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Protection of Lithium Batteries

Rajinder

Jan 30, 2016
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Hi all,
I am looking to parallel a few Lithium Coin Cell Batteries i.e. CR20332.
Could I put in Schottky diodes in replace of the PMOS FETS in the image attached?
Or will I not need to use anything as the batteries are not Lithium Polymer type?
Best regards,
Raj
 

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dave9

Mar 5, 2017
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You do not need to do anything, as long as you use two *identical* batteries, otherwise if they have different voltage levels one may drain the other or at least they won't share the load equally, neither of which is necessarily a huge problem, rather it just means replace the batteries both at the same time with the same brand, age, etc (as close as reasonably possible). This is because they are in parallel instead of series. Series should have protection diodes across the cells rather than ORing diodes.
 

Rajinder

Jan 30, 2016
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You do not need to do anything, as long as you use two *identical* batteries, otherwise if they have different voltage levels one may drain the other or at least they won't share the load equally, neither of which is necessarily a huge problem, rather it just means replace the batteries both at the same time with the same brand, age, etc (as close as reasonably possible). This is because they are in parallel instead of series. Series should have protection diodes across the cells rather than ORing diodes.
Thanks for your reply.
Please can you let me know what you mean by ORing diodes? Is it a wired OR? I dont understand.
Thanks
 

Audioguru

Sep 24, 2016
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Ordinary little CR2032 disposable lithium battery cells are 3V at low current. If you need more current or duration then simply connect a few of them directly in parallel.
 

Rajinder

Jan 30, 2016
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I am looking at energizer AA lithium batteries. These have 3000mAh. Each cell is 1.5V.
I have a further question.
If i have 4 of these. I need to get 3V. So this is easy i.e. put 2 in series.
Can i put 2 more in series and then connect all 4 in parallel to give me 3V at 6000mAh?

What protection circuitry would i need if any.
 

BobK

Jan 5, 2010
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Protection circuitry normally is applied to rechargeable cells rather than primary cells.

You can put 2 in series then parallel the two pairs, as you suggested. Nothing else is necessary. Just be sure the cells are at the same state of charge when connecting them.

Bob
 

Rajinder

Jan 30, 2016
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Protection circuitry normally is applied to rechargeable cells rather than primary cells.

You can put 2 in series then parallel the two pairs, as you suggested. Nothing else is necessary. Just be sure the cells are at the same state of charge when connecting them.

Bob
Thanks for your help.
 
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