What features do I need in a multimeter?

[ABTsportsline]

Looking for an inexpensive unit to measure the batteries for my bikes (I just want something easy to pack for when I'm out on the road.) Guessing I need the basic voltage & amperage at a minimum, but how much amperage capability do I need? I noticed most of the cheaper multimeters don't seem to have amperage capability that matches my batteries capacities, which are 15 ah. So do I need a 20A multimeter? Or is voltage measurement more important for my purposes?

Thanks!

 

[3nslav3]

Voltage, diode tester, resistance

if you confuse AH with Amps then an A-meter isn't for you :wink:

just go for the basic voltage - ohm meter that is accurate enough to measure voltage at cel level

 

[wesnewell]

Depends on what type of batteries you have. For lead or lipo a simple volt meter like this is all you really need.
http://www.ebay.com/itm/Waterproof-Digital-Voltmeter-DC-15V-To-120V-Red-Led-Voltage-Digital-Panel-Meter-/170846310527
For lifepo4 the voltage curve is flat so you really need a watt meter. They cost from ~$10 to $200. Take your pick.
http://www.ebay.com/itm/New-Digital-60V-100A-Battery-Balance-LCD-Voltage-Power-Analyzer-Watt-Meter-/181063403586
http://ebikes.ca/drainbrain.shtml

 

[ABTsportsline]

Sorry, I should have clarified. I have LiFeO4 batteries. I'm looking for something I can use at home to test the batteries when they're off the bike as well, to monitor charge for storage, maintenance charge monitoring, etc...

 

[Ziggurat]

I got a cheap multimeter at Radio Shack several years ago when visiting in U.S: http://www.radioshack.com/product/index.jsp?productId=4214667.

It's very small and light, easily fits in my toolbag I take with me while biking, but I also use it for all home uses because it works quite well for just about everything I need to do. It's readings have always been accurate (matches other devices like my chargers, BM6's etc).

It gets a mediocre rating on the Radio Shack reviews, but if you look at that it is almost always because of the need to buy an unusual small 12 V battery (not included), and the need to use a jeweller screwdriver to open the case to put the battery in. Those who got past these huge barriers [sarcasm] really like it, and so do I. I was just using it today to check battery V before paralleling batteries while building a pack. I'm just now getting low battery after several years of use.

Honestly, something like that is all you really need ... voltage measurement always tells you the state of charge of a battery; you don't need a meter to measure current or Ah put in. If you did (especially routinely) then a cycle analyst or a watts-up meter would probably make more sense. The only other thing I do is check resistance or continuity, both of which this does fine.

 

[biohazardman]

I have one of the amprobe meters similar to this one although I paid more. It is built a bit better than most pocket meters and is all I need when out and about on my bike.

http://www.amazon.com/Amprobe-PM51A-Pocket-Digital-Multimeter/dp/B001L4E9Z6

 

[Gregory]

I use the continuity function on mine a lot, I really like the “beep”. That would be my main thing to look for in a DMM.

10A meter range is fine.
Auto power off is probably in all DMM these days, in the old days I always used to leave it turned on and flatten the battery.
Auto ranging is OK but not necessary.
I don’t think I’ve ever used the Transistor tester my DMM has.


I don’t think a DMM is really suitable for riding. I’d lean toward a cheap Watt Meter for $15 off ebay for that.

 

[wb9k]

I'll put in a vote for my favorite DMM, the Fluke 289. Now, it's not cheap, about $600-700 for a new unit, but it's a very powerful tool with some features that come in very handy when working with batteries and electronics generally. Most notably, this meter is also a single-channel data logger, but other nice features include a high quality capacitance meter, 10A continuous current reading capability, a high-resolution low Ohms range--a must for chasing down short circuits in electronics and very precise measurements of very small resistances in your power transmission path. There's also a thermocouple that comes with for temperature measurements, very handy for testing pack thermal management.

Make sure you get the IR to USB cable for dumping data onto your PC--it's an option, I believe. You can look at data on the 289's monitor, but to get the most out of this you'll want to export your data. For example, you can export into a CSV file to do some very handy things in Excel--like run an accurate capacity test with nothing but a power supply, an appropriate load resistor and this meter. There's also a software package called Fluke View Forms that includes some nice tools for generating reports and so on. If you can swing the money and have the skills to actually use such features it's a very worthwhile purchase IMO.

[Edit: That's 289, not 298. D'Oh!]

dh

 

[hydro-one]

5$ canadian tire on sale. works fine. 10A current (actually goes up to 20!) manual range dmv. cant go wrong i bought three.

 

[dogman dan]

Got a harbor freight in your town? In the USA, if you have a local store, you watch the ads, and get a free cheap multimeter with any purchase. So when they run the ad, I go buy some more zip ties or solder for 3 bucks, and get another one.

Normal price is 10 bucks, but often on sale for 5-6 as well.

If you can't do that, or wait for a mail order, just go buy whatever is cheaper at a car parts store, or home depot. You don't need a super precision tool to check your battery for an ebike.

