My DIY 40 slot 18650 charger

Jason Morris

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Dec 24, 2017
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I finished my 40 slot 18650 charger today. Thought I share some photos. They all have reverse polarity protection to protect the tp4056 boards. If the battery is put in the wrong way the fuse blows.
Ill try to get some better photos tomorrow when I have better lighting


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hbpowerwall

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Chablism

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I have blow 1/2 dozen cheap power brick cases from eBay when I accedently stick a cell in backwards.


I use these just for charging up

I wonder if there is an easy way to fuse one of these for protection.

Also would be nice if you could just swap out a new pub but they are only 3-4 dollars
 

Jason Morris

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Dec 24, 2017
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I bought some tp5100 to experiment with. They claim to have reverse polarity protection.
 

Gummiadler

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Did I get it right, that the "protection" in your charger is a diode, that shorts the cell through a fuse, that blows? The datasheed of the TP4056 mentions a build in reverse current protection. So you should be ok with a reversed cell as long as you do not try to chare it this way.
 

Korishan

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Gummiadler said:
The datasheed of the TP4056 mentions a build in reverse current protection. So you should be ok with a reversed cell as long as you do not try to chare it this way.

Incorrect. This reverse polarity only works if the cell is less than about 2.5V. If it's greater than that, poof! the IC is dead. I've even had some die with lower voltage than that. The TP4056 reverse protection, if any really, is only for nearly dead batteries being installed incorrectly.
Plus, most of us do not power down the TP between swap outs. We pull the cell out and drop a new one in without powering down and restarting the TP. Maybe this is where the reverse protection comes in at. If they were cycled, maybe they wouldn't come on as the internal regulator would keep the IC turned off.

Using a diode with a fuse is a very easy way to make sure the IC stays safe. Not the best way, but a good way. You just have to choose the right diode that has the right amount of Forward and Reverse voltage so it doesn't falsely allow current to flow if the cell is in normal direction, or not turn on if the cell is backwards.
 

Gummiadler

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You are right, I've read a bit further and this protection is for cells that went negative while discharging. So no protection against wrong inserted cells. Man i miss the times when the cells have a mechanical protection and the negative terminal just didn't connect when inserted the wrong way, like the mignon cells did.
 
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