HiLetgo14.8V 4S 30A 18650 Li-ion Lithium Battery BMS PCB Integrated Circuits Protection Board Cell Balance

Like others have reported, I was getting low voltage out until I tried charging through it & voila, it started working! It works great now, I wish I had read Ronnie's review first, but thanks for your report! The sellers need to get a better translation of the description of the item, the last section didn't make sense in English, and better directions would help too. There appear to be two versions of this board, and I was able to figure out the wiring of the plug version from looking at the soldered version, but it would have helped to have that more clearly stated.

Like most of the reviews, I got the board, wired it up according to the picture with four 18650 battery holders, checked all of the connections with a multimeter, put four fully-charged 18650 batteries into the holders, and expected 14.8V or more at the P+ and P- pins. I was getting 2.1V out and thought that these boards must really be defective like so many of the reviews say.As it turns out, the board requires that you apply power to the P+ and P- pins before it "wakes up".Basically you have to have everything wired up including the charging port that you're going to use wired to the P+ and P- pins, have the batteries in the holders, and then "plug it in" briefly to wake up the board. Just one second of being plugged in will do it. Then you can unplug it and it will keep putting out the full 16V or whatever your input voltage is as long as you don't disconnect the batteries.This means don't put a power switch between the batteries and the board. Wire both the battery holders and the charging port straight to the board so that the board is powered from the batteries all the time. If you want to add a power switch, add it between this board's output and the circuit you're trying to power.

Board didn’t work at first. No voltage on the output pads. Came back 5 minutes later and it’s now working. We’ll see how well it works when the pack is fully charged

So far, so very good (April 10th, 2024).As far as I can tell this BMS works as advertised.Setup:I ordered two of these BMSs to create two 4S, 3P lithium battery packs with 14.8V nominal voltage, using for each pack twelve 2,500 mAh LMC cells with each 3.7V nominal voltage (4.2V max) and 10A max discharge rate per cell.The voltage of one 100% charged battery pack is 16.8V and the capacity is 7,500 mAh. The maximum discharge current of 3 cells in parallel is 30A which is what the BMS is rated for.I did the wiring successful using the wiring diagrams from the Amazon pictures. In my application, one battery pack consists of of 4 units of 3 parallel cells. The instructions that came with the BMS were not so helpful but the pictures from Amazon explained everything.Charging:I am using an 18V, 2.7A power supply to charge the two packs connected in parallel.I fried a 12V, 2A powersupply (it got too hot during 1 hour of charging while providing 2.7A), so I found and bought a slightly more capable powersupply that was just right (max current eated at 2.7 A). I verified that the charging cut-off mechanism of the BMS is activated at a battery pack voltage of 16.7-16.8V which is just right at 100% charge. So charging working great now.Discharging:I connected both packs in parallel, hopefully giving me a total of 60A maximum discharge current at 16.8 V maximum voltage, or 1,008 watts of max power.I have only tested low discharge currents of up to 2 ampere so far, and that has worked well. The bms is rated for up to 30 ampere discharge, which I intend to test in future.

I initially bought 2 of these, then requested replacements, the seller sent back another 2, had the same exact issue:I am connecting 4S3P 18650 battery pack to it, I can read all the correct values on each B-, B1, B2, B3, B+ ports, it comes with a P- and P+ ports as well which work as Charge and Discharge ports, it has NO additional Charging or C- port.When I connect a car break light bulb (12v , 55 watt max draw) to the P+ and P- port the bulb doesn't light up and the P ports drop the voltage to 0 and then they go back up to 11v but it never goes back up to 15-16v again. I have tried 4 boards of the exact same model and they all act the same way. It seems like the board is protecting itself but I don't understand why, since the bulb is a 12v and the current for it shouldn't be more than 10 amps, this board is supposed to handle 30A x 12v = 360wNot worth the time waisted in this product.