Home battery tester: measures voltage or current?

[jkn]

Hi Christian

[...]

However, do not fear, almost anything that runs well on 1.5V alkalines will
run fine on 1.2V rechargeables. This is because anything using alkalines
will already have to deal with the actual voltage of the alkalines, which
goes down well below 1.0V before expiry of the battery. As a NiMH battery
will maintain 1.2V to the bitter end, the equipment should handle this. If
it can't, then it can't use alkalines, either!

Yeah, that's what I thought - except I bought a little while ago a
digital voice recorder/player (like a dictaphone but with Flash
memory/USB interface/MP3 etc). This accepts two AAA cells; alkaline
work but NiMH don't ;-( ;-(. This is really annoying as the batteries
run down even when the recorder is not in use. I had presumed that
NiMHs would work without checking (I haven't tried NiCads).

I looked up the processor data sheet online and it described itself as
a '3V' device, but didn't have the full voltage range specification.

Jon N

 

[Rod Speed]

The only time you need to worry about that is with a defective cell.

Yes, but any decent battery tester should do that.

Particularly when it doesnt cost any more to test it under load.

 

[Rod Speed]

Better off not getting one.

Not necessarily. Many dont feel that the much higher
cost of a multimeter is justified and a cheap tester
like that one is certainly better than nothing.

Real meters give real numbers, but
real tests would be the correct way.

Invest in a real meter, and perhaps find uses for it in the future.

Hard to justify the cost for most.

http://www.protektest.com/ProdInfo.asp?prodId=6800

100 times the cost.

Or go all out at ten times the rate!

http://www.protektest.com/ProdInfo.asp?prodId=860

Completely silly using something like that to test batterys.

1000 times the cost.

Easy to see why some dont see its worth it.

It makes a lot more sense to get a better charger
that does the best it can with the batterys instead.

 

[Rod Speed]

The message <[email protected]>


No. Though it doesn't generally matter 'cos the on-load voltage of a
1.2V NiMH is generally higher than the on-load voltage of a 1.5V
primary cell.

After partial discharge, actually, not on load.

 

[Bazzer Smith]

I am in the UK. I have a battery tester from years ago which is still
available. It may also be sold in the US.

http://www.avenuesupplies.co.uk/getimage.php?id=98&type=1&format=2

My multimeter shows that this battery tester puts a load of 500 mA on
the 1.5v battery under test.

I have alkaline, NiCad, and NiMH batteries. I have AA and AAA.

(1) Almost all gets a steady reading of 'GOOD' in green.
(2) No battery goes to 'REPLACE RECHARGE' in red.
(3) One battery starts in GREEN, then slides into RED over 10 seconds.

Is this tester measuring:
(a) the general "health" of the battery

Not necessarilly, depends on what you mean.

(b) the battery's current state of charge?

Yes, basically yes, it's testing if it can deliver the 'correct current',
obviously when it is low on charge it won't be able to maintain this for
long as
in (3) above and will eventually drop into (2).

I am not sure what it says about the rechargability of he batteries though.

Presumably (a) could be done crudely by displaying current and (b) by
displaying voltage? Is this correct?

Yes as the battery brcoms more 'drained' the measured voltage
will drop from say 1.5 V to about 1.0 V.
As for 'measuring the current', how are you planning of doing this?
If you connect it trough the current terminals of a meter you are
short circuiting the battery, not recommended, basically you are
'testing' the battery by draining it. Use the voltage measurement.
A multimeter usually has battery testing settings which are
simply voltage testing setting adjusted to scales of 1.5V, 9V etc...

 

[raden]

Wont load here.
http://www.avenuesupplies.co.uk/index.php?id=602&pid=98&sid=1
does tho.

Aren't Avenue Supplies those dodgy buggers who were linking to the
uk.d-i-y newsgroup last year

I wouldn't touch them with a bargepole

 

[Dave Plowman (News)]

No. Though it doesn't generally matter 'cos the on-load voltage of a
1.2V NiMH is generally higher than the on-load voltage of a 1.5V primary
cell.

If you're loading fresh alkalines down to 1.2 volts they'll have a very
short life.

 

[The Natural Philosopher]

Please excuse the intrusion, but I need to interject a related question.

Recently purchased a new radio scanner which uses AA batteries. Currently,
I'm using the last of my 'Renewal' alkaline rechargeables. I was under the
impression AA, AAA, C, and D are all 1.5 volts (when new), but only differ
in the amount of availabe milliampere-hours. I just measured a freshly
recharged set (4) of the AA's and infact they measure 6.02 volts on my DVM.

Since I will have to replace my alkalines eventually, I started checking the
various rechargeable systems available. In my search, I noted that AA NiMH
cells were labeled as 1.2 volts and had varied milliamp-hour ratings. As my
scanner reports low-battery condition (based on voltage), I want to maximize
my listening time between charges.

Are there any AA rechargeables that are rated at 1.5 volts?

