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Charging Module for 3S 18650 Lipo Batteries

rictrajano

Hello smart people,

I'm making a project that will eventually become a product and I need to get to a conclusion on what battery charging system I'll use.

My constraints are size (needs to be as small as possible), will have to charge 3x 18650 Li-po and needs to charge via USB C.

I found a charging module on aliexpress that looks exactly what I'm looking for but doesn't seem to have a BMS. Is that ok or should I add a BMS and then go from the BSM to the charging module?

Here's the link for the module I'm referring to:

https://www.aliexpress.com/item/1005004759848595.html?productId=1005004759848595&selectedSkuId=12000030370794962&channel=detailPageDealCombineFloor&combineBizType=platformFreeShipping&intent_extra_sku_from=from_add_to_shopcart&type=mergeorder&pdp_npi=4%40dis%21GBP%210.81%21%21%21%210.99%21%21%402103894417407438515762092eb132%2112000030370794962%21fus%21UK%21194086535%21X&trackParams=%7B%22businessScenario%22%3A%22choiceV2%22%2C%22activityType%22%3A%22CHOICE_FREE_SHIPPING%22%7D&spm=a2g0o.detail.fusionpage.0

Do you know of a better alternatives. I'm open to suggestions.


Thanks so much for your help

  • 0

    When you share a link you can (and should) cut off all the characters after and including the first ?

    https://www.aliexpress.com/item/1005004759848595.html

    But to get to your problem - if you are designing a product - it's OK to use Aliexpress parts if you both know what you are doing and are only at the proof of concept level. Aliexpress are a great source for cheap parts that you won't be able to buy tomorrow and don't much care what's in them, and which may not work at all.

    Faulty lipo chargers cause fires and kill people.

    Now the real core of your problem - where is the spec - if you are designing a product to sell you need a full detailed spec of each bought in part or sub assembly.

    Should your charger support all possible modes of USB charging via a USB C type connector, if not then which ones ?

    How accurate must the power metering be ?

    Do you need power metering.

    Do you need cell balancing ?

    And lots, lots more.

    MK

  • 0 in reply to michaelkellett

    Thanks very much for your guidance.

    In relation to that charger in specific, would you say that not having the BMS is an issue or that can be safe to charge 3x 18650 Lithium batteries in series?

    If you had to suggest a similar charging unit would you recommend any in specific?

    Thanks for your help

  • 0 in reply to rictrajano

    BMS is a very general and ill-defined term.

    I suspect that by BMS you mean boards such as this one advertised on Ebay:

    BMS 3S 30A 12V Lithium Battery Protection Board

    for just over £3.

    I think these boards are better described as a "Battery Protection System". I certainly don't think you should use this kind of board unless you can test it fully.

    I would not use such a thing from Ebay or Aliexpress or similar sources unless I had tested it.

    Wiki defines BMS like this:

    https://en.wikipedia.org/wiki/Battery_management_system

    which covers more than just protection issues.

    It is dangerous to charge lithium ion batteries without several levels of protection.

    These should include:

    charge and discharge current limiting

    voltage monitoring - my own view is that there must be voltage monitoring for individual cells.

    temperature monitoring

    If you don't use cell balancing and monitoring you must de-rate the maximum voltage allowed across the stack of batteries.

    The electronic system should be designed so that no single fault can cause a dangerous situation.

    You have told us so little about your project that its hard to give advice.

    One question that springs to mind is why put three cells in series ? Three cells in parallel have no balance issues and can be charged from USB without a boost charger.

    What's the load on the batteries ?

    MK