Victron BMV700 and MMPT setup parameters for lifepo4 battery

[rookie23]

We have purchased a lifepo4 200AH battery pack of 8 x CALB 100AH cells. Hopefully I will get them installed in the next few days! Battery cell info:
https://www.lfp.net.au/product-page/...ell-calb-ca100

I am trying to work out how to setup the Bluesolar MMPT 75/15 regulator and the Victron BMV 700 to get an accurate SOC etc with my charging profiles used and add a low voltage disconnect using the BMV at about 20% SOC. If I could get some help with the specific values for parameters for our setup it would be most appreciated as this will be our first experience with lifepo4. Our chargers and profile settings will be:
- Redarc BCDC1225 set to "AGM/GEL". Max charge: 14.6v Float: 13.3v (used when moving to and from locations, will manually turn this off at times on long trips if needed)
- Projecta mains charger set to "GEL". Max charge: 14.1v Float: 13.7v (used occasionally when preparing for trips to get Fridge cold and/or charge battery. “Float” high but will not be left on for long after charging battery)
- Victron MMPT from solar set to something appropriate for my setup like Max charge: 14.0v Float: 13.2v (I think I should leave "absorption" off)


Victron seem to recommend the following for BMV70x. "For “solar systems” it is recommended 0.3v below “Absorption” voltage and “non solar” 0.3v below “Float” voltage. As my MMPT can create a profile maybe I set it for the Redarc “Float” level. Therefore 13.3 – 0.3 = 13.0v. Therefore the Victron BMV700 values for our pack would be:
Charged voltage: 13.0, Tail Current: 4% (use default) , Charged Detection Time: 3 min (use default) and Peukert Exponent: 1.05 (lifepo4 recommendation). Do these seem reasonable in my case or should the charged voltage level be higher?


As I can program the MMPT, what would be the recommended values to start charging with solar at?

What parameter values should I set the LVD at to get a disconnect at about 20% SOC?

The LVD will be turning ON/OFF via this BCU connected to a latching relay.

BMV Manual: https://www.victronenergy.com/upload...S-SE-PT-IT.pdf

[sebcbien]

Hello,
Found this post, very interesting as Victron doesn't give standard settings for LiFePo4 batteries...
Anyway, did you keep those settings, especially for the bmv ?
Thanks!

[rookie23]

Hi, I don't think i ended up using many of these settings after speaking the supplier of the batteries who had installed a few BMV's with Lithiums.
Since then I have gone to manual syncs rather than using the in built BMV synching as it didn't seem very accurate at least in my case. I may end up going back to it if appears to work better that me doing it manually.

Everything is working well currently but its been an effort to get there!

I am still playing with these values to try and get the SOC more accurate but its still a work in progress. I am not sure to many people understand this well.

[Stu Jackson]

Originally Posted by rookie23

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I am still playing with these values to try and get the SOC more accurate but its still a work in progress. I am not sure to many people understand this well.

Sure we do. Or maybe we don't understand your questions.

But for a coulomb counter, your 700 if my guess is right, there's this link, plus one of many that Maine Sail has written extensively about.

For everyone installing a battery monitor: The "Gotcha Algorithm" thread, a "MUST READ"

Link-series Charging Algorithms -- The "Gotcha" Factor!

DEFAULTS are factory settings that are made to be modified to suit your setup.

Also read this one:

Programming a Battery Monitor (by Maine Sail)

Keeping Your Battery Monitor More Accurate Photo Gallery by Compass Marine How To at pbase.com


Good luck.

[sebcbien]

thanks for all the informations !!

[rookie23]

For these CALB 100 AH batteries (I have 8 of these making a 12v 200Ah battery) , does anyone know what the 20 hour and 1 hour discharge rates would be (to use for Peukert calculation) or Peukert value for these batteries? I have contacted the supplier but they do not know and have not been able to source the answer.
http://evwest.com/support/CALB-CA100Ah.pdf

Does anyone know what the CEF value should be for these batteries with a BMV700 monitor or where a good starting point might be?

[mbartosch]

Originally Posted by rookie23

For these CALB 100 AH batteries (I have 8 of these making a 12v 200Ah battery) , does anyone know what the 20 hour and 1 hour discharge rates would be (to use for Peukert calculation) or Peukert value for these batteries? I have contacted the supplier but they do not know and have not been able to source the answer.
http://evwest.com/support/CALB-CA100Ah.pdf

Does anyone know what the CEF value should be for these batteries with a BMV700 monitor or where a good starting point might be?

LiFePO4 banks are pretty efficient. From the top of my head:
With our installation (12V/400 Ah Winston LiFePO4, BMV 700) I have set the Peukert Exponent to 1.04, Charge Efficiency to 99% and tail current to 4 % IIRC. Accuracy was pretty good during the past year.

BTW, I just read the first post of this thread. 14.6 V absorption and 13.7 V float are way too high for LiFePO4. I suggest to read the excellent threads about LiFePO4 batteries about safer values.

[rookie23]

Thanks for the suggested values, I have learnt a lot since the original post.
My charging is well under control now within generally accepted lower thresholds, just need to get the SOC % to calculate better by getting the BMV parameters more accurate.