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Author Topic: Yaesu FNB-4A Battery Pak  (Read 5219 times)

Posts: 64

« on: September 26, 2011, 04:50:34 PM »

I'm looking to rebuild a Yaesu FNB-4A battery pak. To do this, I need a schematic or a wiring diagram. A simple explanation of some inside wires would also do.

Inside this battery pak, there are 5 wires that I believe connect to the NiCd cells. Some wires have been previously cut so I'm not sure where they connect to. One of the 4 fast charger pin contacts has no connection. Here's what I know and do not know.

White: cell temperature sensor
Black (short): negative battery pak contact strip
Red: positive battery pak contact strip
Blue: Huh?
Black (long): Huh?

Can anyone please shed some light on these connections? I have searched high and low for a schematic or wiring diagram for this battery pak, but have found nothing.

Posts: 2927

« Reply #1 on: September 29, 2011, 03:29:36 PM »

DID YOU KNOW .. there is an Article on how to rebuild the FNB-4A Battery Pack ?
by Jim, KA3EBX

The Yaesu NC-15 is the DESK battery charger for the Yaesu Ni-Cad battery packs (FNB-4A being one of these packs).
The Yaesu NC-18 is the WALL charger that connects to the battery through 3.5 mm coaxial connector (bottom of pack).

Yaesu NC-15 Specifications
Input voltage: 100/110/117/200/220/234 VAC, 50/60 Hz.
Battery packs: Yaesu FNB-3, FNB-4 Ni-Cd packs, with or without transceiver
Charge control: Thermal switch inside battery pack (45°C)
Charging times: 1 hr. for FNB-3 at 25°C ambient, quick mode; 1.5 hr. for FNB-4 at 25°C ambient, quick mode
(trickle mode can be used at any time to prevent self-discharge when the pack is not in use)
Charging current: FNB-3 - approx. 630 mA quick, 20 mA trickle; FNB-4 - approx. 650 mA quick, 20 mA trickle
Operating 'temperature range: 10° to 40° C (500 to 104° F)
AC Adapter output voltage: 12.0 ±0.3 VDC
AC Adapter output current: 1.3 A maximum ,
Specifications for the Yaesu Battery Packs used in the NC-15 charger:
FNB-3A – NiCad Battery Pack 10.8 V - 425 mAh
FNB-4A – NiCad Battery Pack 12.0 V - 500 mAh
MODS.DK has the Yaesu NC-15 Owner's Manual -- the schematic for NC-15 is on the LAST PAGE.
One of the 4 fast charger pin contacts has No connection.
That makes sense.  You have an FNB-4A battery pack.  
That specific pin (no connection) is used ONLY IF you had an FNB-3A pack.
White: cell temperature sensor
Black (short): negative battery pak contact strip
Red: positive battery pak contact strip
Blue: ?
Black (long): ?

4 PIN Assignments (from Battery Charger for FNB-4A)

RED - 12 VDC (charge) -- Used with FNB-4A packs ONLY
N/C -  10.8 VDC (charge) -- Used with FNB-3A packs ONLY
WHITE - Charge control -- Thermal switch inside battery pack (45°C rating)
BLACK (short) - Ground
Are these 2 wires inside the battery pack?
Do they connect to one of the bottom 4 battery pins (charger)?
or do they go to 3.5 mm power receptacle for the NC-18 charger?

BLACK (long) ?? Likely a Ground connection
BLUE ?? Positive connection to the 3.5 mm receptacle??

AC ADAPTER OUTPUT -- Coaxial Connector  
You need to CHECK with a VOM or DVM for correct wiring !

Inside Pin - Ground -
Sleeve - 12 VDC, 1.3 Amp


« Last Edit: September 29, 2011, 04:33:59 PM by W9GB » Logged

Posts: 64

« Reply #2 on: October 01, 2011, 11:43:31 AM »

Yes, I have read the article you mentioned, but the info there doesn't match my battery pak and it ignores additional components inside the pak. Also, some wires in my pak are either cut or missing.

Thanks for the NC-15 info (and) schematic. This helps but it still leaves me in a quandary about the pak's internal wiring and those pesky unknown components inside. One appears to be a diode, and another looks to be a 130k resistor (this is an addition to what appears to be a current limit resistor mounted between two of the 10 cells).

To get the rebuild right, I've got to have some kind of schematic.

Posts: 64

« Reply #3 on: October 01, 2011, 01:37:44 PM »

I have acquired a schematic for Yaesu's FNB-4 battery pak which will permit me to do a good rebuild.

If anyone would like a copy of the schematic, please let me know.
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