Battery meter?

Pardon my innocence, I'm new here, but is there such thing as a battery meter?

Suppose your flashlight runs out of juice, you find a dusty drawer full of batteries of all kinds and need two AA or 123 or D (whatever) of them re-power your light. Given it's not a good thing to mix new batteries with old ones, ideally you'd need to find two batteries that have more or less the same juice content left inside. Is there such a tool that'd help you measure battery power?

Speaking of, why is it not good to mix random batteries together?

If I was in that situation I'd just use a multimeter to find the batteries (of the same chemistry) with the best unloaded voltage.

It's not good to mix old and new batteries or batteries with different chemistries (eg, heavy duty and alkaline, alkaline and NiMH, etc) because one of them will go flat before the other(s) which means it will be reverse charged while the other still has power. That will damage a rechargeable battery and greatly increase the chance of a non-rechargeable leaking - neither is good.

This is better suited to the Battery section, but to answer your question:

There's the ZTS battery tester which applies a load and can determine how much juice is left in a battery. Alternatively, you can simply measure the battery voltage with a multimeter but this is not accurate for some battery chemistries.

As to why it's bad to mix random batteries, you may get two batteries of different charge levels. When the weaker battery dies, it will get reversed charged which will be bad for the battery (NiMH gets damaged, Alkalines leak, Lithium Primary & Li-Ion goes ).

Link Archer VI said:

This is better suited to the Battery section, but to answer your question:

There's the ZTS battery tester which applies a load and can determine how much juice is left in a battery. Alternatively, you can simply measure the battery voltage with a multimeter but this is not accurate for some battery chemistries.

As to why it's bad to mix random batteries, you may get two batteries of different charge levels. When the weaker battery dies, it will get reversed charged which will be bad for the battery (NiMH gets damaged, Alkalines leak, Lithium Primary & Li-Ion goes ).

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oh snap! they can explode? sheesh

Reading the voltage is a very poor indication of remaining life. You may get almost the same voltage at 100% charge as at 20% charge.

One cell with less charge may have a higher voltage than a similar cell with more charge. This varies from cell to cell, over the lifetime of the cell, etc. It varies from brand to brand, batch to batch, and especially from battery type to battery type.

A low enough voltage does tell you the cell is weak, but a pretty weak cell may still have a good voltage.

Now, if you apply a load, and draw some current from the cell, the voltage gets a little bit more meaningful, but it's still not a really good indication.

Even the manufacturers of the batteries can't design a really good "charge remaining" indicator for their batteries.

Rechargeable batteries are even worse. Depending on how the battery has been charged and discharged, a cell with the same "charge" may have a considerable difference in voltage at a certain current. You may even find that the voltage goes up as you discharge the battery.

Some devices with dedicated rechargeable battery packs have smart circuitry that monitors the history of the batteries and does a better job, but even those are often inaccurate if you have let it sit for a while, as the battery ages, etc.

The situation is not hopeless, but even the best battery tester will occasionally tell you a cell is good, but the cell simply won't have much of a charge.

Perhaps approach it differently: use a single-cell light, then the problem goes away.

In addition, some lights like the LiteFlux models can read out the voltage for you - it is its own meter.

I have the ZTS Meters, and they are great. I have one at our studio, one at home, and a small one in with my location/grip equipment.

They put a load on them, and offer a good test.

We have so many things with batteries, I like to test some from time to time.

They are not that expensive, I just buy them at B & H with my camera equipment, lighting and grip supplies.

I will say, that if there are any doubts, just change the battery. Not because it could explode, it may just be dead, and fail when you need it. I do not worry about batteries exploding...at all!

I use a Micronta that tests batteries under load. Its fairly accurate. I bought it at Radio Shack a long time ago & don't know if they still sell em or not. Cat. No. 22-o31.

Testers that test the batteries under load are much better than voltage only testers.

Unfortunately, they may not be able to tell any difference between a battery that has 20% capacity and one that has 80% left.

+1 for the ZTS meter.

I held off picking one up for quite a while. I was having difficulty pulling the trigger because the device is a bit simplistic in the information it provides you given the cost yet I must say that it has been reliable, consistent and couldn't be simpler to use.

