Daly BMS - Bypass Low Battery Question

Borriez

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Sep 22, 2021
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Good day.

I have a Daly BMS on a 24V 202Ah LiFePo4 battery system. I am using a Victron 100/20 MPPT Solar Charger. Currently, the equipment and Charge Controller's Negative wires are connected straight to the Daly's "P-" Black cable and the Equipment and Charge Controller's Positive (Red) wires are connected to the 24V Positive terminal on the battery.
Every afternoon, close to dusk, the equipment loses power for a couple of seconds and the boots up again. I suspect the BMS for some reason switches off the load via its "P-" wire.

I thought it might be a good idea to have the equipment's negative wire be connected straight to the Battery's Negative terminal, thus removing the BMS's capability to switch off the equipment. I can always install a 40C thermal and a 24V cutoff circuit inline between the equipment and the Negative terminal to ensure that I can't discharge the Battery below its minimum capability.

Any comment or suggestions regarding the solution that I have mentioned?
 

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Bob B

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Even if you do a low voltage and high voltage disconnect you will have no cell level voltage protection.
If you bypass the BMS .... what exactly will the BMS be doing for you?
Do you have a cell that is getting out of balance?

Maybe you can adjust your charge controller settings to keep the problem from happening .....
 

Bud Martin

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"Every afternoon, close to dusk, the equipment loses power"
Have you verify for sure that the BMS actually goes into shutdown?
Did the problem just starts now and was it working OK before?
The problem is always repeatly happen at close to dust but not at any other times?
 

Borriez

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"Every afternoon, close to dusk, the equipment loses power"
Have you verify for sure that the BMS actually goes into shutdown?
Did the problem just starts now and was it working OK before?
The problem is always repeatly happen at close to dust but not at any other times?
Good day.

Yes, it happens close to Dusk, only.
We have 8 sites running on the exact same setup. 6 of them do it. One of the sites always powercycles late in the afternoon, around an hour before dusk.

We ran the sites on PWM and Lead-Acid systems before without any issues. The rebooting only started when we switched over to MPPT and LiFePo4/Daly sistems.

Below is how our batteries are connected currently
 

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Borriez

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Sep 22, 2021
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Even if you do a low voltage and high voltage disconnect you will have no cell level voltage protection.
If you bypass the BMS .... what exactly will the BMS be doing for you?
Do you have a cell that is getting out of balance?

Maybe you can adjust your charge controller settings to keep the problem from happening .....
The batteries are basically new. Less than a month old.
We have one site that we tested now without a solar charge controller (we hooked up the system and did not connect a solar panel to the site). It has been running for 2 days without any rebooting and sits now on 50% capacity.
 

pierre

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Dec 21, 2019
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I would suggest that you monitor the output of the mppt around dusk. It could be that at that time , with the panels cooling somewhat , but still with enough incident light , that a voltage spike shuts down the bms cell over voltage protection. Seems like you do not have the Daly Smart with BT otherwise the fault finding would have been much simpler.
Also seems like this common port Daly BMS shuts down both charge and discharge paths together , unlike the JBD BMS that will only shut down the ’charge’ path in this situation.
 
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pierre

Somewhere down South
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Further , you mention a ‘battery low’ shut down. Have you confirmed this by testing the battery voltage at that time ? Not knowing your loading conditions one would expect the batteries to be fully charged at the end of the day.
Your post #5 above would rather point to a ‘cell or battery over voltage’ situation.
 

Borriez

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We have battery monitoring on each site and we get snapshots of the sites every 30 seconds.
When the sites reboot, the parameters on the sites are usually like this:

Battery Voltage: 27.3V
Charging: 1.2A
Load: 1.6A
Temperature: 23.5C

We are using the 100A Daly Smart BMSes and we have Bluetooth modules that we can attach to them.

Something to note is that the power consumption on these sites are actually very low. The sites run at around 40W and the "bigger" sites runs at around 80W. They run at these loads 24/7.

