56 minutes ago, plonkster said:

Incidentally that is precisely what happens in a Victron system. The BMS says 53.2V... Venus says... I reject your reality and substitute my own... 🙂

 

LOL

On 2020/02/25 at 10:05 PM, SiliconKid said:

I need to ask @Coulomb to check the firmware code and confirm or deny for us.

As noted in my PM reply, it may take some time. I have technical difficulties with that part of the code, and I have a few hardware mods to make before I can finish testing some long overdue patched firmware.

20 hours ago, plonkster said:

Incidentally that is precisely what happens in a Victron system. The BMS says 53.2V... Venus says...

As a point of interest, does the Venus also impose a limit of exactly 53.0 V, or is it a different limit, possibly involving more than the target charge voltage?

1 minute ago, Coulomb said:

As a point of interest, does the Venus also impose a limit of exactly 53.0 V, or is it a different limit, possibly involving more than the target charge voltage?

It used to be 52V, and in a development version it is  upped to 52.4V. That is high enough to get a 100% SOC, for the balancer to do its thing, and it leaves room on top for "overvoltage feedin", which is the method used to feed excess solar power into the grid: The solarchargers are instructed to push the voltage to 52.8V while the inverter tries to hold it down to 2.4V. That leaves 1.2V of room at the top before the battery freaks out and switches off.

I agree with the OP’s original statement to a certain degree, but not for the purposes of communicating charge and discharge current limits.

The biggest issue that I have experienced is the ability to control or manage your systems energy based on accurate battery SOC (%). Now the problem lies in, where do you obtain this information from?

1st prize is of course, the battery BMS. But often times either the battery does not support any form of native communication with the inverter or vice versa, the inverter does not support any type of communication available from the battery.

The fall back is to control the system through battery voltage derived SOC. This, unfortunately, is typically quite inaccurate.

A work around though is available in the form of Victron’s range of high precision battery monitors, the BMV700/702/712. These devices are battery agnostic because they measure energy throughput. This way you can calculate the true SOC of any battery, provided you setup the BMV correctly. You then simply need to make sure that you can pass the information from the BMV to the inverter or control system so that your system is now managed based on accurate SOC. 
 

In an advanced hybrid power system, you need an accurate battery monitor. This either needs to be of the form of communication to the BMS or a 3rd party external device like a Victron BMV700.
 

 

Hi all

I've a question/statement,  I have 48v 100ah battery x 5 and they don’t come with comms link to inverter. Unfortunately my inverter a solis 4g doesn’t work the battery without the comms link between the battery and inverter. Can I retro fit a comms link to one battery to act as master.
The reason I’m doing this is because the inverter is already installed and I had a good deal on the batteries, well I thought so upto the time I tried to hook it up. If there’s no comms link between the batteries and the inverter it just won’t work. Can someone please help me. I’m lost at this. 
 

thanks all 

5 hours ago, ignition31313 said:

Hi all

I've a question/statement,  I have 48v 100ah battery x 5 and they don’t come with comms link to inverter. Unfortunately my inverter a solis 4g doesn’t work the battery without the comms link between the battery and inverter. Can I retro fit a comms link to one battery to act as master.
The reason I’m doing this is because the inverter is already installed and I had a good deal on the batteries, well I thought so upto the time I tried to hook it up. If there’s no comms link between the batteries and the inverter it just won’t work. Can someone please help me. I’m lost at this. 
 

thanks all 

Hi

Are those batteries Lithium batteries? I'm guessing no.

Given that your batteries have no BMS (Battery Management System) built in, and are probably not Lithium, the easiest thing for you to do is simply run your inverter in User mode and manually configure your voltages etc.

As you can see from my various posts I prefer using a BMS when it's available and built in, but in your case where your batteries have no BMS at all it makes sense to just hook them up old school without any comms and let your inverter rely on voltage monitoring in User mode.

They are lithium phosphate batteries with a bms. The issue is that there is no comms card and hence can not communicate to the  inverter. 

OK, well what I can tell you is that even the batteries with BMS and comms capability built in have given our community a lot of issues connecting to various inverters, even when they are supposed to be compatible. 

And the reason for that is that each BMS has its own protocol that has to be explicitly supported by the inverter firmware, and each BMS also has its own cable pinout for communicating with it. 

So if you don't have an inverter that natively supports your batteries the only reasonable way I can think of to get that working is to ignore the BMS and just put your inverter into User mode, configure it manually, and use good old voltage monitoring. That seems to be what most of the installers in SA do most of the time anyway, even when they are installing new Li batteries like the PylonTech, with BMS and comms, which shouldn't require User mode. 

You should be able to get it all working well enough that way if you configure the inverter correctly for the spec of those batteries. 

I don't think you will win if you try to retro fit some kind of comms to the BMS purely because you would also need a firmware update for your inverter that supports a mode for that specific BMS protocol, which I'm guessing is not going to be possible to get? Or does your inverter already have an Li profile for that specific make and model of battery? 

42 minutes ago, ignition31313 said:

They are lithium phosphate batteries with a bms. The issue is that there is no comms card and hence can not communicate to the  inverter. 

