Will This Work?

[EasyGoing1]

I want to use these inexpensive 18650 battery chargers but if you accidentally connect the battery in reverse polarity, the charger fries in less than a second. Picture 1 shows the normal operating mode of the charger and the reverse connection NO NO and picture 2 shows what I am thinking might protect the charger from reverse bias damage while still allowing enough current to flow when the batter is connected properly for normal charging.

Will it work?

[sam_sam_sam]

Re: Will This Work?

I would check the cut out voltage to the 18650 and make sure that it does not go any higher than 4.2 volts

Other than that you should be ok

[stj]

Re: Will This Work?

you may want to look at the input polarity on your diagram!

btw:

[EasyGoing1]

Re: Will This Work?

you may want to look at the input polarity on your diagram!

btw:

Yeah, that was a diagram mistake I saw it after I posted.

[budm]

Re: Will This Work?

If you look at the internal circuit of the 4056, you will see what gets damaged when battery is connected in reverse.
https://cdn.badcaps-static.com/pdfs/...47c5c03bfe.pdf

[eccerr0r]

Re: Will This Work?

I wonder if the LT LTC device can withstand the reverse connected battery better than the chinese TP device?

BTW, despite their base part numbers, it looks like they are not pin compatible...

[R_J]

Re: Will This Work?

Is this of any use to you? http://blog.deconinck.info/post/2017...ity-protection
There is also this board https://www.hotmcu.com/tp4056-micro-...ion-p-176.html

[petehall347]

Re: Will This Work?

might be easier to adapt a battery holder that is foolproof .

[sam_sam_sam]

Re: Will This Work?

I have a charger that supposedly has that feature and it works HOWEVER there is a catch to this and if you DO NOT follow this to letter it will burn this feature out and will not work any more

When you have the battery hooked up one way do not reverse the polarity for at least 5 minutes or you will burn it up

[EasyGoing1]

Re: Will This Work?

If you look at the internal circuit of the 4056, you will see what gets damaged when battery is connected in reverse.
https://cdn.badcaps-static.com/pdfs/...47c5c03bfe.pdf

Are you thinking this MOSFET that appears to be directly in the line of fire in a reverse polarity scenario? I'm thinking those series resistors probably put on a nice light show as well ... ???

[EasyGoing1]

Re: Will This Work?

might be easier to adapt a battery holder that is foolproof .

I'd LOVE to see a picture of such a battery holder for 18650's .. I can 3D print whatever I need, but I can't imagine any mechanical way to prevent someone from accidentally plugging the batterys in backwards unless it had some kind of mechanical means like a contact that breaks loose when the lid is up then maybe an LED indicating incorrect insertion ... where the contact cant be made until the lid it closed but beyond that Ive tried to think of a way to do it mechanically and I just cant think of a way that is also simple to implement.

[EasyGoing1]

Re: Will This Work?

Is this of any use to you? http://blog.deconinck.info/post/2017...ity-protection

THIS WAS A GOOD FIND!!! It's almost the same circuit I came up with except for the addition of the PNP transistor which is very elegant and I love how the TP4056 sees NOTHING when the batter is connected incorrectly... this is clean!

There is also this board https://www.hotmcu.com/tp4056-micro-...ion-p-176.html

So I did look at those boards before, but they are technically designed to be made into backup USB chargers for like cell phones when you're camping or whatever and you need to charge your cell phone, you would use your fully charged 18650's connected to that second board you listed .... and yes you can charge 18650's with those boards, there was something about it that I didn't like when I initially looked at them ... and I can't remember what it was now ... but tackling this TP4056 problem has been a back burner "moby dick" pursuit of mine for like two years now ... will be nice to get it behind me.

Thank You!

Mike

[petehall347]

Re: Will This Work?

I'd LOVE to see a picture of such a battery holder for 18650's .. I can 3D print whatever I need, but I can't imagine any mechanical way to prevent someone from accidentally plugging the batterys in backwards unless it had some kind of mechanical means like a contact that breaks loose when the lid is up then maybe an LED indicating incorrect insertion ... where the contact cant be made until the lid it closed but beyond that Ive tried to think of a way to do it mechanically and I just cant think of a way that is also simple to implement.

https://www.thingiverse.com/thing:3531895

[stj]

Re: Will This Work?

that junk wont work on flat-top cells.

[petehall347]

Re: Will This Work?

that junk wont work on flat-top cells.

never said it would .

[stj]

Re: Will This Work?

but flat-top cells are the only ones that are decent - unless you weld your own protection-kit to them.

all the comercial cells with a nipple on the + are complete shit - mostly ending in "fire" yet with not enough real capacity to actually cause one!!

[brethin]

Re: Will This Work?

but flat-top cells are the only ones that are decent - unless you weld your own protection-kit to them.

all the comercial cells with a nipple on the + are complete shit - mostly ending in "fire" yet with not enough real capacity to actually cause one!!

I have recycled over 10,000 18650 batteries, flat tops are no better than nipple. In fact the nipple tend to be better when using then in chargers and banks. I have had 0 fires.