Is this the right voltage meter for me?

[One Awesome Inch]

Wondering how well this unit would work for my situation...

http://www.amazon.com/gp/aw/d/B007Q2HOYK/ref=pd_aw_sbs_auto_6?refRID=1A7E5XDKWXQK0MRQMW8E

Its a voltage meter (and usb power output) that plugs into a cigarette lighter. I will be using a dual rv/marine battery that gives 750 cold cranks and 100 amp hours. I need a battery monitor so I can figure out the status of my battery to make sure it will turn over the engine. If its getting low I can take a drive to get it charged up.

Is this a suitable unit or should I be looking at something else?

 

[GotSmart]

The one I bought is the one shown on that link as frequently purchased with


http://www.amazon.com/INNOVA-3721-Battery-Charging-Monitor/dp/B000EVWDU0/ref=pd_bxgy_e_text_y

 

[One Awesome Inch]

I was looking at that one too.

Does it work well?

Any idea how much power it draws itself?

Do you keep it plugged in or just put it in for a quick check?

 

[MikeRuth]

OAI what is your situation?

these meters are probably fairly accurate. You would never know for sure unless they are compared against at least one other DVM(digital Volt Meter). I generally like to compare against two.

you can leave them plugged in if the vehicle is used on a regular basis, at least once a week but preferably more. Otherwise I'd pull it so as not to put a drain on your battery.

Mike

 

[MikeRuth]

doubled up whoops!

 

[SternWake]

A voltmeter is NOT a battery monitor.

Battery voltage is Not like a fuel level indicator, unless the battery has NOT seen any charging sources or discharging loads for several hours.

However Voltage is better than nothing, and with enough observations one can guestimate the state of charge of their batteries.

A casual glance at voltage on a loaded battery is like throwing a rock at a rubber band, and guessing the weight of the rock by how far the rubber band stretched.

Better than nothing but hardly accurate.

Lots if Ciggy plugs have other loads on the same circuit. A voltmeter plugged into such a receptacle will not yield an accurate voltage.

The voltage reading on a ciggy plug can be quite different than what one measures on the battery terminals themselves. The Ciggy plugs wiring circuit is long and thin with multiple connectors in the electron flow, all of which introduce resistance, and any load on such a circuit will influence readings.

I use 2 Small voltmeters on my dashboard, and they have separate voltage sense wires, which I ran to the Positive battery terminals of each battery. They also have calibration so I was able to match voltage readings taken with a good multimeter on the battery terminals themselves.

My dashboard voltmeters are more for monitoring what the alternator is trying to do, than telling me State of charge.

A real battery monitor counts amps into and out of the battery. A simple voltmeter falls well short of this capability.

These are my dashboard voltmeters, and they power on only with the ignition:

http://www.amazon.com/Digital-Voltm...sr=8-7&keywords=SMAKN+0.28"+Mini+Dc+Voltmeter

Notice they have 3 wires. there are 2 wire versions that are cheaper. The third wire is for the voltage sense, and makes for a more accurate product, so don;t try and save 1.85

 

[akrvbob]

If power is going in or out all volt meters give a false reading. They read high if being charged and low of being discharged (drawn from).

The only time you could be fairly sure it was right is if the amount going in or out is very low. Then it is close enough for our use.

If the battery has rested for a few hours (very little in or out) it is probably pretty accurate.

The best time for that is early in the morning after your overnight use and before solar charging.
Bob

 

[Canine]

So should a basic digital voltmeter be used right on the house battery once or twice a day when it's for sure been "idle" instead of these cig lighter gizmos? Would that be a better way to check?

 

[SoulRaven]

I prefer the low battery cut offs. They seem to be pretty much fool proof and don't need to be monitored.