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Building a 3P16S LiFePO4 Pack

Classicmac

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Joined
Jun 14, 2020
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Hi,

I'm looking at building a 48v pack with 48 3.2v 280Ah LiFePO4 cells 3P16S. I'm thinking of splitting the pack in to 2 levels using a shelf. Is there a more efficient way to build it than the attached picture?

I'm looking at the Chargery BMS16T along with the DCC300HB DCC Contactor.

Currently looking at the Sol-Ark 12k as the inverter/charge controller. About 9.5k in panels. 30 x 315w panels.

Anyone have any feedback on that setup?

Thanks,

Michael
 

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Unless you are using perfectly and properly Matched, Batched & Binned cells (provided with cell test reports) you will have issues with balancing & runner cells. No Joke, plain & simple.
Using the 280's which are popular right now:
* The Matched cells all test out between 282AH-292AH and their IR & Impedance is identical or very close throughout their entire operating range, whether charging or discharging.
* Bulk Commodity cells typically test between 270AH-282AH and their IR will diverge at the hi & low end of their working voltage rangewhich most often presents as Runner Cells which will reach cutoff point well before the others within a pack. Put THAT into a Parallel config and thing get whacky... There IS a lot of unhappy experiences with that noted through the forum (and people don't like to admit they goofed, so many more not mentioned).

There is little to gain and you lose some reliability by building a pack with parallel cells... These are not EV's with 3.5AH Li-Ion cells that are severely tested, matched & batched. If it is to save bucks on a BMS, it's like roofing your house with paper only. It really is not the place to save chump change. Your batteries, equipment & life are worth more than that.

Honestly, the best approach that allows for Load Sharing (reduced system stress), failover in the event of failures / errors and the fault tolerance that comes from that.
3 Packs of 16S in Parallel will split the Discharge load between the 3 packs as well as charge input. (will charge same as if one pack)
Each pack if setup properly can handle the full Charge / Discharge capacity in the event of a pack shutting down.

THE ONE GOTCHA !
With packs in parallel, it really does work well and you can expand the bank if/when needed or wanted. BUT the lurking gotcha.... Assume you have 3x 280AH packs in parallel and want to add another pack. Another 280 would be perfect obviously but if the new pack is much larger / smaller the potential for odd things happening increases, generally if less than 100AH difference it's not bad because the voltage curves are such, it really isn't an issue. If greater than 100AH difference, then you'll get premature cutoffs and such when at the edges of the voltage curve, pending on BMS, this could cause the lower AH cells to draw from the higher AH pack. It can be dealt with but requires fusting and planning.

BTW: With large capacity LFP cells like we use, Passive Balancing is not very helpful because the cells are so big and passive balancing only burns off power from Hi Voltage cells. Active Balancing actually transfers power from Hi Cells to Lo Cells and some can do up to 10A (Not Cheap). I myself use a QNBBM-8S on each of my battery packs. I have 2x 280AH Bulk cells, 1X 280AH Matched & Batched, 2X 175AH Used EV LFP packs (which I was going to mod into a 350AH but the parallel wall hit)

REF: QNBBM Active Balancers by Deligreen: https://deligreen.en.alibaba.com/productgrouplist-806516208/QNBBM_Balancer.html?

Hope it helps, Good Luck.
 
Unless you are using perfectly and properly Matched, Batched & Binned cells (provided with cell test reports) you will have issues with balancing & runner cells. No Joke, plain & simple.
Using the 280's which are popular right now:
* The Matched cells all test out between 282AH-292AH and their IR & Impedance is identical or very close throughout their entire operating range, whether charging or discharging.
* Bulk Commodity cells typically test between 270AH-282AH and their IR will diverge at the hi & low end of their working voltage rangewhich most often presents as Runner Cells which will reach cutoff point well before the others within a pack. Put THAT into a Parallel config and thing get whacky... There IS a lot of unhappy experiences with that noted through the forum (and people don't like to admit they goofed, so many more not mentioned).

There is little to gain and you lose some reliability by building a pack with parallel cells... These are not EV's with 3.5AH Li-Ion cells that are severely tested, matched & batched. If it is to save bucks on a BMS, it's like roofing your house with paper only. It really is not the place to save chump change. Your batteries, equipment & life are worth more than that.

Honestly, the best approach that allows for Load Sharing (reduced system stress), failover in the event of failures / errors and the fault tolerance that comes from that.
3 Packs of 16S in Parallel will split the Discharge load between the 3 packs as well as charge input. (will charge same as if one pack)
Each pack if setup properly can handle the full Charge / Discharge capacity in the event of a pack shutting down.

THE ONE GOTCHA !
With packs in parallel, it really does work well and you can expand the bank if/when needed or wanted. BUT the lurking gotcha.... Assume you have 3x 280AH packs in parallel and want to add another pack. Another 280 would be perfect obviously but if the new pack is much larger / smaller the potential for odd things happening increases, generally if less than 100AH difference it's not bad because the voltage curves are such, it really isn't an issue. If greater than 100AH difference, then you'll get premature cutoffs and such when at the edges of the voltage curve, pending on BMS, this could cause the lower AH cells to draw from the higher AH pack. It can be dealt with but requires fusting and planning.

