Why Daly Smart-BMS doesn't stop charging when balancing?

Hi, Just build my new big LiFePO4 battery. 8* LS280AH, with a Daly Smart-BMS, with Bluetooth dongle. All cells came in fine with 3,22 volts. I build my pack and soldered the balancing-leads to my busbars with a flame. Works perfect!

After a few times charging and discharging switching all looks good. SO I started last night the first FULL charge of the pack. My settings for the BMS are: 3,60 cell volt high protect and 28,50 volt Sum Volt high protect. Balanced open start voltage 3,50 volt.


So my thought are: when one of my cells reaches 3,50 volt. The charging stops and the BMS takes some out of the fullest cell. True, but The charging doesn't stop! So the pack keeps charging until one of the cells hits 3,60 then all stops! Also the balancing! I think it is strange that the charging doesn't stop when balancing a high cell.
Does any one has the same problem or noticed this?

Also very strange, but not a problem... When I take out of my pack the BMS App (Android) sees this as positive Amps and when I charge it will see the Amps as Negative... I would think this should be the other way around.. Let me know what you think of that when you are an Daly Smart BMS user.

Thanks, Love the forum.
Philip

Its normal for the bms to allow charging while balancing.
I've not seen any bms that prevents charging while balancing.
Have you seen a bms that prevents charging while balancing?

Philip71 said:

Hi, Just build my new big LiFePO4 battery. 8* LS280AH, with a Daly Smart-BMS, with Bluetooth dongle. All cells came in fine with 3,22 volts. I build my pack and soldered the balancing-leads to my busbars with a flame. Works perfect!

After a few times charging and discharging switching all looks good. SO I started last night the first FULL charge of the pack. My settings for the BMS are: 3,60 cell volt high protect and 28,50 volt Sum Volt high protect. Balanced open start voltage 3,50 volt.


So my thought are: when one of my cells reaches 3,50 volt. The charging stops and the BMS takes some out of the fullest cell. True, but The charging doesn't stop! So the pack keeps charging until one of the cells hits 3,60 then all stops! Also the balancing! I think it is strange that the charging doesn't stop when balancing a high cell.
Does any one has the same problem or noticed this?

Also very strange, but not a problem... When I take out of my pack the BMS App (Android) sees this as positive Amps and when I charge it will see the Amps as Negative... I would think this should be the other way around.. Let me know what you think of that when you are an Daly Smart BMS user.

Thanks, Love the forum.
Philip

Click to expand...

Set your charger to cut out before the BMS. Look at the BMS as a safety device for cell monitoring, not a charge controller. As for the BMS allowing charging while balancing, look at it this way, you are balancing cells in both directions by continuing charge for the remaining cells. As long as voltage is capped at a level, then current will flow to the cells that are lower in volts until they too reach the cap. This is a smart way of lowering the amp requirement of the mosfets. Voltage is the push and it will only push current to areas of lesser voltage.

I have two Headway 40152S pack both with BMS. Although different types. But they stop the charger, to drop the highest cell voltage. Then restrts charging all cells until one get to high, then charger stops charging and bms takes down the voltage of highest cell. When lowered the charger will start charging the pack again. etc. etc. You can hear that because of the fan of the charger, it starts when charger starts charging. On the bms everytime more blue-LEDlights go on. When the pack is balanced all 8 blue LED lights are on and the 7Amp lifepo4 charger is resting with red and green light.

smoothJoey said:

Its normal for the bms to allow charging while balancing.
I've not seen any bms that prevents charging while balancing.
Have you seen a bms that prevents charging while balancing?

Click to expand...

I have two Headway 40152S pack both with BMS. ALthough different types. But they stop the charger, to drop the highest cell voltage. Then restrts charging all cells until one get to high, then charger stops charging and bms takes down the voltage of highest cell. When lowered the charger will start charging the pack again. etc. etc. You can hear that because of the fan of the charger, it starts when charger starts charging. On the bms everytime more blue-LEDlights go on. When the pack is balanced all 8 blue LED lights are on and the 7Amp lifepo4 charger is resting with red and green light. I do it like this for years. Every day my bike is recharged all blue lights are on on my BMS.

Philip71 said:

I have two Headway 40152S pack both with BMS. ALthough different types. But they stop the charger, to drop the highest cell voltage. Then restrts charging all cells until one get to high, then charger stops charging and bms takes down the voltage of highest cell. When lowered the charger will start charging the pack again. etc. etc. You can hear that because of the fan of the charger, it starts when charger starts charging. On the bms everytime more blue-LEDlights go on. When the pack is balanced all 8 blue LED lights are on and the 7Amp lifepo4 charger is resting with red and green light. I do it like this for years. Every day my bike is recharged all blue lights are on on my BMS.

Click to expand...

Disconnect on high cell voltage or high pack voltage is not the same thing as disconnecting during balance.
Your Daly Smart bms should disconnect the pack on high cell voltage or high pack voltage.

The BMS should protect indeed at high (or low) cell or pack voltage.

There are BMS that stop the charge but allow discharge at high cell level.
Those BMS probably also continue balancing (burning off too high capacity for that cell).

Other BMS just stop.
We se a red line and all systems go offline. Full stop.
That sadly include the balancing.

With a balanced pack there are no problems.

Easy enough to have most cells high charged and the charger goes to constant voltage.
Constant voltage is much lower amperage.

When there is more imbalance*, the total pack voltage might still be at constant current, where one or more cells reach the danger zone.
Charging still goes on at high levels, burning 200mA on 50A charge... Doesn't work well.

Some BMS have grown their balancing to the modern capacity and have close or over 1A balance.
Still not a lot at 50A, but a lot better.

I would not be surprised if your Daly fully hits the breaks and lays dead in the water when it encounter a red line, high cell.
As you need to reset the BMS, you are at the battery array.
Might as well spend your time with 50 watt resistor to burn off the extra capacity of the highest cell.
As during charge it will turn off the system till you do.

Alterative is additional balancers, passive or active, to support the dumpload of the Daly.
If I remember correctly, a whole whooping 80mA...

One can't expect much if that.

*More imbalance can occur due defective cells, bad contact with Bus-bars/terminals or when you don't top Balance every day.

Remember that trick to get 3500 instead of 2000 cycles?
Use down to 10 and max 90% SOC??

Charging to 90% automatically means no top balance.

Just don't expect 80mA to catch up after 10 weeks not top balancing.
You need bigger guns for that.