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Switching from Nicad battery to Lipo: Am I doing this right?
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kjr18:
This charge controller that you're using, is it version with protection? You're talking about charge controller output, so I presume that it's the case, since simple TP4056 boards don't have any output pins, only input and battery. It looks like when transmitting it tries to take too much current, thus tripping overcurrent protection. Can you tell us what model is that Yaesu? It might help to find what current draw is expected.
Nohippychicks:
The place I bought it from (Here's a link: https://www.amazon.com/gp/product/B01DRT4PWY/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1 claims, under "Specifications," that it does have protection but I didn't see anything more than that and blindly just assumed that because it's a knock off of some other design that it'd be OK.

I have bought a new Adafruit "PowerBoost 500," which I've used in the past and they have been reliable for a little over a year so far.

The radio model is an FTC-1143; I didn't even think of posting that!  Or maybe I thought I did and it just slipped.  I'll go with that one...

The battery pack model number is a Yaesu FNB-4, if that's needed as well. 
KL27x:

--- Quote ---I get 4.xV at the lithium cell, 1.1v at the charge controller output and about 1.1v at the output of the boost converter.
--- End quote ---
I am missing something if this makes sense to everyone else.

If you measure 4V at the lithium cell, how is the output of the charge controller 1.1V? Are they not one and the same, connected directly together, along with the input of the boost converter?

Maybe I have mistakenly assumed the charge controller is to charge the (li ion) cell/battery? Or is there more than 1 battery in your circuit?

Earlier you said this:

--- Quote ---1.1V at the output of the charge circuit and 4.x volts at the input of the charge circuit
--- End quote ---
There was a charge circuit. Same as charge controller? Do you have it hooked up backward, by any chance? None of this makes sense.

It sounds like you are powering the charge circuit with the li ion cell. And then using the output of the charging circuit to power the boost converter? 

I feel like the kid that has to sit in the corner with a dunce cap. Cuz this sounds all kinds of stupid to me.
KL27x:
No clarification, no answers from anyone else who is helping. OK, so this is my GUESS.

--- Quote ---Lipo cell ->charge controller-> boost converter->12v load and I'd like some help.
--- End quote ---
Since other smart people are answering this like nothing's wrong, I feel like I am wrong.

But I would expect this to work a hell of a lot better:

Lipo cell > X > IN boost converter OUT > 12.8V output


External power supply > IN charging circuit OUT > X

The LiPo cell, charging circuit output, and the boost converter input are all connected together. (This is why there are two pairs of solder pads in the charge circuit board on the output side, marked as the Battery +- and the Output+-). The voltage you measure on any one of these 3 things will be the same. And it should be something like 3.5 to 4.2V, depending if the radio is on/off and how charged up the lipo is. You cannot measure 4V on the lipo and 1.1V on the charge circuit output unless you have it hooked up in some way I am curious to understand the purpose of. If you cannot draw up a schematic, maybe you can at least tell me what is the charge circuit? Why did you buy it, and what do you expect it to do? It's definitely not going to charge your lipo if you connect the battery to the INput and have no external power source in sight.

[edited for errors]
*Ok, just looked at your link to peek at this board. kjr18 suggests this board might be used for output protection. And looking at the board, he is correct. (But this doesn't change the way you connect it. Still gotta do it my way).

The big chip is the charge IC. The tiny SOT is a voltage detector. The medium chip is the output FET/switch.

The battery goes on the  B+- pads. It looks like the B+ and Out+ are in continuity. The FET looky thing is next to the ground pads, and it would be an NFET, drain on the OUT- and source on the B-. When the voltage goes under the specified level, the detector switches off the NFET and saves the day.

But you have soldered your battery to the Input pads. The input pads will likely be directly connected to the USB connector power and ground. That would be so you could hardwire a 5V power supply in lieu of using the USB connector. So if you plug it into a USB port in this state, and if the power source doesn't cut out immediately, you will damage your cell.

This explains your readings. You are powering the battery charger input with the battery and using the charger output to feed the boost converter. The IC detects no voltage on the battery and initiates trickle charge. This kicks the boost circuit on and gives the radio just enough juice to malfunction. And the resulting voltage at the output of the charger/boost input is 1.1V. Which is not enough to power the voltage detector, either.
kjr18:
If you have your circuit like that one below, there are some possibilities why it has problems with working properly.  If your connections are different, then it might be the cause for your problems.

First problem: Your battery protection ic triggers because of too high current draw. Solution for this is to use different source.
Second problem: Your boost module might be not suited for lower input voltages, with battery voltage drop under load it might stop working.
Third problem: Your boost converter might be too weak to handle this task.

After all we might help you, but we need a bit more info about your circuit, used modules etc.



PS. God, I suck at Paint.
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