BTW: With large capacity LFP cells like we use, Passive Balancing is not very helpful because the cells are so big and passive balancing only burns off power from Hi Voltage cells. Active Balancing actually transfers power from Hi Cells to Lo Cells and some can do up to 10A (Not Cheap). I myself use a QNBBM-8S on each of my battery packs. I have 2x 280AH Bulk cells, 1X 280AH Matched & Batched, 2X 175AH Used EV LFP packs (which I was going to mod into a 350AH but the parallel wall hit)

REF: QNBBM Active Balancers by Deligreen: https://deligreen.en.alibaba.com/productgrouplist-806516208/QNBBM_Balancer.html?

Hope it helps, Good Luck.
Thank you so much for taking the time to reply to my post.

I'm looking at the 280Ah (I'm told they test at around 290) matched cells from Shenzhen Luyuan Technology Co.

Is there a better option than those cells or should I be putting them in another configuration?

I believe the Chargery BMS16T offers active balancing at up to 1.2A per cell. Not sure if their claims are true. Would I run in to issues balancing cells that are in parallel. Does anyone have any feedback on that?

Should I be using the active balancers you linked instead? I'm guessing I would still want a BMS for high/low voltage disconnect?

Thanks!

Michael
 
If you bought from Amy @ Luyuan, You GOT what you paid for and did good.
They will likely work in parallel fine after a very good Top Balancing.
The reliability & fault tolerance with separate packs in parallel is still a more reliable & dependable way to go.
I do hope you realize what that is going to weigh, (5kg/11lbs per cell).

Chargery BMS is passive balancing only. I use BMS8T's and know a bit about Chargery.
An Active Balancer is NOT a BMS, it is only a balancer. The QNBBM's are reasonable and known good. there are many out there that are crap. There is also Heltec who offers a variety for different chemistries & at different Amperage ratings & Types according to the application which can climb into serious bucks fast.

have a look at my "About My System" link in my signature & other links, they'll get ya going with a lot of the info you'll be looking for.
Hope it helps, Good Luck
 
I haven't pulled the trigger on the batteries yet. Just making sure my configuration is sound and that I have everything I need. Based on your experience with Chargery would you go with the 16T or would another BMS manufacturer or model be better?

Do I understand correctly that if I go with the Chargery 16T I should add an active top balancer as well?

Thanks for all of the information. I'm still pretty new here. I'm going to read through your material and hopefully get up to speed.
 
Ideally a SmartBMS with Active Balancer built-in would be a winning combo. Jason from Chargery worked with us here and they developed a new "P" Series with Active Balancing & better Communication interfaces but thanks to chip shortage production is held back. I have no idea when they will be available which is a Real Bummer. A BMS with Active Balancing is a Rare Bird at this point and I do not know of any that I could / would recommend, just not enough info.

Top Balancing is when we Manually charge all the cells in Parallel to 100% full and saturated prior to assembling a battery pack into its final Series Configuration.

An Active balancer only manages the cells to keep them close together in voltage and will transfer voltage from Hi Cells to Low cells internally within the pack. This reduces/prevents cells from deviating too much maximizing the useable capacity.

I myself have really come to appreciate having an Active Balancer on all the packs but then I am also used mixed grades/classes. With the Matched cells from Luyuan/AMY you likely would not "need" an Active Balancer but I cannot be certain and it's also up to you personally as to how finicky you are.

I Like Chargery and like all other "Generic" BMS' they have their Quirks & Foibles because there are Compromises that have to be made so these can be flexible. Remember a BMS in an EV or Genuine Tesla PowerWall for example are Custom Built & Programmed for the very specific application, but in the Aftermarket like our DIY Universe the BMS' have to be generic because who knows what cells, size/capacity/chemistry an End User will put together.

Chargery BMS16T 300A with External Power Adapter (to power BMS from BATT terminals as opposed to through the Cell Harness which causes errors)
Chargery DCC-300 with ISO Board.
Use the DCC on the POSITIVE side (WITH ISO Board between DCC & BMS) and that takes care of the precharge concerns and flattens some jitter.

Hope it helps, Good Luck
 
Thank you so much for taking the time to reply to my post.

I'm looking at the 280Ah (I'm told they test at around 290) matched cells from Shenzhen Luyuan Technology Co.

Is there a better option than those cells or should I be putting them in another configuration?

I believe the Chargery BMS16T offers active balancing at up to 1.2A per cell. Not sure if their claims are true. Would I run in to issues balancing cells that are in parallel. Does anyone have any feedback on that?

Should I be using the active balancers you linked instead? I'm guessing I would still want a BMS for high/low voltage disconnect?

Thanks!

