Is it Voltmeter or Volt Meter?

[bcope01]

I'm thinking of installing a 2-wire digital voltmeter for monitoring my coach batteries. Has anyone done this? How is it working out? Where did you purchase your meter?

Thanks, Bill

[w5vthdonb]

If you have a cigaret lighter circuit for your TV's, and it is wired to the house batteries, save your money on a didgital meter and purchase a LCD meter that will plug into the cigeret lighter. Unplug your unit from houshold power and wait awhile and you can tell the static charge on your batteries. Also when you conect to household power you can tell if everything is charging corectrly as well as the generator from the engine working also.
The part number is #19983.
It is located on page 130 of the master catalog.
Cost $17.99

Don USN ret.

[whemme]

Don,

You list the P/N, the master catalog page number, and the cost - but precisely what catalog are you referring to?

[Mel Wilbur]

Bill, that is a camping world part number.

[Randy Wilson]

Wal-Mart carries a similar item in the auto dep0artment

[bcope01]

Bill, Mel, Randy & Don:

Thanks for your responses.

Let me start by saying that "sparky" isn't my middle name. When it comes to anything electric, "crispy" is probably a more appropriate nickname for me.

There are two reviews of this item on the Camping World retail web site.

One gives it good marks, although the reviewer states that his two consistently read about 0.2 volts above what the professional self-powered multimeters say. He adjusts it in his mind when he takes a reading. He also says that the display occasionally goes blank requiring him to jiggle it in the 12V socket. No big deal.

The other reviewer is definitely not happy. This reviewer says that when he plugs it in, he gets a different reading each time. If he wiggles it, or taps it, he always gets another reading. If he plugs it in securely and waits, the tenths of a volt reading moves up to half a volt! Thinking this might be a connection issue, he elected to break off the plug and use it wired directly to 12 volt source. It was still innacurate. He doesn't recommend it.

If you own this (or similar) plug-in voltmeter, what has been your experience? It seems to me that consistently .2 volts off the mark is significant, especially when all of the battery charge status charts provide voltages to the hundredths of a volt. Or am I wrong? And if, as the second reviewer says, it reads all over the map each time it is plugged in, and drifts for no reason, is it something we want to depend on? Or was his experience different than yours? Maybe he just got a bad unit?

I'd like to get something I can rely on since I like to do a lot of boondocking and want to be able to keep an eye on the charge status of my batteries. If the Camping World plug-in voltmeter will do the job, then this is what I want because it is easy to install and priced right.

If not, then I'd be willing to chip in another $10 and get an accurate meter (+or- 0.01 volt), even though it costs more and installation will be more extensive. If I need to go this route, I was thinking of a 2-wire LCD Datel meter like this:
http://www.metercenter.com/cgi-bin/webs ... -da144.htm

Thanks again, Bill

[bcope01]

Just a quick update...

I just went down and purchased the Camping World plug-in voltmeter recommended by Don in the above post. The good news was that it was on sale for only $11.69 to Club members. The bad news was that it reads 0.3 to 0.4 volts (drifting back and forth) higher than my multimeter. I believe my multimeter to be fairly accurate, so this plug-in is quite a bit off. I think I will return it and get a refund.

Bill

[Randy Wilson]

The lighter plug meter is for quick reference and will not be as accurate as a dedicated meter connected directly to the battery. That being said, I too experienced disappointing results with the unit from camping world. It seemed to increase its reading if left plugged in. I assumed it was due to heat generated by the internal light. I bought a similar item at Wal-Mart that appears to be more stable, but is not lighted.

The accuracy of these meters depends partly on where the measurement is taken. There is some voltage drop on circuits with other loads, and the measurement should be taken as close to the battery as possible. If connected to the same point, my Wal-Mart meter reads about 0.1 volt low when compared with my calibrated Fluke digital multimeter - not bad considering the price difference.

If you are real serious about monitoring battery use, there are systems such as the Link 10 or the Xantrex XBM that will monitor current (amperage) and time as well as voltage. These systems connect directly to the battery including inserting a shunt in series with the battery cable and can be adjusted to match the amp hour capacity of your batteries. They use a microprocessor to provide a continuing record of usage and remaing capacity. See this link:

http://www.xantrex.com/web/id/96/p/1/pt/5/product.asp

[bcope01]

If you are real serious about monitoring battery use, there are systems such as the Link 10 or the Xantrex XBM that will monitor current (amperage) and time as well as voltage. These systems connect directly to the battery including inserting a shunt in series with the battery cable and can be adjusted to match the amp hour capacity of your batteries. They use a microprocessor to provide a continuing record of usage and remaing capacity. See this link:

http://www.xantrex.com/web/id/96/p/1/pt/5/product.asp

Randy:

Thanks for the information. I'm serious about monitoring my batteries, but I don't want to spend serious money, at least not the kind that these units cost. I think I would be happy with a reasonably accurate meter that is fairly simple to hook up. I may check out the Wal-Mart plug-in meter before I up the ante.

