Adding a Digital Volt Meter to show battery state of charge

[NetBoy]

Hi, I decided to add a digital volt meter to my motorhome to show the state of charge of the batteries - it will be handy when dry camping.

Here is a table from the web site "The 12 Volt Side of Life" that shows voltage vs state of charge (a great web site to learn about living on 12 volts):


I ordered a digital volt meter from eBay for $5 including shipping:



I mounted the meter, and a momentary contact switch, in a piece of plastic from an old car litter basket:




I will mount the meter in some convenient location in the motorhome tomorrow. And I'll include a printout of the above voltage chart.

Pretty cool for five bucks!

Note that battery voltage should be read when the batteries are at "rest" -- that is, wait a half hour after any big discharge (for example, such as running a microwave on an inverter).

[qtla9111]

NetBoy wrote:

1rosario wrote:
What local store might have a digital meter?
We're leaving Sunday, too soon to order off eBay.

Camping world carries a little digital volt meter that plugs into a cigarette lighter socket... they work fine, and cost less than $20. Click HERE.

I have that one, works great!

[tenbear]

I finally finished the project I started a couple of years ago. Now I have a 12 VDC voltmeter, an ammeter measuring the current into or out of the battery, and a 120 VAC voltmeter. Each meter has a switch, down at the lower left.

[soling2003]

I did it the same as ScottG, but have the full set, volts on both banks, amps dc for what is used by the trailer, then ac volts and amps. OCD??? maybe, but they are fun to watch change as you turn on the fireplace and the ac amps go up.

[xplodn]

ScottG wrote:
I have a whole set!
ACV/ACA/DCV/DCA (for some reason the pic isn't legible but they are clear and easy to read.

Do you have links to these? I have been looking for matching DC and AC displays because my OCD is kicking in and I have to have them matching...

[tenbear]

My class C has the idiot lights to indicate the charge level of the battery. No way could I fit a meter where the lights are.

Here is a link to a voltmeter that plugs into the cigarette lighter.

You could also buy a multimeter. That is more useful but not as convenient.

[sherpaxc]

RangerEZ wrote:
Excellent thread. I will be putting one in mine soon.

I was thinking of removing the simple meter (Full, 3/4, 50%, 25%) that came with the trailer and replacing it in the same spot with one of these. Any reason that wouldn't work?

To help, I made a chart that you can print out as a 5 x 7 print. It gives you four small charts--essentially wallet size--for posting beside your meter if you like, or wherever.

Hope it is helpful.

Couple things.
1. Can someone answer this question? Can it just be mounted where the standard one is?
2. Is there a handheld one that I could buy at say radioshack? I know nothing about all this but am trying to learn. Got the LEDs. Getting the inverter/gennie.

[RoyB]

I made up my battery system using inexpensive digital meters from SURE ELECTRONICS ebay/china. These three meters monitor the DC VOLTAGE of my two battery banks and the DC being drawn or provided by the Trailer system. They generator read the same DC VOLTAGE since I have them switched together feeding my trailer system.

My three meters are mounted in one of those speciality 3-gang switch covers and all is mounted vertical in a regular PVC electrical switch box... The three meters fit perfect behind the 3-gang switch panel and I have them rubber cemented in place. I also have included an ON/OFF switch for each meter as sometimes being on is brighter than a night light.


This panel is mounted near my OFF-ROAD POPUP entrance door just below the Jensen AM/FM Radio shown here. I need to get a photo of it mounted...


The SURE ELECTRONICS DC AMPMETER model ME-SP230 is a +/- 70AMP model and uses HALL EFFECT DC current sensor module where the main 4AWG DC FEED line to the trailer is routed through the current sensor head. There is no high DC current shunt used with this meter. This DC current sensor monitors how much current is being drawn from the two battery banks being used by the trailer systems as well as how much current is being drawn by the batteries when being chargerd by my PD9260C Converter/charger unit when in boost 14.4VDC charge mode.


This is where my BATTERY DC MONITOR panel is wired into my battery bank system


This is my best resource being used when camping off the power grid. I can watch my battery DC VOLTAGE slowly start dropping down when using all of my desired 120VAC and 12VDC items during the evening. The battery banks capacity is all planned out to provide the power I want to have during the one day/night camping run and at 8AM the next morning when my battery read around 12.0VDC I will want to re-charge my battery banks to 90% charge state in as little as three hours time using smart-mode charging technology with my trailer shore power cable connected to 2KW Honda Generator using a RV30A-15A long cord adapter.

Once re-charged we can do all of this over again for the next day/night camping run from the batteries.

Works great for us... We get to use almost everything in the trailer except the air conditioner and high wattage microwave of course.

I might add I really should have used the BOGART Monitor system talked about in the above post but my setup was about $60 less to purchase all of the parts and three meters always ON to view without switching. The part I really would like to have that the BOGART model has is the settable ALARM that will indicate when the batteries are approaching 50% charge state. All of the battery history stored with the BOGART model would be very useful as well.

NOTE: Looks like I'm loosing it haha... I have already put in my two cents here... At least I said about the same thing in both entries... Getting old is so much fun... Thought this post sounded familiar...

Roy Ken

[Jimf1234]

This is a great tool to track not only voltage but also how many ah have been used. http://www.bogartengineering.com/products/TriMetric%20

[westend]

john b,
I hope some of what I do and share is for the greater good but I'm old enough to know my way isn't for everyone. Yeah, blue LED's are now consigned to audio gear, only. You can see in the picture above that the indicator lights on the gauges are red.

BTW, when I catch the Polish Princess staring at the top of my head where there was once hair, I remark,"Moss doesn't grow on a busy street!", lol.

[john_b1]

westend wrote:
Hey Ranger, thanks for the effort! Those charts should help out many folks.

For myself, I went analog, mainly because I had them and I can see a needle position easier than the illuminated digital displays. The gauges can also be adjusted/calibrated to mirror measurements from my Fluke DMM.

I like your way Westend plus I have been following all your projects. as having all those blue lights all over the place is not in my best interest as they drive me nutz Ha Ha !
Nice job though but for me I learned a long time ago I don't need to be anal about anything any more as most of it doesn't register anymore anyways>!!
Have a great one guys as you give me good learning and make me use my mind or whats left of it Ha Ha

[westend]

Hey Ranger, thanks for the effort! Those charts should help out many folks.

For myself, I went analog, mainly because I had them and I can see a needle position easier than the illuminated digital displays. The gauges can also be adjusted/calibrated to mirror measurements from my Fluke DMM.

[RangerEZ]

Excellent thread. I will be putting one in mine soon.

I was thinking of removing the simple meter (Full, 3/4, 50%, 25%) that came with the trailer and replacing it in the same spot with one of these. Any reason that wouldn't work?

To help, I made a chart that you can print out as a 5 x 7 print. It gives you four small charts--essentially wallet size--for posting beside your meter if you like, or wherever.

Hope it is helpful.

[time2roll]

walker2413 wrote:
I am just curious if people with solar panels have to switch off the panels before checking their voltage this way? I suppose they could wait until dark also.

Bill W

During the day the voltmeter would be monitoring the solar charging.

[walker2413]

I am just curious if people with solar panels have to switch off the panels before checking their voltage this way? I suppose they could wait until dark also.

Bill W