from the battery. Good to know that I would not get an accurate reading from it. But as it is a switched receptacle it would not be normally powered up unless I forgot to switch it off. The switch is inside by the door.

[Raz]

The ideal is a meter that doesn't effect what you are trying to measure. A meter with it's own power source and a digital read out is the best. A plug in meter can effect the measurement in two ways. First, as it gets it's power from the battery it is measuring, a drop in voltage could occur due to an effect called loading. Any time you draw current from a battery it's terminal voltage drops. Second, as it draws current, a voltage drop due to wire resistance may occur. As these plug in voltmeters draw about 10 mA and a lead acid battery has lots of energy, neither of these should be a problem. Parasitic load is probably the bigger concern. Much like an LP detector, if it's always connected sooner or later it will discharge your battery. Disconnecting your battery when you get home will cure that problem. Raz

[Victor Benz]

Originally Posted by rick in arvada

... the voltmeter inside the trailer will give readings of .2 or more less than the voltmeter at the battery. For an accurate reading, the closer to the battery, the better.

True; that is why I re-wired my battery connection to the trailer with 4 gauge booster cable.

As well, the actual battery voltage at the specific appliance is also very important. For example, most trailer furnaces need a minimum of 10.5 volts to get sufficient fan speed to close the sail switch and initiate the furnace ignition sequence.

Vic

[k0wtz]

First of all a .2 drop in voltage is nothing not to offend. Why run a 4g wire for this meter makes no sense to me again not to offend just my opinion.

I purchased a 3 guage setup off ebay I have the meter, cig lighter tap and 2 taps for the phone charger the charger has a dropping resistor to reduce voltage to 5v not 12v which is not good for a phone.

I put mine at the top of the kitchen cabinent so I can monitor voltage I even put a switch there so I can turn it all off when not needed.

the KISS principle works everytime!

bob

[John Linck]

Back in my younger days (fifties) and with my first Scamp I ran a #8 cable from the tongue mounted battery to my converter under the rear dinette. The Scamp's original wiring was a bit circuitous and I'm sure I saved 3 or 4 feet. In my defense I had the cable laying around going to waste. Can't say I noticed any difference, but then I have few high amp draws. On my current Scamp I just left the stock wiring in place and I am surprised how the amps make their way from my Subaru's alternator all the way back to my now rear mounted battery next to the converter. It seems an hour of towing tops off the battery nicely despite the increased conductor length.

I understand the physics of conductor size and voltage drop, but wonder if its really an issue with the small loads I use, water pump and furnace (I don't even count the LED lights). Are we trying to count the number of angels that can dance on a pinhead? Now, had I an inverter its draw would be 10-20 times more and a different calculation. But I don't.

Also I see some folks using huge wire size to run to their solar panels. This also seems overkill to me unless the distances are dozens of feet. I used #12 copper for the 9 feet between solar panel and battery and it works very well carrying my measly 100 watts in full sun.

OTOH I am a born tinkerer. I spend way more time making small and large mods to my trailer then could ever be justified on any level. Its fun and some are quite successful and useful. Some not so much.

Happy November, john

Pic of shoreline somewhere in the San Juan Islands

[k0wtz]

john I used to run ham radio a lot I read so much stuff on wire size I just gave up and used rg58 I could never get it hot no matter how much power I hit it with!

the gain on using rg8 was so slight it just wasn't worth it to me!

bob

[Buggeee]

Originally Posted by Victor Benz

...I re-wired my battery connection to the trailer with 4 gauge booster cable.

Vic

Nice

Originally Posted by John Linck

...born tinkerer. I spend way more time making small and large mods to my trailer then could ever be justified on any level.

True that!!!

[Buggeee]

Originally Posted by John Linck

...I am surprised how the amps make their way from my Subaru's alternator all the way back to my now rear mounted battery next to the converter. It seems an hour of towing tops off the battery nicely despite the increased conductor length.

...Are we trying to count the number of angels that can dance on a pinhead? ...

...I see some folks using huge wire size to run to their solar panels...

Yes, exactly. With solar we're capturing angels living on the head of a pin. The 100w solar panel puts out 4 or 5 amps in the middle of the afternoon on a sunny day. A couple of angels flitting away as heat are sorely missed.

The Subaru alternator puts out 100 amps give or take twenty. Its like water flowing down a mountain. No matter the waste, something's getting wet at the bottom.

Anyway, that's my unedumicated understanding. What a fun hobby. I really respect the engineers that see this electricity in their mind.