 

On 2020/02/24 at 10:20 PM, plonkster said:

But I would not say a managed BMS is the be-all and end-all... simply because there are many many more systems out there without it, and they work just fine. If you design the system in proportion, a BMS should never have to intervene in any case.

With due respect, I cannot possibly agree... certainly not with the conclusion that a BMS is somehow "optional albeit useful" as regards lithium. OP makes a valid point.

From a cost vs lifetime perspective, active cell-level balancing is absolutely essential - and this is not something your inverter charger is going to do for you - not even a fancy Victron. They will see only the overall battery,  not the individual cells. Caveat emptor, unless you want to risk severely unbalanced cells and the knock-on effects of that over time (cells with permanently different profiles, at best resulting in capacities reduced to the lowest common denominator).

For a few days' test though? Fine without. Manually rebalance your cells and carry on.

Put another way: after spending $2000+ on cells, are you really going to skimp on spending another $100 (passive) to $200 (smart) dollars on a half decent BMS to perform cell level balancing?

Bottom line for newcomers - be wise - get a BMS that can talk your inverter. Always. In 2020 (onward) there is very little reason not to.

(And no, I don't buy that older lithium systems that were set up without BMS & only inverter settings, are "just fine", unless that means only functional... functional does not imply optimal. If it were optimal, then BMS technology and sales wouldn't be advancing at a rapid pace... BMS would be no more than a curious side feature of the lithium market.)

Edited August 8, 20206 yr by Wick

Quote

active cell-level balancing

 

8 hours ago, Wick said:

cannot possibly agree

You're not reading the full context of my answer. In a properly designed system the BMS never has to intervene. You still need the BMS for safety, and balancing of course. I'm not contesting that. I'm contesting the idea that you cannot possibly run a lithium bank without the highest level of control (aka canbus control) and that's just not true. Lots of people run daly bmses that has no comms. Even victron's smart lithiums essentially have a two-signal BMS. 

Edited August 8, 20206 yr by plonkster

This thread is a most interesting discussion with much valuable information from @plonkster. What I would find informative would be input about a scenario where I replace my Trojan T105s with LiFePO4 cells from ??????????????? with an ANT BMS. Since my Axperts are controlled by ICC-Pi which in turn gets input about battery parameters from a Victron  BMS700, what purpose would a connection  between the BMS and the inverters serve. It would seem that the present setup already addresses all requirements or am I missing something. Perhaps you would be so kind as to give your views @plonkster or anyone else with experience. There must be many Axpert users that will benefit by an informed opinion. 

 

 

 

 

 

 

X

15 hours ago, plonkster said:

In a properly designed system the BMS never has to intervene

i agree and can confirm (based on my 8 month experience) that a system without battery-inverter communication can work very well. My Goodwe inverter is to old to talk to the Pylontech batteries without a very expensive external control box. What is important is that you can accurately track SOC and set the required battery charge and discharge parameters (both are possible with my inverter). To be able to manually set the optimum battery charge/discharge parameters for your specific case is in my view also better than what the BMS would dictate.

@ebrsa Please don't hijack threads; rather start a new one to ask about your specific situation.

You mean BMV-7xx series battery monitors, not BMS-700 (it is not a BMS). BMV is only going to offer battery-level monitoring, not cell-level monitoring, and certainly not cell-level balancing (as they are _monitors_ only, they don't control charge / discharge) which is essential for LiFePO4 - hence my remarks above. It is for newbies like you that I gave that warning - DO NOT avoid a BMS with LiFePO4. This is to preserve your cells' lifetime.

For lead acid chemistries (which is what you have had in your Trojan), a BMS is purely optional, which is why you don't have one. For lithium chemistries which are very sensitive, BMS are strongly recommended even if not technically mandatory.

So in conclusion: your present setup does not address all requirements for LiFePO4, since your lead acid setup lacks a BMS for cell level balancing.

 

Edited August 9, 20206 yr by Wick

11 minutes ago, Fuenkli said:

i agree and can confirm (based on my 8 month experience) that a system without battery-inverter communication can work very well.

It would be interesting to view the variation in profiles between your cells by this stage, especially after 8 months of heavy usage. The main purpose of a BMS is cell-level balancing, which through evening out charge and discharge between cells, ultimately preserves individual cell lifetimes across the pack(s), rather than allowing some to age more quickly than others (through "getting out of balance" relative to one another).

Edited August 9, 20206 yr by Wick

2 minutes ago, Wick said:

It would be interesting to view the variation in profiles between your cells by this stage, especially after 8 months of heavy usage

Cell balance is perfect (check regularly with the Pylontech battery view app). Maybe you are not aware that the Pylontech batteries have a build in BMS.

Quote

Cell balance is perfect (check regularly with the Pylontech battery view app). Maybe you are not aware that the Pylontech batteries have a build in BMS.

Having now clearly stated you're using a PylonTech - you are using a BMS per se - nothing wrong with your setup. Cell-level balancing is happening all the time. Congrats.

My claim is that, for newcomers, not using any BMS at all for lithium, is unsafe, as newcomers may not be rigourous about manual cell-balancing and failure to do so can cause problems and loss of durability over the longer term. "BMS / inverter comms or not" is a whole separate discussion from what I broached here yesterday.

