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You write "with the cells being rather new i see no imbalance happening soon." - this I would not bet too much on! If you do not cycle your batteries all the way through, i.e. also allow for full charging following by balancing (DALY BMS is supposed to balance cells as well), this will not work...

Stick with six panels as a meaningful start! Have always two connected in series, they then usually called strings. So you'll have three strings of two panels in series each. For best performance, you can orient one string facing dead south, one string facing more towards east and one more...

There's a general problem I had to encounter unfortunately (independent of paralleled batteries): When charging my batteries with a solar MPPT charger and the (last) BMS decided to switch off because the battery was fully charged, there had been a voltage spike destroying my inverter input...

Try this as also the product number sounds like a DALY BMS: https://diysolarforum.com/resources/daly-bms-monitor-to-monitor-8-boards.167/ Just disregard the board number stuff described on the page. Your BMS should come up as board 1 ... if it works.

Again, I don’t know your tool! But start try monitoring what you send with another machine (e.g. a RS485-to-USB adaptor on a laptop). Most probably you’re sending not in Hex. To monitor I use hterm in Windows and I have to select “View in hex” not to see garbled stuff. You can compare what...

Can you please explain further? I assume, with backfeed you refer to some unwanted back and forth charging/discharging between batteries. Can this be controlled by controlling the charge MOSFET on a smart BMS? I think along the lines of preventing charging of two batteries out of a...

To my knowledge, the DALY BMS 4S version does not support RS485.

Thanks for uploading the protocol description in the Resources section. Some comments: The document you posted does say "MODBUS" protocol but MODBUS is a specific protocol that definitely looks different (see MODBUS on Wikipedia). So I assume the author used this name because it probably uses...

OK, well, I don't know this DALY BMS as this seems to have an open PCB (as he points out when the red LED is on). Also, the RS485 connector goes in sideways. So sorry, I can't help any further ... and you haven't revealed the type of your BMS either.

Hm, not sure what guidance your "actual solar professionals" have given you, but for myself, I was director of solar panel development at Bosch Solar Energy, a company you might have heard of ... And in that position, I had my share of discussions with good and not so good solar professionals...

@snoobler - you are correct! Thanks for the clarification! I was expecting we are talking about similar panels with the only difference being poly vs. mono crystalline cells. To be as clear as possible: IMHO one can connect different types of panels as long as both VoC and Umpp are within 3% or...

I read through the manual - it seems to be the same as mine. My unit also can run without a battery, but I never tried it. I've found the attached description of the mode you're probably referring to (page 32/60). It seems indeed as if the internal inverter synchronizes its output to the grid...

You're right: It's either BT or UART. There is another advantage of using RS485: While the UART as well as the BT only "jumps on", when the battery is charged or "activated" by additional accessory, by using RS485 the battery can be woken up simply by querying it. In other words, just sending a...

Yes, the body diode heat dissipation is the weak point of this idea ... Any idea on the hardware-based control of the MOSFET switch?

Interesting way to motivate valuable contributions!

Well, I hope, I overthink it, but I am not sure, hence the discussion here ... My line of (over-)thought: As I do not have 100% identical batteries plus the connecting cables are slightly different, this all adds up to different series resistors (differently aged cells, connector resistance...

So I'll keep my fingers crossed that it works for you. Please report ?

Yes, exactly like this if you have two strings. You mentioned however to have one string facing south, the other north - if you have only a restricted roof, then that might be OK, but for maximum energy harvest go with both strings facing south (as snoobler suggested). If you want to save on...

It's there under resources ... https://diysolarforum.com/resources/daly-bms-firmware-to-assign-board-numbers-dalybmsapp_20210216b-s19.168/ https://diysolarforum.com/resources/daly-bms-monitor-to-monitor-8-boards.167/

Puh, I am an Arduino level programmer and was not planning to develop my own BMS ... Furthermore, when I can predict my charge/discharge currents, I do not expect to have huge problems with body diode power dissipation. This is because if leaving a high load status (i.e. switching back to more...

Yes, this is a great feature. Unfortunately, in Germany, utility provider do not allow for such systems to be installed.

When you want to connect them in parallel, then this should be no problem. However, if you need to put them in series, this is not recommended as the solar efficiency as well as the spectral sensitivity of mono vs. poly crystalline modules is different. If you put them in series, the weaker...

Hi Rusty, Not sure, if my advice will be any help, but here it goes: Balancing is quite an important part for cells in a battery as Lithium based cells are somewhat sensitive towards overcharging etc. Hence each Lithium based battery needs a BMS (battery management system). Now your Shunbin...

My two cents: If you keep your two 55W modules in parallel, you'll end up at maximum power point with Vmpp of 18V and Impp of 2x 3.06A = 6.12A If you then put your 110W module in series, at least Impp (AKA current at maximum power point) is also 6.12A according to the specs you've given above...

I spend a day or two on interfacing the DALY Smart BMS. My 16S version offers UART, RS485 and CAN. However, RS485 is not Modbus (which e.g. EPever talks) and CAN is not CAN-protocol either. It seems, they use just standard UART protocol over RS485 or CAN physical layer. I got it to communicate...

Thanks for the soothing words. I am well aware of the issue with weak cells in a battery pack and I also follow your thoughts regarding low SoC behaviour. My worries are around the moment a high load switches off and equalizing currents run from high series resistance batteries to those with low...

Are you trying this via Bluetooth? GATT is in my understanding a BT protocol profile (https://learn.adafruit.com/introduction-to-bluetooth-low-energy/gatt: "GATT is an acronym for the Generic Attribute Profile, and it defines the way that two Bluetooth Low Energy devices transfer data back and...

Well, this sounds reasonable to me! Maybe the "Do not use in series or parallel!" statement is just to scare people off to avoid trouble later on. Which of course makes sense, because when dealing with these amounts of energy you'd better know what you're doing! An arc burns for quite a long...

Have you tried logging the Bluetooth protocol that is sent between the BMS and e.g. your phone with an ordinary Bluetooth sniffer/logger? I've heard, there are a few good sniffer out there and you might be able to see, what protocol the BMS BT adapter is actually using. As the Bluetooth adapter...

They may have sent you the generic pinout. Are you sure, you bought a 4S with RS485 functionality? Because all 4S DALY Smart BMS I have seen so far come only with Bluetooth/UART. The RS485 as well as the CAN versions start with 8S at least for the LiFePo4-BMS types. But maybe I am not up to date...