Conect XW voltage too inaccurate for LFP charging?

I recently cut over to LFP batteries for my off-grid, XW6848 + dual MPPT60 controllers. Also included are SCP and AGS controlling backup generator. The LFP batteries are stand-alone with respect to the XW system, and I am trying to get the XW charge settings to work appropriately. While doing this, I'm seeing two problems.
1) Reported voltages between the MPPTs and XW6848 are different, and the spread increased as battery voltage rises. The two MPPTs are within about 100mv of each other, and within about 100mv of fluke measured bank voltage. But the XW6848 is reporting about 500mv higher, and towards the end of charge as bank voltage climbs to 54+ volts, the difference seems to grow to as much as 900mv. That's a huge inaccuracy for LFP operation. I have checked voltages at the device terminals while under XW charge load of 115A and measured voltages are the same as bank V, so not wiring issues or losses. This would appear to just be crappy metering in the XW?
2) The Bulk to Absorb transition doesn't appear to be happening at the programmed voltages. I have bulk and absorb both set to 55.2v (3.45Vpc). But the transition to Absorb happens at about 54.5v. And that happens for both the XW and the MPPTs. Both are stopping prematurely. As an experiment I tried raising the XW bulk/absorb set point to 52.7V, and the transition point rose, but only by 200mv.
So far I have been using the Custom settings in both devices, and not the Lithium settings. But for 3 stage charging with Lithium, there is no documented difference between what I'm doing now.
Comments
If you have equipment that is not in support life they may just tell you that.
Schneider gives a field direct phone number to people like me who install and sell their equipment.
I have heard that they are working on an interactive FAQ for users with non supported equipment.
They have investor share holders and have to be profitable. Going out of business is not acceptable to me and so I respect their decision.
You have choices, no one makes you use their equipment.
Good Luck with your battery setup. What make is it?
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Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
If Schneider was in end sales--They would be getting more of the retail $$$ to support a larger support crew.
I ran into this issue decades ago with outsourcing and offshoring of manufacturing.
I, as a design engineer, used my local suppliers and mfg representatives to get me the support I needed to design and implement their parts on my designs.
In the meantime, my MBA VPs of Manufacturing were telling the upper management how much they could save with outsourcing to other states/countries.
And my support from local suppliers/distributors/Mfg. Reps was starting to dry up as they were nowhere near the money flow other than for the first 5-10 prototypes.
They were literally telling me to contact the overseas contract suppliers' vendors/mfg reps in China for support. What we got from data books and the Web was all were were going to get locally.
Buying complex/expensive hardware from a reliable local "authorized" retailer/distributor does raise costs. But you ain't going to get very much support from somebody on EBay that sold a FOT (fell off the truck) unit.
Good support costs money. It can make or break your product. I am sure that Schneider is not making these decisions in a vacuum.
-Bill
BMS is the key and how well it is integrated. The ones I use are designed by the battery manufacturer.
One of the Engineers there said the most common call was what does the red LED mean on an mppt-80.....
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The Classics also can sync charge states such that whoever gets to Vabs first triggers everyone else to change mode also. Wouldn't be surprised if yours does similar.
.75V strikes me as a lot of slop even for LA, let alone lithium.
Back in the day, some of my (better) network gear makers supported usenet groups or forums (not unlike this one) where the vendor had someone clueful lurk and sometimes help otherwise clueful but stuck folks using their gear. The RTFM stuff like what does the blinky light mean got weeded out by more clueful users. Actual vendor engineers got to interact with actual clueful users though too, to the benefit of both IMHO.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
These devices generally have fairly simple brains, and it could be just "when [condition] do [something]", without much sanity checking. The CCs, for example, may not be able to check and say to the inverter "hey bud, you aren't charging anyway, so thanks for the tip but we'll carry on charging anyway". They may just hear and obey.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
With regards to the voltage difference displayed, I too have noticed deviation between MPPT display and SW via SCP. Since the resolution of both is only 100 milivolts, not that accurate, I choose to monitor actual battery voltage as well as individual cell voltages via a BMS display which corresponds with my Fluke meter readings. The conductors from CC to battery, battery to inverter, will always have some voltage drop and the higher the current, the larger the drop. Depending on actual inverter load these discrepancies are greater, why I ignore them, as long as the voltage is correct at the battery that's what I consider important. Are the device in you case all connected to a common point such as a DC distribution, or on seperate feeders?
As for settings what I use are, bulk/absorption 56V, absorption 6 minutes float 54V, EQ disabled, temperature compensation 0mV/C, battery capacity 20Ah per Kw of installed capacity, default battery temperature warm, recharge 50.5V, maximum charge rate 10A per installed Kw.
Inverter charger settings same as above except, 2 stage no float, LBCO 48V, LBCO hysteresis 2v, LBCO delay 10 seconds, high battery cut out 60V.
