BMV Values

[PaulF007]

Here is a Quick one for julle slim oukes.

Looking at the data from the BMV - 702 - (H17) Discharged Energy.

How accurate would you say that this value is and could one assume that it is the energy that one used since first start up or could there be some "testing" values involved as well. I didn't know that this value was available and as such I never checked when I installed the BMV...

Second  H6 - mAh Cumulative Amp Hours drawn , same as above.

Regards

Paul

[Guest]

It looks to me very accurate. I often compare it with the inverter load, Also add the inverter use of about 80 watt together with the inverter load to match the total

 

[PaulF007]

Cool thanks Manie!

[PeterGutti]

What are the recommended BMV-700 settings?

I have installed 24 OPzV (Gel) Batteries (48V). These days i have to use the generator to charge them (we have cloudy and rainy weather since weeks).

Starting and stoping the gen is under control of the BMV-700. BMV uses batt voltage and SOC to "decide" to open or close the relay.  Since weeks i try to find the right configuration.  With the gen its almost impossible to charge the batteries higher than 51V (see graph attached).  

These are the settings of the BMV-700:

Is there anbody else having a similar installation?  I would be glad to discuss and exchange knowldege.

[cvzyl]

Hi Peter

I am not an expert on this but is the charging rate of 2kW (40A) not way too low for a 1500 Ah bank? Could that be the reason why the generator charging is unable to increase voltage above 51V. I'm not sure I'm reading the graph correctly but it looks like the generator was stopped at around 89% SoC, maybe letting it run longer to reach closer to 100% it will be able to achieve higher voltage?

Cobus

[Gerald_db]

1500Ah battery bank should be bulk charged at up to 150A. Certainly not below 100A.

Sent from my SM-G920F using Tapatalk

[PaulF007]

Hi Peter

Can you maybe give us a little bit more info on your setup. What charge controller do you use? What is your solar setup (Panels , type of inverter). I assume you know that the BMV will only show what is going in and out of your batteries. Did you have a look at your  aH consumed on your BMV? As this wil also give you an idea as to how much is going back into your batts.Your charge controller is supposed to "ramp" up the volts even if the amps is a bit low , but I could be wrong on that one.I agree with Gerald and Cobus that you will have increase you charge amps if you want to get the batts fully charged. 

But first lets get an ideas as to what your setup looks like before you ga and change settings..

Regards

Paul

[Don]

Hi Peter, I think your charged voltage of 52.8 is way too low. You will never get them to 100%. The charge voltage should be 57,6 V and float voltage at 54.4 Volts. And as Gerald said, increase the charging amps to 150 Amps.

[Don]

Paul, the only value I am not so sure about is the Average Depth of Discharge. I have been watching this value for the last 5 charge cycles. Mine seem to be stuck on -189.4 Ah. I had 4 charge cycles at around 100 Ah and last night one of 240 Ah. On the last 5 charge cycles it has not even changed a decimal point on the Average Depth of Discharge. 

[PeterGutti]

Thank you all for your replies and very valuable input. I was away for a few days. 

To the background: I life in Spain, Costa Blanca.  I use the generator to charge the batteries only when there is no solar power available for a few days.  My batteries (24xEnersys OPzV Gel 1500Ah) are good enough to feed my house for 2 to 4 days. After that time, when the voltage drops to 46,5 V the gen should only charge to overcome a short period of a few hours, until sunpower takes over again.  From 47V up to 56V would take days to run the genarator.  Therfore the upper Voltage, to end the generator, is at a that low value of 51,8V (that is what can be reached within an affordable amont of time). 

In the statistics i use (Emoncms feeded by AICC) i saw that during charging time (from the gen), the voltage stays at about 51V for a very long time.  It raises slowly later. Therefore i limited to 51V (now at 51,8). 

[Mark]

Hi Peter

Lovely set of batteries (I am envious!!)

What panels how many and how are the wired for your system?

Thanks

Mark

 

[PeterGutti]

Hi Mark,

just saw your question (from december, sorry). 

I have 24 panels polycrystalline, 25W, 60C, 24V. Dont understand what you mean about wiring.

[PeterGutti]

On 20/12/2016 at 9:24 PM, Don said:

Hi Peter, I think your charged voltage of 52.8 is way too low. You will never get them to 100%. The charge voltage should be 57,6 V and float voltage at 54.4 Volts. And as Gerald said, increase the charging amps to 150 Amps.

Don, with the generator i'm limited to 30A or so.  The reason is, that the generator cannot deliver more. If set higher, the charge controller requests more from the gen than it can deliver.   After a few minutes, the gen dies!

[Don]

Hi @PeterGutti, if you are limited to charging at 30 Amps, that is not a battery killer, it would just take longer to charge.

On 12/28/2016 at 11:56 PM, PeterGutti said:

Therefore i limited to 51V (now at 51,8)

That low voltage setting is a concern to me. It is way to low to charge your batteries properly. You are constantly undercharging your batteries. That would impact on your battery capacity in no time. Don't be surprised if your current capacity of 2-4 day drops down to 1 day in the near future. If you run on solar, do you change the charge voltage to 57.6 Volts, or do you just leave it at 51.8 Volts?  

