diy solar

diy solar

Daly BMS 200 amps cutting off

RRRRRRRRRRudy

New Member
Joined
Jan 30, 2021
Messages
15
I bought the LiFePO4 280ah battery from one seller on Alibaba and with that I bought a 120amps 4S Daly BMS.

These are installed in my RV and I used to have lead battery (4- 6 volts X235amps) and I was able to use my microwave.

Now with the 120 amps BMS...the BMS cut off the battery...silly me...the microwave use at least 125amps !

So I bought another Daly 4S BMS of 200 amps and still cutting off the battery.

I did equalizing the cells, I did charge the cells, I did verify all the connections !!
I am waiting for a solution from my seller, but any of you have ideas ?

*Sorry screen capture are in french
 

Attachments

  • Screenshot_20210714-112201_SMART BMS.jpg
    Screenshot_20210714-112201_SMART BMS.jpg
    183.3 KB · Views: 12
  • Screenshot_20210714-112242_SMART BMS.jpg
    Screenshot_20210714-112242_SMART BMS.jpg
    148.8 KB · Views: 12
  • Screenshot_20210714-112226_SMART BMS.jpg
    Screenshot_20210714-112226_SMART BMS.jpg
    187.6 KB · Views: 12
  • Screenshot_20210714-112232_SMART BMS.jpg
    Screenshot_20210714-112232_SMART BMS.jpg
    179.8 KB · Views: 12
  • Screenshot_20210714-112219_SMART BMS.jpg
    Screenshot_20210714-112219_SMART BMS.jpg
    195.4 KB · Views: 11
  • Screenshot_20210714-112238_SMART BMS.jpg
    Screenshot_20210714-112238_SMART BMS.jpg
    205.1 KB · Views: 11
My microwave pulls 155 amps constant at 13.6 float volts. So, my guess is that the momentary spike exceeds what the BMS can provide. That 200 amps is constant not peak.

The BMS should have a spec like 230 amps for 6.3 ms. Once I see specs like ms, that is much to quick for me to measure peak amperage with the equipment I have.

I was told by my 12 volt lead acid battery manufacturer that my batteries can provide up to 350 amps. I have four of those, so that covers the surge for the microwave. I am doing a Lithium upgrade to 24 volts and my BMS will provide 200 amps, but that is the equivalant wattage of 400 amps in 12 volts, so I'm sure the BMS I will use will run the microwave.
 
There are a few forum members that recommend de-rating the lower tier of BMS by 50%. If so, that still puts you below the 100 amp threshold.

The Overkill Solar (aka JBD) BMS has been tested to run at the rated amps just fine. I have that BMS, but haven't pushed it to that limit.
 
My advice with the Daly (I have 3 of them) is to only buy the 250A model without the fan. It has 2 gauge wire, not sure what wire is on the 200A model. I suspect 4 gauge, but I am not sure.

You could of course change the overcurrent settings, but be very careful, the FETs tend to fail as a short. This means that they might fail and you would not notice until a problem needs the BMS to shut down.

The JBD seems much more accurately rated and tested. Daly, is apparently not as well tested/calibrated.

Does the Daly give any error messages?
 
Back
Top