Gigaset S675IP or S685IP voltage question

[Guiseppe]

Would someone measure the voltage at the pins of the charging cradle for me please.

[tristen]

Hmmm....more relevant background information would be useful.

What precisely are the items you refer to in the thread heading?

What precisely is the problem you are attempting to solve?

[Guiseppe]

The items are VOIP phones, the base unit plugs into the modem/router - I am not sure of the exact model No. of our unit so I used what was stated on the Installation Guide. The handset sits in the charging cradle.

I suspect that the NiMH batteries need replacing but thought I would do some measuring first ...

[loopyloo]

Does the display indicate charging ? ... if so then it will have the correct voltage applied. It might need several hours on the cradle before charging even starts if the batteries are flat. I have uniden phones that if the batteries are flat, take around 12 hours on the cradle before the phone even lights up.
If no indication, check the cradle and phone contacts are clean and connecting properly.
If still no charging, buy new batteries.

[Guiseppe]

Does the display indicate charging ?

Yes.

However the reason for my OP was that the charger states 4V DC output but the voltage at the cradle is 8.08V. I am wondering if the batteries are, in fact, being overcharged - the display does not indicate fully charged batteries. I am sure it did in the early days.

EDIT: In all other aspects the phone works as expected.

[Uncle Fester]

Yes.

However the reason for my OP was that the charger states 4V DC output but the voltage at the cradle is 8.08V. I am wondering if the batteries are, in fact, being overcharged - the display does not indicate fully charged batteries. I am sure it did in the early days.

EDIT: In all other aspects the phone works as expected.

Measuring the voltage open circuit on the cradle like that will not give you any useful information.

NiMh and Nicad have a constant current type charging. For that to work the voltage is usually a lot higher than the battery voltage.
For a 3.6V 3cell pack 8V sounds about right to me.

The best way to check is measure the voltage on the battery WHILE it is being charged.
It should be at something between 3.6V to 4.5V.
If one of the cells is faulty(shorted) it will not reach that voltage and will never show fully charged.
If the phone was not in use for a year or more the NiMh has likely self discharged itself to destruction.

Take out the battery and measure it's voltage after it was on the crade for a few hours.
If it is less than 3.6V, the 3 cell battery is definitely faulty.

[Guiseppe]

It is 2.4V i.e. 2 x 1.2v NiMH AAA. The cells measure 1.4V which would indicate full or very close to full charge.

As a matter of interest I will measure the voltage across the batteries while on charge.

[loopyloo]

It is 2.4V i.e. 2 x 1.2v NiMH AAA. The cells measure 1.4V which would indicate full or very close to full charge.

As a matter of interest I will measure the voltage across the batteries while on charge.

If you mean 1.4v per cell then it sounds like a problem with the phone or the battery connector, or perhaps the batteries are on the verge of degradation, meaning they have the volts but the current capacity is down.
How long does standby last ?

[tristen]

You will NOT get a reliable indicator of a battery's condition by measuring its open circuit terminal voltage.

The battery MUST be under load at the time of measurement.

Reference to the likes of should give you a better understanding.

[Guiseppe]

If you mean 1.4v per cell then it sounds like a problem with the phone or the battery connector, or perhaps the batteries are on the verge of degradation, meaning they have the volts but the current capacity is down.
How long does standby last ?

I read somewhere that straight off the charger the measured voltage of a fully charged cell was about/above (I cannot remember which) 1.4V.

The batteries have served us well hence the earlier comment about replacement - standby time seems to be down from what it used to be.

You will NOT get a reliable indicator of a battery's condition by measuring its open circuit terminal voltage.

The battery MUST be under load at the time of measurement.

Reference to the likes of should give you a better understanding.

I was simply measuring cell voltage knowing that, as you state, it is no indication of condition.

That is a good link. It brought back memories of battery testing in a QEX magazine of many years ago.

I am surprised at the mention of 600mAh as the capacity of an AA cell. I have seen claims of 2600mAh - hmm!