The long subject line should prepare you: I know nothing.

My cordless screwdriver has served me for eight years. Now the battery charger does not charge anymore. I venture however that the problem lies with the (detachable) power supply unit rather than with the charger itself.

So... I try to find a replacement via the Internet and in the local stores. What I find are a multitude of power supply units, many for variable output, but none which corresponds exactly to the values that my charger expects: either the good voltage is between two of the possible values or the power is.

Now I think. P=V*I (P=U*I, actually)

If I accept a slightly lower voltage but achieve the right power this way, then the current is higher and this may mean a lot of things; I venture, that something could heat up quicker and in a way which should be avoided.

On the other hand, I have no idea what consequences a lower output power would produce... charging takes longer, it does not, the battery suffers, or not...

Do you have an opinion to share? Wisdom is acceptable, too, but do not sell me certitudes, I do not trust those...

Cheerio.

In my experience, when a rechargeable appliance won't recharge any more, it's because the battery is at EOL. Rechargeable batteries have a finite number of recharge cycles. Eight years is a pretty long life for a rechargeable battery. IMO, it's unlikely that the charger is defective.

Have the battery checked and (probably) replaced.

I have a second unit, which is of equal age and the batteries (both) are okay. I should have mentioned, that two batteries are concerned at once and that the charger does no longer indicate anything, neither charging activity, nor idleness, nor anything else. Both batteries have worked perfectly, before.

Batteries or not, the charger does nothing, which is less than I expect even with rotten batteries.

As this charger is totally basic, in the way that I consider it possible to “branch” the batteries directly on the cables, I deem it highly improbably, however, that the charger itself is defect but keep blaming the power supply.

...and the batteries can be charged on the second charger, and hold the charge?
Then I stand corrected. Sorry I'm not of more help.

Sorry again. My English may not fail me, but my use of it does.

The second “unit” is a different model. Anyway. A Timeline:

- Both batteries are charged alternatingly
[eight years pass]
- The charger is suddenly dead
- No battery is charged anymore, that is, simultaneously, at once, the same day, the same hour, the same minute. But I did not expect anything else, as “The Charger Is Dead”.

How do you know that the problem lies with the power adapter?

The power adapter can be checked with a voltmeter to see if it is still outputs a voltage. While not an absolute check it should be a reasonable indication if the charger is broken or not. The power adapter is not very complex compared to the charger and it would also seem reasonable that the charger would break sooner. I assume the power adapter has not been abused...

Without knowing the design specifications of the charger it is impossible to say what are its maximum/minimum input voltage values.

There are little LEDs on it which lighten up, when there is electrical energy passing through them. They don't currently, although the energy is there alright...

I appear to approach my aim asymptotically, once again, in this thread.

How about this: A completely theoretical power supply unit is available, producing either a voltage or a power below the ideal value, never both.

Which one would you prefer to connect to an arbitrary type of ... electrical thing, in the hope that something useful could result from the exercise?

Have I mentioned that the producer of my arbitrary electrical thing is unavailable?

As usual, not much depends on a resolution of this problem and alternatives exist. I keep the question up for another day or so, although I regret having asked.

Without knowing the ideal or what you mean by slightly lower values I am not sure anyone would want to reply. If the output current is more than ideal it does not matter since Li-ion battery chargers control current. If the output voltage is within +0.3% or so of ideal I would guess it would be ok.

Cool. Thank you.