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It Charges, It Charges Not

Jordan Scott Reaser (K6TAR) on October 28, 2018
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It Charges, It Charges Not
Scott Reaser, K6TAR

Look alike Yaesu NiMh battery packs: Some will work in the bundled drop in charger. Some donít do anything. That situation can be readily fixed.

There are at least two flavors of the FNB battery packs. All will physically fit and function in a wide range of Yaesu handhelds. Packs designated with a suffix of 2 numbers will charge with the US market drop in charger. Packs labeled with a letter suffix and 2 numbers do not activate the drop-in charger. The flip side is that US market Yaesu handhelds do not activate NiMh battery charging via the external power port.

What is going on here? First, the left button is always the plus side of the battery pack via a reverse polarity protection internal diode. Continuing, the charging key is a 10K sense resistor connected between the center pack contact button, minus, and the right most button, pack sense, as shown in Figure 1 (FNB Pack Variants). Number suffix packs have this part installed internally. Adding this resistor internally to the letter suffix style packs would be a gross undertaking. But an external resistor can be tacked on in minutes.

A trial installation was done with a 1/2 watt resistor on hand. Works great. The charger is none the wiser. A nice installation would be to add the part either as a small 1/8 watt leaded or SMT part trenched into the pack ABS case. Figure 2 (Modified Pack Clearance) shows how the added part clears the handheld belt clip and the drop-in charger frame.

The FNB battery packs have an inner side pick up point for the ground side of the battery pack. The installed pack mates this point with a tab within the handheld as shown in Figure 3 (Internal Battery Pack Charge Connection). Conceptually all packs could be charged via the external power plug. However, that contact tab is not activated in US market units. Adding a wire would fix this although some disassembly would be required.

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It Charges, It Charges Not  
by KJ4DGE on October 28, 2018 Mail this to a friend!
Good article, well wrote, that solves a issue I did not even know existed. Thank You!
It Charges, It Charges Not  
by DL8OV on October 28, 2018 Mail this to a friend!
There can't be that many of these transceivers worldwide, so I wonder why Yaesu decided to make two different versions, one for the USA and one for the rest of the world?

Anyway, now that we know this mod exists I would do it with the thinest wire possible and a SMT resistor, then cover it with a piece of black tape. That way it looks a bit better and it can't be shorted.

Peter DL8OV
RE: It Charges, It Charges Not  
by KJ4DGE on October 30, 2018 Mail this to a friend!
The FB-83 battery pack shown is still used in the Yaesu FT-60R and many older monoband Vertex VX series HT's.

The two different chargers are likely for EU voltages versus USA 110. I have found that the charger will go long before the battery will with some Yaesu NIcads outlasting them. Case in point a VERY old VX-1R I have with a 15 + year old battery that still charges up to 3.7, 3.9 volts every time I charge it and lasts about 3 days with normal use. Exception not the norm I know but Yaesu never skimped on their battery packs.
RE: It Charges, It Charges Not  
by K6TAR on October 30, 2018 Mail this to a friend!
Other than US, the pack charges in place via external DC jack on handheld. Power to that point could come from any number of DC sources. That mode does not cut off when the pack has reached full charge.
It Charges, It Charges Not  
by KB5ZSM on November 3, 2018 Mail this to a friend!
I'm a little concerned about the 10k resister. Are you sure that it's not a thermistor used to monitor the battery temp while charging? A lot of battery packs had protection circuits to prevent overheating.
RE: It Charges, It Charges Not  
by K6TAR on November 3, 2018 Mail this to a friend!
I have used the case of an expired pack as an external dc battery eliminator. The 10K internal part is not thermally connected to the NiMh cells. I.e., part knows only internal air temperature. The drop in charger senses pack voltage, and terminates charging upon reaching nominal full-charge pack voltage. Setups charging through the handheld external power jack can overcharge the battery pack if left running too long.
It Charges, It Charges Not  
by N1KDO on November 5, 2018 Mail this to a friend!
My FT-60R can charge the FNB-83 in the radio with the external DC adapter.

Then there is this:

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