Michael

The true grade A cells like Amy sells should pretty much eliminate the need for an active balancer. You can always add it later if you find it necessary. Remember, 3.65v on every cell at the same time is NOT a normal charge. A "normal" charge as defined by Eve will settle to 3.4v per cell after an hour with no load. For top balancing, you want them to settle above 3.45v, preferably above 3.5v when measured 24 hours later.
 
Thank you everyone for your feedback.

After thinking more about it I'm contemplating switching to 16S3P. That would allow me to have each cell monitored by a BMS.

Instead of the 300A Chargery I'm thinking of doing 3 150A Daly BMS. The Sol-Ark charge controller/inverter says it can do 185A continuous charging output so hopefully even if I have one BMS shut down the other two will be able to handle the load.

Is it a bad idea to set it up in that configuration? Is there a better way to do this?
 
3 Packs with a 16S BMS each is the best way, really, it is the most tolerant and something to be said for independence in case stuff happens. But as you are building packs that have the physical capacity to handle 280A out & 140A in and you going to Handicap it with a Daly 150A BMS ?
Bicycle tires on a Corvette. Honestly, this is a shortcut that has little value and one which most likely results in a Grumle or Two.

At a minimum, I would get a BMS that can deliver 250A and take a 125A charge.
IF FET Based (regardless of brand) oversize it by 20% to provide safety margin (much experience here with that NEED, people learned at their cost) that the labels specs are the "Edge Limits".

No BMS is perfect in our context, they all have compromised by the very nature of this target market and having to be flexible & adaptable. Each BMS brand/type has quirks, foibles and even lurking gotcha's, which includes the real cheapo's right up to REC, Orion, and the other High End "After Market" ones.

The BMS is the brains & muscle power guarding and maintaining your cell investment and the last stop to protect it. For me, that is a huge investment and it's important to keep it just right, certainly not worth risking by skimping.
 
3 Packs with a 16S BMS each is the best way, really, it is the most tolerant and something to be said for independence in case stuff happens. But as you are building packs that have the physical capacity to handle 280A out & 140A in and you going to Handicap it with a Daly 150A BMS ?
Bicycle tires on a Corvette. Honestly, this is a shortcut that has little value and one which most likely results in a Grumle or Two.

At a minimum, I would get a BMS that can deliver 250A and take a 125A charge.
IF FET Based (regardless of brand) oversize it by 20% to provide safety margin (much experience here with that NEED, people learned at their cost) that the labels specs are the "Edge Limits".

You took the words right out of my mouth.
3 parallel battery packs = good
Each should be able to handle the load
 
I am in a similar situation, had planned for 3p16s. Had planned to use CATL 302Ah cells from Jenny Wu - Docan Technology. Paired with an Overkill Solar 48V 16S BMS.

I'm rethinking based on the recommendations here. Also, the Overkill is out of stock.

Classicmac, can you share which BMS you ended up using? I'm looking for an alternative to the Overkill. Hoping to complete this project over the holidays.
 
I am in a similar situation, had planned for 3p16s. Had planned to use CATL 302Ah cells from Jenny Wu - Docan Technology. Paired with an Overkill Solar 48V 16S BMS.

I'm rethinking based on the recommendations here. Also, the Overkill is out of stock.

Classicmac, can you share which BMS you ended up using? I'm looking for an alternative to the Overkill. Hoping to complete this project over the holidays.
Just order the JBD. The Overkill has better warranty and support, but it is a JBD.
 
I am in a similar situation, had planned for 3p16s. Had planned to use CATL 302Ah cells from Jenny Wu - Docan Technology. Paired with an Overkill Solar 48V 16S BMS.

I'm rethinking based on the recommendations here. Also, the Overkill is out of stock.

Classicmac, can you share which BMS you ended up using? I'm looking for an alternative to the Overkill. Hoping to complete this project over the holidays.
I ended up getting 3x 16S Daly 250A BMS. I just received my shipment of batteries and BMSs last week. I built my 8s packs but haven't built the 16s packs yet. I also ended up getting Daly 150A for the 8s packs.

I have only been running the 8S Daly for less than a day but so far I am happy. It was easy to configure and monitor through Bluetooth using the app.
 
I ended up getting 3x 16S Daly 250A BMS. I just received my shipment of batteries and BMSs last week. I built my 8s packs but haven't built the 16s packs yet. I also ended up getting Daly 150A for the 8s packs.

I have only been running the 8S Daly for less than a day but so far I am happy. It was easy to configure and monitor through Bluetooth using the app.
Do you mind sharing the prices you paid to get the BMS's and batteries to your door? Was it a 2-3month wait time?
 
Things will probably be different for you. I'm in Hawaii and had to find my own shipping. I worked with a local customs broker for the customs process. Total time for my shipment was about two months.

If everything went perfectly it could be less for you. This is because Hawaii shipments go to the U.S. Mainland first before coming to Hawaii. I think there was also about a week and a half from the time the container arrived until customs inspected it and it became available for pickup.
 
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