Daly Bluetooth BMS Settings

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Kakakee

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Hey does anyone know what all the settings inside the app actually do and control? For some reason, my pack isn't charging I believe I need to change something in the settings but I don't know what it might be.
 

ajw22

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Nov 16, 2018
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You'll have to provide more information than that. Daly produces dozens of different BMSs. Pictures of the setup and configuration screen always help.
Is the thermal sensor connected? BMS might have shut off due to invalid temperature.
 

Kakakee

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model is: RS485 7S 24V 100A 3.7V Li-ion
Pictures attached and the thermal sensor is connected.
 

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ajw22

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I'm not familiar with Daly BMSs, but the first thing to investigate is the voltage of each cell, since the interface mentions
Fault: "Cell volt high level 2" (whatever "level 2" means)

The default settings for cell high alarm voltage is >4.25v, and "release" (reset) of the alarm when voltage is reduced to <4.15v
It may be that with your current alarm settings (>4.10V), the new reset voltage has moved to <4.00v. So the BMS may still be in the alarm state.

So I'd either changing the max cell voltage settings back to 4.25v, or try discharging the battery until all the cells are below 4.00v
 

ajw22

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If you're planning to charge the battery to just 4.10v/cell, setting the BMS limit to 4.10v is the wrong move. The BMS is not designed for that purpose, and you'll trigger the alarm every time you charge the battery. You have to set the BMS limit to something like 4.20v/cell, and set your charger voltage to 28.7v (4.10v * 7)
 

ajw22

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Also, from my experience, "balance start volt" of 3.80v is too low and often leads to unexpected, counterproductive balancing, particularly when using old cells.
If your top voltage is 4.10v, I would set the BMS to start balancing at no higher _lower_ than 4.00v
 
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Kakakee

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That woked! It's charging!

Can you explain the "balance start volt" reasoning a little better so I can understand it?

Thank you so much!!!!
 

Korishan

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Can you explain the "balance start volt" reasoning
Generally you want to start balancing before the cells are full so you don't accidentally over charge them, even by a little bit. This also allows the cells to equal out a little faster as well.
 

Kakakee

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Generally you want to start balancing before the cells are full so you don't accidentally over charge them, even by a little bit. This also allows the cells to equal out a little faster as well.
So wouldn't you want that process to start as low as possible? Right now it's set to start at 3.8V
 

Korishan

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No, because then you would be wasting a lot of energy. You don't need to slow it down at the beginning of the race, you only need to slow it down as they approach the finish line.

It's possible that the one taking a charger faster (getting a higher voltage) may slow down at it reaches the upper limit, which will allow the others to catch up. All without wasting energy by burning off the "unbalanced" amount.
Take note, we're only talking a few 10's to 100 of milivolt difference. If the cells are further than that (something like 3.7V and 3.9V) consistantly, you need to find out why that slower pack is being drug down. After an initial balancing, they *should* stay pretty close. If not, you have an issue somewhere. Either a bad connection, weak cell, or a self-discharging cell or high IR in some cells. Those issues need to be fixed. A BMS is not a permanent patch for a problem.
 

Kakakee

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They all seem to stay within a .15v delta from each row/grouping. So when should I have it start balancing? 3.9v?
 

Kakakee

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No, because then you would be wasting a lot of energy. You don't need to slow it down at the beginning of the race, you only need to slow it down as they approach the finish line.

It's possible that the one taking a charger faster (getting a higher voltage) may slow down at it reaches the upper limit, which will allow the others to catch up. All without wasting energy by burning off the "unbalanced" amount.
Take note, we're only talking a few 10's to 100 of milivolt difference. If the cells are further than that (something like 3.7V and 3.9V) consistantly, you need to find out why that slower pack is being drug down. After an initial balancing, they *should* stay pretty close. If not, you have an issue somewhere. Either a bad connection, weak cell, or a self-discharging cell or high IR in some cells. Those issues need to be fixed. A BMS is not a permanent patch for a problem.
They all seem to stay within a .15v delta from each row/grouping. So when should I have it start balancing? 3.9v?
 

Korishan

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Should generally be about 100-150 millivolts before end of charge. So, if your top voltage is 4.1V, then start balancing around 4.0V. Balancing really doesn't need to be done until almost the end.
 

ajw22

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So wouldn't you want that process to start as low as possible? Right now it's set to start at 3.8V
If you had all new cells that are the same (same model, same batch), then yes.
When the cells get older, or you have a mix of brands/batches (technically: different internal resistances), then voltages may rise at slightly different rates during charging, and catch up towards the end.
So if the balance start voltage is set too low, you could end up with the situation where cells #1~#6 get balanced (slowly discharged) around 3.8V, but then #7 starts to shoot ahead towards 4.1V and all the previous balancing was a total waste.

You should only ever need strong/long balancing once, after putting together the new battery. After that, _minimal_ balancing should suffice - if not, one or more cells have gone bad and needs to be replaced. High level of balancing just masks that/those damaged cell(s).

Also, there's no need for the cells to have exactly the same voltages. It's perfectly fine for one cell to cycle between 4.12v ~ 3.12v, while another cycles between 4.08v ~ 3.08v.
 

Kakakee

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If you had all new cells that are the same (same model, same batch), then yes.
When the cells get older, or you have a mix of brands/batches (technically: different internal resistances), then voltages may rise at slightly different rates during charging, and catch up towards the end.
So if the balance start voltage is set too low, you could end up with the situation where cells #1~#6 get balanced (slowly discharged) around 3.8V, but then #7 starts to shoot ahead towards 4.1V and all the previous balancing was a total waste.

You should only ever need strong/long balancing once, after putting together the new battery. After that, _minimal_ balancing should suffice - if not, one or more cells have gone bad and needs to be replaced. High level of balancing just masks that/those damaged cell(s).

Also, there's no need for the cells to have exactly the same voltages. It's perfectly fine for one cell to cycle between 4.12v ~ 3.12v, while another cycles between 4.08v ~ 3.08v.
Got it, that makes a lot more sense thank you for explaining, I'm going to have it start balancing at 4v since it should start to top some of the groups off around 4.15v
 

Kakakee

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Should generally be about 100-150 millivolts before end of charge. So, if your top voltage is 4.1V, then start balancing around 4.0V. Balancing really doesn't need to be done until almost the end.
Perfect, thank you!
 
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