On the road to see your amps and ah, you'd love a cyclanalyst, but if you can't afford that go to ebay, and get the wattmeter in the blue box for less than 20 bucks shipped.

 

[dnmun]

the last time i saw the harbor freight voltmeters on sale here i bot 3 for $2 each. it is getting harder to find them for the $3 price now too.

 

[friendly1uk]

B6 Balance charger perhaps? $20 and can be used in the field to tell you voltage of each cell, and balance. It also charges, and you can tell it your charging for storage reasons, thus it will half charge them not brim them. Only 6S though. I don't know what you have...

 

[richmpdx]

For most uses a cheap meter is fine. If you are going to adjust the output of a charger, then you need something that is accurate. I used a cheap multimeter for years, but noticed that the voltage reading was always substantially different than the cycle analyst reading of pack voltage. So to adjust charge voltage I finally bought one of the less expensive Fluke meters. Rich

 

[el_walto]

Make sure you get one with a beep option. My Canadian tire one doesn't have this.

 

[999zip999]

I had a radio shack one and had problems went to radio shack and the guy open a door and he had three broken ones in there.

 

[dogman dan]

You need a multimeter for some things, like probing to read individual cell voltages. The Harbor Freight ones are quite cheap and don't last long. Good reason to get that one free.

But it sounds like the functions you want are more served by a wattmeter. The cheap one on ebay will read out voltage, amps, watts, and amp hours discharged. Not super accurate, but good enough to ride around on, know you got a charge etc. I have CA's on the bikes, but keep one of these cheap wattmeters on my charger.

 

[izeman]

i think a $5 multimeter is better than touching the cables with your tongue to see if there is some voltage
but i guess "shit in shit out" goes for multimeters as well. we buy batteries for a few hundred dollars/euros, so is think tools should match that. invest a BIT more and get a reasonable brand one. for 20-30.- you should find good ones that do all you need with high enough accuracy.

 

[ABTsportsline]

Thanks guys, I'm realizing my confusion was really just about whether or not I needed a specific amperage rating out of a multimeter for these batteries. Now that I know I could use just about any multimeter, my question has been answered.

FWIW- I already have a computer display for this info installed on the bike itself, just wanted to know what would work for monitoring batteries at home and when I roadtrip/travel. I don't have intentions of building battery packs or doing real-time monitoring with this particular device while I'm riding, so spending $$ on a Fluke is probably overboard for me.

One thing I've noticed from scouring the web: unless it's a Fluke, it will have bad reviews somewhere. Very difficult to separate the good from bad in the sub-$50 multimeters category. Seems hard to find a consensus about an effective portable multimeter without breaking the bank. $35 multimeters on Amazon have similar ratings to the $10 ones, etc...

 

[Ykick]

Just buy a couple cheapos and then you'll be able to check one against the other, etc.

No shortage of "meter snobs" in the industry. Good reasons for high dollar meters just like any high dollar tool but for hobby purposes, a couple cheapos will be more than enough to wet your appetite to "see" what's going on in the world of "holes & charges".

 

[aroundqube]

A feature that I like for a multimeter- the base of the test probe tip has threads to screw on insulated ( rubber boot ) alligator clips.

 

[alsmith]

It sounds like your biggest confusion is about the Amp rating. These meters will have low current ranges of under 1 amp. Then some will have a range of 10A or maybe 20A. But these ranges are generally unfused, and can only be used for maybe 10 seconds every 15-20 minutes. They aren't for, and aren't safe for, measuring heavy currents on a regular or continuous basis. It's not to often that you'll need to use the current range too often for testing your ebike stuff, Voltage and resistance are the main ones you'll use.
If you want to measure the current that is being drawn from your battery either on a continuous basis, just because you want to know or for testing puposes you really need an Ampmeter that specifically is designed for that purpose. They aren't necessarily expensive- there are many options from cheap ones on ebay where you put a very low resistance shunt in a feed wire and your current draw is worked out and displayed for you, it can be 50Amps, 100 Amps or more.

There's nothing to stop you getting an Ampmeter so you can see the current draw from the battery, and a multimeter for electrical testing and diagnostics on your bike. This is probably the best overall solution, but it really depends on exactly what you want to achieve. Can you clarify and explain that?- it will help point to the right answer for you. It doesn't need to be too expensive.

 

[izeman]

maybe 10 posts above he stated:

Sorry, I should have clarified. I have LiFeO4 batteries. I'm looking for something I can use at home to test the batteries when they're off the bike as well, to monitor charge for storage, maintenance charge monitoring, etc...

so he doesn't want to monitor his bikes functions while riding, but check the battery and parts of if on the shelf. so a small multimeter is the exact right thing for this purpose. the 10-20a of a dmm are sufficient to check amps of the charger as it only takes a second or so. he can check total pack voltage, single cell voltage, with this data and a big load he can calculate internal resistance (of the pack and a single cell), and he can test any diode, transistor and measure resistors. pretty every dmm should be able to do it. as someone said: a beeep for testing continuity is a very welcome thing as well.
so as i said: invest $30 and you can find a low-end, but still fine dmm of some known brand.