Best Way to Monitor a Battery Status for a single battery system?

[LR Max]

2011 Ford F-150, right?

You already have a system in place. Your on board computers monitor your electrical system and takes care of all of that for you.

Also you can simply get a bluetooth OBD2 reader, and see all of the data readouts on your phone. On top of that, you can data log to see trends. Much cleaner, easier, and multi-purpose.

 

[Bravo1782]

@LR Max, that's an interesting idea. For me, I'm interested in being able to monitor battery status primarily while the vehicle is off. I run lights, chargers, and a fridge while the truck is off, and I'd love to know how close i am to killing my battery. My truck doesn't even have a volts meter, so I feel like having something to monitor the battery would be nice.

 

[rayra]

powerwerx.com has all sorts of nice stuff, at reasonable prices. They've got a standard size round face voltmeter for $20

https://powerwerx.com/panel-mount-digital-volt-meter-blue

Here it is about 5x actual size

1-3/16" hole in any dash or trim panel, a bit of wire. Put it somewhere visible when you are out of the vehicle. Or even in the rear cargo area, if that is part of your camp setup.

Or spend a great deal more on a solar charge controller sort of device with a low-voltage auto cutoff, audible alarms, etc.


If you've got the real estate, Powerwerx has a nice line of panel mounts that let you mix and match power outlets, etc. You're running wire anyway for the voltmeter, so put it to use and add a power port too, while you are at it.
https://powerwerx.com/panel-mounts

 

[rayra]

Another inexpensive no-fuss solution is a cig-lighter adapter that gives both USB power plus and a volt readout. Especially if you don' twant to cut holes in things.
https://www.amazon.com/Car-Charger-...1471025994&sr=1-31&keywords=digital+voltmeter

 

[4x4junkie]

Great info guys!

The thing that I really need the most is state of charge of the house battery; I just want a simple way to see if my battery is getting low. The F-150 doesn't include a voltmeter, but I was of the understanding that Voltage is not the same as state of charge. .

I've noticed some people get waayyy too caught up on the tiniest of minor details, and as a result things often get blown way out of proportion (especially when it's on internet forums). Voltage vs SoC seems to be one of those subjects that this happens a lot with.

Voltage is a quite acceptable means for monitoring battery status as it discharges. Knowing whether it is at 68% or 64% SoC really isn't of much consequence (even the high-tech gizmatical monitors would be hard-pressed to provide that level of precision, especially after a few partial charge/discharge cycles). What it sounds like you need is something to simply show, for example, whether your battery is close to needing a recharge in the next hour or so, or whether you can carry on through the night with it, which a voltmeter (and familiarity with how the voltage correlates with SoC) will do quite well for.

Like said earlier, it shouldn't take long to become familiar with it's readings and how various loads affect it (for example, the ~4 amp load of a DC fridge running typically drops the volt reading of a healthy battery by roughly 0.15V or so). However even without taking that into account, you'd only be off by around 10% of the SoC such voltage would indicate. So you can see that the level of required precision is not real great.

I have the exact meter v-man pictured that I installed on a regulated DC power supply I use for absorptive charging of batteries (so can vouch for it's quality), though there are nice bright LED ones of many colors that are available too. The one I use in my vehicle is a small 3-digit (two + tenths) LED that I simply sticky-taped to the inside surface of the C-pillar, and I've seen little need for more precision than that. Make sure whatever meter you get has a trimmer adjustment or some other means of adjusting it (or is of decent quality), as I've seen some of the cheapest ones be off by 0.2V or more.

 

[dBeau]

I use a Victron BMV to keep track of my aux batteries. It uses a shunt based current sensor and counts up what goes in and out of the battery. The approach is solid but like others have pointed out, has it's problems. Of course there are problems with just using a volt meter too. After using the BMV for a couple of years though I've noticed that I only use the SOC as a guide. What's really helpful are the voltage and especially current readings. Once you know what to expect they'll tell you a lot about your system and it's health.

If your battery is fully charged you'll see a fairly high voltage and minimal current flowing from the charger into the battery. If the battery is really low (and your charging system is functioning properly) you'll see a voltage that matches the charging system and lot of current flowing into the battery. If the SOC reads 100% but there still a lot of current flowing into the battery, it's probably time to re-calibrate the SOC.

Not all systems are the same so the numbers and behaviors will vary some. But voltage and current are two properties that exist in all systems. Understanding how they relate and what to expect of them in your system will tell you a lot about what's going on.

 

[Ducky's Dad]

Most battery manufacturers' websites have graphs that show SOC vs OCV. Put a copy of the appropriate graph in your glove box, and and long as you know approximate OCV, you will know approximate SOC. It's close enough for all practical purposes.

