DIYBMS v4

Question, as i have not found a clear answer.

  1. Can i use multiple AllInOne boards in series (for multiple banks)?
  2. do i have to connect all batteries to one diy shunt? or can i have separate?

Request: i would be interesting if the Victron shund could integrated into the diybms

Yes multiple all-in-one boards are supported for multiple banks

Unfortunately, only a single current shunt is supported - so this would have to go into the main feed to the entire battery.

Yeah - just in the code :frowning:

Thanks for the answer.
As i use the Victron Lynx, the Lynx shunt would be a logical step. Are there plans to import those values into diybms?

None at the moment, sorry.

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Hello, do you have done simulate pylontech over RS485? Thank you.

I can see it in setting DIYBMS, but I am not able to communicate with Axpert King II - firmware 50.05.
So I do not know if is problem in Axpert or DIYBMS.

I have - v4.61; Compiled: 2024-02-06T12:40:00.542Z; 16x v4.5
p.s. it is restarting once per day

I will try firmware from ruza87, I red it should be working with RS485 comm. I will see if it is working to me, if not then I update Axperts firmware.

I would like to ask, if I “downgrade” DIYBMS firmware, can I leave memory card without changes, will it remember correction voltage for each modul and other settings, or I should erase it?
Thank you very much.

It should be okay to leave the memory card in, you will likely need to restore the previous settings after a major upgrade/downgrade - so worth downloading the configuration file to your laptop first.

(this is all done from the storage menu/flash memory page - click Save Configuration, then click the filename to download)

Hello, I am looking for a diy solution for a bms to a home solar and this project seems exactly what i need. My only question is to number of cells. I want to build a battery for a HV hybrid and i need about 130 to 140 lfp cells in seris. I watched some video and in some there was a limit to 100 cells… is it sw or hw limit?

thank you

I would always recommend using low voltage DC where you can. Are you looking to use off the shelf LFP cells? If so, build 16S packs (48V nominal) and stay safe!

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I built 20+ lfp batteries so far… first with daly bms and now only with jk bms. I know it is working great, but most of those batteries were used for 3kW UPS or 5kW hybrid solar, but i want to build my house with 20kWp solar and that is really a lot for a 48V. Other problem is that 10kW 48V deye hybrid cost almost the same as 20kW deye HV hybrid… that HV hybrid has a limit of 37A to or from battery, and battery voltage needs to be within 160-700V so for full power it needs somewhere about 180 cells in series… and that is really expensive. Maybe this is not the way to go…

not really you can charge 300Ah cells with 150A. you need 3x 16s packs to stay in this limit
but i suggest to use 4x 16s because its is not so much capacity for 20kwp solar.
keep in mind the zero load power consumption is really high if the inverter is over 10kw. important for winter.

so use 4 16s paralel and you can use the victron lynx power in

your system can look similar like mine
now im using 2packs 32cells 230Ah each in 2p config

you have done it really nice… I forgot to mention that 20kW HV hybrid costs pretty much the same as 10kW 48V hybrid. Thats is also the reason why i am considering it and trying to find possible solution.

you forgot the redundancy if one cell off your 120 goes bad then the whole pack will shut down.
its not the costs what you should first look for.

i have a overall system efficency of 93%, this is not bad for a 48v system

if yo dont need the 20kw most of the time the efficency will be lower then with a 10kw inverter
deye has also a 12kw 48v inverter SUN-12K -SG04LP3-EU

so if you decide to go 48v you just need 4x the new jk inverter bms it can talk via can to the deye
i am using diy bms as a second stage for controls if the diy bms do strange things i have a dumb seplos bms to protect the battery

for 90% of the load i will be fine with single phase 5kW inverter i know…
10 or 12kW cost pretty much the same.
I am also considering buying a tesla and it will charge mostly over night so inverter power and battery capacity is also a good thing here.

But hey… this is so far far away… i dont have a house yet… I am looking for options while waiting for building permit.

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in our pv diy forum i read sometimes users want to build a hv diy sytem but after we discuss the disadvantages mainly safety issues, we never hear back from them
i hope they are doing fine and are not in hospital…

ther is no protection from electric shock
in house installation you have RCD but not at the battery, this can kill you easily.

so think about it, is a cheaper inverter more worth than your life?

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Me personally , i just put at work a verry big solar array. 195Kwp in solar panels , 3 x 50Kw DEYE hybrid inverters and almost 1Mwh LFP energy storage at 770V ( 700V nominal) divided into 14 16S 280Ah packs per rack and 5 racks in parallel. It can continuously deliver 900Kw peak power at charge/discharge. As for safety concerns there are none as far as i can see. The BMS knows how to do isolation teste every once in a while , and touching the rack metal frame does nothing. but bridging the rack metal frame with a resistor across the positive or negative terminal , the bms opens the contactors verry fast throwing an isolation fault alarm. Holding the positive cable alone in my hand by the copper part does nothing , same for the negative cable. Holding both cables at the same time by the copper connectors ensures a verry fast meeting with god. The packs has separate fuses and separate contactors , turning off the bms turns off all packs. disconnecting the comms cable from the inverters , turns off the bms after 5 seconds. I do not see any real danger , unless the owner is an i***t and has a death wish.

Got my add-on shunt in place on the 4.2 controller, just wanted to show that you don’t have to run long wires if you run a tiny jumper R7 on the other side.
Also to avoid having the shunt wires dangling relay 1 was removed to use the screw terminals for the shunt wires.

Edit:

Testing on my 8s nicd 6v100Ah battery bank (voltage dividers 47k)

Now just need to find a way so (c1+c2)/2=c1, (c3+c4)=c2, …

The other bank has voltmeters :slight_smile:

how old are they?

some 2002 others 2010