August 8, 20233 yr Hi forum guru's I hooked up three 18650 to a HX-3S-FL25A-A three cell BMS. Wiring diagram with the unit showed this: and my project looks like this post soldering and wiring: I get nice clean voltage onto B+ & B- when testing with my multimeter, however when testing the load/input (P+,P-) I get 0,1V. It seems as if the voltage does not flow all the way through to my load. My wiring was done as per the spec for B1 and B2. Any guesses as to why this is happening? LD
August 8, 20233 yr 5 hours ago, L_D said: Hi forum guru's I hooked up three 18650 to a HX-3S-FL25A-A three cell BMS. Wiring diagram with the unit showed this: and my project looks like this post soldering and wiring: I get nice clean voltage onto B+ & B- when testing with my multimeter, however when testing the load/input (P+,P-) I get 0,1V. It seems as if the voltage does not flow all the way through to my load. My wiring was done as per the spec for B1 and B2. Any guesses as to why this is happening? LD Your B1 and B2 are swapped from what the diagram shows
August 8, 20233 yr 2 hours ago, HendrikBigChief said: Your B1 and B2 are swapped from what the diagram shows Yes, thats the first that came to mind, before reading your post. The 0.1v suggest the mosfets are off, probably due to descrepancy regarding the sense voltages.
August 8, 20233 yr Author 6 hours ago, HendrikBigChief said: Your B1 and B2 are swapped from what the diagram shows 🙈 SUCH a rookie mistake, thank you @HendrikBigChief for pointing that out, I assume the BMS wouldnt have any suffered any damage due to this. Will redo this and give feedback.
August 9, 20233 yr Author 22 hours ago, HendrikBigChief said: Your B1 and B2 are swapped from what the diagram shows Hi @HendrikBigChief I swopped B1 & B2. Same problem persists. Load is near dead on the voltage. Any ideas? Read on a post that a BMS will turn loads off if there is a cell imbalance, more specifically if the cell voltage is below the "Allowed to Discharge" setting. Popped the 18650 into the normal USB charger and saw they were running @25% or less. This could be the cause. Charging al three up to 100% and giving the thing another go after that... My BMS Values: Overload Voltage: 4.25 - 4.5V Charging Voltage: 12.6-13V Working Range: 20-25A Operating Temperature: -40 C ~ +50 C Immediate Stream: 35-40A No Load: <30uA Edited August 9, 20233 yr by L_D
August 10, 20233 yr L_D Remove the DC/DC converter from the output of the bms and see if the bms powers on. what is this that you are making?
August 10, 20233 yr 17 hours ago, L_D said: Hi @HendrikBigChief I swopped B1 & B2. Same problem persists. Load is near dead on the voltage. Any ideas? Read on a post that a BMS will turn loads off if there is a cell imbalance, more specifically if the cell voltage is below the "Allowed to Discharge" setting. Popped the 18650 into the normal USB charger and saw they were running @25% or less. This could be the cause. Charging al three up to 100% and giving the thing another go after that... My BMS Values: Overload Voltage: 4.25 - 4.5V Charging Voltage: 12.6-13V Working Range: 20-25A Operating Temperature: -40 C ~ +50 C Immediate Stream: 35-40A No Load: <30uA Why does your board only have half the mosfets? This board from online shops show 8:
August 10, 20233 yr 56 minutes ago, HendrikBigChief said: Why does your board only have half the mosfets? This board from online shops show 8: it depends on the amp rating of the board, more mosfets = more amps these small cheap boards I ignore amp rating and work with 5amps per mosfet(one row for charging and 1 row for discharging) for longevity and a cooler running temp.
August 10, 20233 yr Author 7 hours ago, stefan44 said: it depends on the amp rating of the board, more mosfets = more amps these small cheap boards I ignore amp rating and work with 5amps per mosfet(one row for charging and 1 row for discharging) for longevity and a cooler running temp. This BMS goes up to 25A. I am only going to power two Sonoff 4CH R2's that use very little power. This BMS should be fine right or should I get something else?
August 10, 20233 yr Author 8 hours ago, HendrikBigChief said: Why does your board only have half the mosfets? This board from online shops show 8: Well spotted @HendrikBigChief!! I brought the mosfet issue under @Robofactory's attention , their product image displays 8 mosfets, yet mine only had 4.