[PeterGutti]

On 30/4/2017 at 10:30 AM, Don said:

Hi @PeterGutti, if you are limited to charging at 30 Amps, that is not a battery killer, it would just take longer to charge.

That low voltage setting is a concern to me. It is way to low to charge your batteries properly. You are constantly undercharging your batteries. That would impact on your battery capacity in no time. Don't be surprised if your current capacity of 2-4 day drops down to 1 day in the near future. If you run on solar, do you change the charge voltage to 57.6 Volts, or do you just leave it at 51.8 Volts?  

Hi @Don- thats exactly what is specified: Bulk(Parm 26) 56,4V  Float(Parm 27) 54,8V.  Utility is the diesel Generator = emergeny situation, i'm off grid.  Only using it 3-4 times a year when there is a longer period of real bad weather. In spain we mostly have sunny weather (too sunny, we should get rain! the land drys out)

[ebrsa]

Hi @PeterGutti, A few day ago I read this thread again and Googled your OPvZ batteries. The recommendations for charging you batteries, according to the user manual follow.

1.4 Recharging : The PowerSafe® OPzV battery should be recharged by using a unique floating and recharge voltage at 2.23-2.25 V/cell at 20°C. No current limitation is required in the majority of application cases. If the PowerSafe OPzV battery has to be charged more quickly, a recharge voltage of 2.35 volts (boost charge) per cell can be used with current limited to 0.4C10

So if you recharge at 2.35V per cell, the Axpert parameter 26 should be set at 56.4V which would be safe as you are hardly likely to ever charge at 0.4C10 which would be 600A for your 1500AH battery bank. Charging at a higher voltage will probably damage your batteries, at least according to the manual. You could set the floating voltage at 2.25V per cell which means parameter 27 should be set to 54V. 

Your BMV parameter 2 should, according to the BMV manual, be set to the float voltage minus 0.2V or 0.3V which is 53.8V or 53.7V. However in correspondence I had with Victron, they recommended setting this parameter to the bulk charge voltage minus 0.2V in the case of solar installations where the charge current may vary quite a bit. If you set the Axpert parameter 26 at 56.4V, this would mean setting parameter 2 on the BMV at 56.2V. I have the Axpert V72.70B firmware installed and have set the new parameter 32 at 180 minutes. This keeps the charge voltage at my bulk charge voltage for that time before it drops to float because my Trojan batteries requires a higher bulk charge voltage than what the Axpert can supply.

I hope this helps in arriving at the optimal settings for your batteries.

[ebrsa]

Hi @Chris Hobson, I see you read my post above and as I recall you are also using Trojan T105 batteries. I would like to hear what you think about setting Axpert parameter 32, available on firmware 72.70B, to a fairly long time to ensure that the Trojans are perhaps fully charged. In e-mail with Trojan which I posted before, they did confirm that one could charge at a lower bulk voltage than the recommended 59.3V, but for a longer time. The new parameter 32 enables one to force such a longer bulk charge and thereby preventing a premature drop to float voltage, at least in my view. Maybe now  with the availability of parameter 32, T105 batteries used with Axpert MKS inverters, capable of 58.4V maximum bulk charge voltage, will be fine.

[PeterGutti]

1 hour ago, ebrsa said:

Hi @PeterGutti, A few day ago I read this thread again and Googled your OPvZ batteries. The recommendations for charging you batteries, according to the user manual follow.

1.4 Recharging : The PowerSafe® OPzV battery should be recharged by using a unique floating and recharge voltage at 2.23-2.25 V/cell at 20°C. No current limitation is required in the majority of application cases. If the PowerSafe OPzV battery has to be charged more quickly, a recharge voltage of 2.35 volts (boost charge) per cell can be used with current limited to 0.4C10

So if you recharge at 2.35V per cell, the Axpert parameter 26 should be set at 56.4V which would be safe as you are hardly likely to ever charge at 0.4C10 which would be 600A for your 1500AH battery bank. Charging at a higher voltage will probably damage your batteries, at least according to the manual. You could set the floating voltage at 2.25V per cell which means parameter 27 should be set to 54V. 

Your BMV parameter 2 should, according to the BMV manual, be set to the float voltage minus 0.2V or 0.3V which is 53.8V or 53.7V. However in correspondence I had with Victron, they recommended setting this parameter to the bulk charge voltage minus 0.2V in the case of solar installations where the charge current may vary quite a bit. If you set the Axpert parameter 26 at 56.4V, this would mean setting parameter 2 on the BMV at 56.2V. I have the Axpert V72.70B firmware installed and have set the new parameter 32 at 180 minutes. This keeps the charge voltage at my bulk charge voltage for that time before it drops to float because my Trojan batteries requires a higher bulk charge voltage than what the Axpert can supply.

I hope this helps in arriving at the optimal settings for your batteries.

Hey @ebrsa - muchas gracias! thank you for this analysis. Send me your banking data so i can transfer an amount.

