I have been working on a small li-ion charging circuit for my 18650 cells .. But I wanted a low voltage indicator but figured I would better off with a battery protection circuit.. I know there are alot of parts out there for this job but I don't want to buy anything premade.. So I am looking for a IC/Parts and would like some help or suggestion on attempting this ??

 

18650 cells with the protection built in are available, in fact I think they are the more common type.

Bob

 

18650 cells with the protection built in are available, in fact I think they are the more common type.

Bob

Thanks and I am not looking to buy new cell because I already have a nice stash but just unprotected cells...

 

Home-brew is commendable, but in the interests of safety it might be wiser on this occasion to use available dedicated protection circuits.

 

I have been working on a small li-ion charging circuit for my 18650 cells .. But I wanted a low voltage indicator but figured I would better off with a battery protection circuit.. I know there are alot of parts out there for this job but I don't want to buy anything premade.. So I am looking for a IC/Parts and would like some help or suggestion on attempting this ??

Maxim do a small selection of voltage monitor chips.

 

Home-brew is commendable, but in the interests of safety it might be wiser on this occasion to use available dedicated protection circuits.

Thanks for the concern. I understand what ur saying but I really need to learn how to build these circuits and why & how they work.. Plus I have been learning they most stuff made in china sucks and doesn't always work or even right..

Maxim do a small selection of voltage monitor chips.

Thanks I will have to check them out..

 

TI has a nice selection of devices for this.

 

Thanks for the concern. I understand what ur saying but I really need to learn how to build these circuits and why & how they work.. Plus I have been learning they most stuff made in china sucks and doesn't always work or even right..

Thanks I will have to check them out..

For several years now, I've been using a TL431 based shunt regulator for my E-cigarette.

So far - I haven't bothered with low voltage shutdown, but the E-cig uses a logic level MOSFET controlled by a low rated tact switch pushbutton. That is a UVLO of sorts when the cell voltage no longer exceeds VGSthr.

 

For several years now, I've been using a TL431 based shunt regulator for my E-cigarette.

So far - I haven't bothered with low voltage shutdown, but the E-cig uses a logic level MOSFET controlled by a low rated tact switch pushbutton. That is a UVLO of sorts when the cell voltage no longer exceeds VGSthr.

My plan was to use a proper timed charge ic to charge the li-ion. I realied that I needed some kind of low voltage protection to keep the cell healthy.. Your circuit seems pretty cool and will have too look into it .. Would you happen to have the schematic ??

Thanks

 

My plan was to use a proper timed charge ic to charge the li-ion. I realied that I needed some kind of low voltage protection to keep the cell healthy.. Your circuit seems pretty cool and will have too look into it .. Would you happen to have the schematic ??

Thanks

It was published in Elektor a few years back - I sold them the rights to it.

There's an updated version recently sent, they haven't contacted me yet.

The shunt regulator must handle all the charging current when the cell reaches the specified terminal voltage - the basic TL431 can sink 100mA.

You can boost the current capability by making a hybrid Sziklai pair with the TL431 and a PNP power transistor.