can I use two of these( one for two 14s200p strings) BMSs:https://www.banggood.com/6S-to-28S-...-p-1658226.html?rmmds=search&cur_warehouse=CNdaromer said:You need 1 bms per battery string or a bms that can take 4 strings such as Batrium or DIY BMS.
You need a bms that can handle the full load on one string. If you never plan to remove any string thats that the 3 inverters in total can draw from the battery bank
A 4048 can easily pull up to 8kW from the battery in short time. The max charging from solar alone is 80a but combined with ac its 160A....
8Kw at lets say lowest voltage of 40V is 200A.. Thats a single unit. 3 units is then 600A.
You need to be able to surge 600A from the Battery bank.
Having 4 strings of each 14s200p should handle this. You need atleast 200A bms per battery string at minimum if you ask me!
Will it be cheap? NO. But this is something you should design for before you start building and buying stuff. You really should get a proper BMS that can handle it. You already have tons of cells, 3 rather larger inverters.. And i guess you will power a more expensive house?
Look into DIY bms and then atleast one larger 500A ABB shunt example S5 series.
Not in a bad light but batruim is not expensive comparing to the work it does. And can do any kind of series and parallel you want.Also you can balance from as low as 3.70v all the way to 4.20v. Can handle 350Amp charge current (in my setup) amd drain 400Amps! Chinese bms is no good. not relaible. But its my thinking.Ibiza said:i am finishing my 4x14s200p 18650 li-ionpower wall.
do I need four 70A BMS's as I use 3 4048 PIP's. each inverter can draw 80A.
please advise which BMS to useexcept Batrium which I can't afford.
Charly144 said:I went the route with 5 china bms and now Im switching to 5 strings each with diybms and 5 large relays. Be aware that in case 4 of my 5 bms switched off, all load is running over one bms. This happened several times in my setup and burned all my bmses...
daromer said:And if you cant afford batrium the question is how much you want to tinker? DIY BMS if you know your way around programming and soldering.
Daly, Ant and some others offers higher end Ebike BMS systems that can and many use for powerwalls with set able values.
daromer said:Thats why you dont add multiple small bms in parallel. Its just wrong way of thinking and in the end what happens is what you found out. A bms must be able to operate alone IF something happens.
Dont use relay. Use a breaker with shunt trip function.
Ant aning others are ebike bms systems a d therefore thats why they are designed like that
supplier says it's 300A unit. my 3inverter can draw 12000w/48v witch is 250A if my math is correct.daromer said:Costly one when people dont listen
Ibiza then i hope its designed so that 1 bms can take full load easily? Else you end up with same issues and a waste of money
I apologize for delayed response @DAROMER . your post is very precious for us who are not so familyar with electronics and we can learn a lot from you and other guys who are willing to share their knowledge and experience .daromer said:if you got 3 4kw inverters your mx is alot more.
12kw is the nominal draw on the inverter side. What is the max of the inverters? If its pip 4kw inverter its 8kw..
Neither less 12kw nominal is easy 15kw at the battery side. At the battery side lets say you run 14s?
14*2.8V as minimum during sag thats 39V. 15000/39 = 390A. So just with the nominal max wattage you are way above what that bms can take!!
Then guess what happens if you have a spike as an example. If its the pip the pip is capable of 2x the factor and thats up towards 30kW at the battery side during couple of seconds. You can do the math
Note that above is worst scenarios BUT that's what the BMS is there to protect for.