2pcs 4S 40A Li-ion Lithium Battery 18650 Charger PCB BMS Protection Board with Balance for Drill Motor 14.8V 16.8V Lipo Cell Module

I connected this board according to the illustration in the photos with the product description page. I then checked each pin on the connector to be sure it was connected properly and got the proper readings across all 5 pins as expected. So this confirmed the connector was correctly connected. Then I soldered the P+ and P- and B+ and B- wires again according to the illustration. I then connected the battery to my power supply and set the charging voltage to 18.0v and 1A. The board seemed to work and there was no smoke, fire or sparks like others have reported and the battery. Gradually it charged to 16.8v total and I measured each cell and found they were close, but not balanced. The difference being .5v maximum.I kept an eye on the pack and expected it to stop charging at 17.2v as advertised give or take and it did.I used a clamp meter on each of the leads from the white connector and measured approximately 50-60mA during charging with minor difference between the leads so it appeared to be balancing the cells. After the charged finished the pack was indeed balanced so that's a plus.It would be my opinion but I would say the device does exactly as advertised. Not to point at anyone, but I'm wondering if connection and or improper wiring may have caused some of the other issues? All I did was carefully follow the wiring schematic shown in the pictures and it worked first time no issues. Maybe it's because electronics is my hobby and I may be more familiar with soldering techniques and BMS devices more so than some had failures? Not sure.I did test the load Amps up to 7A with no problem and the device did not get hot during that test. For my purposes I will rarely go above 5 Amps.Overall I found these devices to work as advertised and will use them for now. If I experience any premature failures I'll come back and post an update. So far so good.

Product arrived quickly and was exactly as described. Only drawback was no wiring documentation but easily found what was needed on the internet.

This board worked perfect for me. I built a 4s 8P pack for a flood light with USB charge ports. The recycled 18650 cells I used are 2200 mah capacity - with low output, max 3a each. Charge amps on them is likely low too, I don't know the spec. I pre-charged the cells to about nominal 3.6v before building the pack. I always add an extra lead to my packs to plug into external device later and check series voltage independently. Once I built it with this BMS properly installed, I started charging with my knockoff imax charger, using no balance function (relying on this BMS). I monitored on PC using my real Imax charger. It was hooked to that extra lead from the pack. I charged at 6amps. Killowatt proves that showing about 80watts. Balance results were good - see pics. As for output tests, I did hook the pack to an inverter when it was charged to 15v. I ran a 300 watt sander. It worked. Keep in mind my limitation is my cells, so I can not comment on this BMS and its max output capability. The format of the light I built will not allow for any high output. Thats why I chose a cheap BMS :-) I also brought the pack all the way down. Undercharge cut off somewhere just below 11.75v. So its safe, but it is below 3v each if that's a concern for you. For my use, this BMS appears fully functional. I'll post back if it fails or gets them out of balance after some cycles.

2. Update back to 1 star:After I installed the second board, I initially thought it would now finally provide balancer features. However, that's not the case. Not when the charger is connected directly to the batteries at B+ and B- nor when the charger is connected to P+ and P-.In addition, I have not seen the over discharge cut-off trigger, either - on both boards!++++++++++++++++++++++++++++++++++++++Essentially, this board doesn't do anything at all!++++++++++++++++++++++++++++++++++++++UPDATE from 1 to 2 stars:I took the battery pack apart again and rewired the balancer board wires with a thicker gauge. I also switched to the second of the two boards. After I manually balanced my Lipo cells first, they are now finally balancing by themselves. So one board appears to have been DOA. I still need to test the protective features. So far I was only able to get the balancer to work on one board.Original:Once I wired up a 4S pack to the balance port and the B- and B+ terminals, I noticed that the P- and P+ is outputting 0.26V lower Voltage than the battery pack Voltage. I also noticed that even after two days, absolutely no balancing had taken place. One of the cells was 0.12V off and was never pulled up / the others never pulled down to equalize and allow additional charge.It almost looks like there is no controller chip on the board that would allow accurate charge control. So when charging using a LiPo charger the charge never ends as the voltage constantly fluctuates. Not sure if two chargers are confusing each other or what's happening here.Worst of all:++++++++++The power output pins don't cut power when only one cell is low. It only cuts power when the entire pack goes under 3V or less. Since it didn't balance, one cell was at 2.45V when I turned off the device while the others were still hovering at 3.2V. Quite disappointing!

Boards function still to be assessed. Product was delivered in a timely way.PCB quality good.

I have a few battery banks I've made for various purposes and these do the job of balance charging. My only wish is that they had a charge indicator. However, for the price these are great and I haven't had any failures or problems of any kind.