August 10, 20233 yr Author 13 hours ago, stefan44 said: L_D Remove the DC/DC converter from the output of the bms and see if the bms powers on. what is this that you are making? This is the battery power for two Sonoff 4CH R2's. The charging voltage coming in is via a 18W PV panel that is regulated by a voltage regulator trimming voltage down to a constant 12,6V. The Sonoff's DC input range is 9-23V. The Sonoff's power consumption in standby mode is 0.5W. @stefan44 when I disconnected the voltage regulator I got current on my BMS load (P+ & P-) This does not make sense at all because the regulator is not connected to any pv input and the output of the regulator is not generating any input power. I am using this regulator. Edited August 10, 20233 yr by L_D
August 11, 20233 yr 14 hours ago, L_D said: This is the battery power for two Sonoff 4CH R2's. The charging voltage coming in is via a 18W PV panel that is regulated by a voltage regulator trimming voltage down to a constant 12,6V. The Sonoff's DC input range is 9-23V. The Sonoff's power consumption in standby mode is 0.5W. @stefan44 when I disconnected the voltage regulator I got current on my BMS load (P+ & P-) This does not make sense at all because the regulator is not connected to any pv input and the output of the regulator is not generating any input power. I am using this regulator. yup seen this happen before with dc/dc regulators. my uneducated guess is that the BMS sees the low resistance of the regulator as a dead short and protects the cells as soon as you connect it.
August 11, 20233 yr On 2023/08/08 at 10:30 AM, L_D said: Hi forum guru's I hooked up three 18650 to a HX-3S-FL25A-A three cell BMS. Wiring diagram with the unit showed this: and my project looks like this post soldering and wiring: I get nice clean voltage onto B+ & B- when testing with my multimeter, however when testing the load/input (P+,P-) I get 0,1V. It seems as if the voltage does not flow all the way through to my load. My wiring was done as per the spec for B1 and B2. Any guesses as to why this is happening? LD Hi @L_D there is the possibility that your bms module have bootstrap issue, which is not uncommon with many bms and power bricks. The P+ and P- is a bidirectional port for both charge and discharge. Apply an initial charge voltage on these terminals, the voltage being in the limits of charging spec of the module. Remove the charging voltage after a couple of seconds, and then check if the battery voltage appears on the output. By the way, the missing mosfets is consistent with a lower current rating offered by manufacturer. Edited August 11, 20233 yr by BritishRacingGreen
August 11, 20233 yr 18 hours ago, L_D said: This is the battery power for two Sonoff 4CH R2's. The charging voltage coming in is via a 18W PV panel that is regulated by a voltage regulator trimming voltage down to a constant 12,6V. The Sonoff's DC input range is 9-23V. The Sonoff's power consumption in standby mode is 0.5W. @stefan44 when I disconnected the voltage regulator I got current on my BMS load (P+ & P-) This does not make sense at all because the regulator is not connected to any pv input and the output of the regulator is not generating any input power. I am using this regulator. what you can try and I think it will work is to remove the connection from bms P- to regulator negative output, now connect your pv panel and test the regulator output (should get 12.6v) and only now connect the bms P- to the output negative of the regulator, now the board should be powered where are you going to connect the sonoffs?
August 11, 20233 yr Author On 2023/08/11 at 11:10 AM, stefan44 said: what you can try and I think it will work is to remove the connection from bms P- to regulator negative output, now connect your pv panel and test the regulator output (should get 12.6v) and only now connect the bms P- to the output negative of the regulator, now the board should be powered where are you going to connect the sonoffs? I did exactly that before reading your post and the BMS jumped into action once the PV source was added. The Sonoff's remain nicely powered and I am running a full day test to see what the actual consumption/load is on the batteries every hour. So far the voltage drops with between 0,05v and 0,08v per hour with one unit connected. The Sonoffs are going to power my Hunter DC solenoids. <<Update 13 Aug>> So I connected the batteries and tried to measure every hour. The usage is well within the reach of these three lithiums. Happy days 😁 Edited August 13, 20233 yr by L_D
August 14, 20233 yr On 2023/08/11 at 2:52 PM, L_D said: I did exactly that before reading your post and the BMS jumped into action once the PV source was added. The Sonoff's remain nicely powered and I am running a full day test to see what the actual consumption/load is on the batteries every hour. So far the voltage drops with between 0,05v and 0,08v per hour with one unit connected. The Sonoffs are going to power my Hunter DC solenoids. <<Update 13 Aug>> So I connected the batteries and tried to measure every hour. The usage is well within the reach of these three lithiums. Happy days 😁 from 9:55 up to 20:17 and only lost 0.06v, you could go for days without sun. sometimes you just have to figure out the logic behind the board's parameters and your own system working.
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