Notes and observations: Voltages doubled from my actual 24V nominal values, LBCO is the highest setting available 50.2V would be more desirable. During solar charging the controller display voltage reaches the programed 28V but battery terminal voltage is 27.6V when charge current is ~36 A, voltage drop, cell voltages 3.454 +/- 18mV once in float all cells are <10mV. apart. Been operating for 5 months without issues, haven't needed generator so little testing done with regards to that. Have contacted Schneider support regarding LBCO they have been useless, never reply despite auto reply stating will respond next business day, I'm still waiting a month later, pretty poor.
Edit, found document where settings were sourced, see attached pdf.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Can you please provide a link or pdf for the BMS you're using, it just interests me to know what's out there, may I ask if you if previously used LA and made the switch to LFP, or just took the plunge? What are your options regarding the performance, in comparison to LA, if applicable. There aren't many who use a DIY system in this theater, dialog is extremely useful because I believe it's a hidden treasure many overlooked primarily out of fear of the unknown.
Personally I did have LA before, the primary reason for the switch was temperature, the efficiency of LFP which greatly reduces battery temperature, the enemy of LA, in a tropical environment there is a distinct advantage, perhaps not so in cold climates, where there are other challenges in keeping the bank warm.
For what it's worth, I have 2 Fluke 179's and Fluke 20, all measure different voltage +/- 10 mV, sometimes consistent, there are tollerance variations even with the best tools.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Thanks for the link to a very interesting blog, quite an endeavor to to actually make a BMS with a PLC, so this is what you are using?
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Why is it the people you bought it from are not there for your really old firmware?
You turned down my offer for sending you a combox or config tool to upgrade your old firmware.
You seem to have handcuffs on and the key is in your pocket. Shheesh!
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As a general comment here, if one buys from an online store that is the cheapest price on the internet and the store has very little experience, support is just not going to be there. It really is the source of the equipment that takes on the support. If you have a warranty claim then yes Schneider will take care of that and does.
My opinion only but when Schneider bought xantrex they were asked by many of us to reinstate the Xantrex user forum to help users who are DIY. Outback still does this and I use them often for that reason. Both Xantrex and Schneider decided that they were really after the professional installation market and could not spend resources on DIY. It is their business
If Schneider says the voltage is within tolerance and you can't offset the numbers to charge correctly, then you have a problem. I do not understand why you can't offset it. There is the solar voltage charging and the XW charging voltages, why do they have to agree?
Most Gen users offset all the time to get max solar and minimum fuel usage when both charging types are running. I agree that I do not see more than a couple 100mV max difference over the voltages.
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The gear purchased was from an authorized distributor recommend by Schneider, not from an online store, the distributor refers me to local support, local support refers me to the distributor, after contacting support in Canada they recommend contacting support in Thailand who bounce me back to the distributor who refuse to answer emails.
The equipment should have been sold with firmware that is up to date, as such it's their responsibility as a distributor to correct the issue, or pressure local support, failing that, it is in my opinion that head office should intervene as the parent. Your offer to assist is greatly appreciated, there was no refusal of the offer, just thought I would wait for a response from support in Canada as promised, I believe it's the companies responsibility to resolve problems, which it appears they are unwilling to do, they too do not reply as they claim they will, or perhaps I'm being impatient, it's only been a month, took three months last time.
Schneider's choice to alienate DIY users to focus on "professional installers " should then exclude sales to all other than registered installers, or at very least have a disclaimer stating as an independent installer all support is void. While they're at it removing or the fluffy "we're committed to support" videos, or amend them to include unless you're not an installer. Eventually reputation will exclude Schneider from consideration at a customer level, their market share will diminish to a point where even the installers get no support, but will be left holding the ball.
As mentioned before the equipment is great, sure I could buy a ComBox but really have no use for it, other than installing firmware, it works as is, it's shortcomings can be compensated for by external control already in use so no big deal, when it comes to replacement though, I'll look elsewhere.
Apologies to @twistedtree for any derailment.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
It is a ridiculous statement that the firmware should be up to date on a new product that was going thru updates. You should have bought the more mature XW in that case, especially in a developing country with very few people there to support what they sold you. How much money should Schneider spend on someone like you or in a country with that bad of a dealer network?
twistedtree If you post your settings and there are quite a few I will take a peak. What you describe does not sound right. There are at least 3 things that could cause metering errors. I assume this means voltage?
Just because a voltage anomaly does not vary with current, does not mean that there is not a wiring defect. You should triple check any older equipment by removing the wires and inspecting. Sometimes just removing the connection will remove a "diode effect" defect.
You can see in my previous screen shot how little error there is in the mppts. The -60 mppt is a beta from 2006.
Beautiful day here today. Where ever you guys are be sure and go outside and enjoy it. Electronics can be over rated
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