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So Confused about which BMS to go for

Berseker

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Mar 22, 2020
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So this issue has been thoroughly discussed, but i have gone through so many bms threads, am getting a lil confused.
so here is my planned setup.

IST INSTALL
8 x 280ah 3.2v lifepo4 cells, 1.5kw 24 dumb inverter. max load on the setup is a 250w submersible pump. / 4 x 280w panels connected to a 50amp or 60amp mppt charge controller - primary charging source, as its an offgrid setup.

am confused on 2 areas. - COMMON PORT SMART BMS WITH ACTIVE BALANCER, and slightly on standalone active balancer.
for this my planned setup, which is recommended?. common port or separate port bms?. would appreciate specific alibaba or aliexpress links of any recommended bms.
a 120amp or 150amp 8s bms should be ok??


2ND INSTALL
16 x 280ah 3.2v lifepo4 cells. / 3.2kw 48v hybrid inverter - sorotec / 10 x 280w solar panels. max load would be a 1.5hp submersible pump. am thinking of getting a 250amp smart bluetooth bms, but confused if common or dual port would be ideal.

i also need a bms that will keep track of battery cycle count, in addition to other useful parameters
 
Your 1st install doesn't have much of a load. A 100 amp BMS would work fine.

For your 2nd install, you need to determine the max load that the motor will pull. I suspect that a 48v battery won't need a 250 amp BMS, but you need to get the actual load to know that.

I have a common port BMS in my RV trailer. It's the Overkill Solar (aka JBD) BMS. I haven't had any problems. I believe it has a battery cycle counter, but it's been while since I looked through the parameters.
 
I suspect that a 48v battery won't need a 250 amp BMS, but you need to get the actual load to know that.
Wondering about the surge current since pump motors are notorious for high surge. It could be 10x the running current.
1.5hp = 1118W
1118W / 48V = 23A

Depending on the actual surge amps, 250A BMS might be about right (especially if using a value priced BMS).
 
Thanks gents for the responses. the 1.5hp sumo has a 6x surge at start up, so about 150amps @48v. i was reading that dual port bms, the amperage should be halved. so a 250amp dual port bms is actually 125amps charging, 250amps draw, and to extend its life, best to keep everything at 100amps. which at 48v, is easy for me.

so i have penciled down 2 bms, could you confirm if they are ok, or which is superior.

1. https://www.alibaba.com/product-det...ml?spm=a27ai.12350312.valid-supplier.3.Tgf5Dj

2. https://www.alibaba.com/product-det...ml?spm=a27ai.12350312.valid-supplier.3.XtzEck
 
Single Port BMS means it uses the same wiring for Charge & Discharge. So when it cuts off, it is OFF no charge/discharge.
Separate Port BMS uses one wire set for Discharge, One set for Charge (configs vary). It can cutoff either or both (depends on design).

Very FEW BMS' have Active Balancing and those that do, are typically very low power, <2A transfer rate. Many BMS' have Passive Balancing (which only burns off Hi Voltage) at less that 1.5A capacity and are generally of little value for Large Cells above 100AH.

Active Balancers can go up to 10A Transfer Rate (very very $$) and there are several types, NOT ALL Are Suitable for LFP. Large Capacity Cells above 100AH typically benefit from 5A Active Balancers. Capacitance Balancers work well... I myself use QNBBM Active Balancers on my Production Packs and Heltec Active Capacitance Balancers on my utility packs.

280AH Cells are capable of delivering 1C or 280A for One Hour. In such a build, my personal take is to build them to 250A Handling Capacity because what I use today likely won't be what I use tomorrow (Real World Lessons Learned) and we all know that "Stuff Happens" and all of a sudden we need more power & more access fro some reason... Ask anyone suffering wildfires, hurricanes, tornado's etc... OR who own Teenagers ! A Storm all of their own at times. Additionally having battery packs which can be swapped & moved between solar systems (I have 2) is only logical & rational and one which you'll appreciate IF you do ever need to swap them in/out or add onto.

Myself, my Production Packs use the Chargery BMS8T-300A BMS with 300A DCC (Solid State Contactor) and I use JBD 150A FET Based 8S BMS in my utility packs.

OF the TWO BMS' you linked, the QUCC 300A with Relay (as sod by EFire) is what I would choose from both of those. It uses a TE/Kilovac AANA Energy Saver Relay which is good. As for the Active Balancing at 260Ma is a laugh but far better than passive. Would probably be OK with perfect Matched & Batched cells (NOT Bulk stuff).