Not with nickel technology, no.

 

[Roy L. Fuchs]

Yes, but any decent battery tester should do that.

Particularly when it doesnt cost any more to test it under load.

It does cost. It costs "juice". There is only so much in there.

 

[Rod Speed]

It does cost. It costs "juice". There is only so much in there.

Bugger all if you dont leave it on the tester longer than you need to.

 

[kony]

Yes, but any decent battery tester should do that.

Particularly when it doesnt cost any more to test it under load.

Wrong. Internal resistance is a property of ALL batteries,
including brand new, fully charged, perfectly working ones.
ALL OF THEM. The load current must be weighed against the
particular cell's resistance to determine what the
acceptible voltage drop will be. The cost is that cells
may be deemed more drained than they actually are and
discarded prematurely. In other words, as it applies to
this thread, 500mA is a rather high current for smaller
alkalines, but more appropriate for mid-sized. Likewise,
it's way too low for a battery with even lower resistance
like a car battery or typical laptop battery.


Anyone who's tried to use Alkaline batteries in a digital
camera may have observed this, the batteries don't seem to
last very long because their internal resistance is high
relative to the current consumed by the camera.

 

[HankG]

If you're loading fresh alkalines down to 1.2 volts they'll have a very
short life.

Dave: Please clarify your remark. Are you referring to alkaline
rechargeables (my Renewals), or the non-renwable type? I was talking about
new NiMH rechargeables as being 1.2V. My renewals recharge to 1.5V. Gonna
miss them.

HankG

 

[Rod Speed]

Wrong.

We'll see...

Internal resistance is a property of ALL batteries, including brand
new, fully charged, perfectly working ones. ALL OF THEM.

Duh. What matters is whether the internal resistance
has increased substantially so that it can no longer
deliver the voltage it should deliver with a decent
load, particularly when the batterys are used to
power the higher current devices.

Just measuring the unloaded voltage doesnt tell you
anything about batterys that have gone higher resistance.

The load current must be weighed against the particular cell's
resistance to determine what the acceptible voltage drop will be.

And thats not feasible with as simple a battery tester
as the one being discussed. It certainly makes more
sense to load the battery than not load it at all tho.

The cost is that cells may be deemed more drained
than they actually are and discarded prematurely.

Yes, but thats better than claiming the battery is fine when its
internal resistance has increased substantially and it will no
longer supply the voltage its supposed to supply when loaded.

In other words, as it applies to this thread, 500mA is a rather high
current for smaller alkalines, but more appropriate for mid-sized.

Not for the devices that have motors in them etc.

Likewise, it's way too low for a battery with even lower
resistance like a car battery or typical laptop battery.

It clearly isnt intended to be used for either of those.

Anyone who's tried to use Alkaline batteries in a digital
camera may have observed this, the batteries don't seem
to last very long because their internal resistance is high
relative to the current consumed by the camera.

Separate matter entirely to whether its better for a very
cheap battery tester to measure loaded or unloaded batterys.

 

[Dave Plowman (News)]

Dave: Please clarify your remark. Are you referring to alkaline
rechargeables (my Renewals), or the non-renwable type? I was talking
about new NiMH rechargeables as being 1.2V. My renewals recharge to
1.5V. Gonna miss them.

Not sure about the effects of heavy loading on rechargeable alkaline as
I've never tried them. I was referring to disposables.

 

[kony]

We'll see...


Duh. What matters is whether the internal resistance
has increased substantially so that it can no longer
deliver the voltage it should deliver with a decent
load, particularly when the batterys are used to
power the higher current devices.

Pretty much splitting hairs there, fact is that on a
perfectly working cell it's impedance is an issue when
driving relatively high current loads, it is not a matter of
defect alone, it is a factor in every use of brand new
perfect cells too.

Just measuring the unloaded voltage doesnt tell you
anything about batterys that have gone higher resistance.

never suggested it did.
The load has to be appropriate for the battery chemistry,
design and size and the margin for error rapidly goes up as
one deviates from that ideal.

And thats not feasible with as simple a battery tester
as the one being discussed. It certainly makes more
sense to load the battery than not load it at all tho.

never claimed otherwise, but only randomly thinking "load"
vs "no load" is pretty irrelevant, the ACTUAL load has
beconsidered (by either the tester or designer of the test
equipment).

Yes, but thats better than claiming the battery is fine when its
internal resistance has increased substantially and it will no
longer supply the voltage its supposed to supply when loaded.

not better or worse overall, depends on the criteria. Some
want most lifespan, or lowest cost, or longest runtime per
outting, several different things can matter most.

The one thing that should always be avoided is unreliable
indication of the battery state so one can't even make a
reasonable attempt to choose their own strategy for
replacement or recharge intervals.

Not for the devices that have motors in them etc.

Yes for devices that have motors.
While the motor might load it more, that does not matter!
To indicate the battery state it is necessary to load it
appropriate to it's size, design and chemistry.

