16 3.2v cells, 1 BMS or 2

[Jimmynik1]

Goal is a 564 (or whatever is available at the time) bank. Comprised of 16 cells in a 8s 2p configuration.
Is there a correct way to manage this system in regarding to 1 or 2 BMS being used?
I was initially going to with 2 Daly 100a 8s BMS's but then was encouraged to use the same BMS but on the entire bank, from what I gather that meant not every individual battery would have a wire to it, rather making the 16 cells into 8 cells monitoring paralleled pairs. If only one BMS of the same size is used vs two wouldn't that also reduce my available current draw and charge rate?
Not sure if that makes sense so if I need to clarify please advise, but I'm sure someone has done this or at least understands what I'm trying to say.
Lastly once that is resolved I'm searching for the most user friendly BMS for this.
I pulled these two pictures from a similar thread, on the first photo, C and D make the most sense for me as I want to stick this on a cart and have it be somewhat mobile, second photo is how I was planning on doing this before I knew one BMS was an option, but ultimately looking for the best and safest way to do this.
Appreciate any and all advice.

 

[Samsonite801]

Me, I prefer 2 BMS, to have more redundancy. Just treat them as separate batteries, and parallel them together. Put a separate breaker on each bank so if something shorts on that pack it can break off the main bus, and other battery stays up. Also allows for maintenance on a bank without taking both legs offline.

Have you looked at Overkill's 100a 8s BMS for 24v banks?

 

[Jimmynik1]

Me, I prefer 2 BMS, to have more redundancy. Just treat them as separate batteries, and parallel them together. Put a separate breaker on each bank so if something shorts on that pack it can break off the main bus, and other battery stays up. Also allows for maintenance on a bank without taking both legs offline.

Have you looked at Overkill's 100a 8s BMS for 24v banks?

Thanks, I'm leaning that way too.
Yea I've been to overkills site, sent a email months ago asking a really simple question and planned to order when I heard back. Never did. I saw their posts about being busy and what not but solely based on them basically saying they're busy and wont answer questions turned me off. Before anyone jumps down my throat, I run a small business too and the way I avoid having a huge backlog is to simply not take orders for services/products I can't provide at that moment or in a reasonable amount of time and if I did I most certainly would not take money upfront before even having product on hand. Super unpopular opinion I know, but I feel as though I work super hard for the little I have and the money I spend should be appreciated by that business, additionally for a China manufactured product anyway I'd rather not deal with any headache or extended wait times.
Anyway I like the look of the Daly and think 2 100a ones will work for my application.

 

[Samsonite801]

Yeah, plenty of people here use the Daly BMS, I don't have any experience with them. They seem good from many people's opinions here. I had thought about a set for mine before, but it seemed to me it could be hit-miss as to whether the low-temp charge cutoff actually worked (under some of Will's testing). I think it sometimes would depending on the model, but there wasn't like a chart showing which ones it would actually work on or not.

That was really the only reason I went for the OverKill because they explicitly state on the product page, that the low-temp cutoff for sure works. I live in a region where it gets cold in the Winter so it was an important feature for me to protect my batteries from charging at freezing temps...

Anyways good luck, report back with a thread on the Daly if it all works out good for you and whatnot...

 

[HRTKD]

Daly would not be my first choice. Probably not even my second or third choice.

Overkill Solar first, then JBD (similar thing, different source). After that, maybe REC or Chargery. Batrium if I had a bigger, more complicated battery configuration.

There is a new source for the JBD BMS here on the forum. He should have stock any day now.

 

[Jimmynik1]

Daly would not be my first choice. Probably not even my second or third choice.

Overkill Solar first, then JBD (similar thing, different source). After that, maybe REC or Chargery. Batrium if I had a bigger, more complicated battery configuration.

There is a new source for the JBD BMS here on the forum. He should have stock any day now.

Did you have a bad experience with Daly? Do you recall the name of the jbd supplier?

 

[HRTKD]

Did you have a bad experience with Daly? Do you recall the name of the jbd supplier?

See this thread for the new source:

JBD BMS USA Inventory - Is there Community Interest?

