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I have 13 no. 18650 batteries each is of different capacity, i want to connect those in parallel so wondering directly connecting them in parallel would be obviously bad idea so i was thinking that if i add protection ckt of there own individually i.e 13 bms (1s 3.7v 2.5a li-ion bms) and connecting them in parallel will it work then to achive high current the protection ckt i will use is cheap 1s 3.7v 2.5a li-ion bms

Those batteries were laying arround so thought to put them in my amplifier to make it portable

I want to get high current which will be fed into an boost converter which will convert it to 23v with approx 5A current which will used to drive an audio amplifier

Here is the link of circuits im using "https://m.aliexpress.com/s/item/32798161809.html?spm=a2g0n.search-cache.0.0.7e63d460phvt6V"

The Fed up Enggineer
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    There's a lot that I need to know before answering (and be sure and edit this into your question): 1) What are you trying to accomplish? If you connect these batteries in parallel, would it achieve your goal? 2) Why are you using different batteries with different charges? 3) Saying "protection circuit" is _extremely vague_. Can we get details on this? 4) Can you clean up your very long run-on sentence? Your English is really good (even if you're a native speaker or not) therefore I know you're capable of structuring it. –  Dec 27 '17 at 17:26
  • This q may provide insight : https://electronics.stackexchange.com/q/336961/152903 – Solar Mike Dec 27 '17 at 18:47
  • I looked at it , in that post he is using tp4056 which is not in my case i will upload link of ckt i will use – The Fed up Enggineer Dec 28 '17 at 07:47

1 Answers1

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The challenge in Series strings is over/under voltage while in Shunt it is over/under current.

With current sensing and limiting , one can prevent current hogging from cells with the lowest ESR. e.g. 5 mohm) vs poor cells >>50 mohm.

Ensure your design has over current protection for each cell, which can be done in many ways.

Tony Stewart EE75
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  • I have over current ,over voltag,e and over charge, over discharge for each every cell but thing is one will drain faster then other but theres protection still i doubt will be there any bad consequences – The Fed up Enggineer Dec 28 '17 at 07:40
  • The weakest cell will always fail first in a series unless you have an active balance circuit that works to bypass the current. Passive shunt balancers work usually only in phase 2 during CV mode due to power limits. With no balancers the % imbalance capacity accelerates after each cycle. – Tony Stewart EE75 Dec 28 '17 at 16:29