I could use some help setting Deligreene BMS parameters.

[Jwtravel]

I’m working on a 24v mobile system. I built a 8s with Eneramp 3.2 cells, for a 24v back. I have top balanced (that was exciting) the pack with a bench top power source and installed the Deligreene 24v 200a BMS.
My question is: how to I determine the best parameters for longevity? I have a bit of change and more importantly time invested in the build and I want to do what is best for my batteries.
Thanks, Jayson
Here’s a pic of the batteries with the BMS installed.

 

[John Frum]

A BMS should never have to disconnect charge sources or loads under normal operating conditions.
That means all your loads should have appropriately configured low voltage disconnect independent of the bms.
Your charge parameters should be well within the safe envelope as well.

What is your low voltage disconnect strategy?
What are your charge parameters?

 

[Jwtravel]

A BMS should never have to disconnect charge sources or loads under normal operating conditions.
That means all your loads should have appropriately configured low voltage disconnect independent of the bms.
Your charge parameters should be well within the safe envelope as well.

What is your low voltage disconnect strategy?
What are your charge parameters?

Low voltage disconnect strategy? Do you mean my mppt? It is a Epever 40a 4215.
That would be my next question.
When I go to user set parameters and try to set them manually (per Will Prowse’s suggestions for longevity) I get a para. Error and it will not let me enter them. So, I need help there as well but reading through as many posts as I can it seems like I need to figure the BMS stuff out first and then maybe make a new post concerning the mppt settings. I feel like I’m swimming in circles here.

 

[John Frum]

Low voltage disconnect strategy?

Low voltage disconnect strategy is about loads not charge sources.
What inverter do you have?
Do you have other dc loads?

It is a Epever 40a 4215.

Is that your only charge source?

If you bought the BMS from https://www.currentconnected.com/ Dexter can help you with what sounds like bms error.

 

[Jwtravel]

Low voltage disconnect strategy is about loads not charge sources.
What inverter do you have?
Do you have other dc loads?


Is that your only charge source?

If you bought the BMS from https://www.currentconnected.com/ Dexter can help you with what sounds like bms error.

I have a Giandel 24v 2000/4000 surge inverter and a 24v to 12v converter.
I’m running an Iceco 60l fridge freezer, diesel heater, water pump, a couple of led strips, I charge a few tool batteries, a maxx fan and cell phones and computer.
The SCC is my only charge source.
The error I’m getting in on my mppt.
I thought I was keeping it simple but dayum!

 

[John Frum]

The low voltage disconnect on your your inverter appears to be 19.6 volts which is way to low.
2.5 volts is dead empty for a lifepo4 cell 19.6 / 8 = 2.45 volts.
Tripping a fet based BMS at ~100 amps is sheer brutality.

 

[Jwtravel]

This is what my BMS parameters look like.

 

[John Frum]

Please tell me those are not the defaults.

 

[Jwtravel]

The low voltage disconnect on your your inverter appears to be 19.6 volts which is way to low.
2.5 volts is dead empty for a lifepo4 cell 19.6 / 8 = 2.45 volts.
Tripping a fet based BMS at ~100 amps is sheer brutality.

Well, wouldn’t I be avoiding this with the parameters with my mppt. If I set the low voltage disconnect to 25a the inverter should never be near it’s disconnect limits should it?
I hope I’m understanding these questions?

Please tell me those are not the defaults.

Ummm! I’ve screwed with all kinds of stuff. How do I get back to default settings?
Reset under system settings?

 

[John Frum]

Well, wouldn’t I be avoiding this with the parameters with my mppt.

No.
We are talking about loads not charge sources.

If I set the low voltage disconnect to 25a the inverter should never be near it’s disconnect limits should it?
I hope I’m understanding these questions?

I not sure you are.
The low voltage disconnect metric is volts.
Are you talking about a bms parameter or an inverter parameter or something else?

Ummm! I’ve screwed with all kinds of stuff. How do I get back to default settings?
Reset under system settings?

Sounds like a plan.
Assuming that the BMS has sensible defaults very little should need to be changed there.

 

[John Frum]

The bms protects the battery.
Use one of these to protect the bms.

