I have a "knockoff" Daly 200A 16S BMS managing 16 3.2V 280AH LiPo cells in series to provide 48V to a 6000 watt inverter. I've used it for maybe a week total and lately I've been getting some really bizarre readings and intermittent cutoffs for exceeding the cell voltage limit that I have set at 3.65V. The crazy part is that it floats around the series and no single cell is a regular culprit. When tested with my meter every cell is within .01 volt of all the others but the BMS updates every second and may report cell differences as high a >1 volt with top readings in the >4 volt range and low cell readings in the <2 volt range. It gets crazier. While cell x may report a voltage of 4.3V one second, within a few seconds it may report 2.6V. The only way I can get it calmed down is to disconnect the BMS and wait till I hear the multiple beeps indicating it is no longer energized, then hook it back up restart it. When it initializes it typically reports all cells at about 3.3V +- .015V. Unfortunately this stability disappears within seconds and it starts scrambling the readings into the ozone again. Any ideas? The idea that a BMS has a utility life of less than a month isn't exactly the reliability I was looking for.
Schizophrenic BMS??
- Thread starter gnomie
- Start date
sunshine_eggo
Happy Breffast!
Scour your connections for issues. Poor crimps, loose wires, and bad connections can behave much like what you describe.
TomC4306
Solar Obsessive
Agree with sunshine.
But, your expectation of reliability and your decision to buy a knockoff Daly contradict one another.
But, your expectation of reliability and your decision to buy a knockoff Daly contradict one another.
Yeah, Daly isn't known for high quality. A knockoff Daly? They sure could have chosen a better BMS to copy.
Been there, done that. A loose nut on one cell was throwing a bad reading some months ago. Not a ridiculous reading but consistently out of range. Snugging the nut fixed it. This isn't that. Pretty sure the BMS is toast. Readings bounce wildly among the 16 cells with as much as a 2 VOLT variation between random cells. My meter says that they are all within .01V of each other. Of course, a BMS is nothing more than a set of trip wires to disable charge and discharge functions when it recognizes parameters that could damage your cells. Its efficacy is directly related to its ability to ACCURATELY recognize those parameters. When the BMS reports cell X at >4V and your meter shows 3.31V on that same cell, I'm going with the meter. I have an active balancer that I've never installed, assuming that the balance charger on the "smart" BMS would keep everything tight. For now, I'm going to ditch the BMS and replace it with the Active Balancer. My charge controller/inverter has its own set of trip wires to protect itself and the battery bank. It reports the sum battery voltage, and I can set the maximum charge voltage to 58V which shouldn't allow any damaging level of current to hit the battery bank. I'll test daily with the meter to spot any discrepancies that the active balancer may not be addressing. Past that, unless someone can give me a better reason to run a BMS on this build, I may not bother to replace it.
Honestly, I was shopping online and looked at dozens of BMS configurations. Saw a good price on a unit that looked identical at a glance. Thought it was a Daly. Surprise surprise. It worked great for about a week. I'll have to do a lot more research before I replace it. Would love to get a BMS that can actually communicate with my Growatt 6000 but trying to convert a USB output to an RJ45 input has proven to be a little daunting. Oh well.. DIY solar emergency backup is nothing if not a trial-and-error curve.
Got to admit I was influenced by the "best seller" ratings on Daly gear. Beginning to realize that when people are buying stuff that they have almost NO knowledge of or experience with, a cheap price and some sexy pictures can move you right to the top in sales.
TomC4306
Solar Obsessive
Do you own a small value torque wrench?
Like this.
TEKTON 1/4 Inch Drive Dual-Direction Click Torque Wrench (10-150 in.-lb.) | TRQ21101 https://a.co/d/9fJr3we
Very nice, impressive quality.
Torque battery connections to 4 or 5 nm.
Like this.
TEKTON 1/4 Inch Drive Dual-Direction Click Torque Wrench (10-150 in.-lb.) | TRQ21101 https://a.co/d/9fJr3we
Very nice, impressive quality.
Torque battery connections to 4 or 5 nm.
Quattrohead
Solar Wizard
I would set your charge voltage to 55 to 56 volts but double check it with a proper meter as the growatts are not exactly known for accuracy in their calibration. If your active balancer has monitoring then between that and the inverter, you kind of have a crude BMS setup anyway but I would only do it for testing not long-term use.