Smaller alkalines shouldn't be used in any high current
motorized device to begin with, but if they're used, there
will be a voltage depression from the higher current load
(same as when tested), a voltage that will RISE AGAIN after
the device is turned off, relative to what it was when last
running. This completely invalidates a high (relative)
current test on those cells, unless your only goal was not
testing the battery at all, rather qualifying for particular
device usage. Toward that end it is a fair test, a
determination of alkaline (for example) is fit at all, or
better to use something like NiCad.

 

[kony]

Not sure about the effects of heavy loading on rechargeable alkaline as
I've never tried them. I was referring to disposables.

Rechargeable alkalines have a lower internal resistance,
respond better to loads. Not a lot though, if one is
heavily loading packs they're not the best choice, rather
such frequent drains suggests NiMH is the better
alternative.

 

[Rod Speed]

Pretty much splitting hairs there,
Nope.

fact is that on a perfectly working cell it's impedance
is an issue when driving relatively high current loads,

Nope, the device obviously has to be designed
to allow for the internal resistance of a good cell.

it is not a matter of defect alone, it is a factor
in every use of brand new perfect cells too.

Only for the designer, not for the individual
deciding if a particular battery is good or not.

Who's mindlessly hair splitting now ?

never suggested it did.

Never suggested you did.

The load has to be appropriate for the battery
chemistry, design and size and the margin for error
rapidly goes up as one deviates from that ideal.

And that cheap battery tester clearly isnt
even attempting to consider any of that.

never claimed otherwise,

Never claimed you did.

but only randomly thinking "load" vs "no load" is pretty irrelevant,

Nope, not with a cheap battery tester like that.

the ACTUAL load has beconsidered (by either
the tester or designer of the test equipment).

Not even possible with a cheap battery tester like that.

ALL the designer of a cheap battery tester like that gets
to do is either measure it loaded or unloaded and to use
what he considers to be a useful load that will indicate
whether the battery can deliver that sort of load fine.

not better or worse overall, depends on the criteria.

Gets sillier by the minute. The criteria with
a cheap battery tester like that, there is just
ONE criteria, is the battery still usable or isnt it.

Some want most lifespan, or lowest cost, or longest
runtime per outting, several different things can matter most.

Not WITH A CHEAP BATTERY TESTER LIKE THAT.

The one thing that should always be avoided is
unreliable indication of the battery state so one can't
even make a reasonable attempt to choose their own
strategy for replacement or recharge intervals.

And measuring the battery loaded is the best way to do that.

Yes for devices that have motors.
While the motor might load it more, that does not matter!

Corse it does when testing to see if the battery
can deliver the voltage it should do with that load.

To indicate the battery state it is necessary to load
it appropriate to it's size, design and chemistry.

Not even possible with very cheap battery testers like that.

Smaller alkalines shouldn't be used in any
high current motorized device to begin with,

Tell that to the designers who do just that.

but if they're used, there will be a voltage depression
from the higher current load (same as when tested),
a voltage that will RISE AGAIN after the device is
turned off, relative to what it was when last running.

Irrelevant to what is feasible with as cheap a battery tester as that.

This completely invalidates a high (relative) current test on those cells,

No it doesnt, it shows that the battery can deliver that
current fine. And so will handle a lighter load fine too.

unless your only goal was not testing the battery
at all, rather qualifying for particular device usage.

Its clearly a battery tester.

Toward that end it is a fair test, a determination of alkaline
(for example) is fit at all, or better to use something like NiCad.

That aint what that particular battery tester is about.

 

[kony]

Nope, the device obviously has to be designed
to allow for the internal resistance of a good cell.

Obviously you haven't a clue.
The devices are designed for a target battery type. "Some"
can be used with another type but it's not the target. Take
a laptop, did you think you could chuck out the Li or NiMH
and put some Alkaline in there and use it? Good luck,
you'll need it. Too high a load for alkaline.

Only for the designer, not for the individual
deciding if a particular battery is good or not.

The individual putting a load on a cell has to use a load
causing a current draw that is reaonably compatible with
what the battery can provide. To do othewise will result in
a misleading reading.

 

[Rod Speed]

Obviously you haven't a clue.

Never ever could bullshit its way out of a wet paper bag.

The devices are designed for a target battery type.

Not those very cheap battery testers.

"Some" can be used with another type but it's not the target.

Corse it is with those very cheap battery testers.

Take a laptop,

No thanks, those very cheap battery testers
dont even claim to test those batterys.

did you think you could chuck out the Li or NiMH
and put some Alkaline in there and use it? Good
luck, you'll need it. Too high a load for alkaline.

Completely and utterly irrelevant to what those very
cheap battery testers test battery technology wise.

The individual putting a load on a cell has to use
a load causing a current draw that is reaonably
compatible with what the battery can provide.
To do othewise will result in a misleading reading.

And the load that particular battery tester puts
on the individual battery is fine in that regard.