Heyo (Daly) 4S 12v Smart BMS - Intermittently turning off 'Discharge MOS'

[AaronColby]

I have a Heyo F4S12V150A BT (did not realize it was a Daly knock-off at time of purchase) connected to my 278ah LFP battery pack (4x 3.2v cells in series). Despite some set backs at the beginning (read below, might help with your problem) I've got it working. It has been running for a week in hot weather with various loads (0.5a to 80a with inverter running) but in pretty much constant usage. After 1 week in the evening (temps low) with mild usage (4-6a) it just shut off (van not moving, no change in power being pulled). I pulled up the BT app and it showed the 'Dischg MOS' disabled. I found the screen to enable/disable this feature. I had to turn it off then back on and it is running again. Same thing happens two days later (same time in the evening, this time just turned an overhead light on). This is in a conversion van while stopped so a loose wire is unlikely, it would have flipped off while driving if this was the case. There is no error in the app and all settings are within my parameters I have set.

See the attached photos of my current system settings.

Running firmware: 20210512-3031T
https://www.aliexpress.com/snapshot...d=8131735621032765&productId=1005001349754494

Any advice would be appreciate, at this point I'm ready to throw money at a more reliable unit. I keep my dog in the van sometimes during the day with an exhaust fan and swamp cooler running. My old AGM setup was bullet proof but this new LFP with extra power is proving to be a headache. I would be extremely hesitant to leave my pup in there now in case the BMS just decides to crap out at some point.


Previous issues:

1. No android app on Play store, they want you to use Huawei app store which is blocked on my phone. Can instead use Smart BMS for Daly on Play store, works fine.
2. Undocumented on/off switch. I mocked up the battery the night before and all was well, took it apart to build out final battery box and unit would not turn back on and no LED or other indicators on the BMS that it may be on or off, BT app would not find it. They should be sending an activation switch with this instead of the UART to USB cable which most people will not use. However, you can make one yourself as follows, looking at the lightboard cable insert, with the thermometer panel on the left, there should be 8 pins, with pin 1 starting on the left. If you short pins 6 & 7 this is the reset signal which will reset your device and it should show up easily in the Smart BMS app. I was able to use the UART to USB cable to make my own by using a hot knife to cut out the 2 pins I needed from the connector and strip out the wires from the cable.

 

[AaronColby]

Pulled everything apart and found a very slightly loose negative voltage lead wire to terminal one. Tightening that up has solved all the problems. Talked to my friend who does solar installations and he had a similar issue with loosening nuts causing bad voltage readings. May want to use lock washers when setting up your own battery.

 

[AaronColby]

To elaborate further, the situation got much worse over the next few days and the system was turning off every 30 minutes or so and everytime on heavy load. I loaded up the BT app and watched as the voltage reading from cell 1 would drop REALLY low, sometimes it would slowly drop until the low voltage and/or voltage difference disconnect would trigger. Very frustrating that I had to catch it in the act to see this rather than have it log these details that I could pull up.