How to get a lower charge level per cell on a BMS

[Pablito]

Hello, I have purchased this https://es.aliexpress.com/item/48V-...246.html?spm=a2g0s.9042311.0.0.53eb63c0hKSBoO BMS, and latter on learned about the benefits of charging the 18650 cells to a lower voltage in order to achieve more discharge cycles. https://batteryuniversity.com/index...prolong_lithium_based_batteries/subscribe_thx

The webpage where i bought the bms states that a minimun input voltage of 54.4 is desirable for my BMS, but that would leave me to charge each cell at 4.18 volts, and I would like to aim for a voltage of 4.00 volts x cell, in order to acheive longevity. I would like to clear my doubt with the company but it is in china and hard to reach.

My question is this, how does a BMS behave when supplied with a lower voltage? Do they still manage to charge, or they shut down completley. If so, what kind of BMS could I get that is adjustable or that matches my desired charged voltage more closeley? Are there other more manual techniques like manually connecting the cables before the desired voltage is reached?

This is my first build, and I´m a novice in the world of electronics. Thank you very much for your time.

 

[999zip999]

Firstbuild don't worry about it just enjoy. Get fancy later. Use it as it came. If you like 3/4 charge before you use it that day if you wait a week or 3 days charge it then to the full advantage made for the battery pack.

 

[amberwolf]

The BMS only needs to do anything when:

-- the cells get low enough in voltage to trigger LVC, to cut off discharge.

-- the cells get high enough in voltage to trigger HVC, to cut off charge, and then to balance by discharging any cells above the balance trigger point until they are below that (at which point the BMS re-allows charge).

If the cells never get to the balance trigger point, then they never balance. As long as all the cells stay about the same voltage, that's ok. But as the pack ages, or if it's used harder than the cells were really made for, it's less likely that they'll stay the same.

When they start to get very different in voltage it means they are also different in capacity. When that happens, then the lowest-capacity cell limits your total pack capacity, meaning you get less range than you used to. Eventually the imbalance gets bad enough to cause serious range loss, or operational problems like cutouts under load.

So if you use a programmable charger like the Cycle Satiator from Grin, or others that can be set to different voltages, then you can charge at the lower voltage most of the time, and whenever you need to you can still charge at the higher voltage to balance.


If you want a different BMS that has a lower balance point, you can either have a factory program one if you find one that will, or you can get a programmable BMS, like some of the Bluetooth (BT) BMS units discussed in various threads here on ES. You can do a search for Bluetooth or Blue tooth BMS to find those.