Best BMS to use

[Sgt Raven]

I am still trying to figure out the proper way to size a bms. i have a 12 volt 200 watt hour battery, a 40 amp charge controller and 2000 watt inverter. should the bms be sized to the charge controller, since that is what current it is seeing or to the battery. do i need a 200a bms or can i get away with a 100a bms?

I don't know which size, but the 100-200A is sized to your load, if I understand it right.

 

[jasonhc73]

I wonder how hard the learning curve was to get it all set up and dialed in? Any comments you care to share about that piece? Look like allot of good details to monitor and adjust that are making more sense to me as consider my investment in a 8 or 16 piece 24v 280 Ah or 560 Ah LifePO4 set . Looking to learn more about my BMS options here. Thanks for sharing ;+) Bill

Being a little bit OCD helps/hurts in this matter.
Sooooo... here goes.
New batteries from the same supplier and the same lot, 99.999% chance will never have an issue that the BMS will have to step in and shut everything down.

There are basically two ways to make a LiFePO4 battery fail.
Charging too hard when the cells are cold. (Yes you can charge below 0°C, but only do so very slowly.
And Overcharging the cells.
As soon as one or the other happens, the cells are irreversibly damaged. It is nothing at all like lead-acid batteries where you can equalize them. The ion exchange changes what you have inside the battery, and that cannot be undone.
You can do two things to keep this damage from happening.
One, don't overcharge the cells. Simple enough, just never charge more than 3.65V per cell. It is really that simple.
Two, don't charge when the battery cells are less than 1°C. Yuuup, it's that simple also.

Use the battery as storage energy centers and not motor starters and it will be very hard to over amp them also.
I modern decent inverter has cutoff limits that can be set and will for the most part work plenty good enough, without a BMS.

A BMS can really only actually do just three things. Monitor/display the voltage and temperature of the cells and open the electrical circuit.
So if you have new cells all made at the same time with the same materials from the same production line, 99.999% of the time these cells are going to all behave the same way, all the time. They will have the same Internal Resistance, so they will be able to charge and discharge at the same rate.

So, if you have used old abused cells, the likely hood of having matching cells is pretty slim. So the BMS can step in and interrupt catastrophic damage much sooner than a simple Inverter/Charger is capable of. One cell in a series of 16 and have extremely low IR and discharge 10 times faster than the rest of the cells, and if that one cell dive bombs less than 2.0V that entire battery is done, this is where the BMS would step in and stop the discharge. The same can be said the opposite direction when charging. If you charge more than 4.2V you can have a volcano.

The Charger only sees the entire battery, which is the average of all the cells. The BMS monitors each cell and will save the battery, but severely limits the entire usable capacity. The limit from the BMS is a good thing though because 50% usable battery is still far more than 0%!

 

[jasonhc73]

I don't know which size, but the 100-200A is sized to your load, if I understand it right.

I am still trying to figure out the proper way to size a bms. i have a 12 volt 200 watt hour battery, a 40 amp charge controller and 2000 watt inverter. should the bms be sized to the charge controller, since that is what current it is seeing or to the battery. do i need a 200a bms or can i get away with a 100a bms?

You size the BMS to what your loads will be. You can always oversize the BMS, and as long as it has a way to configure it, you can limit the AMPS through the configuration setup.

I set mine to 15AMP once, turned on my microwave and then my entire house got shutoff. I then set it to 150AMP like I meant to, and imagine that everything worked. The largest amp pull I have ever been able to do is 94 amps DC. That is running my entire house, heater, all the lights, TV, Home Theater blasting, Washer and Dryer all on, just as a test to see if it could do it, that was 8700 watts AC. My normal use is about 8 to 20 AMPS DC from the battery(That's what the BMSes sees), or 1200 watts AC. I have charged my car at 32amps AC a few times but that is kind of dumb, transferring the house battery to the car. But when you have 40 amps of solar blasting the battery, it doesn't really matter.

 

[mkaye]

a 2000W inverter needs ~166A for the max 2000W
a 100A BMS will shut down

 

[ghostwriter66]

SOOOO thats why several of us use the CHARGERY BMS -- it controls MECHANICAL relays .. I have a 600A relay on my 12V system which allows me to use probably a 8000 watt inverter if I ever had to ...

 

[Capt Bill]

you might be interested:

In getting ready for a battery order/ I just made my purchase of the Chargery BMS16T 2S-16S w accessories 300 amp/ on Alibaba express for $ 147.74 ... w shipping /to be shipped 23 hours / w Alibaba sales page saying: Free Shipping to United States via AliExpress Standard Shipping/ Estimated Delivery on 04/30

This is the Active type BMS: Chargery BMS16T on Alibba express

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In studying this forum for reference help in my choice related to my upcoming my DIY 24 v LifePO4 280 Ah build ( possibly 16 piece 560Ah build), and selecting a matching BMS.

... I just learned the "newer Active style of BMS deal with cell voltage imbalance via transporting volt - amps from one cell to the other, while many load balancing boards use transistor to just burn off the higher voltage cell levels as heat. That is the newer lesson I am registering in my brain!


