What is the max voltage that a cordless phone may handle above its original rate?

Hi.
I am familiar with the fact that,today,most of the cordless phones have smps adaptors,which supplies a constant voltage to the base unit(opposed to the unregulated linear adaptors,which their rated voltage varies accordingly to the current load).I am,also,familiar that too much input voltage may cause heating of the electronic components in the base unit,may reduce their life or cause them to fail.My question is,as a rule of thumb/in general,How much voltage,in percentage(+10%,+20%...),can the cordless phone handle,beyond its original rated voltage,without having an adverse effects,as i mentioned above?

Thanks.

There was a time when rechargeable batteries could tolerate carelessness. Cheap 'wall wart' DC adapters usually provided much higher voltage than the label states. So 3 nicads in series might receive 6 or 7or 8 volts, even though they produce under 4V.

Laptop computer chargers typically put out 18 or 19V even though 12V is normal internal board voltage.
Nowadays batteries cannot tolerate abuse well. (Perhaps it's a necessary tradeoff for their higher capacity and smaller size.) Consumer demand is always for faster charging times. Hence the charging voltage needs to push sufficient Amperes into the battery pack. I suppose you might safely apply 50 percent higher than the nominal voltage of the rechargeables. That's probably safe for the circuitry as well. But you never know what reliability you're getting these days. Suppose a manufacturer makes a phone running on 4V internal. He might decide against using capacitors rated 12V, and instead install capacitors rated 7V because they're smaller and cheaper.

Hi BradtheRad.

You said that i might safely apply 50% higher than the nominal voltage of the rechargeables.
But i am not sure if we are talking about the same thing.
Lets take,for example,a cordless phone which rated for 9VDC input and it is designed to work with 9vdc switch mode adaptor.Now,if i connnect to the base unit a 9vdc linear power adaptor which has 13.5vdc open circuit voltage,the voltage input from the power adaptor(while it is connected)is decrease only to 11Vdc.So,the cordless phone is received 11vdc(+22%).
Inside the cordless phone unit,i assume,there is a charge controller and a kind of regulator,which received this 11vdc and convert it to the right voltage for charging the 3.6v nicd batteries and to the right voltage that the components in the circuit needs.I understand that too much voltage above the rated voltage input may damage/reduce the life(heat issue) of the components in the base unit,that need to regulate the 11vdc input voltage.So,did the 50% that you mentioned refer to that situation?
How much voltage above the 9VDC can the voltage regulator/battery controller can
handle without adverse effect?

Hi,

I don't think it's a good idea to ask someone whether it is OK to run a device beyond it's limits.
It's always your own risk.
If you want to try it, then try it.

I wouldn't jump with a bungee rope that is specified for 70kg when my wheight is 100kg.

With your phone:
Fir sure it may work for many years, but you can't be sure of.
Maybe it runs for month, then it catches fire ... worst if you are not at home.
An overvoltage might not cause immediate damage...it may take a long time.

Have you ever seen a tantalum capacitor explode because of overvoltage?

Klaus

Hi KlauseST
It is not,exactly,what i am asking"...whether it is OK to run a device beyond it's limits...".
I am asking what are the regulator/charge controller limits?
How much voltage above the 9VDC can the voltage regulator/battery controller
handle without adverse effect?
It maybe sound the same,but it is not that i use a 12vdc adaptor,i am using the right 9vdc adaptor,which is the rated voltage of the cordless phone,but as you know(and as i described before)i am using a linear adaptor(it is what i have right now)that provides higher voltage than 9vdc,while the original switch mode adaptor of the cordless phone,unfortunately,failed.The regulator/charge controller,which reduce the input voltage from the power adaptor may have limit voltage above 9v,that's what i would like to know,an educate answer regard to the inside component of the cordless phone in accordance to my question.

As a 'rule of thumb', as you said, you should not run a device above the manufacturer's recommendation. You seem to be asking how much above the manufacturer's spec you can go. The "rule of thumb" is: You're on you're own.

Does anyone know how many voltage regulators there are in a typical cordless phone?
I,assume,that there is the one that regulates the voltage from the power adaptor to a voltage that
suitable for charging the batteries.But what about the other components like the receiver/transmiter,the microphone/speaker the lcd screen etc.Do they also have voltage regulators?

Hi,

"Does anyone know how many voltage regulators there are in a typical cordless phone?" - That is not a serious/well-thought out question on a number of levels, is it?

At the end of the day, you can't tell me how many whiskers my cat has by telepathy, she's beautiful and stripey if that helps you to answer how many she has; nor can anyone here or on any other forum guess the circuit you are talking about so I'm afraid your questions are alarming and simplistic, if not to add - futile.

The best I can suggest is to take the phone apart/Open the casing and inspect the PCB. If you can identify the ICs, then you can look for the datasheets online and check the Absolute Maximum Ratings of each device you are interested in. Even so, the capacitors and resistors will not have any way of knowing if they are 50V, 100V, 25V, 16V, etc.

Absolute Maximum Ratings...which are not the Electrical Characteristics operating conditions any/all manufacturers actually endorse for permanent use.

Sorry.

Okay,so i assume that i need to take the base unit aparts.Refer to your explanation about the capacitors and the resistors:

d123 said:

...Even so, the capacitors and resistors will not have any way of knowing if they are 50V, 100V, 25V, 16V, etc...

Click to expand...

If there isn't any voltage information printed on the capacitor and the resistor,is there any other possibility to find their voltage(approximately)according to their size,color etc.?

If your phone is assembled with SMT components, the chip capacitors will not have any information whatsoever. (The only exception are electrolytics and some large tantalums).
And no, neither size nor color will offer any clue.

Your "power adapter" has an operating voltage of 11V that is too high. The phone might work fine or a part inside might overheat then fail. if the battery overheats then it might burst and spray its guts all over the phone's circuit or all over your face.

It is not good that we can't identify the type of the resistor or the capacitor.
If one of those component will fail and i will need to solder a replacement
This will make a problem.
Anyway,thanks alot for all the replies.:thumbsup: