The answer is in your image; it shows two cells that read 0V, and an error message that two cell connections are interrupted.
When a BMS reads a cell voltage outside the allowable range (for that specific BMS's settings), it will shut off the discharge FETs and under some conditions (like these) the input FETs as well (because a cell at 0V is damaged and unsafe to recharge, could lead to fire).
It doesn't really know that the cell is disconnected, as it can't test the wires, but it knows they are reading no voltage, or an invalid voltage, so since it can't know what the actual cell condition is, then regardless of the total pack voltage, it will shutdown output/input so no (further) damage can happen.
The charger being connected making the controller power up means your BMS is most likely of the common-port type, where the same pad on the BMS is used for charge and discharge (P- and C- are connected together, and B- goes to the cells). So the charger connector is thus directly wired to the controller, and will work even if the BMS is completely shut off or blown up, etc.
Most likely all that is wrong is that the wires to those two cells are either broken or not connected, or the connector contacts are not correctly mating.
If it had this problem from first wiring up of the BMS, it could be those two wires were installed reversed, and it damaged the two cell monitoring channels in the BMS so they can't read anything anymore. But the cells might be ok (or they could be shorted out by the BMS circultry and the miswire, and be drained to zero).
Could just be two bad channels in the BMS.
Could be actually two groups of dead cells, totally discharged.
I would recommend using a multimeter set to 20VDC and measuring every cell group (each pair of wires on the BMS balance connector, and if they don't all read about the same voltage, then at the cells themselves across each group), and listing those voltages here, starting from the most negative end of the pack going to the most positive.
If the 74.2v total pack voltage shown on screen is what the cells really read in total, then those two cell groups are actually dead, 0V, assuming a 20s pack, since the 12 non-zero-volt groups visible plus the (presumably six) non-visible ones (assuming they're similar to the visible ones) would total up to about that.
If it's an 18s pack, and there are only four non-visible groups, then those two cell groups are probably fine and really measure the same as the rest of the cells, just the BMS can't read them due to faulty connection to the cells and/or BMS failure/damage on those two channels.
If you can tell us the details of your pack, it may help us help you better. For example, a 20s pack would be 20x3.7=74v average, 84v full; a "74v" pack. An 18s pack would be 18x3.7v=66.6v average, 18x4.2v=75.6v full (a "66v" or "67v" pack). Etc. If you have some other type of cells with different average and full values, then it could be completely different than any of the above.
Your title also says you have kelly controller problems as well as pack wiring problems; what specific problems are you having with the controller, if different than what's already posted?
Pattersonimages said:
I’m using an ant BMS / and running a 75v pack-
WHEN I AM CONNECTED TO BLUETOOTH THE BMS READS TRUE PACK VOLTAGE.
I’ve gone through the wiring a couple of times now and cannot figure out where I have gone wrong. The pack internally is reading 75 V the pack after running the ground through the BMS is reading much less.
When I plug in the charger everything fires up as it should, key switches work and the throttle reacts. Without the charger plugged in the controller will not power up at all - I have attached a video. un-sure where I went wrong and wondering if anyone has ideas?
[youtube]https://www.youtube.com/watch?v=IOp8IrcFOdw[/youtube]
https://share.icloud.com/photos/0bdH5A-8ymRwpwDng0Dg52_yA
