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Electronics => Projects, Designs, and Technical Stuff => Topic started by: Nikos A. on November 07, 2019, 05:42:27 pm

Title: Battery pack & Short circuit protection
Post by: Nikos A. on November 07, 2019, 05:42:27 pm

Hi everyone, I am designing a circuit and I need to place two batteries in parallel. I purchased this battery holder from Banggood

https://www.banggood.com/2-x-3_7V-18650-Battery-Holder-Box-Container-With-Wire-Leads-p-1448993.html?rmmds=myorder&cur_warehouse=CN (https://www.banggood.com/2-x-3_7V-18650-Battery-Holder-Box-Container-With-Wire-Leads-p-1448993.html?rmmds=myorder&cur_warehouse=CN)

My problem is that if someone accidentally connects the batteries in series everything will blow up (the batteries will be shorted out). I am looking for a solution to protect against short circuits the batteries. I want to avoid the fuse solution.

I found this battery holder that seems to have an embedded PCB that prevents from shorting the batteries but I am cautious..

https://www.batteryspace.com/Battery-holder-Li-Ion-18650-Battery-Holder-1S2P-With-2.6-long-20AWG.aspx (https://www.batteryspace.com/Battery-holder-Li-Ion-18650-Battery-Holder-1S2P-With-2.6-long-20AWG.aspx)

Thanks in advance

Title: Re: Battery pack & Short circuit protection
Post by: Nikos A. on November 07, 2019, 05:57:41 pm

Also, I want to avoid the diodes solution due to the unavoidable voltage drop.

Title: Re: Battery pack & Short circuit protection
Post by: Gallardo on November 09, 2019, 04:15:22 pm

In the absence of a more suitable battery holder, we can enhance the marking and try to start with the battery, such as the 18650 battery with protection.
https://de.aliexpress.com/item/32805302685.html?spm=a2g0x.12010612.8148356.7.25273fd89sX4hc (https://de.aliexpress.com/item/32805302685.html?spm=a2g0x.12010612.8148356.7.25273fd89sX4hc)

Title: Re: Battery pack & Short circuit protection
Post by: Nikos A. on November 09, 2019, 04:34:34 pm

In general I am looking for a protection circuit that I could integrade in my pcb design.
I am thinking to use a mosfet to protect the bateries from shorting. What do you think?

Title: Re: Battery pack & Short circuit protection
Post by: Siwastaja on November 09, 2019, 04:50:43 pm

Note that the batteries will be equally "shorted" and destroyed (possibly resulting in a fire) if the user connects them in parallel, as you intended. Unless they are so lucky that the cell voltages happen to match.

You need the diodes, or active diode-like circuit, for the bare minimum. The protection PCBs usually won't properly protect from excessive charging currents.

Title: Re: Battery pack & Short circuit protection
Post by: Gallardo on November 09, 2019, 04:52:36 pm

I think it is a good idea in the case of small currents! :-+

Title: Re: Battery pack & Short circuit protection
Post by: Nikos A. on November 09, 2019, 05:05:29 pm

I am thinking of using two Mosfet, one at each cell.

(https://i.ibb.co/mNmysVQ/GhvtS.png)[/url]

If the user connects on of the batteries on the wrong polarity then they wont shorted out isn't it?

Title: Re: Battery pack & Short circuit protection
Post by: Nikos A. on November 11, 2019, 09:15:25 am

Anyone? :)