NiZn batteries?

Hi, I just stumbled over NiZn batteries, and I wonder why this is not a big thing for driving battery operated 3.3V circuits. Two NiZn cells give 3.2V, as far as I read over a large part of the discharge cycle. They are also cold resistant, which makes them interesting for outdoor use.
Compared to LiPos, no LDO is required for all the stuff that can only take 3.6V max ...

The German Wikipedia has a distinct Pro/Con section, and they seem perfect for the use in those situations ... Why are they apparently never mentioned?

From Wikipedia:

Nickel–zinc cells have an open circuit voltage of 1.85 volts when fully charged

So no, two in series would not be safe to use with 3.3V circuitry, without an LDO.

There are a lot of "3.3V" devices around, that are specified for up to 3.6V. That is very close. Especially since you specified open circuit.

It is never advisable to run a chip at its absolute maximum voltage.

3.3V parts in sleep mode are essentially "open circuit".

I am not talking about absolute maximum ratings, but about the normal specified range.
Example: http://www.hoperf.com/upload/rf/RFM69HW-V1.3.pdf

There is a lot like that around.

The following statement by you, in your first post, is incorrect.

Compared to LiPos, no LDO is required for all the stuff that can only take 3.6V max

Please do not confuse the inexperienced people on this forum with such nonsense.

Yeah sure. Whatever you say.

ElCaron:
Compared to LiPos, no LDO is required for all the stuff that can only take 3.6V max ...

And as has been pointed out already, that is incorrect.

2 x 1.85v = 3.7V.

And if my maths is correct that exceeds the 'absolute maximum' rating of a lot of 3.3V devices.

Its also not good to plan for operating a device even on the limit, taken from the datasheet of one device with an absolute maximum of 3.6V;

"The limiting values given are in accordance with the Absolute Maximum Rating System (IEC 134). Stress
above one or more of the limiting values may cause permanent damage to the device. These are stress
ratings only and operation of the device at these or at any other conditions above those given in the
characteristics sections of the specification is not implied. Exposure to these limits for extended periods
may affect device reliability"

I can only state this again:

  1. 1.85V is OPEN CIRCUIT. It is quite probably that it is 1.8V or less when connected.
  2. I don't know why jremington hallucinated an "absolute" to my max and then had the impertinence to call MY statements "nonsense", but I can only repeat myself: I am NOT talking about absolute maximum ratings. I am talking about the NORMAL ratings, that are given as "min", "typ", "max" values in datasheets and give the range of safe operation. For these the max rating vor "3.3V" devices is 3.6V quite often. The ABSOLUTE max rating in my example datasheet is 3.9V. I would not recommend to rum it with two 1.95V batteries because of that. (but it could give an indication, that a very short period of 3.7V is most probably ok, especially in a hobbyist project, even if the 1.85V where not ope circuit voltage).
    A USB power supply can give 5.25V continuously and be fully in spec. You guys must live in constant worry about your 5V devices.

To answer my own question: It is probably the high self discharge.

ElCaron:

  1. 1.85V is OPEN CIRCUIT. It is quite probably that it is 1.8V or less when connected.

I was just measuring one of my ‘projects’ it contains several 3.6V maximum rated devices.

The ‘project’ spends large amounts of time (more than 95%) in sleep mode and the measured current is then from 35uA to 200uA.

I would suggest that a high current capability battery is going to see my ‘project’ as open circuit.