Hope it helps, Good Luck.
Steve_S
 
Single Port BMS means it uses the same wiring for Charge & Discharge. So when it cuts off, it is OFF no charge/discharge.
Separate Port BMS uses one wire set for Discharge, One set for Charge (configs vary). It can cutoff either or both (depends on design).

Very FEW BMS' have Active Balancing and those that do, are typically very low power, <2A transfer rate. Many BMS' have Passive Balancing (which only burns off Hi Voltage) at less that 1.5A capacity and are generally of little value for Large Cells above 100AH.

Active Balancers can go up to 10A Transfer Rate (very very $$) and there are several types, NOT ALL Are Suitable for LFP. Large Capacity Cells above 100AH typically benefit from 5A Active Balancers. Capacitance Balancers work well... I myself use QNBBM Active Balancers on my Production Packs and Heltec Active Capacitance Balancers on my utility packs.

280AH Cells are capable of delivering 1C or 280A for One Hour. In such a build, my personal take is to build them to 250A Handling Capacity because what I use today likely won't be what I use tomorrow (Real World Lessons Learned) and we all know that "Stuff Happens" and all of a sudden we need more power & more access fro some reason... Ask anyone suffering wildfires, hurricanes, tornado's etc... OR who own Teenagers ! A Storm all of their own at times. Additionally having battery packs which can be swapped & moved between solar systems (I have 2) is only logical & rational and one which you'll appreciate IF you do ever need to swap them in/out or add onto.

Myself, my Production Packs use the Chargery BMS8T-300A BMS with 300A DCC (Solid State Contactor) and I use JBD 150A FET Based 8S BMS in my utility packs.

OF the TWO BMS' you linked, the QUCC 300A with Relay (as sod by EFire) is what I would choose from both of those. It uses a TE/Kilovac AANA Energy Saver Relay which is good. As for the Active Balancing at 260Ma is a laugh but far better than passive. Would probably be OK with perfect Matched & Batched cells (NOT Bulk stuff).

Hope it helps, Good Luck.
Steve_S
Thanks for the concise analysis. To prevent damage to the SCC, am considering connecting the SCC directly to the battery, on the offchance that the bms initiates a LVD/HVD, so the SCC wont get damaged due to having the battery bank suddenly disconnected. this is for the single port QUCC bms. is there anything wrong with my proposed plan?
 
Thanks for the concise analysis. To prevent damage to the SCC, am considering connecting the SCC directly to the battery, on the offchance that the bms initiates a LVD/HVD, so the SCC wont get damaged due to having the battery bank suddenly disconnected. this is for the single port QUCC bms. is there anything wrong with my proposed plan?

This is probably not necessary. Most BMS (like my Overkill Solar/JBD) still have discharge active even though charge is disabled. If you hit the low voltage disconnect, do you really want your solar charge controller to continue draining the battery?

Will Prowse did a test of a few solar charge controllers and he was unable to kill them on a disconnect.
 
This is probably not necessary. Most BMS (like my Overkill Solar/JBD) still have discharge active even though charge is disabled. If you hit the low voltage disconnect, do you really want your solar charge controller to continue draining the battery?

Will Prowse did a test of a few solar charge controllers and he was unable to kill them on a disconnect.
Also, if you connect the SCC directly to the battery, the cycle count and SOC functions of the BMS will not work. The SCC will not be damaged if the BMS disconnects.
 
Single Port BMS means it uses the same wiring for Charge & Discharge. So when it cuts off, it is OFF no charge/discharge.
Separate Port BMS uses one wire set for Discharge, One set for Charge (configs vary). It can cutoff either or both (depends on design).
Some clarification. Most single port BMS's still offer the ability to selectively stop either charge or discharge. Only one wire, but still 2 sets of FET's.
The really cheap ones won't do this, so check the specs before you buy.
 
Some clarification. Most single port BMS's still offer the ability to selectively stop either charge or discharge. Only one wire, but still 2 sets of FET's.
The really cheap ones won't do this, so check the specs before you buy.
Always check specs, there are so many variations and well "Cheap" is well... All I can say, Stick with KNOWN GOOD BMS' like everything else to avoid issues.
 
Some clarification. Most single port BMS's still offer the ability to selectively stop either charge or discharge. Only one wire, but still 2 sets of FET's.
The really cheap ones won't do this, so check the specs before you buy.
YEAH, FINALLY WENT WITH THE dALY SINGLE PORT 250AMPS 16S BMS. IT HAS A TOGGLE FOR DISCHARGE AND CHARGE. i connected the scc through the bms, and the system is running great so far. had an ahha moment initially while trying to turn on the bms. Daly requires some tweaking to turn on
 
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