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Battery FNB-83 Different voltage readings

 
Edited

When I charged my 60r to full, I took my vom and measured the voltages at the 3 gold colored contacts on the back of the FNB-83 battery, it is 7.49 I removed the battery and checked the voltage at the 2 (+ & - ) silver colored tabs that connect to the 60r and get a 8.6v reading. When battery is inserted in the 60r I get a 8.6 voltage reading in the display when I turn it on.
?
Is there a reason for the voltage difference?
 

This is due to voltage drop across the internal diode.


On Fri, 9 Dec 2022, 18:32 dcx3420 via , <dcx3420=[email protected]> wrote:
When I charge my 60r to full, I took my vom and measured the voltages at the 3 gold colored contacts on the back of the FNB-83 battery, it is 7.49 I remover the battery and checked the voltage at the silver colored tabs that connect to the 60r and get a 8.6 voltage reading. 60r also read 8.6v.

Is there a reason for the voltage difference?

 

Thank you Dale
 

A diode acting as a resistor? If it was, I would expect to experience heat ...
--
Clint Bradford K6LCS
http//www.work-sat.com
 

I may be missing?your?point when you say "diodes acting as resistors" - if so, I apologize.

Diodes only get warm when there is current flowing.? Think of a diode more as a battery. Semiconductor?junctions have voltage drops:??0.7 volts for silicon and 0.3 volts for germanium and they do not vary a?lot as the current changes: they do vary,?just not too much.? When the current is zero thru a diode, the power dissipated?in the diode is zero but the voltage drop?is still present.

Andy
KI6SEP

On Fri, Dec 9, 2022 at 7:48 PM Clint Bradford via <clintbradford=[email protected]> wrote:
A diode acting as a resistor? If it was, I would expect to experience heat ...
--
Clint Bradford K6LCS
http//

 

Diodes are not resistors. Someone stated that the voltage drop in this scenario was caused by a diode. Diodes do not block - they allow current in one direction. Why would a diode cause this voltage drop?
--
Clint Bradford K6LCS
http//www.work-sat.com
 

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Diodes allow current flow when forward biased and stop current flow when reverse biased.? However, there is always a voltage drop when forward biased caused by the potential difference at the p/n junction.? That difference must be overcome to allow correct to flow.? Fo silicone diodes the difference in potential is approximately 0.7V.? If you measure the voltage across a diode not connected to a circuit you'll see that voltage in the forward direction.? That causes you voltage reading of the battery to be about 0.7V less when measured through the diode than when measured across the terminal that do not have a diode present.

73 de AC7EW
Kelly

From: [email protected] <[email protected]> on behalf of Clint Bradford via groups.io <clintbradford@...>
Sent: Saturday, December 10, 2022 11:17:13 AM
To: [email protected] <[email protected]>
Subject: Re: [Yaesu-FT-60] Battery FNB-83 Different voltage readings
?
Diodes are not resistors. Someone stated that the voltage drop in this scenario was caused by a diode. Diodes do not block - they allow current in one direction. Why would a diode cause this voltage drop?
--
Clint Bradford K6LCS
http//www.work-sat.com

 

Hi Clint,

It was me who said the voltage drop is due to the diode inside the battery pack.

All semiconductors have a voltage drop.
A standard silicon diode is around 0.7V but can vary slightly.
 
Edited

Well, now when the battery voltage drops to 8v on the display & I check the voltage via the 3 gold colored charging tabs I am getting about 3.75v from the the left tab to far right tab & the on the tab to the left of it. At 8,6v on the display as I stated the voltages on the charging tabs are 7.49v. Is there a switching diode that cause this. I am thinking the when it is charging it is charging the two cells in series. When the voltage drops to 8v I am reading the 3.75 as parallel.

I hope I am explaining myself to where I am able to make mt point understandable.

Can anyone confirm this with doing a few voltage checks.. I have the US model without the "E"
 

One of the terminals is temperature sensor. Possibly 10K so you will get a very low voltage reading if you measure across that terminal.


On Sat, 10 Dec 2022, 20:29 dcx3420 via , <dcx3420=[email protected]> wrote:
Well, When the battery voltage drops to 8v on the display & I check the voltage via the 3 gold colored charging tabs I am getting about 3.75v from the the left tab to far right tab & the on the tab to the left of it. At 8,6v on the display as I stated the voltages on the charging tabs are 7.49v. Is there a switching diode that cause this. I am thinking the when it is charging it is charging the two cells in series. When the voltage drops to 8v I am reading the 3.75 as parallel.

I hope I am explaining myself to where I am able to make mt point understandable.

Can anyone confirm this with doing a few voltage checks.. I have the US model without the "E"?

 

I get the low voltages across both terminals.
 

Because even diodes have some internal resistance.? Absolutely minimal forward and a total block in reverse.? But yes, the voltage drop through a diode is enough to give the difference shown on the battery pack.

Dave J.? ? AF0DJ.
 

Dave, I am getting a reading of 3.75v across the charging gold colored tabs, when battery display voltage is around 8v. On a full charge the reading are around 7.75v across the 3 charging tabs on the back of the radio. Diodes would account for this?
 

Looking at the rear of the FNB-83 there are 3 terminals, from the left going to the right they are as follows.

Positive (Through Diode) | Negative | Temperature sensor
If you measure using the Positive and Negative terminals you will see a voltage that is lower than what the radio displays due to the voltage drop through the diode. i.e. 7.75V, not 3.75V.
If you measure from the Temperature sensor which is 10K you will read an even lower voltage.

Ignoring what voltage the radio says, take the battery off the radio, measure across the Positive And Negative terminals on the back of the battery.?
Write down this voltage or remember it.

Flip the battery over and measure across the other terminals that connect to the radio. these are on the top of the battery pack, these terminals do not have a diode inline and are connected directly to the battery. You will see the actual voltage of the battery pack.?
 

Just did a fresh charge. Getting 8.6v @ the battery tab that go to radio & 7.9 on the charge tabs, looks like all is working well.

The battery was completely discharged yesterday, had been sitting for 8 months or so. I charged it yesterday to full & finally was able to discharge it today according to the charge icon flashing. Then recharge again. I think it needed a few charge/discharge cycles to function normally.

Maybe on that first charge yesterday there was a glitch to show the 3.75V

I just wanted to make sure it is operating as it should. A new Ham just past his tech test and wants to buy it from me, I got it and only used it a few times, can't hit any repeaters here, my elevation is too low.

Thank you again es 73
Gary KY8M

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