The fortress I installed if I can remember did recommend a lower voltage for open loop vs closed loop. With closed loop being closer to 56v or what the inverter is programmed with. Now why they recommended lower open loop wasn’t clear.
The 54.4v is the lower end of many 51.2v prismatic charging ranges. The eg4 which I was just looking at is 56.2 +/- .8v which makes the lower end at 54.4. I would like to know given this 1.6v charge range what are the pros and cons of the 54.4 vs 57v? if anyone knows pls chime in. As to your comment below that you go with longer absorb to get better balance of SOC between the batteries, is this what you are finding in practice? thanks jay > On Jul 15, 2025, at 6:31 AM, Maverick Brown via RE-wrenches > <[email protected]> wrote: > > Jay > > A little bit of both. > > Here is the integration guide from Outback and from Fortress > > https://outbackpower.com/downloads/documents/appnotes/fortress_app_note.pdf > https://www.fortresspower.com/wp-content/uploads/2021/11/Fortress-Power-Integration-Guide-with-Outback-inverter-Rev1.5_5.16.2021.pdf > Then, I added more time to the Absorb to get better SOC between the > batteries. > > I’m trying to stay lower volts based on these guides. > > Another issue is to make sure the voltage that the charge controller thinks > it has verses what the battery terminals or the bms report. I have bumped up > the voltage on charge controller to calibrate what the battery actually > thinks it’s getting. I know the outback charge controller has a calibration > offset, but sometimes they can’t get high enough. > > Let me know what you think. > > > Thank you, > > Maverick > > Maverick Brown > Off-Grid Solar Commander since 2006 > Maverick Solar Enterprises, Inc. > • Solar Commander Remote Power > • SunFlow Systems Cathodic Protection > [email protected] > 512-460-9825 > > > >> On Jul 14, 2025, at 12:49 PM, Jay via RE-wrenches >> <[email protected]> wrote: >> >> >> Hi Maverick >> >> That is a unique to me charging parameters. >> Did you figure this out on your own or did you get this from a OEM? >> >> Is the long absorb time for making sure the internal passive balancing has >> time to work? >> >> I don’t understand the very low charge voltage. Can you explain please? >> Thanks >> Jay >> >> >> >> >>> On Jul 14, 2025, at 11:12 AM, Maverick Brown via RE-wrenches >>> <[email protected]> wrote: >>> >>> Jason >>> >>> It looks like you are in great shape to do what you’re trying to do. >>> >>> For legacy inverter systems, I have set the absorb quite long: 4 to 6 hours >>> depending on the quantity of individual batteries. >>> >>> Here at my own house, I have 8 eFlex batteries and 8 Pytes batteries. All >>> in parallel on an outback radian. I have 55.2v absorb set for six hours >>> with zero end amps. For the E flex batteries I have the fortress guardian >>> and I can see the battery state of charge remotely individually. When the >>> individual battery state of charge variation gets too large, I run an >>> equalize session getting the battery voltage up to 56 V. >>> >>> I have other customers with various mixes of batteries. They are all 16 S >>> lithium iron phosphate and as long as somebody is paying attention so far >>> it’s been working fine. >>> >>> For this customer, I would select Pytes as the brand of battery to add to >>> the system because in the future, you can still add more batteries to that >>> rack. And you can get the individual battery state of charge using solar >>> assistant. >>> >>> Thank you, >>> >>> Maverick >>> >>> Maverick Brown >>> Off-Grid Solar Commander since 2006 >>> Maverick Solar Enterprises, Inc. >>> • Solar Commander Remote Power >>> • SunFlow Systems Cathodic Protection >>> [email protected] >>> 512-460-9825 >>> >>> >>> >>>> On Jul 14, 2025, at 10:56 AM, Jason Szumlanski via RE-wrenches >>>> <[email protected]> wrote: >>>> >>>> >>>> This client has been advised that it's not a good idea, and any failures >>>> might result in a complete battery replacement. If he goes forward, it >>>> will be at his own risk. >>>> >>>> They have a full-time homewatch person who is quite capable. He could >>>> monitor SOC and also isolate banks for balancing efforts if necessary. We >>>> have a nice Midnite 2000A battery combiner there with breakers for each >>>> battery, so it would be pretty convenient. >>>> >>>> Self-insured. I don't think any of my off-grid barrier island clients have >>>> insurance. The mainland insurance market is messed up in Florida. Forget >>>> about the islands. >>>> >>>> >>>> Jason Szumlanski >>>> Principal Solar Designer | Florida Solar Design Group >>>> NABCEP Certified Solar Professional (PVIP) >>>> Florida State Certified Solar Contractor CVC56956 >>>> Florida Certified Electrical Contractor EC13013208 >>>> >>>> >>>> On Mon, Jul 14, 