Distinguishing between Different Battery-Types

One of the things I recently did, was to pair my Linux-laptop, which I name ‘Klystron’, with an external Bluetooth-Mouse, because even though this advanced, HP laptop has as its hardware, an advanced Synaptics touchpad, that emulates a mouse quite well, we can grow tired of always using the built-in touchpad. I documented here, what I needed to do, to accomplish this pairing.

Well one of the features which the KDE Desktop Manager gives us under Linux, is to indicate the battery-charge-levels, not only of the laptop’s built-in battery, but also those of attached BT-mice, or of anything else which is connected, that has a battery, and the hardware of which is able to report as telemetry, the battery-level.

What was surprising me about this arrangement, was that the indicated battery-level of the mouse seemed to track accurately over the days, that the mouse was connected. This surprised me, because as I was remembering events, I had placed Nickel-Metal-Hydride batteries into the mouse some time ago, and most devices which are physically designed to accept batteries in the AA-format, or in the AAA-battery-format, would be calibrated for Alkaline, Zinc-Manganese-Oxide batteries. When such accessories try to gauge the battery-level, if they have the chip to do so, the voltage-curve of a Ni-MH battery tends to remain lower than that of an Alkaline. A fully-charged Ni-MH only generates about 1.2V per cell, while an Alkaline generates 1.5V. And so when a Ni-MH battery is inserted, this chip will usually indicate a partially-discharged battery, even immediately after it has been charged, and then, when this battery-type finally goes dead, its voltage will collapse almost instantly.

Before the indicated charge-level dropped below ‘70%’, I decided to take the AA-format batteries out, and to put them into a charger I have, that’s designed for Ni-MH batteries, and what I found was, that the LEDs in the charger refused to light up, for the inserted batteries. They did not indicate partially-charged or anything, they just stayed ‘off’.

And so next, my thinking was, ‘Darned! I now have either batteries which have failed on me, or worse – a charger which has failed on me 100%…’

When I inspected these AA-format batteries again, I next discovered, that they were Rechargeable Alkalines, of the brand “Juice”, and not even Ni-MH batteries! By not lighting up its LEDs, the charger was just recognizing my stupid mistake, and refusing even to attempt to charge those.

What I next had to do, was put these batteries into a charger meant for rechargeable alkaline batteries, in which the LEDs did light up and start blinking, to tell me that my batteries were partially discharged, and being charged.

This discovery therefore also explains, why the chip in the BT-mouse was able to state the charge-level in a progressive, apparently-accurate way. If those had been Ni-MH batteries, then the behavior of the charge-indicator in question would have been, what I’ve often come to expect.

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I often use rechargeable alkaline batteries, for devices that draw very little power, or which draw no power for long periods of time, because that battery-type performs better in such devices, than the Ni-MH type would. This could be seen as a modern-day equivalent, of the ancient practice of only putting ‘dry cells’ into certain devices, because the power-drain of those devices, back in the 1970s or 1980s, did not justify putting a battery-type that delivers high amounts of current, with little effect on voltage, which is exactly what the Ni-MH battery-type delivers today.

Also, Li-Ion batteries will deliver high amounts of current, with little effect on voltage. But those neither tend to come in the AA or the AAA format, which means that it’s harder to get them confused, and Their voltage-ranges depend on what type of composition is being used for their positive electrode, mainly. Their fully-charged voltage could be 3.5V per cell, or it could be 4.2V per cell, just depending on what substance was chosen as their positive electrode.

Finally, giving a full charge to a partially-charged rechargeable alkaline battery-type is generally safer, than it would be to do so, for other battery-types. With the rechargeable alkalines, this can be done at any time safely, while the same guarantee is not generally given for other types. And, the chances of being able to recharge alkalines improves, if we don’t allow them to go completely flat, before trying to recharge them. If we allow those to go completely flat first, chances are we won’t be able to bring them up to full charge (potential) afterward.


I have a personal habit, when recharging alkaline batteries, that is more idiosyncratic, than what some first approximations might suggest. I put the batteries I’m replacing in one compartment of the charger – which holds 4 – while putting older batteries of the same type, on the other side of the same charger. Next, when the batteries I’m in the process of replacing have reached full charge, I put those back in the box, and when the batteries from the box seem fully charged, I put those into the device.

What I sometimes notice in the process, is that batteries which I take out of the box randomly, which have been there in storage for months, seem to indicate ‘fully charged’ within less time in the charger than half an hour. This tends to lead me to the suspicion, that the batteries in question might be defective.

When given such examples, I will next put those batteries into an appliance, and test whether the appliance can be made to power up. Often, the appliance will not power up with those batteries. What can happen sometimes, is that the electrical behavior of the battery can seem to be as if, the electrodes had become disconnected. The charger will then indicate ‘fully charged’, but the appliance will indicate ‘I have no power at all.’

Those are defective; I throw them away.

But, because simply to throw any batteries away that seem to have taken less than half an hour to charge – after having been abandoned for months – could cause me to waste batteries, I test them in an appliance first – maybe even in the appliance I’m replacing the batteries of – to see whether that appliance powers up. If it does, and if the mouse next indicates ‘fully charged, 100%’, then all I may have been confronted with, is either batteries which did not stay in my box for very long, because I’m taking some out at random, or batteries which are very healthy.

But usually, rechargeable alkaline batteries that have simply been lying in a box for months, will take longer than half an hour to indicate ‘fully charged’. And, batteries which I’ve discharged through active use, will typically take around 6 hours to recharge, given the charger I’m using.


 

(Edit : )

The reader might be wondering, why it is that ‘alkaline batteries’, like the older ‘dry cells’, tended to produce 1.5V per cell when fully charged.

When Chemists list the properties of substances, especially metals, but not only of metals, they list their electrode potentials. Since voltages are relative, the standard way to list electrode potentials, is relative to hydrogen. This tends to produce a listing, in which their potentials seem absolute.

Zinc-Manganese-Oxide, and Zinc-Carbon Batteries, tend to produce hydrogen electrodes as their positive electrodes. It’s just that the choice of positive electrode, and of electrolyte-properties, produces hydrogen electrodes with different degrees of efficiency.

FWIW, A hydrogen-electrode qualifies as a poorly-functioning electrode in any case, because hydrogen gas does not conduct. Hence, the way in which the old zinc-carbon batteries went dead, was that their cathodes would be ‘rendered passive’, and what this meant in fact, was that microscopic hydrogen bubbles formed in the carbon-powder, that in turn insulated against the further flow of current.

By making the electrolyte alkaline, and the electrode composition manganese oxide, a hydrogen electrode emerges, that can absorb greater quantities of hydrogen, before being rendered passive, than carbon powder could.

These batteries produced -1.5V, because that is in fact the electrode-potential of Zinc.

 

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