What's a Good, Cheap Voltage Meter?

I am realizing, reluctantly, that this whole flashlight and battery interest is fast becoming a monkey on my back. So I think I need a way of measuring the charge of my batteries. Is this what a voltage meter does? Does it just measure a cell's voltage, such as 1.2 V, etc.? Does it also measure the Mah level? You can probably tell right away that I have an electrical engineering degree from MIT.

I don't want to spend a lot of money, which to me means not over $25. I'd be grateful for suggestions.

Mass. Wine Guy said:

You can probably tell right away that I have an electrical engineering degree from MIT.

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A voltage meter does exactly what you said, measure the voltage.

A multi-meter is able to measure the voltage, current, resistance, etc., and is quite useful for various things. You can get cheap ones that range from $10-50, but you might be better off in the long run with a Fluke multi-meter. They're very well made and are very accurate, but come with a premium along the lines of $150-$300. Do some more research and see what's best for you.

To measure a cell's mAh (capacity), you need a hobby charger. They charge and discharge cells and measure their voltage as well as capacity. Cheap ones like the Accucel-6 is around $25-$30 shipped and good ones like an iCharger 106B+ run you about $80-$100.

I personally have two Flukes and also an old Simpson 260. Another good vintage analog meter would be an old Triplett 630.

However, if all you're going to do is measure batteries and possibly troubleshoot stuff around the house, honestly, one of the little Harbor Freight DMMs are perfectly fine and under $10. If it gets tossed into a fire, no loss, just go buy another one.

If I could only measure a battery's voltage, would that be a good indicator of its current state?

Ni-Mh:
1.40-1.45: fully charged
1.3: 70%
1.25: 40%
1.20:20%
Below: should recharge.

Li-Ion:
4.17-4.20: fully charged
4.00: 65%
3.85: 50%
3.70: 30%
3.60: 0%
Below: should recharge. (ASAP)

These figures are approximates, but it's easier to determine a li-ion's remaining capacity rather than Ni-Mh's using voltage.

ryansoh3 said:

Ni-Mh:
1.40-1.45: fully charged
1.3: 70%
1.25: 40%
1.20:20%
Below: should recharge.

Li-Ion:
4.17-4.20: fully charged
4.00: 65%
3.85: 50%
3.70: 30%
3.60: 0%
Below: should recharge. (ASAP)

These figures are approximates, but it's easier to determine a li-ion's remaining capacity rather than Ni-Mh's using voltage.

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Sorry, can't ignore this.
Ni-Mh open circuit voltage readings are close to meaningless.
OP is starting from scratch, asking for help, should not steer him wrong.

Measuring NiMh voltage under load can give some indication, still not very usefull though unless cell is very close to 100% or 0% charge.

Agree with that too. Primary purpose for voltmeter would be checking/matching lithium primaries or Li-Ions in multicell lights.

If you need to check state of charge of NiMHs or check/match them, a smart charger is your best bet, e.g. C9000

Yes, I entirely agree. For li-ions, voltage is a good estimate, but unfortunately that's not the case for Ni-Mh's.

Does this seem ok?:

http://www.amazon.com/dp/B0024V97V6/?tag=cpf0b6-20

Are these easy to use? I'm looking at the dials and don't understand.

Mass. Wine Guy said:

Does this seem ok?:

http://www.amazon.com/dp/B0024V97V6/?tag=cpf0b6-20

Are these easy to use? I'm looking at the dials and don't understand.

Click to expand...

Personally, I'd look for one with a dial switch.
You should have seen some by now with the common big round "dial switch"

Reason - DC Voltage will be one of your more common measurements. You will become familiar with where to put the dial.
It is less mistake prone than a couple of buttons.

You will need to read up on use.
Basics - voltage measurements are done "across" a circuit.
Current measurements done "in" circuit - ie you need to break circuit.

Get either of these wrong and you can destroy things (meter included)
That's why dial is better. Wrong selection can mean bang and loss of money.

This seems ok, with a dial switch, too. I still don't have much of a clue about how to use it:

http://www.amazon.com/dp/B003JJCGF6/?tag=cpf0b6-20

If you watch the circulars (adds) for the harbor freight add about every 3 weeks there will be a coupon for a free DMM. They give out them, gloves and a screw driver set in rotation so within the next month there will be a DMM one. I have a nice EXTech EX420 multi meter with all the bells and whistles but I still have several of the free HF ones around the house & shop.

I purchased a cheap Innova 3300 off Amazon. It does the job.

You should read Simple guide to using a DMM for measurements .

Norm

Wow! Thank you, Norm. What a handy and convenient guide.

I was actually just at HF today and their inexpensive "Cen-Tech" DMM was about $6. I have a store literally in walking distance (evil) and I was in need of a fin rake (unfortunately, the one they had was kind of useless for the condenser on my Jeep.)