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Good morning All, I'm obviously a complete novice as far as 18650 and Li-Ion or LiPo batteries is concerned although I do have a reasonable amount of knowledge as far as Electronics design goes, however I have a few questions which I'm hoping someone Wise here can answer.

  1. what is the difference between an enhanced BMS and a Protected BMS ?
  2. If using unprotected cells (for argument sake we'll say 3s 18650 @2500mAh each can I use a 15 Amp BMS or does it need to match the (3x2500) 7500mAh pack ?
  3. Can I use a BMS charger (once again for argument sake well say an Imax B6) to charge a single protected cell ? A Single unprotected cell?

I'm sure these sound like simpleton questions to the "initiated" however before I commit dollars in any significant way to this extension of my endeavours (I currently use NiMh batteries for a number of projects) I'd be extremely grateful for the answers to the questions that have arisen in my thinking But for which Google & Co seem to have NO answers. Regards, Leigh

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  • \$\begingroup\$ I’m not sure whether my contributions qualify as an answer but here goes: 1. I wouldn’t assume that ‘enhanced’ or ‘protected’ means anything - read the datasheet. A BMS for LiPo should protect against under- and over-voltage and against excessive current both charging and discharging. 2. A BMS has to be appropriate for the pack voltage and the expected charge/discharge rates but not necessarily the Ah capacity. 3. I’m not sure what you mean by BMS charger, but a charger that can charge an unprotected cell should be fine for a protected cell. \$\endgroup\$
    – Frog
    Commented Apr 4, 2021 at 0:55
  • \$\begingroup\$ Apologies about the BMS charger (bloody thing is on my brain) it should have read Li-Ion/Lipo. \$\endgroup\$
    – Leigh Donald
    Commented Apr 4, 2021 at 2:41
  • \$\begingroup\$ Thanks for your response Frog. I note also that a number of the BMS's have multiple take off points (3.7, 7.4, 11.1 V etc.) does this mean that you Could charge 1 or 1s, 2 or 2s (or 2s x X parallel) or 3 or 3s (or 3s x X parallel) depending on what/where you connected them and provided you don't exceed the BMS max Amperage? \$\endgroup\$
    – Leigh Donald
    Commented Apr 4, 2021 at 2:55
  • \$\begingroup\$ almost certainly not - these BMS allow for charge balancing for series cells, which is a good thing. For NiMH you can trickle charge indefinitely and so the whole pack will charge fully eventually, but with LiPo it’s important not to overcharge, so the BMS will bypass the first cells to reach max voltage and allow the others to catch up. \$\endgroup\$
    – Frog
    Commented Apr 4, 2021 at 20:30
  • \$\begingroup\$ Thanks again Frog . (Oh Gawd I feel like the dumbest kid in the classroom [again], NiMh was so much easier for a knucklehead to grasp, I'm begining to get the feeling I'd better hunt around for some mighty good insurance on the Lab/Workspace if I continue my current obsession with Li Ion/LiPo) \$\endgroup\$
    – Leigh Donald
    Commented Apr 4, 2021 at 20:52

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