2025 at 11:31 AM Dave Angelini Offgrid Solar via >>>> RE-wrenches <[email protected]> wrote: >>>>> Does the client know that they can't blame you for doing something that >>>>> has chances of being a bad choice? >>>>> >>>>> Can the client keep track of two different Soc and be responsible about >>>>> it? >>>>> >>>>> I would also look into how a home insurance policy would react to a claim. >>>>> >>>>> Dave Angelini Offgrid Solar >>>>> "we go where powerlines don't" >>>>> <http://members.sti.net/offgridsolar/>https://offgridsolar1.com/ >>>>> <http://members.sti.net/offgridsolar/> >>>>> e-mail [email protected] <mailto:[email protected]> >>>>> text 209 813 0060 >>>>> >>>>> >>>>> On 2025-07-14 6:45 am, Jason Szumlanski via RE-wrenches wrote: >>>>> >>>>>> They are Lithionics. >>>>>> >>>>>> >>>>>> Jason Szumlanski >>>>>> Principal Solar Designer | Florida Solar Design Group >>>>>> NABCEP Certified Solar Professional (PVIP) >>>>>> Florida State Certified Solar Contractor CVC56956 >>>>>> Florida Certified Electrical Contractor EC13013208 >>>>>> >>>>>> On Mon, Jul 14, 2025, 9:33 AM jay via RE-wrenches >>>>>> <[email protected] >>>>>> <mailto:[email protected]>> wrote: >>>>>> Hi Jason, >>>>>> >>>>>> can you let us know what the old battery is so we can dig up the specs >>>>>> and see if there would be any issues. >>>>>> >>>>>> There are a few odd ball like simpliphi which while a 51.2v has a very >>>>>> narrow window for operation compared to most other prismatic cells. >>>>>> >>>>>> jay >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>> On Jul 14, 2025, at 5:07 AM, Jason Szumlanski via RE-wrenches >>>>>>> <[email protected] >>>>>>> <mailto:[email protected]>> wrote: >>>>>>> >>>>>>> There are never-ending videos on YouTube showing different brands and >>>>>>> capacities of LFP batteries working in parallel. I have never tried it >>>>>>> myself, and every instinct says don't do it, but I have a situation >>>>>>> where it would be very helpful. >>>>>>> >>>>>>> I have a client with an older 60 kWh battery that is discontinued and >>>>>>> incompatible with any other battery from the same manufacturer. It has >>>>>>> a BMS with a 51.2 volt nominal rating. They need another 20 kWh of >>>>>>> capacity. It is too costly to scrap the existing battery and start >>>>>>> over, and the existing battery has been tested and confirmed to hold >>>>>>> very close to its rated capacity. >>>>>>> >>>>>>> What is the real deal on mixing and matching? Is anyone doing this >>>>>>> safely and successfully? I wonder what the battery manufacturers say >>>>>>> about it. >>>>>>> >>>>>>> Jason Szumlanski >>>>>>> Florida Solar Design Group >>>>>>> >>>>>>> _______________________________________________ >>>>>>> List sponsored by Redwood Alliance >>>>>>> >>>>>>> Pay optional member dues here: http://re-wrenches.org >>>>>>> <http://re-wrenches.org/> >>>>>>> >>>>>>> List Address: [email protected] >>>>>>> <mailto:[email protected]> >>>>>>> >>>>>>> Change listserver email address & settings: >>>>>>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >>>>>>> >>>>>>> There are two list archives for searching. When one doesn't work, try >>>>>>> the other: >>>>>>> https://www.mail-archive.com/[email protected]/ >>>>>>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >>>>>>> >>>>>>> List rules & etiquette: >>>>>>> http://www.re-wrenches.org/etiquette.htm >>>>>>> >>>>>>> Check out or update participant bios: >>>>>>> http://www.members.re-wrenches.org <http://www.members.re-wrenches.org/> >>>>>>> >>>>>> _______________________________________________ >>>>>> List sponsored by Redwood Alliance >>>>>> >>>>>> Pay optional member dues here: http://re-wrenches.org >>>>>> <http://re-wrenches.org/> >>>>>> >>>>>> List Address: [email protected] >>>>>> <mailto:[email protected]> >>>>>> >>>>>> Change listserver email address & settings: >>>>>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >>>>>> >>>>>> There are two list archives for searching. 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When one doesn't work, try the >>>>> other: >>>>> https://www.mail-archive.com/[email protected]/ >>>>> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >>>>> >>>>> List rules & etiquette: >>>>> http://www.re-wrenches.org/etiquette.htm >>>>> >>>>> Check out or update participant bios: >>>>> http://www.members.re-wrenches.org <http://www.members.re-wrenches.org/> >>>>> >>>> _______________________________________________ >>>> List sponsored by Redwood Alliance >>>> >>>> Pay optional member dues here: http://re-wrenches.org >>>> >>>> List Address: [email protected] >>>> >>>> Change listserver email address & settings: >>>> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >>>> >>>> There are two list archives for searching. 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