What do you lose when not using BMS

[Andre grobler]

Hi, yes i’s a noob…

we are looking at installing a phocos hybrid inverter, they have only pylontech as a compatible BMS. the supplier is suggesting BYD box lite. Which seems to be fine, we just have to set the battery up manually on inverter, so no bms comm.s.

so it seems like there is no real big issue with doing that, but i imagine there has to be some drawbacks in what the inverter can 1 tell you about the battery, and 2 how well it knows what it must give or take to/from the battery…

can anyone tell me or point me to info that would help understand the drawbacks of not having compatibility?

[Bobster.]

The simple solution is to get Pylontechs - or something that looks like a Pylontech to the inverter. There's hardly an inverter on the planet that won't get on with Pylontech.

Or try to see if SolarAssistant or a similar product can provide comms between the battery and inverter.

[Nexuss]

41 minutes ago, Andre grobler said:

Hi, yes i’s a noob…

we are looking at installing a phocos hybrid inverter, they have only pylontech as a compatible BMS. the supplier is suggesting BYD box lite. Which seems to be fine, we just have to set the battery up manually on inverter, so no bms comm.s.

so it seems like there is no real big issue with doing that, but i imagine there has to be some drawbacks in what the inverter can 1 tell you about the battery, and 2 how well it knows what it must give or take to/from the battery…

can anyone tell me or point me to info that would help understand the drawbacks of not having compatibility?

I would suggest you go with a more well known inverter like the Sunsynk.  If you do not have BMS comms with your battery you will not be able to accurately determine the SOC of the battery ,especially if its a LFP battery like the BYD and Pylons. This is because the voltage curve from 0-100% SOC is very flat and this makes it very hard to determine the SOC from voltage figures alone. When you have BMS comms the BMS can tell the inverter exactly what it wants and how it wants to be treated,instead of the inverter having to guess.

[Andre grobler]

Thanks… the phocos is a rebadged voltronic… as dar as we can tell, with just more dedicated people doing the programming

[Nexuss]

12 minutes ago, Andre grobler said:

Thanks… the phocos is a rebadged voltronic… as dar as we can tell, with just more dedicated people doing the programming

Yes but i stand by my advice , i had a Axpert/Voltronic inverter before the Sunsynk and its day and night difference,for the price of the Phocos and Solar assistant you are at about the price of the Sunsynk... 

[Andre grobler]

What is the difference? It is hard to get a feel for what they do differently

[Nexuss]

2 hours ago, Andre grobler said:

What is the difference? It is hard to get a feel for what they do differently

I had a quick look at the spec sheet of the 5kw unit. There is quite a few benefits to the Sunsynk. You can have more PV 4,8kw DC to AC(6kw max array) vs 5kw DC to AC and 1,5kw DC to DC for a total of 6,5kw with the Sunsynk. Better efficiency from the battery and slightly better from PV. Better IP rating IP21 vs IP65. The most important difference IMO being 2 vs 5 year warranty and the user interface advantage. Im sure there are many more benefits to the Sunsynk than what i can think of right now but i would suggest you do your own research.

[Steve87]

Hi Andre,

The Phocos is a Rebranded Voltronics inverter. Phocos is a German company that imports the inverters from Voltronics in China and they are slightly different looking but the insides are Voltronics factory build, but under German quality control.

If I I was to embark on the same journey you are about to I would definitely go for the Original Voltronics machine just because it's slightly cheaper money and for the 5kW price of the Phocos you can get the 7.2kW higher spec Off Grid hybrid from Voltronics. 

Don't let the compatibly issues stop you getting the battery that you want. Solar assistant will bridge the gap for the inverter and it will work with just about any battery that exposes the RS485/ CAN via an RJ45 cable from the battery. So for the price of +-R3k you not only have now compatible battery and inverter Comms but also Real time system monitoring and it's on your mobile phone or any number of people that want to have access to the plant.

The Solar Assistant is a massive Bridge in the gap for not only Comms and it's becoming a global market leading tool for anyone that has a Voltronics inverter and any said battery.

[Andre grobler]

Will take a look, are looking at 8kW-10kW machines. Sunsynk and deye are the same… the phocos wifi thingy is an optional extra in any case. So replacing that should be fine… 

we are one of those funny wifi less households, all cables… i see that solar assistant runs desktop too… 

[Steve87]

The solar assistant does not need WiFi, it can work as a standalone backbone system without networking. But one losses a lot of remote setting flexibility in doing so. 

[Andre grobler]

So is there no benefit in having someone redesign the interfaces?

so voltronic does just about every inverter out there except for victron, deye/sunsynk, and probably the sma stuff.

And i wonder what they did to make the 7.2kW look like 8kW? Probably just changed Rating systems i guess. 

[Andre grobler]

Understood, i like that flexibility, one can just switch it on when you need that. 

[Beat]

I have no communication between BMS and inverters. But I monitor the batteries via hardwired RS485/USB cable real-time on a laptop very closely. I simply ignore the SOC display from the inverter, it's meaningless. On the other hand I monitor and control the Synergj/Voltronic inverters (2x MKS5K parallel) hardwired (RS232) alternatively on the remote panel or on another laptop with Watchpower. Yes, that requires me to go into the office but that's not that often. Even so my solar installation has become sort of a new hobby.