Bill

[Mike Jean Bandfield]

Bill,

This battery monitoring process might be more difficult and less precise than you imagine it. Most people I know just learn to live with a certain amount of ambiguity.

All loads on the battery will lower your voltage reading. The more current draw the lower your reading. Remove the load and the voltage will slowly rise to a new static voltage. The percent of discharge charts are based on a no-load static voltage reading. To get this reading will require you to disconnect all loads from the battery and wait for the battery to stabilize - usually about 30 minutes. If you think about it, this is a pain in the wazoo. You are dry camping and are quite dependent on your batteries but to get your reading you have to disconnect them for 30 minutes (i.e., no tv, no lights, no refridgerator cooling, no fan, etc or you run the genny with the battery disconnected which is counter productive). If its night time, the light you use to read the meter will throw off your measurement a few of hundred millivolts. During the day, you'd also have to disconnect your solar panels for 30 minutes - and that's also counter productive.

I don't have a fool proof procedure. Like most people - I guess at it. I take voltage measurements occasionally with a digital VOM at night when the solar panels aren't charging, with 1 light on, and as few loads connected as possible. Compare this to a real static measurement taken at the same time a few times; and with some practice you'll get a feel for the relative capacity of your batteries. If you are consistent regarding the loads when you take your readings, even though your reading is not a true static reading it is consistent relative to the true static value.

Dry camping is not an exact science either. Some days are cold, some days are hot. Some days the sun shines and some days it does not. Some days my batteries end up at 12.4Vdc and some days they end up under 11vdc. (stuff happens). The fact is dry camping can be hard on batteries.

People who get 6+ years out of their batteries don't boondock a lot or they spend a lot of time in the cold and dark. I suspect most of those only use their batteries at the rest stops between RV resorts.

Bottom line: Getting exact measurements is quite difficult and spending more on monitoring devices doesn't make the process easier. Become familiar with your system and how much daily use you can safely get out of your batteries. Buy a good brand battery. Never over charge, avoid over discharging and keep the plates covered with distilled water. Keep the battery case clean and the connections tight. If you get 3+ years out of your batteries you're doing OK.

Of course, you can do everything right and still cross the battery gods. Shorted plates and other defects can happen at any time.

Mike

[bcope01]

Mike:

Thanks for all the good information - these are certainly things eveyone needs to know about.

I'd also like to add that another important part of battery maintenance is the monitoring of the voltage coming from the charger. Most of us started out in our BFs with the Parallax/Magnetek 7300 series charger/converter (or some less capable predecessor). Although this unit adjusted the amperage going to the battery during charging, it provided a steady 13.8 volts. We all know that if left plugged in to shore power for an extended period of time, that many constant volts will eventually fry your batteries.

This is what may have happened to the previous owner of our BFT. I suspect they were already toast when we picked up our BFT from the factory in Humboldt. When we got home 5 days later, I called Interstate and they replaced them for free since they were only 9 months old. Since then, I have babied these batteries because we keep the coach plugged into shore power while it is stored next to our home. In order to make this process less cumbersome, I added the Qwik-Fillâ„¢ Dual 12-Volt Battery Watering System with Filler. This item takes the hassle out of checking levels and adding water when necessary. Also, I recently converted the lower section of the 7300 to a IOTA DLS-55 Amp with built-in IQ Smart Controller. This unit operates as an automatic 3-stage "smart charger," providing the benefit of bulk, absorption, and float stage charging, and hopefully, ensuring proper and safe battery charging and minimizing over-charging.

This is where a voltmeter also comes into play. I think I'd use a voltmeter as much to check the charging voltages from charger as much as I would the charge status of the batteries. Usually, it is just a matter of a couple of tenths of a volt between the 3 stages of a smart charger. A couple of tenths can make a difference. For example, you can float charge a battery at 13.6 volts without damaging the battery, but not at 13.8 volts. I'd use the voltmeter to keep the charger honest, checking to make sure it is cycling through all 3 stages, and that the correct voltage is supplied at each of the stages.

Overkill? Probably so, but hey, I'm retired and looking for something to do.

Bill

[Mike Jean Bandfield]

Thanks Bill. Battery maintenance is a very complicated subject. My comments were primarily directed at battery monitoring while dry camping. I don't know how the average RVer finds the middle road to reasonable battery maintenance without destroying a few along the way to becoming a battery guru. Your point about charging voltage is right on the mark.

Being the cheapee that I am, I've taken a somewhat different approach. Rather than buy a fancy 3 stage charging system I usually keep the battery switch disconnected when the 7300 is plugged in. Its a good 12Vdc source but a lousy battery charger. As it turns out, its a rare situation when I need to use it to charge the batteries. Our solar panels work nicely to keep the batteries topped off while dry camping and in storage and the solar controller tapers off the maintenance voltage to ~13.4v (and it is adjustable ). So I don't feel the need to upgrade the converter.

Mike

[bcope01]

Mike:

When it comes to being a cheapee, I think I've got you beat. Thats why I don't have a
solar charger system -------------------------- yet.

Bill