A friend suggested that I increase the load as the BMS has a "sleeping" function that might turn on because it doesn't really pick up that there are equipment on the battery due the large Amperage of the BMS and the low Load of the equipment (1.5 - 2% of the max load that the BMS can run at). I do not want to increase the load, I would rather decrease the load as to get more standby out of the batteries and that is why we changed over to Lithium in the first place. Our sites are very remote and are located at places that you can't get to when it has been raining. The idea behind the LiFePo4 systems is to have a week of terrible weather and not worry about the site going offline and then not being able to get to the site to change out the batteries. Unfortunately, the batteries reboot every day and the clients are getting impatient as this never happened before.

Thus the question arises to bypass the "off switch" (Black cable) of the BMS and running the equipment straight from the battery. I will then install 65A Victron Battery Protectors "inline" that would shutdown the load when it reaches 24V (17% capacity) so that we don't deplete and damage the batteries when the weather is bad for too long.
 
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pierre

Somewhere down South
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903
This is not ideal but I think that as the loads are very light you should be able to connect the load directly to the battery terminals ( with protection as you described ). The SCC will still run through the BMS thereby protecting the cells against over voltage and do cell balancing etc. Not sure how voltage sensitive your load equipment is but you should be able to run the batteries down to about 23v.
Maybe do a test run and see. It will however be most interesting to cure the cause rather than the symptoms.
If they were JBD BMSs I would have offered to run a few tests for you but I am unfamiliar with the Daly Smart.
Can you maybe post a snapshot of your BMS settings ? The cure may be as simple as a setting change.
Good luck and keep posting - following with great interest.
 
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mikefitz

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Change to a different BMS, the Daly BMS in some variants will not record currents at low values, often loads below 2 amps will not be recorded. ( in one case the BMS would not record load currents lower than 9 amps).
This is perhaps your problem. Apart from sleeping issues, the SOC recorded by the BMS will be inaccurate.

The JBD/Overkill BMS does not have this problem, recording charge and discharge currents with reasonable accuracy down to 100mA.

Changing to a different BMS would be an alternative to using a Victron Battery Protect, however the Battery Protect may be an easier engineering solution.

Mike
 

RV10flyer

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Change to a different BMS, the Daly BMS in some variants will not record currents at low values, often loads below 2 amps will not be recorded. ( in one case the BMS would not record load currents lower than 9 amps).
This is perhaps your problem. Apart from sleeping issues, the SOC recorded by the BMS will be inaccurate.

The JBD/Overkill BMS does not have this problem, recording charge and discharge currents with reasonable accuracy down to 100mA.

Changing to a different BMS would be an alternative to using a Victron Battery Protect, however the Battery Protect may be an easier engineering solution.

Mike
You’re right on the money. My Daly’s don’t show under 2A and inaccurate SOC. Work great otherwise. My current reading is within 1 A, after the zero calibration. Plenty close enough for our needs.
 
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rickst29

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If your Daly is programmable, you can increase its sleep timer. But even with that done, my "Smart" Daly does not track current correctly, and it therefore shows incorrect SOC when monitoring via Bluetooth. (I have two batteries in parallel, both with Dlay "smart" BMS.) I use a separate coulomb-counter monitor to track what's really happening with the Batteries.
 

Bud Martin

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I am still trying to understand why it only happen only at dusk, if it is due to low current draw I would think it then should have the issue at any time of the day since the same amount of loads are being used 24/7.
 

Just John

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Good day.

Yes, it happens close to Dusk, only.
We have 8 sites running on the exact same setup. 6 of them do it. One of the sites always powercycles late in the afternoon, around an hour before dusk.

We ran the sites on PWM and Lead-Acid systems before without any issues. The rebooting only started when we switched over to MPPT and LiFePo4/Daly sistems.

Below is how our batteries are connected currently
Did you top balance the cells? What do the cell voltages read when this happens.
Bypassing the BMS is going to cause problems in the future. I would suggest top balancing the cells, and try a JBD BMS.
 
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Berseker

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Mar 22, 2020
Messages
167
Good day.

Yes, it happens close to Dusk, only.
We have 8 sites running on the exact same setup. 6 of them do it. One of the sites always powercycles late in the afternoon, around an hour before dusk.

We ran the sites on PWM and Lead-Acid systems before without any issues. The rebooting only started when we switched over to MPPT and LiFePo4/Daly sistems.