Hi everyone! My purpose of this thread is to ask the community if they would be interested in a line of BMS units that I would like to offer for sale. First thing, I love the members of this community and value their feedback so strongly. All I want is feedback because my business would...

diysolarforum.com

 

[Just John]

Anyway I like the look of the Daly and think 2 100a ones will work for my application.

If all you need is 100 amps, big mistake to go with the Daly.
JBD makes a much more trouble free BMS. That's what Overkill uses (with better testing).

 

[Just John]

Did you have a bad experience with Daly? Do you recall the name of the jbd supplier?

I own 3 Daly, and 2 JBD. If it meets your needs for current, the JBD is much less trouble.

@HighTechLab should have stock soon. I believe his website is currentconnected.com

 

[Cheap 4-life]

What is the amp hours of the 2 cells in parallel. Why not use one 8s bms? Are these cells matched/batched? Will you be using a lot of amps to charge/discharge?

 

[Jimmynik1]

If all you need is 100 amps, big mistake to go with the Daly.
JBD makes a much more trouble free BMS. That's what Overkill uses (with better testing).

What's the issue with the Dalys?

 

[Jimmynik1]

I own 3 Daly, and 2 JBD. If it meets your needs for current, the JBD is much less trouble.

@HighTechLab should have stock soon. I believe his website is currentconnected.com

Yeah I messaged him, waiting for reply.

 

[Just John]

What's the issue with the Dalys?

Poor quality control, poor documentation, poor support, poor calibration.
That about sums it up.

That said, if you get one with no problems, they work well. Don't heat up under load, low temperature disconnect works, and generally do their job well.

Out of my sample size of 3, one had problems.
Look around the board, count how many people have had problems with their Daly.

 

[Just John]

Did you have a bad experience with Daly? Do you recall the name of the jbd supplier?

FYI, this is where I purchased mine (12v model):

37.25US $ 42% OFF|Jbd Smart Bms 4s Lifepo4 100a With Free Bluetooth 3s 12v Bms Board 150a 120a 100a 80a 60a For Lithium Battery 3.2v Lifepo4 Bms - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

 

[Samsonite801]

Since I never tried a Daly, I cannot say about a particular experience with them, but I have seen that in many cases from other people, the low temperature charge cutoff didn't work. But some models it supposedly did work. I remember Will testing one that said it should work, like it had an external temp probe, but it didn't actually work. So to me that said it could be hit-miss if I tried a Daly (where I needed confidence it would provide this feature).

The JBD ones that OverKill sold he had actually tested and confirmed low-temp charging cutoff works. If I look up just some random JBD specs I find (off a 16s), I see a lot more parameters listed in general regarding to temp specs:



If you live in a climate that never freezes or always have the batteries in a temp controlled environment then you may not care about low temp charging cutoff, but in my case, I am not sure exactly what conditions the batteries will be exposed to yet on my 48v banks. I know my 12v banks for the RV use, will definitely be in the cold. I will use heat pads with them, but the low temp cutoff is the last line of defense to protect your battery investment.

 

[Steve_S]

I'd like to clear up a few ticks in here.

A 24V 8S battery pack be it1P,2P or 3P with cells in parallel is still an 8S pack.
Paralleled cells are viewed as one cell by the BMS, because in essence, they are.
Bulk Cells that are not properly Matched & Batched but only Voltage & IR matched (which is what most vendors do) are bad candidates to parallel.

You did not mention what AmpHour sized cells you are considering and what your load usage will be in watts/amps.
An example with the currently popular 280AH cells.
They are capable of 1C output of 280A for one hour, and 0.5C Charge input of 140A for two hours. These are the Maximums.
The general recommendation is not to exceed 250A draw from a battery bank.
12V@250A=3000W (25A AC), 24V@250A=6000W (50A AC), 48V@250A=12,000W (100A AC)

A BMS should be capable of handling not only the normal draws and high draws but also the surge capacities that will happen whenever a motor or heavy device starts and that can be quite significant. Therefore it should be sized accordingly. The BMS is the guard dog / emergency break, that's its primary job, other features/functions are a bonus. NB: These BMS' for DIY and "generic" or compromise devices because of the multitude of applications and use cases they must be flexible and adaptable, which sometimes means little effort, and other times it may be a more complex effort. They all have their own peculiar quirks & foibles as a result but none too nuts.

