Daly BMS failing under load

ned · Jul 19, 2023

Hi all,

I have a lifepo4 4S setup in my car, and it used to work, but after spending the evening prodding wwith a voltmeter and trying to charge it with an external charger, it seems like the BMS may be broken

It can handle a 1 amp load, but if I try put a 6 amp load on it, it dies completely.
I can reset if by shorting the fat wires, and then it will come on and handle a 1 amp load again.

The battery voltages are normal and the battery can handle a 20 amp load from its terminals.

Its the BMS in this pic

Texas-Mark · Jul 19, 2023

Can you post a picture of your battery and how the BMS is connected to it.

Texas-Mark · Jul 19, 2023

ned said:
I can reset if by shorting the fat wires,

Have you tried removing the sense cable to reset it?

ned · Jul 19, 2023

Hey there, thanks for replying. I'm not sure this was the best way to do it, but it did work for a year or so

The 1, 2, 3, 4, 5 refers to the route the negative line goes through to reach the fuse block.

I need the battery for the weekend so I will probaly bypass the bms for now, and charge the battery with 13.6v through the battery terminals, just to make it usable.

RSahan · Jul 19, 2023

Did you check the settings? Maybe a discharge current limit is set?

FoxMeister88 · Jul 20, 2023

Start simple. I would just remove everything from the circuit and just leave the battery and BMS and see if everything works. Battery > BMS > Load. If it doesn't work then you know it's the BMS. If the issue still persists and all settings are correct on the BMS, then you need a new BMS.

ned · Jul 20, 2023

Cheers guys, very much appreciate your thoughts!

I dont think its possible to alter any settings on this BMS, it doesnt have bluetooth, I dont think I have any means of communicating with it.

I'll do as you say and remove the shunt from the circuit and see how BMS acts then.

ned · Jul 20, 2023

Okay so I disconnectd the shunt and wired the BMS directly into the battery negative

And it behaved the same, can handle a 1 amp load but not 6 amps

So ive deleted the BMS for now, and im gonna wire the two negatives you see in red below, together.

So now I dont have a BMS.

I still need the battery, so Ill use the battery as-is until I get a new BMS in a few weeks. Any recommedations? Im in Ireland and the Overkill 100 amp model is pretty expensive from here, like 260 euros.

I'm gonna charge the battery at 13.6 volts using a power supply, for the moment. I thik thats safe enough, from what I have read.

mikefitz · Jul 20, 2023

Similar to the Overkill, from llt power, pay a little extra for airfreight , they accept PayPal.

4S or 3S 12V Li ion or Lifepo4 Battery smart BMS with Bluetooth function UART and RS485 communication with 60A to 120A constant current - LLT POWER ELECTRONIC

1) Application:this smart BMS can work for 3 to 4S Lithium ion or Lifepo4 Battery ,client can choose based on your battery chemistry features 2) Current : constant current of this version BMS can be made with 40A to 120A in accoridng to the different demand 3) Dimension: :Max 138*102*15mm for...

www.lithiumbatterypcb.com

I get delivery to UK within 7 days.

Advice on your system, the cells and the BMS is the 'battery ', everything else, shunt, breaker is outside 'the 'battery'. So it's B- to the most negative cell, then P- is the negative of the 'battery'. No external stuff connects to B-, everything negative connects to P-.

Mike

ned · Jul 20, 2023

Thank you! I'm not brilliant at wiring, very much appreciate the pointer regarding the wiring, and the link to the BMS!

Berseker · Jul 20, 2023

ned said:
Okay so I disconnectd the shunt and wired the BMS directly into the battery negative

And it behaved the same, can handle a 1 amp load but not 6 amps

So ive deleted the BMS for now, and im gonna wire the two negatives you see in red below, together.

View attachment 158447

So now I dont have a BMS.

I still need the battery, so Ill use the battery as-is until I get a new BMS in a few weeks. Any recommedations? Im in Ireland and the Overkill 100 amp model is pretty expensive from here, like 260 euros.

I'm gonna charge the battery at 13.6 volts using a power supply, for the moment. I thik thats safe enough, from what I have read.

if its critical you use the battery without a bms. try and get these small dc voltage displays and attach to each cell...so you can see the voltage on each cell.. or if your cells were properlly top balanced///then you wudnt have any issue

Daly BMS failing under load

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4S or 3S 12V Li ion or Lifepo4 Battery smart BMS with Bluetooth function UART and RS485 communication with 60A to 120A constant current - LLT POWER ELECTRONIC

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