Why not use a Daly Dumb BMS.

[FilterGuy]

@Will Prowse recently did a 'cheapest 12V battery' video using a 250A Daly dumb BMS.

At the end of the video he talked about how well the BMS handled the over-current and then said he would never use it on a large system.....but did not elaborate.

I know there are downsides to the Daly dumb BMS. In particular:

• They do not have low temp disconnect
• They are not configurable. In general the Daly Dumbs set their High and Low cut-offs at the far end of what is acceptable, but if you are using the BMS as your last line of defense, that is not such a bad thing.
• The charge current is only 1/2 the discharge current.

So my question is this: Other than the above 3 points, what are the down sides to the Daly dumb if you are looking for a high current FET Based BMS?

 

[Burke]

I am going to use the non smart DALY BMS for my battery. I am building a critical circuit UPS/battery backup for the house using LiFePO4 cells (16S) and an all in one low frequency inverter. In my case the batteries will be in the basement, and if it gets that cold down there I have much bigger problems so I am not too concerned about the low temp cutoff. However, I think the low temp protection is essential if you have a mobile systems where you know that it likely to happen (freezing) like any mobile application or in unheated sheds (if you live in that type of climate anyway). Resistive balancing in most BMS units I've looked at aren't all that effective unless your batteries are already well balanced and only do tweaking really. Balancing properly is super important when you build the pack. If balancing was really important to someone, there are good active balancers that shift power between cells and are a lot more effective.

 

[codfish]

@Will Prowse recently did a 'cheapest 12V battery' video using a 250A Daly dumb BMS.

At the end of the video he talked about how well the BMS handled the over-current and then said he would never use it on a large system.....but did not elaborate.

I know there are downsides to the Daly dumb BMS. In particular:

• They do not have low temp disconnect
• They are not configurable. In general the Daly Dumbs set their High and Low cut-offs at the far end of what is acceptable, but if you are using the BMS as your last line of defense, that is not such a bad thing.
• The charge current is only 1/2 the discharge current.

So my question is this: Other than the above 3 points, what are the down sides to the Daly dumb if you are looking for a high current FET Based BMS?

Another possible usage...
Use a Low current dumb Daly BMS to control just the coil voltage of a high current Gigavac or Kilovac contactor (400 - 500 amps). Just pick a model number that matches your pack voltage. High current charge & discharge.
Then add a reasonably capable multi-amp active balancer.
A simple low current SPST switch in the coil circuit acts as a high current disconnect.

 

[FilterGuy]

Another possible usage...
Use a Low current dumb Daly BMS to control just the coil voltage of a high current Gigavac or Kilovac contactor (400 - 500 amps). Just pick a model number that matches your pack voltage. High current charge & discharge.
Then add a reasonably capable multi-amp active balancer.
A simple low current SPST switch in the coil circuit acts as a high current disconnect.

If I were to go that rout I would use a chargery, eelctrodaucus, batrium or 123 to generate the signals and then I would use the signals to directly control my loads and chargers.

That is not the direction I want to go with the design I am working on now.....and that prompted my question.

 

[John Frum]

@Will Prowse recently did a 'cheapest 12V battery' video using a 250A Daly dumb BMS.

At the end of the video he talked about how well the BMS handled the over-current and then said he would never use it on a large system.....but did not elaborate.

I know there are downsides to the Daly dumb BMS. In particular:

• They do not have low temp disconnect
• They are not configurable. In general the Daly Dumbs set their High and Low cut-offs at the far end of what is acceptable, but if you are using the BMS as your last line of defense, that is not such a bad thing.
• The charge current is only 1/2 the discharge current.

So my question is this: Other than the above 3 points, what are the down sides to the Daly dumb if you are looking for a high current FET Based BMS?

The big problem I see with using a dumb bms is in order to test it you have to take your battery to the extremes or of the bms itself.
Its even worse with the Daly BMS as the low and high cutoffs are very low and very high.
Fets have a tendancy to fail closed and with a Daly you probably won't know until your batteries are damaged.
With a smart bms like my overkill, I can flip a toggle to test the fets.

 

[codfish]

If I were to go that rout I would use a chargery, eelctrodaucus, batrium or 123 to generate the signals and then I would use the signals to directly control my loads and chargers.

That is not the direction I want to go with the design I am working on now.....and that prompted my question.

All true. I find a certain elegance in using simple devices designed for one purpose that can be combined independently.
Failures are more isolated.
The dumb Daly has simple analog chips one per cell (no A/D, no processor, no ...).
The contactor is designed to carry high amps and one could bypass the BMS if it was an emergency.
And if you want smarts, a programable balancer like JK with bluetooth etc, but doesn't carry any load.

But I can see wanting it all in one.

 

[Burke]

The big problem I see with using a dumb bms is in order to test it you have to take your battery to the extremes or of the bms itself.
Its even worse with the Daly BMS as the low and high cutoffs are very low and very high.
Fets have a tendancy to fail closed and with a Daly you probably won't know until your batteries are damaged.
With a smart bms like my overkill, I can flip a toggle to test the fets.

In my case, I can set all of those parameters in the charge controller which is part of the all in one hybrid inverter (charging limits) and that will look after the battery. I am fine just relying on the BMS as a last defense against a failure in the charge controller. If you ONLY have a BMS protecting your battery, it would be nice to have that additional control of a highly configurable BMS system.

 

[John Frum]

In my case, I can set all of those parameters in the charge controller which is part of the all in one hybrid inverter (charging limits) and that will look after the battery.

Your solar charge controller doesn't not know what is happening to the battery at the cell level and is therefore a bad choice to look after your battery.

 

[Burke]

Your solar charge controller doesn't not know what is happening to the battery at the cell level and is therefore a bad choice to look after your battery.

Right, that is why it has a BMS... I was referring to the overall SOC, and modified limits of charge and discharge.

 

[Cal]

It boils down to price/performance ratio. Given the performance is perhaps 60% of a better bms, the cost should be 50% of a better bms for me to consider it. However, since disconnects are not programmable, I would never use it.

 

[PeSCaLo]

Hi @Burke , Im interested to know the Low Frequency Inverter you’r using in your whole house backup. Im now in the planning stages of one myself

 

[isstuff]

i have almost this exact setup, except it is the 24v version and a 200a BMS. I am not sure if I have made a horrible mistake or it will be fine. It is for a camper van. I am combining it with a renogy rover 30amp charge controller and 800w of panels. I have already worked around the lack of a low temperature cutoff using a packaged temperature sensor and a relay that disconnects the solar input when it’s too cold. I think the only thing I am at risk of is lower level of discharge permitted by the BMS. But even then we won’t want to drain the battery to zero since who wants to do that in a off grid setup anyway. Am I missing anything?

 

[RV10flyer]

I have four Daly BMS’s. 2 8S for van and 2 16S for home, all 250A. ALL have low temperature cutoff. I will be using the 16S models on a 122 kWh battery bank.

 

[isstuff]

Wish mine did, I only got balance leads, with nowhere to plug anything else in. Truely dumb.