[Andre grobler]

So how does the socalled “intelligent” charging work? Does the battery ms in the battery just draw what it wants from inverter charger?

[BritishRacingGreen]

2 hours ago, Andre grobler said:

So how does the socalled “intelligent” charging work? Does the battery ms in the battery just draw what it wants from inverter charger?

No , the BMS merely tells the charger what the max charging current and max charger voltage must be at any given time. The Chargers honours this .   

There are two major benefits with BMS comms : 

 

1. The battery instructs the charger what the limits are . This is more safe and secure than allowing a user to play around with settings. 

 

2 the BMS may want to limit max charge and voltage even further at the tail end of the charge cycle. The reason for this is the cell voltage rises rapidly during this phase and outliers may cause the BMS to protect and switch off.  So BMS comms will prevent this rather gracefully. 

 

so the whole notion of smart BMS charging has a lot of merits. However there are no industry standard , so it's a compatibility hell out there , to the tune that lots of user give up on it.

[FixAMess]

On 2022/05/10 at 12:32 PM, Andre grobler said:

What is the difference? It is hard to get a feel for what they do differently

Very simple...The forum support and ease of use of Sunsync is priceless! Remote control is also available...

[Andre grobler]

Ja… out of the 5 installer suppliers we interviewed… only one could hold a logical train of thought… and understand what we want… so i am a little reluctant to start all over again… 

[Steve87]

Unfortunately, solar is quite a technical endeavour. So just as much as any newish up and coming industry, there are good and bad operators out there. 

But forums and chat rooms like these help to share and understand knowledge. Making the journey easier to embark on. I have no doubt your path whichever chosen will be a good one. But like in all things there are no guarantees. But at least you can ask and share here. Good pool of knowledgeable Ppl on this forum. 

[Andre grobler]

That is why i wanted a good installer, so i don’t have to rabbit hole the gear, just the basic good system philosophy… but that ship has now sailed i guess

[Beat]

22 hours ago, BritishRacingGreen said:

There are two major benefits with BMS comms : 

1. The battery instructs the charger what the limits are . This is more safe and secure than allowing a user to play around with settings. 

2 the BMS may want to limit max charge and voltage even further at the tail end of the charge cycle. The reason for this is the cell voltage rises rapidly during this phase and outliers may cause the BMS to protect and switch off.  So BMS comms will prevent this rather gracefully. 

I see that somewhat differently.

The data sheet of the battery packs gives recommended and maximum limits for charging and de-charging currents, as well as for voltages. By setting the inverter/charger to these limits keeps the battery in shape. I.e. I set max utility charging to recommended limit, however no limit to PV charging, as I do not want to loose solar energy. That is anyway limited by the capacity of the PV panals total. And I set bulk and floating charge voltages to batteries datasheet recommendations. De-charging currents are dictated by the load anyway. I doubt that a BMS can do much better. Note that my system is off grid.

Edited May 12, 2022 by Beat

[Andre grobler]

Apparently the BMS monitors and manages the charging the temps and state of charge of each individual cell within the pack. It also can report the overall status to the computer or inverter. So, it safeguards everything. So i am assuming if your bms functions, it can accept or deny current from the inverter. We hope. Otherwise, you might as well be charging into the unknown, but probably be fine mostly

 

https://www.ufo-battery.com/how-does-a-lithium-battery-bms-work

[Beat]

9 minutes ago, Andre grobler said:

So i am assuming if your bms functions, it can accept or deny current from the inverter.

I don't think it can deny current from the charger. In my understanding the BMS only informs. The only exception is the low voltage cut off. According to the datasheet of my Averge LFP it cuts off at 40.5V. I set the inverter cut off (29) to 42V.

Example of informative display of battery pack N° 3.

[Tinuva]

@Andre grobler

I know you have already spent a lot of time going the voltronics route, but really, do yourself a favour and look again at the Sunsynk with a lot more attention.

You can not go wrong with it even over Victron in my opinion. There are just too many positives and I think a select few negatives. It beats most of the competition with value for money. The features are best for the price and there are no compromises, except that it is a single unit vs separate units such as the Victron.

Otherwise, if you stay with the voltronics then at least go with the pylontech batteries.

 

[Andre grobler]

Believe me, i am… i so do not need comebacks on the system…

[BritishRacingGreen]

2 hours ago, Beat said:

these limits keeps the battery in shape. I.e. I set max utility charging to recommended limit, however no limit to PV charging, as I do not want to loose solar energy. That is anyway limited by the capacity of the PV panals total.

@Beat your argument is not applicable to the function of BMS , it's energy management settings applicable to inverter.  This means you must anyway perform  these settings with or without BMS comms.

As far as your argument regarding manual charge settings , I really do not agree or disagree . If you know your charger and your batteries , and you feel your manual settings is optimal , by all means. But there are also a lot of owners that knows very very little re inverter systems. So the benefit of manufacturer settings exposed via BMS comms integration must not be overlooked. 

Kind regards