I have recently gravitated from my consideration of the dependable and simple Daly common port (got one quote that fits a 24v LifePO4 8s 200 amp ... for $132 ... to Zeroing In on what appears to me as the newer/better technology, plus a way to monitor and adjust the way more details. Could be a headache for the non tech inclined folks. In studying these two options ... I leaned towards the newer Chargery / a sealed version w accessories

*************
Active type BMS: Chargery BMS16T BMS With 300A Shunt For 2S-16S Li-ion LiPo LiFePo4 LTO with 1.2A Balance
(a bunch of choices/ study before purchase:

7.03US $ 11% OFF|Balance 1.2A Chargery BMS16P V4.05 2S 16S lifepo4 LTO Li ion Battery Protection Board LCD 100A 300A 600A BMS Smart 10S 13S 8S|Battery Accessories| - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Balance 1.2A Chargery BMS16T V4.0 2S - 16S lifepo4 LTO Li-ion Battery BMS Smart | eBay

Add RS232 port, external device can read out all data from BMS16T. detection circuit. it can drive larger current. protection prevent BMS from overheating, and has a over current protection for each cell.

www.ebay.com

I like how this one I chose can be used with as little as 2 cells (S2), 8 cells (S8) or up to 16 cells (S2 - S16)
/ plus can handle a variety of battery voltages like 24v, and possible 48 v I could possibly upgrade to .

found great review on YouTube for a smaller 8s battery version:
Chargery BMS Overview for BYD 24 Volt Batteries

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and this BMS also look good to me: that fhost from Thailand just hooked up. fhost has some must see tips for anyone who obtained and setting up one of these. ( I think the Chargery BMS16T might be an easier set up? ... for sure FIND: the "New A grade lifepo4 cells, 120Ah for $37.50, 152Ah $43 and 280Ah for $79.80" thread for fhort Info. if you are setting one of these up/

Active Balance Battery Protection Board Smart BMS 14S ~ 24S 100A 150A 200A 300A 400A Phone APP Lifepo4 li-ion LTO 16S 20S

7.6US $ 24% OFF|1a/2a Active Balance Battery Protection Board Smart Bms 7s ~ 24s 100a 150a 300a Can Rs485 Gps App Lifepo4 Li-ion Lto Jk 16s 20s - Battery Accessories & Charger Accessories - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

m=a2g0o.cart.0.0.97833c00WaE76m&mp=1[/URL]

 

[LukeVader]

I think I'm giving up on the BMS from aliexpress. They said they had no stock of the 4s so I cancelled and ordered an 8s cause I'm now making a 24v battery anyway and now its just more of the same ........ we ship we ship but the tracking number after eight days is still not active and other parts I ordered from others on aliexpress are already in Canada. I want to buy one of the many options this ebay auction is selling. Which amp size do I need for my setup? 24v 560ah and 1540 watts of solar? Or is it always just get the biggest available? I know fuses arent like that though. How does the low temp cutoff work on this one? Have you tested it like Will does with a cup of ice water and confirms it actually works? Thanks.

How many cells will be in the series?

When you parallel batteries, they passively equalize to each other by being connected to each other. This is not the case for the series batteries though.

I use a blue-tooth controlled BMS, it has all these functions:

• Cell High Alarm
• Cell Low Alarm
• Cell Hight Protect
• Cell Low Protect
• Total Volt High Protect (this protects the entire battery, not just the cell)
• Total Volt Low Protect
• Charge Over Current Protect
• Discharge Over Current Protect (This means it will turn off the battery before you even come close to tripping a circuit breaker)
• Cell Difference to start Balancing
• Charge High-Temperature Protection
• Discharge High-Temperature Protection
• Mosfet high-temperature protection (The BMS has built-in protection for itself!)
• Charge Low-Temperature Protection
• Discharge Low-Temperature Protection
• System Shut down cell voltage - This is probably the most important protection you can have, never empty a LiFePO4 battery to its absolute minimum.

This is what I bought:

Smart Lifepo4 li-ion Lipo LTO Battery Protection Board BMS 48V 72V Bluetooth 20S | eBay

You can use 4p wire to connect bms and lcd display. 8S to 20S version : 8S to 20S Li-ion Battery; 8S to 20S Lifepo4 Battery; 8S to 20S LTO Battery. 7-16S Li-ion Battery; 8-16S Lifepo4 Battery; 8-16S Titanium LTO lithium.

www.ebay.com

I have a 16S setup. I have the little LCD screen with it, but you do not have to have the screen, everything is on your Bluetooth connected app. This BMS shows how to set up any number of series batteries, 2-20. The LCD shows capability to work with upto a 32S BMS.

I have already had the protect mode come on from Cell High Volt, Cell Low Volt, Discharge Over Current (I had it set way too low). My charger is controlled through its front panel, and a software program on a computer.

Controlling the voltage and current during a low-temperature setting is all on me to set it right.

 

[jasonhc73]

I think I'm giving up on the BMS from aliexpress. They said they had no stock of the 4s so I cancelled and ordered an 8s cause I'm now making a 24v battery anyway and now its just more of the same ........ we ship we ship but the tracking number after eight days is still not active and other parts I ordered from others on aliexpress are already in Canada. I want to buy one of the many options this ebay auction is selling. Which amp size do I need for my setup? 24v 560ah and 1540 watts of solar? Or is it always just get the biggest available? I know fuses arent like that though. How does the low temp cutoff work on this one? Have you tested it like Will does with a cup of ice water and confirms it actually works? Thanks.

I didn't bother testing the low temp cutoff. But my garage did get to 2°C once, so I set the BMS to 1ºC as the cutoff, and it cut off.

 

[johntaves]

You might consider the Electrodacus BMS. The current does not flow through it, so the size of the panels and loads etc don't matter. However, the inverter and chargers need to be able to start/stop from signals from the SBMS0. This seems to me an excellent choice because it allows the panels, battery, inverter, charger to grow

 

[Ragnar]

You can check for modular and plug n play system

Battery Management Systems

volrad.com.tr