ElectricGod wrote: ↑
Jun 25 2018 10:23am
Back in May I got 5 of these BMS/balancers and an LCD. Over this past weekend I finally got time to set them up. The 4 pin JST connectors are labeled COM1 and COM2. They are the communications interconnects between each board and how you program via a USB adapter too. The right hand 7 pin connector goes to the LCD. The left hand 8 pin JST is the 7S balance connector.
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They can be daisy chained together up to 16 in a row. When you use them as a single 7S board, the mosfets can be used for up to 30 amps. When you chain them together, they become balancers. This is the boards on 32S, 16,000mah LIPO packs before and after securing them together with nylon spacers. The "stack" is about 1" thick. Board 1 is on top and board 5 is on the bottom.
The documentation is not overly clear in some regards of wiring these BMS so in the end, I just ignored the manual and wired them with the balance connections only. I'm not using B-, C- or P- at all. Probably the LCD won't display charge or discharge amps as a result. Oh well. My LIPO packs are 4S each so I pulled out 9 4S JST male connectors and started chaining together the 5 BMS balance connections so they could span my 8 LIPO packs. The high pin in the first balance connector is common with the lowest pin in the second BMS balance connector. The second BMS high pin is common with the third BMS low pin...and so on. The LCD is plugged into the lowest BMS, but I don't know if that matters or not. With just the lowest 4S pack plugged in, a few seconds later I was seeing cell voltages on the LCD. There's an LED next to the COM2 connector that flashes randomly. As I plugged in more 4S sections, after a few seconds, they too would be added to the list and their LED would flash. Once all 5 boards were plugged together and had the full 32S connected, they all flash their LEDs at seemingly random intervals. I'm guessing the LED indicates data on the 4 wire buss. I don't know why, but the LCD won't display more than the first 28 cells. Maybe there's a setting in the BMS that tells it to scroll through the entire 32S or maybe I need a second LCD? The manual doesn't say and ICGOGOGO was clueless. They just wanted to sell another LCD...so that's on it's way and more boards too.
The manual is horribly incomplete and even though it's supposedly in English, all the screen shots are of the Chinese config app and then the actual settings are not explained at all. This is the first step in programming the BMS and that's literally all the better it gets for the rest of it.
This is the English config application. Based on the pictures in the documentation, you enter commands in that lower left pane that tell the BMS what do to. However, the manual does not explain what you type there.
This sequence of pictures is what the LCD shows. It sort "cycles" at random, but then the only thing that changes is the voltage at the bottom. As you can see the cell voltages are the same. So much for showing all 32 cells. There's no physical buttons to press on the LCD and no solder connections that could possibly be connections for buttons. I really wish it was back lit! Notice the temp reading (20C), I have no idea where the thermistor is. It's not on the LCD and looking at the boards closely there's not one on them either. I don't see in the STM32 docs that they have an internal thermistor. I'm wondering if this is fake data. In messing around, I couldn't get it to go up or down.
I want to mention the balance connector some more. Silk screened on the back side of the board is this battery layout. It is accurate for the BMS.
On the top side of the board, notice the orientation of the balance connector. This is exactly opposite of an actual balance connector on a battery pack. If you attempt to plug in a batteries balance lead directly into this connector, you will destroy the BMS. Where B- is silk screened on the board, in an actual battery balance cable, that's B+. DON'T plug a battery pack directly into the BMS!!! I didn't do it, but a friend who also has these boards did and fried at least one of his boards.
Notice the balancing resistors. 3R3 or 3.3 ohms at 4.2 volts per cell that's 1.27 amps. The specs on ICGOGOGO say "balance the current 60mA-1.2A (4.2V)". OK close enough to V/R=I, but then look at those 7 tiny mosfets or transistors on the board. They clearly connect to the resistors and source to drain across each cell. Do you seriously think they can handle 1.2 amps? My guess is that "1.2" amps is more like momentary drain and reality is more like 500mA continuous. The 4 pin packages are KPC357NT opto-isolators. I think the lowest mosfet is controlled directly by the STM32 CPU and the other 6 channels are behind the 6 opto-isolators.
IMHO, the mosfets are pretty useless and I'll never use them. I bought this board purely for it's daisy chain balancing ability at 112 cells. I intend to use 48S. The mosfets are NCE1540's. They are good for virtually nothing I'm likely to ever do where I need mosfets. I seriously doubt I'd ever build an EV that maxed out at 30 amps.
This is in the manual. Currently I don't have it jumpered at all on any of the boards. My theory, is to set this up in programming and NOT use these jumpers. That's how every other smart BMS works. It is cool that it will support LTO and LION. Most BMS won't do the full range of lithium chemistries.