Below is how our batteries are connected currently
i think a HVD is being triggered...somehow. till you have a bluetooth connected, so you can read of the individual cell voltages. we wont have a clear picture of what is really going on. the loads are connected directly to the bms or through an inverter?.

swapping to a new/different bms may be a faster resolution to this issue. jbd/ant are cheap and get the job done...IMO
 

legg

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Nov 16, 2021
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We have battery monitoring on each site and we get snapshots of the sites every 30 seconds.
When the sites reboot, the parameters on the sites are usually like this:

Battery Voltage: 27.3V
Charging: 1.2A
Load: 1.6A
Temperature: 23.5C

We are using the 100A Daly Smart BMSes and we have Bluetooth modules that we can attach to them.

Something to note is that the power consumption on these sites are actually very low. The sites run at around 40W and the "bigger" sites runs at around 80W. They run at these loads 24/7.

A friend suggested that I increase the load as the BMS has a "sleeping" function that might turn on because it doesn't really pick up that there are equipment on the battery due the large Amperage of the BMS and the low Load of the equipment (1.5 - 2% of the max load that the BMS can run at). I do not want to increase the load, I would rather decrease the load as to get more standby out of the batteries and that is why we changed over to Lithium in the first place. Our sites are very remote and are located at places that you can't get to when it has been raining. The idea behind the LiFePo4 systems is to have a week of terrible weather and not worry about the site going offline and then not being able to get to the site to change out the batteries. Unfortunately, the batteries reboot every day and the clients are getting impatient as this never happened before.

Thus the question arises to bypass the "off switch" (Black cable) of the BMS and running the equipment straight from the battery. I will then install 65A Victron Battery Protectors "inline" that would shutdown the load when it reaches 24V (17% capacity) so that we don't deplete and damage the batteries when the weather is bad for too long.
Sounds like you're BMS is passing slowly through the zero current condition and is getting confused.
It doesn't sound like it's a nonrecoverable condition, requiring manual interference, from what you've related.
I have no 8S experience, but the 4S types seem pretty confused around there.
 

legg

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Nov 16, 2021
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We have battery monitoring on each site and we get snapshots of the sites every 30 seconds.
When the sites reboot, the parameters on the sites are usually like this:

Battery Voltage: 27.3V
Charging: 1.2A
Load: 1.6A
Temperature: 23.5C

We are using the 100A Daly Smart BMSes and we have Bluetooth modules that we can attach to them.
What do you mean by reboot? Is this an operator intervention?
 

rickst29

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Joined
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Messages
558
Location
Reno, NV
Without switching to JDB BMS units, you might be able to add lightboards to the current Daly units (in addition to raising the sleep timers), in order to avoid restarting so frequently.

I have a double Daly configuration (two parallel 12v batteries as 4S each, 120A and 100A., Both units have light boards attached. They are subject to "phantiom loads" of about 1A within the travel trailer, and I have raised the sleep timer on both units. They are NOT being charged at all - which is the same situation which happens to you, once each night.

With a lightboard, my120 Amp BMS never sleeps, responding to cellphone-Bluetooth monitor connections all the time. It's been unattended and otherwise untouched for many weeks But after about 11 days (?) the 100A unit has gone quiet, and no longer offers to pair on Bluetooth. This has been a significant difference between the behavior of my 100A and 120A Daly 4S units.

But even my 100A 4S unit does not sleep every night - in fact, that shutdown after 11 days might have been related to my timeout value, a 'magic number' somewhat larger than 15000. it was supposed to be a 'magic number' to prevent shutdowns, but maybe the 100A microcode doesn't respect that 'magic number', and the BMS simply shut down after the specified number of minutes. The magic number has been effective on the 120A unit.

My 10+ days versus your daily shutdowns are different behaviors, and I don't know how to solve your problem completely. But maybe the addition of lightboards, along with reset of the sleep timers, can at least get you to at least 10+ days between shutdowns. With the magic number disrespected, maybe try setting the sleep timer up to 65,535? If that works, you could have about 45 days between shutdowns.

What ARE your current sleep timers?
 

legg

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Nov 16, 2021
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I'm reporting comm trials with a Daly 4S BMS on another thread, that may be of interest.


These show that comm integrity may be software-related, with behavioral characteristics
similar to those reported anecdotally, elsewhere, including time-of-day repeated faults.
 
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