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TP5000 module review (and technical details)
#21
2 resistors give you a little more fine control over the current flow. Though, most of these applications really don't need "that" fine of control of charging. There's probably another reason, though.

In a 2s configuration using brand new cells, a bms wouldn't really be necessary. But using used cells, I would definitely add some level protection, even if it was just over/under-voltage protection on each cell (DW01 for example)
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#22
(03-26-2019, 12:35 PM)Korishan Wrote:
(03-26-2019, 04:01 AM)rebelrider.mike Wrote: Looks like the TP5100 is cheaper, but has 2 current control resistors in parallel. I'm not sure why that is, but I guess they could be replaced by a single resistor to get the desired current.

Where are you seeing the 2 resistors?  In the datasheet for the TP5100 it only shows 1. If it's a PCB designed that way, they probably did that use existing resistors on hand and paralleled them to get a lower setting than what a single resistor would do.

https://cdn.datasheetspdf.com/pdf-down/T...pPower.pdf


Or are you referring to a design like this:


The circled resistors do appear to be in parallel. Not sure why they did that in that design, unless it's specifically to keep heat down. Each resistor would take 1/2 the heat generated. So if that's the case, fannel could still do a resistor ladder, but just run two parallel ladders, like a real ladder with 2 uprights and rungs at each step.

I'm still waiting for my TP5100 package to arrive from China. Looking at the pictures, the resistors are SMD, so there are no holes on the PCB where I could solder resistors. I have never worked on a PCB before and am now beginning to wonder if I will be able to desolder the SMD resistors and solder new ones in place. I am thinking of removing the SMD resistors, drilling holes four holes on the PCB, installing 2.54 mm female pin headers and then installing interchangeable resistors on the pin headers. What do you think about this plan?
Korishan, I'm not sure I really understand "like a real ladder with 2 uprights and rungs at each step." I'm attaching a diagram below. Is it something like that?
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#23
(04-04-2019, 06:19 PM)fannel Wrote: I'm still waiting for my TP5100 package to arrive from China. Looking at the pictures, the resistors are SMD, so there are no holes on the PCB where I could solder resistors. I have never worked on a PCB before and am now beginning to wonder if I will be able to desolder the SMD resistors and solder new ones in place. I am thinking of removing the SMD resistors, drilling holes four holes on the PCB, installing 2.54 mm female pin headers and then installing interchangeable resistors on the pin headers. What do you think about this plan?
Korishan, I'm not sure I really understand "like a real ladder with 2 uprights and rungs at each step." I'm attaching a diagram below. Is it something like that?

A resistor ladder like this:


Then to change values, you tap into the point between them to get different values. Running two of these in parallel would help you get a finer control of the resistance value, but not necessary.

As for your drilling thru the pcb, this might be a bad idea. The bottom of the board is most likely copper filled and is the Negative rail of the board. So drilling through the board would make contact with that copper and would cause a short, potentially.

If you want to remove the SMD resistors and use standard ones, you still can. just solder directly to the top with a little extra solder. What you could do is lay a pin header down side ways on the board and solder it to the board, like this:



But you'd remove the middle pin, and use the 2 pads on either side of the resistors for contact pads for the pins. Then you can connect any size resistor to the other end of the pins.
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#24
Thanks for the heads up Korishan. I didn't think of the possible negative copper on the other side of the PCB. Your solutiion with the horizontal headers is practical an easier to do. Thanks
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#25
Work smarter, not harder Wink
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#26
I did a similar thing on my TP4056's. Replaced the surface mount resistor with a potentiometer. I know you're looking for a different solution, but it is possible to solder onto the little surface pads. Though it is tricky. I've been successful 5 out of 6 times so far.

That's hot glue holding it in place by the way. Not snot. Smile
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-Mike G
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#27
(04-05-2019, 09:32 AM)rebelrider.mike Wrote: That's hot glue holding it in place by the way. Not snot. Smile

well, hot snot Tongue
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#28
Well, I'm pulling up this old thread again, but it's still the one that shows up on searches for TP5000, and I have one last contribution.

I bought the red version of the board a while back, and thought I'd share what I've learned about it. It's a little different than the one the OP shared, but most of the characteristics are the same. I stole a picture off the internet and added to it, so this is not all my work. But the picture of the board was so good, I didn't think I could duplicate it, so there it is, with some extra info I picked up:

[Image: b243d66d2f8396277932034e466d6b35.jpg]
I wasn't able to find all this on a single webpage, and I didn't get any instructions when I purchased the board. (This is pretty common, buying little circuit boards.) So this is as much for my future reference as it is for others. Smile

I bought this to charge an old LiFePO4 battery I have for my digital camera. Not sure the battery is any good though.
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-Mike G
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#29
(12-28-2019, 09:53 AM)rebelrider.mike Wrote: Well, I'm pulling up this old thread again, but it's still the one that shows up on searches for TP5000, and I have one last contribution.

I bought the red version of the board a while back, and thought I'd share what I've learned about it. It's a little different than the one the OP shared, but most of the characteristics are the same. I stole a picture off the internet and added to it, so this is not all my work. But the picture of the board was so good, I didn't think I could duplicate it, so there it is, with some extra info I picked up:

[Image: b243d66d2f8396277932034e466d6b35.jpg]
I wasn't able to find all this on a single webpage, and I didn't get any instructions when I purchased the board. (This is pretty common, buying little circuit boards.) So this is as much for my future reference as it is for others. Smile

I bought this to charge an old LiFePO4 battery I have for my digital camera. Not sure the battery is any good though.
Thanks Mike for this reply. Much more information than I could find so far. Unfortunately, I've been away for quite a while and couldn't keep up with the forum due to some difficulties I had. My TP 5100's arrived some time ago and are still lying on my work bench. I also ordered some Pin headers as suggested by Korishan, but when the TP5100's arrived, i realized very fast that i won't be able to be fumbling with those tiny SMD resistors. My purpose of wanting to change the resistors was to achieve slower charge rates. For cells that need slow charge rates, i'll just go with my Opus Bt 3100. Since I have only 2 BT's, it will take me long because i have about 200 cells i was going to process at slow charge rate until they are recovered before bumping up the charge rate to charge fully
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#30
I often put 2 or 3 cells in parallel on the TP4056 boards. That way, each cell only sees 500 or 333 mA. I try to group them by similar Voltage. Keeps one from discharging into another, and hopefully, they'll be in about the same condition. Especially if they came out of the same battery. I imagine you could do the same with the TP5100.

Those tiny resistors are a challenge to get off. I've managed with a fine tip iron and tweesers. Not every attempt has been a success though. I've had to through out a few failures.

I hope things go well, whatever you do. Smile
-Mike G
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