Wireless keyboard Drains only 1 battery

[Saltheart]

This is very curious to me. My wireless keyboard (logitech) has two batteries in it. When it stops working , I always check the batteries with a battery tester and one is drained completely dead as a fart but the other is at peek , just like new.

Now I know the batteries will get used up but how is it even possible that one goes totally dead and the other appears to not drain at all. The batteries are in serries so to me this is almost an impossible occurance???? The time between battery changes is very long too. Maybe 2 times a year or even once every 8 to 9 months.

Any ideas how this is even possible in our space time continuum??

[Raven]

not a clue
but if you were to switch to rechargeable s
that are recharged every 3 months
the problem will be gone

[Saltheart]

I have the NiMH rechargeables all over the house in thermostats and in my mouse. With such long life from an alkaline battery in the keyboard I just use one from like a 24 pack I buy for about 25 cents a battery. They last way longer than the rechargeables do between charges. Now in my mouse that chews up batteries fast , i have the rechargeables that I rotate in and out.

The whole point here is this impossible thing that only one of the two batteries is losing its charge. I cannot figure out how that happens?

[Raven]

you'd literally have to deconstruct the unit so that it still works

to test it for the drain ,,, it would appear...very strange indeed.

[jon2465]

just switch the batterys lol

[Saltheart]

Originally Posted by jon2465

just switch the batterys lol

Not a bad idea really! I suppose it would best to do it say 2/3 of the way through the battery life cycle.

Its also amazing how the one drained battery is so totally dead. I mean dead dead dead! The needle on the tester doesn't budge of rock bottom when you put that one battery in it.

[spence]

It doesn't seem to make a lot of sense does it. Only thing I can think of is if the batteries somehow are not in phase but still allow current to flow. If a battery was defective this would make sense, but if it's happening over and over doesn't really...

I have noticed that some devices simply won't function if you mix battery brands or new and old. I just went through this is with three AAA's on a kids toy. 2 Duracell and 1 Energizer. They all read 1.58 on the meter, but it wouldn't work. I swapped out the Energizer for a Duracell and it worked.

-spence

[JohnR]

Different functions. One runs wireless and eats quick, other powers keyboard itself. This is somewhat common on wireless peripherals.

[spence]

Originally Posted by JohnR

Different functions. One runs wireless and eats quick, other powers keyboard itself. This is somewhat common on wireless peripherals.

I thought he said the batteries were in series?

-spence

[Redsoxticket]

Possibly the design of the keyboard lacks Zenor diode which acts as voltage stabilizer for low current applications.
Posted from my iPhone/Mobile device

[Redsoxticket]

The batteries could be defective or poor quality when used in series. What brand batteries are you using ?
Posted from my iPhone/Mobile device

[Saltheart]

In the keyboard they are in series. Maybe in the mouse , in parallel , maybe not. They both go to the same USB receiver which has no battery.

My only thought to try to think of something even possible is that the interface between the two batteries provides enough resistance such that the extremely low current draw doesn't happen across that interface but only where the battery that dies touches the Nickel or whatever coated contact. The fact that current flows until one battery is totally dead says that in doesn't need the 3+ volts between the two batteries but just the 1.5 or less between the two ends of the dying battery. Maybe the keyboard just needs some potential difference (could be just 1.5 volts) to work.

Volt meters , for example have a theoretically infinite resistance (and therefore theoretically no current flow) but still sense the potential difference between two ends. Now suppose the keyboard circuit just needs some minimum voltage to operate and the current draw is super super small. The 1.6 volts between the two ends of the battery that eventually dies provides enough driving force to push that tiny current. As it does , its voltage drops until the voltage sensed between the ends of the two batteries in series drops below say 2 volts (1.6 in one and .4 in the dying battery). Maybe when the keboard circuit senses less than the suggested 2 volts total ( 2 being just an example) , it shuts down.

So anyway , the idea is that the resistance between the P and N ends of the batteries where they touch in the center is high compared to where the dying battery touches the Ni plated contacts at its end. The current all flows do to the 1.6 or less voltage in the one battery but the keyboard senses the 3 volts even though no current is flowing between the two batteries , just like the volt meter senses the 3 volts between them in series even though it has the theoretically infinite resistance so no current flows through it.

Now of course there is no infinite resistance and so there must be some electrons flowing to allow the keyboard to sense the 3 volts but that amount is almost nothing compared to what flows out of the single battery just driven by the 1.6 volts because the resistance on that end is lower.

Make sense?......



Now let me tell you about the Tooth Fairy.

[Saltheart]

It varies. Now there are Kodaks , the last set were Duracels. it doesn't seem to matter.

[JohnR]

Originally Posted by spence

I thought he said the batteries were in series?

-spence

Are they for certain in series because you place one behind imediately behind and touching the other? Or do the go side by side and appear to be in series? I've seen both. And I have seen these using batteries for different functions and deplete at independent rates.

[Redsoxticket]

JohnR
In fishing terms series is like the hooks that are tandem in a sluggo and parallel is like a redgill teaser and hab's needlefish tied off from a swivel.
Posted from my iPhone/Mobile device

[Redsoxticket]

JohnR I know what you meant that the batteries appear to be parallel but are in series.
Saltheart I agree what you stated above
Posted from my iPhone/Mobile device

[Saltheart]

The keyboard is definitely ,100% certain, no possibility otherwise, in series . The mouse may be parralell or series for the reasons you say John.