I have to agree with the others that simple voltage checks without load, at least in my hands, have been misleading and offered no indication of how much life was left in a cell from my experience.

a word of caution. there are a lot of cheap so called battery meters out there that are essentially worthless. so either cough up the coins for something decent or don't bother at all. in the long run you'll have saved yourself some cash.

scriverdog said:

+1 for the ZTS meter.

I held off picking one up for quite a while. I was having difficulty pulling the trigger because the device is a bit simplistic in the information it provides you given the cost yet I must say that it has been reliable, consistent and couldn't be simpler to use.

I have to agree with the others that simple voltage checks without load, at least in my hands, have been misleading and offered no indication of how much life was left in a cell from my experience.

a word of caution. there are a lot of cheap so called battery meters out there that are essentially worthless. so either cough up the coins for something decent or don't bother at all. in the long run you'll have saved yourself some cash.

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Ya, I agree, you need the load, not just a reading.

A good meter is something that a household really needs these days. We all run so many things with batteries.

I have a simple AA/AAA meter which either glows red or not at all to replace,puts no load so it just gives me an idea only in my box of mixed batteries if they still work and I never mix cells.

I have a much better meter under the Radio Shack (aka Tandy as it was in the UK) logo which I have had for well over 30 years but still going strong and will measure near on any type of battery including cars.

RedLed said:

A good meter is something that a household really needs these days. We all run so many things with batteries.

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Um, why? I use mostly Eneloops and don't have a drawer full of partly used alkalines, and I imagine most households are the same (apart from the Eneloop bit). Most people put new alkaline or freshly charged NiMH batteries into a device and replace the batteries when they go flat. Sure, it might be a nice thing to have, but why would most households need one? Most households don't even have a good NiMH charger.

Well, all I can say is every person I know has things that take batteries galore. If you have kids, My teen is always taking the tester, and checking batteries.

In fact, one Christmas, I gave them out as gifts, and people loved them. I still get thanks for giving them.

If you have alkalines laying around, it may be nice to find out if they are good and you can still use them.

As for the Eneloop batteries, they are not well known here yet. Most people are more familiar with other brands. The Eneloops are not in all the stores yet. I bought ours from B & H.

RedLed said:

If you have alkalines laying around, it may be nice to find out if they are good and you can still use them.

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If they're lying around out of a packet, chances are that they won't be new, and that they'll not have much useful life left. There would have been a reason they were taken out of whatever they were in.

Keep up that battery giving - that's a nice practical gift.

+1 ZTS meter :thumbsup:

TorchBoy said:

If they're lying around out of a packet, chances are that they won't be new, and that they'll not have much useful life left. There would have been a reason they were taken out of whatever they were in.

Keep up that battery giving - that's a nice practical gift.

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Well, you see if I shoot a big project, I always put in new batteries - no matter what, as I do not want a failure with VIPs. or any client.

It is funny now, it was a long time ago, but at the time it seemed like a disaster. I was part of the Vice President of the United States Press Pool. We toured a factory with the VP, and when the photo Op came up I had a bad battery in my flash. it was bad from the factory.

I did the fastest battery change on a flash in history. In front of the Vice President, I just threw the old batteries on the floor behind me, and put in new ones. It was odd and embarrassing, as the Secret Service seemed alarmed.

I put in new batteries the night before to be set, and one was a dud.

Later when I was getting in the press van in the motorcade, the VP walked by and told me he thought it was funny. I was just dripping with sweat.

It was soon forgotten as when we got to the Marine Base to board AF 2, the NY Times photographer dropped his camera, and it broke in to a ton of parts. The VP asked if we were all OK.

As a result I end up with quite a few batteries, and give them to my teen daughter, and wife. They can still get plenty of use out of them, so batteries can have a second life. They do here.

For almost 20 years, I have used hundreds of batteries a month.

The eneloops will save me about $1200 -$1500 year.

I am looking forward to the system. My wife is the IT for our company, and she ordered enough for us to supply ten flashes.

All the best,

RL