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.
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
(b) the battery's current state of charge?
Presumably (a) could be done crudely by displaying current and (b) by
displaying voltage? Is this correct?
They place a fixed load, and test for voltage. The problem is that
with the batteries the world has been using, the charge/discharge
curve is a long straight line right up until it avalanches with a
pretty quick slew to near zero volts.
I'll bet that repeat tests will have the cycle occur more quickly
each time. That battery is likely near discharge.
The meter is reading the voltage through a fixed load, so I'd say
it's the voltage that is dropping. When removed from the load,
certain batteries "bounce back" a bit. This is only by voltage, and
it will again fall under loaded tests, eventually yielding no further
rebounds of significance.
To be certain.
Loaded testing has always puzzled me with batteries, as they are
limited fill storage devices. Upon a loaded test, I find myself
wanting to "top off" the battery again. Also, as you stated,
performing such tests doesn't really reveal charge level.
At the rates modern batteries are slow charged, the best solution to
one's unknown battery condition is to "top 'em off". In other words,
put them back in the charger and let its built in detection routine
decide the battery's fill level. Those "watchdog" chips are pretty
For charge rate, and or fill level, one would have to know the
physical characteristics of the battery under test.
It's fully charged internal resistance, and it's internal resistance
right at the discharge avalanche point, and its very nearly fully
discharged internal resistance. With this knowledge, one can test a
battery while it is being charged at a known fixed current limited
rate. It can be determined by knowing the at rest fully charged cell
voltage, and comparing it to the voltage required to get the battery
to take charge at any given point during a charge cycle (not including
fully charged of course).
With these chargers being current limited, what takes place is that
the voltage is just above that required to pump electrons into the
battery. Any more and the charge rate current would be exceeded.
So, a dead battery impresses a very small voltage, or emf when near
dead. Hook up a smart charger, and it will raise its voltage until it
just starts to pump current into the battery, it will bring it up to
the current limit rate and slowly raise the voltage as the battery
charges up keeping said current rate steady as she goes. At some
point near the end of the charge cycle the chip is programmed to
provide, the voltage of the battery will no longer continue to rise
and the current will begin to fall off. The chip will sense this and
change the charge indicator to green and discontinue charging
operations. Usually, in chargers, there is a chip for each battery.
I have even seen batteries themselves with them built in. Particularly
when there is an array, or true "battery" of cells arranged, and
designers want to insure that all cells get charged evenly and fully.
Memory effect got shot in da head.
The activity doesn't puzzle me, the logic does.
Even a loaded test doesn't tell one a battery is full. It can only
tell one something if one witnesses the battery in its death throws.
So to me, it is pointless at any point during a battery's life as
the thing is LIMITED, why take more away from a fixed amount?
A simple voltage test, and knowledge of the battery tells a lot. If
it is a 1.2 or a 1.5 volt battery, and you are reading that or even a
bit more, you know the dang thing is charged.
I have seen NiCads in particular discharge with an incremental drop
in voltage through the cycle. I can tell when it is charged too. I
was using an HP lab supply with a 4.5 digit meter on it and very
precise constant current or constant voltage modes.
Really all one needs is a good meter and a lab supply. Read the
battery voltage. Set the supply to just over that, say a half a tenth
of a volt to start. Set the current limit on the supply to the battery
maker's spec. Place the battery on the supply, and read voltage with
the handheld, reading current on the supply meter. If the power
supply is set to the battery spec charged voltage, and there is no
current flow, it is charged. Turn up the voltage to see the current
rise up to the limit point, and read the supply voltage. It should
not be much more than the correctly charged battery voltage is.
Remove battery from charger, and let it sit for a few minutes to let
its internal thermals re-homogenize. Read battery voltage with meter.
Make a report that has each battery's serial number and fully charged
and settled battery voltage (we should really be saying "cell" Replace
the word "battery" with "cell" throughout this post). Do that with
all of your CELLS. Any time you want to know a CELL'S condition, read
its voltage, and refer to the chart. The closer it is to that value,
the closer to fully charged it is. The increment is very small.
One could also find out the rate the battery is, and discharge what
would be half that, and take readings on each battery, and log the
value. Then one could extrapolate charge level from voltage reading
fairly well. They avalanche late in their duty cycle, but the line
from the beginning to the avalanche point is a smooth, slow, small
decline over a couple tenths of a volt. Meter needs to read
hundredths at least.
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.
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.
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.
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 for the devices that have motors in them etc.
It clearly isnt intended to be used for either of those.
Separate matter entirely to whether its better for a very
cheap battery tester to measure loaded or unloaded batterys.
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.
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.
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
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.
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.
Nope, the device obviously has to be designed
to allow for the internal resistance of a good cell.
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 you did.
And that cheap battery tester clearly isnt
even attempting to consider any of that.
Never claimed you did.
Nope, not with a cheap battery tester like that.
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.
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.
Not WITH A CHEAP BATTERY TESTER LIKE THAT.
And measuring the battery loaded is the best way to do that.
Corse it does when testing to see if the battery
can deliver the voltage it should do with that load.
Not even possible with very cheap battery testers like that.
Tell that to the designers who do just that.
Irrelevant to what is feasible with as cheap a battery tester as that.
No it doesnt, it shows that the battery can deliver that
current fine. And so will handle a lighter load fine too.
Its clearly a battery tester.
That aint what that particular battery tester is about.
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.
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.
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