 

[Bravo1782]

Thanks for all this info! I really do appreciate it! I guess, for me, it seems like this should be such a simple thing...I can look at my phone or my laptop and see how much charge I have left, so why do I have to guess with my vehicle? And you're right, I don't need an EXACT measure, just a "good enough." Something so that I can quickly check to see if I should run the truck or charge the battery. I've still got a lot to learn, and this is helpful.

So, to recap, the general consensus is a SOC meter is going to be more accurate, if you need the accuracy, but generally, a good volt meter, properly installed, will work for this application.

 

[rayra]

properly interpolated, rather than installed. The install is easy.

What you seem to be after is a charge state indicator graph. The solar / RV / off grid power genres have all sorts of discussion of such things, but most of it comes down to a graph something like this -

There are a lot of variations, but they all fall roughly in the same zones.

https://www.google.com/search?q=sol...xFRsWV7&q=solar power battery discharge volts



Basically when your battery is heading below 12.0v, you need to be recharging it. And you need to get a feel for that rate of discharge or know what your electrical loads are so you can forecast if you can take those loads overnight. Or run a much more robust and complicated battery power / management system at much higher cost.

 

[4x4junkie]

So, to recap, the general consensus is a SOC meter is going to be more accurate, if you need the accuracy, but generally, a good volt meter, properly installed, will work for this application.

Agreed.
Properly "installed" is nothing more than attaching the voltmeter's wire right to the battery itself (not off of an aux power socket or some other wiring connection) with a 1A or so fuse, done.
Deciding whether to cut/drill a hole (and where & how) or surface-mount it with 3M bonding tape or something similar will probably be your bigger concern of "properly installing" it.

 

[Ducky's Dad]

And use the manufacturer's SOC chart for your specific battery.

 

[4x4junkie]

^^
If one is available... (I don't recall if the OP said what battery he has or plans to use)
It seems many (most?) manufacturers don't have SoC charts for automotive & marine style batteries. Some very costly brands like LifeLine or Odyssey make them available if you dig deep enough (Exide does too), but they seem harder to find for others such as Deka, Interstate, etc. or most any house-branded battery (a bit surprisingly I failed to find one on the Northstar site too... maybe I just missed it?).
I wouldn't suggest anyone use the charts posted above though (a battery headed to 11.8V should trigger a red-alert, not caution-yellow). Taking a battery much below 12.0 volts with any regularity is a certain quick way to commit battery-homicide.


If you know the composition of your battery's construction (lead-calcium, lead-antimony, or pure-lead), a manufacturer's chart isn't that important. All batteries of the same composition typically are within a few percent of each other:

So-called "maintenance-free" and sealed batteries (both FLA and AGM) will nearly always be lead-calcium or pure-lead.
These will be approx 12.85-13.1 VOC @ 100% SoC, and 12.2-12.35 VOC @ 50% SoC.
These are the numbers you will probably want to pay attention to since this is by far & wide the most common type among all automotive & marine style batteries.

Lead-antimony automotive batteries are much less common now, a very small number of flooded deep-cycle batteries of this type remain (such batteries were sometimes called "low-maintenance"). These consume water during charging (requiring you check the levels occasionally), which a byproduct of this was the significant hydrogen gas they created.
A lead-antimony battery will be approx 12.65-12.75 VOC @ 100% SoC, and 12.15-12.25 VOC @ 50% SoC.

The voltage vs. SoC charts on this page break it down for the above types with more detail:
http://jgdarden.com/batteryfaq/carfaq4.htm#mf_soc

 

[HotNotch]

Here is what I whipped up. Waterjetted a plate that I welded onto my ammo can console with 3 holes for a volt meter, a dual usb charger, and 12 volt outlet, and 2 rocker switches. The rocker switches are key here: one is a single rocker with indicator light, and the other is a DPDT double rocker ( two positions) I have it wired straight off the battery feeding the double rocker switch. When pushed forward, it sends power to the 2 12v outlets, the usb charger, and the single lighted rocker switch. The single rocker switch controls the volt meter. This way I can charge stuff straight off the battery without the key on but still be able to shut it off when necessary, as well as turn the volt meter off and on when necessary as it is very bright during the night. Cushion on top is just a molle vest cut up with some foam underneath and a couple pouches to keep stuff organized. Works pretty well. Very handy to air ATV tires up, charge multiple devices, and keep an eye on voltage.

 

[Offroadmuch]

This would do it with easy install...
http://ultra-gauge.com/ultragauge/ultragauge_wired.htm

 

[mjac]

2011 Ford F-150, right?

You already have a system in place. Your on board computers monitor your electrical system and takes care of all of that for you.

Also you can simply get a bluetooth OBD2 reader, and see all of the data readouts on your phone. On top of that, you can data log to see trends. Much cleaner, easier, and multi-purpose.

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