The Axpert parameters are quite close to your recommendations: 26: 56,8   27: 54,8.  But the BMV parm  2 is at 52,8. This influences the SOC calculation, i assume.

Axpert Level is 72.40

 

Will modify the BMV settings.  BMV is used to start the Generator in case of low battery due to bad weather.  This happens only 2-3 times per year.

[PeterGutti]

about USB:

command lsusb reports the following status:

USB status:
pi@aicc:~/AICC $ lsusb
Bus 001 Device 005: ID 0665:5161 Cypress Semiconductor USB to Serial
Bus 001 Device 004: ID 0403:6015 Future Technology Devices International, Ltd Bridge(I2C/SPI/UART/FIFO)
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. SMSC9512/9514 Fast Ethernet Adapter
Bus 001 Device 002: ID 0424:9514 Standard Microsystems Corp. 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub

If i remember correctly, ID 0665:5161 is the Axpert USB port. What surprises me, is the text "USB to Serial" !  

[ebrsa]

Hi @PeterGutti, There is no need for transferring money to my bank account but thank you for the kind offer. We are after all just trying to help one another and not duplicate the great amount of effort needed to optimise out systems.

The function of BMV parameter 2 is to determine when the batteries are charged and then switch the charger to the battery float voltage. Victron explained it as follows in an e-mail reply to a question from me. When you have a steady current such as a generator or the grid, one would set parameter 2 to the float voltage minus 0.2V to 0.3V. Three conditions have to be met for switching to float, the setting of parameter 2 and the tail current (parameter 3). Both these have to be valid for the charged detection time (parameter 4). When charging from solar it is possible that cloud cover for instance could result in a charge current equal to the tail current and a voltage equal to the setting of parameter 2, all for the detection time before the batteries have reached the fully charged voltage. Victron recommended that, when using solar panels, parameter 2 be set to the charged voltage minus 0.2V to 0.3V. This will ensure that the charged voltage is reached before the BMW switches the charger to float voltage. @Don refined his setting further by setting the tail current to a small value 0.5 x AH and he also increased the charged detection time to 50 minutes as far as I remember.

If I had your batteries, which seems to be really outstanding, I would be inclined to use the settings as described in the manual with the Victron recommendations for solar applied. After all according to the manual one could charge at 54V which is also the float voltage. The higher voltage of 56.4V will just optimise charging from solar panels.

As far as the USB to Serial device detected by lsusb, I wonder if it might perhaps be the Victron USB converter that is detected.

[Chris Hobson]

20 hours ago, ebrsa said:

Hi @Chris Hobson, I see you read my post above and as I recall you are also using Trojan T105 batteries. I would like to hear what you think about setting Axpert parameter 32, available on firmware 72.70B, to a fairly long time to ensure that the Trojans are perhaps fully charged. In e-mail with Trojan which I posted before, they did confirm that one could charge at a lower bulk voltage than the recommended 59.3V, but for a longer time. The new parameter 32 enables one to force such a longer bulk charge and thereby preventing a premature drop to float voltage, at least in my view. Maybe now  with the availability of parameter 32, T105 batteries used with Axpert MKS inverters, capable of 58.4V maximum bulk charge voltage, will be fine.

HI Ed

No I have CBSolar AGMs which are now 2 years old and I am nursing them in their old age. At the moment the batteries of choice as replacements are 370Ah L16REBs.

I have recently been looking at Lithium as there are some new offerings on the market.

[Guest]

FWIW, the cheapest standard lead acid batts I found was IND33-2v.

I have them at about R1.52 per kWh. 

[Chris Hobson]

1 hour ago, The Terrible Triplett said:

FWIW, the cheapest standard lead acid batts I found was IND33-2v.

I have them at about R1.52 per kWh. 

They are 1850Ah batteries so besides costing a bank robbery worthy amount of money I wonder whether I have enough panels to charge them. Yes I would only cycle them by 10-15% under normal circumstances but accidents happen. As much as I would be envious of such a bank, my current setup would as mismatched as Billy Joel (panels and inverter) and Christie Brinkley (batteries). Some of the younger forumites will have to resort to google to find out what the "old goat" is on about.

[Guest]

48 minutes ago, Chris Hobson said:

1850Ah batteries

A 48v bank you need 24 of them ... costs the same as a small farm!!!

With loads to match the bank, I would like them for 12v system with more than one controller in parallel to make it happen on the charging front.

Once my T105RE's are done, and load shedding returns, I will get these batts.

And with them being industrial, 2800 cycles to 50%, I would not have them stand idle at 10-15% use. Will cycle them to 50% as that is where the R1.52 comes in at. Currently I am paying R2.28 kWh, but there is no way I can justify spending that kind of money on any batts in today's economical situation.

Let the #GuptaLeaks run its course first, then I wait for my current bank to go and only then if there are regular power failures will these batts become viable.

[___]

13 hours ago, Chris Hobson said:

mismatched as Billy Joel (panels and inverter) and

Just don't start any new fires, 'mkay?