ProLatch-R - Zero Volt drop Latching Relay, 160 amp marine grade relay

ProLatch-R -160 amp model - 0 volt drop, Programmable Latching Relay -12v or 24v autosense

www.sterling-power-usa.com

 

[Jwtravel]

No.
We are talking about loads not charge sources.


I not sure you are.
The low voltage disconnect metric is volts.
Are you talking about a bms parameter or an inverter parameter or something else?


Sounds like a plan.
Assuming that the BMS has sensible defaults very little should need to be changed there.

Ok, seems like these are perhaps the factory default settings. I just spoke with Dexter (what a helpful dude) and he is sending me his settings. I will reset those shortly.
So, the low voltage disconnect on the inverter disconnects if the battery falls below 19.6 per the manual. Is that correct?

 

[John Frum]

So, the low voltage disconnect on the inverter disconnects if the battery falls below 19.6 per the manual. Is that correct?

Yes and it will never hit 19.6 because that is below the lowest sane setting for the bms.
The bms low cell cutoff should be no lower than 2.5 volts and low pack cutoff should be no lower than 20 volts.
The bms is meant to be a "reserve parachute".
A good low voltage disconnect for the system loads is ~24 volts.
Drawing your cells down into the low knee is not a good idea for multiple reasons.

 

[John Frum]

As for charge parameters for your Eneramp cells.
Dexter should have the best idea on this.

 

[HighTechLab]

Hey, just found this thread! So I chatted on the phone with OP and we got everything squared away. There were two settings on the BMS that we adjusted back, namely the sum low volt disconnect and the cell high voltage disconnect.

Also gave OP a ton of info on the system and how things work. He has my cell phone number to call/text if he gets stuck and need more help.

 

[Jwtravel]

Hey everyone.
They folks at Current Connected have been so helpful. They answer the phone, they answer questions and they return phone calls. Their stuff is top notch.
And as of today my I’m harnessing the sun’s energy!
Thanks to all

 

[Just John]

This is what my BMS parameters look like.View attachment 58340

Set your balance start back to the default of 3.4v. Everyone thinks this will help keep them in balance, but since cells don't start to diverge until above 3.4v, you are actually undoing any top balance you have done. There is a reason the default is 3.4v.

Set your inverter disconnect to 25v, once you have the BMS set to 24v. I would actually recommend 3.0v per cell (for low voltage disconnect), and thus 24v for BMS and 25v for the inverter.

Edit for bad math, duh!

 

[HighTechLab]

Set your balance start back to the default of 3.4v. Everyone thinks this will help keep them in balance, but since cells don't start to diverge until above 3.4v, you are actually undoing any top balance you have done. There is a reason the default is 3.4v.

Set your inverter disconnect to 25v, once you have the BMS set to 24v. I would actually recommend 3.0v per cell (for low voltage disconnect), and thus 24v for BMS and 25v for the inverter.

Edit for bad math, duh!

Hey John,

With the cells he got from me, LVD can be at 2.5v/cell without any issue. 25v sum low voltage is too high, as the BMS will cut out before any inverter or other device.

Remember the BMS is there to protect the pack in the case of an emergency. It is not a charge/discharge controller, it is an emergency device.

A good analogy, is that you wouldn't use the front bumper of a modern car to slow you down when traffic on the highway comes to a stop...We have brakes, and if the brakes fail, the front bumper helps to soften the blow. BMSs aren't meant to constantly trip...All it takes is for one fet to get stuck closed and now you have zero safety measures.

Will did something similar to this on a video with a battery charger, leading to massive overcharging of a battery pack:

 

[Jwtravel]

Howdy folks. So, I have a couple fault alarms from the BMS. A sum volt high (level 2) and cell voltage high (level 1). What should I be looking at to correct this?

 

[John Frum]

Howdy folks. So, I have a couple fault alarms from the BMS. A sum volt high (level 2) and cell voltage high (level 1). What should I be looking at to correct this?

First of all what are these bms parameters set to?
Second what are the details of your charge profile?
Hint, the charge profile is defined on your charge source.
Different chargers use slightly different names.
The idea is to have your charge profile not bump into the bms limits.
Its not necessary and actually counter productive to have the bms trip because your charge profile bumps.

Also what is the cell delta when the bms tripped?