Hope that clarifies. It is important, given the viewership of sites like this, and quantities of money involved, to advise in the most responsible way possible.

Edited August 9, 20206 yr by Wick

@Wick  If you read my post with some more care, you would have noticed that I did mention replacement of T105s with LiFePO4 cells AND AN ANT BMS. You will also notice that my posts over several years are a total of  536 compared to your 27. So I do believe that my question is relevant and it could hardly be interpreted as high jacking the thread, a comment which I find unnecessarily offensive. Likewise your reference to me as a newby with no understanding of the matters under discussion. It is true that I do not have a BMS in use with my FLA batteries, after all who does, although I have HA02 balancers. Regarding my typing error of BMS700 Instead of BMV700 you are of course correct.

So I look forward to a possible reply from @plonkster or someone with some relevant information.

 

 

43 minutes ago, ebrsa said:

@Wick  If you read my post with some more care, you would have noticed that I did mention replacement of T105s with LiFePO4 cells AND AN ANT BMS. You will also notice that my posts over several years are a total of  536 compared to your 27. So I do believe that my question is relevant and it could hardly be interpreted as high jacking the thread, a comment which I find unnecessarily offensive. Likewise your reference to me as a newby with no understanding of the matters under discussion. It is true that I do not have a BMS in use with my FLA batteries, after all who does, although I have HA02 balancers. Regarding my typing error of BMS700 Instead of BMV700 you are of course correct.

So I look forward to a possible reply from @plonkster or someone with some relevant information.

 

I read your post and understood it very clearly. I'm not sure the reverse could be said, or that you follow the actual issue brought up in this thread yesterday. Prior to that, this thread had been dormant for some time and it was for the sole reason of warning LiFePO4 newcomers that I woke it up. You can find it as offensive as you like: that's what it's called when someone tries to steer a thread in a direction that is self-serving and / or doesn't have to do with the original topic. And the fact remains you _are_ a newbie to LiFePO4. As are many of us.

Well, you've been helped and weren't interested in the accurate answers I gave you, given your minimal knowledge of LiFePO4 setups as admitted by you. Indeed your tone is at best unfriendly, at worst aggressive, for reasons I'm not entirely clear on. Remember that  it serves the learner to keep an open mind. Plonkster teaches all of us, incidentally.

Best of luck to you.

Edited August 9, 20206 yr by Wick

Wick,  which good BMS's for LiFePO4 would you recommend for DIY enthusiasts ?

@Plaasjapie Have answered you privately so as to avoid derailing thread further.

Edited August 9, 20206 yr by Wick

@Wick  When a reply starts with an accusation, as yours to my first post did, I find it aggressive and offensive. Clearly you did not read that I referred  to LifePO4 and a BMS in my first post. Again your reply above makes assumptions and levels accusations at me for no reason that I can fathom. That has never been the spirit in which commmunications on this forum has been conducted and I sincerely hope it is not an indication of what is to come.

My experience and interest in electricity and electronics started as a kid when as a twelve year old I repaired and maintained our windcharger  on my late father's  farm in the North West Cape. Now at 82 I have had 70 years of aquiring knowledge, including having manufactured electronic equipment. So while solar power storage on modern types of batteries are recent, I have, as a retiree, the advantage of time and the internet to research whatever I am interested in. That includes a wealth of knowledge that I have learned from others during my 6 year membership of this forum which seems about 5 years and 11 months longer than yours.

That being said I will not persue the matter other than to learn what others may advise. @Fuenkli has already largely and informatively answered my question with his post relating to his experience over the past 8 months. That makes sense to me as a bank of LifePO4 cells with a BMS to protect and regulate charges and discharges coupled to an inverter controlled by ICC-Pi with connected BMV7xx, would probably not require a connection between the BMS and the inverter, at least not as far as I can comprehend. But I may be wrong, hence the reason for my original post. And sadly I do not much believe in luck but rather accurate and relevant information.

27 minutes ago, ebrsa said:

@Wick  When a reply blah blah blah blah blah blah

*user ignored for gaaning aan and derailing thread further*

Edited August 9, 20206 yr by Wick

18 hours ago, plonkster said:

You're not reading the full context of my answer. In a properly designed system the BMS never has to intervene. You still need the BMS for safety, and balancing of course. I'm not contesting that. I'm contesting the idea that you cannot possibly run a lithium bank without the highest level of control (aka canbus control) and that's just not true. Lots of people run daly bmses that has no comms. Even victron's smart lithiums essentially have a two-signal BMS. 

@plonkster  I have re-read the thread and noticed that you have essentially answered my question. Your reply confirms my perception that communication between a BMS and a properly controlled inverter is not a requirement. It would seem that if a supported BMS is connected to a RPi running ICC-Pi  a BMV7xx connected to the RPi is not required as the BMS would communicate the required accurate information. So if one already has a RPi with connected BMV7xx and replaces lead-acid batteries with LifePO4 cells and a suitable BMS, there would be no benefit or indeed purpose in also connecting the BMS to a RPi running ICC-Pi.