BMS' should also be "derated", many companies Power handling numbers are too close to performance edge of the components. So if you are going to handle 200A then get the next size up BMS. I'm built for 250A handling and all the gear (BMS' Relays, etc) is 300A. 20% Larger than what you need is often quite good for "comfort" and longevity.

As for TWO BMS' on one pack, I've never heard of such a thing, it's pointless and adds more complexity to create issues. KISS RULES ALWAYS !

Hope it helps, Good Luck. PS, have a look at the links in my signature, the assembly guide will help you quite a bit.
Steve

 

[Just John]

Since I never tried a Daly, I cannot say about a particular experience with them, but I have seen that in many cases from other people, the low temperature charge cutoff didn't work. But some models it supposedly did work. I remember Will testing one that said it should work, like it had an external temp probe, but it didn't actually work. So to me that said it could be hit-miss if I tried a Daly (where I needed confidence it would provide this feature).

The JBD ones that OverKill sold he had actually tested and confirmed low-temp charging cutoff works. If I look up just some random JBD specs I find (off a 16s), I see a lot more parameters listed in general regarding to temp specs:

View attachment 56467

If you live in a climate that never freezes or always have the batteries in a temp controlled environment then you may not care about low temp charging cutoff, but in my case, I am not sure exactly what conditions the batteries will be exposed to yet on my 48v banks. I know my 12v banks for the RV use, will definitely be in the cold. I will use heat pads with them, but the low temp cutoff is the last line of defense to protect your battery investment.

It works fine (low temperature cutoff) in the newer models that support/have it. Just unplug the temperature sensor, it won't start/boot the BMS if you do. I have certainly tested it on the three Daly BMS I own. If it doesn't have an external temperature sensor, it doesn't support it. Basically, their models with NTC listed (their abbreviation for temperature sensor) have it.

Certainly the JBD is a better quality product if it meets your needs for current draw.
Some of the JBD models have heat pad ports built in.

67.08US $ 34% OFF|JBD Smart Bms 4S 12V Free Bluetooth 100A 150A Same Port Balance Board with Heating For Lithium Battery Inverter 12V Power Supply|Battery Accessories| - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

 

[Steve_S]

8S - search result, Dongguan Jiabaida Electronic Technology Co., Ltd.

Search results for 8S from Dongguan Jiabaida Electronic Technology Co., Ltd.. Get exactly what you're looking for.

dgjbd.en.alibaba.com

 

[HRTKD]

As for TWO BMS' on one pack, I've never heard of such a thing, it's pointless and adds more complexity to create issues. KISS RULES ALWAYS !

There are a couple threads where users are either asking about this, or have implemented it. One of the forum members that implemented it and reported back that it worked subsequently decided to switch to multiple batteries with a BMS on each battery.

Not saying I agree with the concept (which I don't), just saying it has been posted about here.

 

[Jimmynik1]

A 24V 8S battery pack be it1P,2P or 3P with cells in parallel is still an 8S pack.

Great info thanks, cleared it up for me.

You did not mention what AmpHour sized cells you are considering and what your load usage will be in watts/amps.

When I said initially the goal was for a 564ah bank I was intending on using 282s or 300s, whichever is easier to get at the time.
It'll be really for backup with maybe a 10a @ 120v constant draw.

BMS' should also be "derated", many companies Power handling numbers are too close to performance edge of the components. So if you are going to handle 200A then get the next size up BMS. I'm built for 250A handling and all the gear (BMS' Relays, etc) is 300A. 20% Larger than what you need is often quite good for "comfort" and longevity.

I think with a max constant draw of 55adc id be fine going with the 8s150a bms in the off chance I surge more at some point.

As for TWO BMS' on one pack, I've never heard of such a thing, it's pointless and adds more complexity to create issues. KISS RULES ALWAYS !

I only knew of doing it with two until I was told one was an option.
Someone showed me this first picture long ago and I've been going off of it for a while but you suggest using any setup the second photo's?