Daly BMS reduced to 12 W discharge, time to go Overkill ?

[StarsScraper]

So I have a Daly BMS (C 30A / D 60A / 12V) and a Ninthcit / Aliexpress LiFePO4 battery (4S / 176 Ah).
I have been using this rig since 2021 without much fuss.
Today I connected a 12 V / 220 V converter to power a 220 W bulb.
It ran for 10 minutes and then the BMS turned off.
I am surprised because the current was less than 18 A and the maximum discharge capacity of my model is 60 A.
After that I tested different loads.
With 46 W the BMS turns off.
With 35 W it turns off too.
The BMS is currently working with a 12W load, but for how long ?

So time to go Overkill ?

 

[sunshine_eggo]

So I have a Daly BMS (C 30A / D 60A / 12V) and a Ninthcit / Aliexpress LiFePO4 battery (4S / 176 Ah).
I have been using this rig since 2021 without much fuss.
Today I connected a 12 V / 220 V converter to power a 220 W bulb.
It ran for 10 minutes and then the BMS turned off.
I am surprised because the current was less than 18 A and the maximum discharge capacity of my model is 60 A.
After that I tested different loads.
With 46 W the BMS turns off.
With 35 W it turns off too.
The BMS is currently working with a 12W load, but for how long ?

So time to go Overkill ?

Have you measured the cell voltages to confirm none are at cut-off?

 

[StarsScraper]

Have you measured the cell voltages to confirm none are at cut-off?

Thanks for your input.
So I tested the cells, all of them are around 3.30 V.
But the situation is evolving, now the BMS cannot even stand a 12 W load.
As a last try, I connected a camping lantern that draws 0.5 A and the BMS is currently working, but for how long ?
The BMS seems to be dying in front of me, so I think the OP question will be answered soon by the BMS itself ...

 

[sunshine_eggo]

Thanks for your input.
So I tested the cells, all of them are around 3.30 V.
But the situation is evolving, now the BMS cannot even stand a 12 W load.
As a last try, I connected a camping lantern that draws 0.5 A and the BMS is currently working, but for how long ?
The BMS seems to be dying in front of me, so I think the OP question will be answered soon by the BMS itself ...

Agreed.

 

[Lt.Dan]

Strange though, I wonder what is making it cutoff at such low amperage? It cutting off means the mosfetts are still operational right?

 

[Checkthisout]

Are Dalys considered problematic?

 

[sunshine_eggo]

Are Dalys considered problematic?

within the last few weeks/months, it seems there are many posts about failed DALYs.

 

[StarsScraper]

Strange though, I wonder what is making it cutoff at such low amperage? It cutting off means the mosfetts are still operational right?

How can I tell if the mosfetts are still operational ?

 

[sunshine_eggo]

How can I tell if the mosfetts are still operational ?

They're cutting discharge.

 

[Lt.Dan]

Daly was probably the most common DIY BMS for a while, so there are thousands, if not more out in the wild. Its typical to see more of them fail.

I personally had 2x different Daly's fail as well, but the mosfetts failed and didn't disconnect the battery and discharged to 1v/cell a couple times

 

[Checkthisout]

Daly was probably the most common DIY BMS for a while, so there are thousands, if not more out in the wild. Its typical to see more of them fail.

I personally had 2x different Daly's fail as well, but the mosfetts failed and didn't disconnect the battery and discharged to 1v/cell a we

So they fail closed? Weird

 

[Lt.Dan]

So they fail closed? Weird

Typically mosfetts do. There is exceptions im sure.

That's also why some prefer a contactor based BMS, so it won't continue to allow charge/discharge if it fails.

 

[Samsonite801]

So time to go Overkill ?

FYI, I have 6 Overkill 120a 4s BMSs in parallel 12v battery banks, still going strong, use bluetooth w/ Xiaoxiang app, and it's been about 2 years and they still are working same as when installed. So far I give them a positive rating ★★★★★

There was a day back then when I had almost went with Daly brand, but instead decided on the Overkill and seems like it was a sound choice...