Where is my power going?

[Zwy]

I would not have float at 56.0V.

There is a reading on my batteries on the status screen that says BmsSat: 0000
What does that mean?

I'd ignore it if nothing in is in the manual. I believe it is for communication which under USER set in the inverter you don't need. Don't make this more complicated than it needs to be.

Also, are my inverters also my BMS?

No, the BMS will be inside the battery case.

 

[smr.ruby]

Also, are my inverters also my BMS?

No, the BMS is inside the Big Battery box and it is monitoring the individual cells. Unless you are using communication cables from inverter to batteries the only thing the inverter knows about is the DC bus voltage to both batteries. I do think if any of the responses to you have been confusing the bits about "don't go over 3.xx" cell voltage" are not helpful for you because you are not (from what I've seen) changing the settings in your BMS (those are usually locked out to most users anyway).

 

[New England Rhinoceros]

I would not have float at 56.0V.



I'd ignore it if nothing in is in the manual. I believe it is for communication which under USER set in the inverter you don't need. Don't make this more complicated than it needs to be.


No, the BMS will be inside the battery case.

Thanks. I feel so stupid on this forum. Seems like there is a ton of shit I don’t know/understand.

 

[Zwy]

Thanks. I feel so stupid on this forum. Seems like there is a ton of shit I don’t know/understand.

You will be fine, you just need to get the 2 batteries in balance.

It's not complicated once you get the hang of it.

Here is why I would not use 56.0V for float. The bulk charge rate you have been using most likely has some cells running up near BMS high voltage disconnect. This hasn't helped keep both batteries in balance, the BMS could have a disconnect during the day when charging occurs and you would not know the difference as your system keeps working. When charging is done for the day and DC bus voltage drops low enough for the BMS to reconnect, one battery could be near 100% and the other at 80%. This starts the imbalance as battery cell voltage might be for example 3.35V across both batteries but one battery is close to 100% SOC while the other isn't. This is due to the flat discharge curve of LFP.

There is no reason to float LFP at higher voltage. If float is set so cells get to 3.4V and that is when balancing begins, the cells will balance over time. As stated before, the few Ah's above 3.4V per cell don't amount to squat while there may be reduced cell lifespan.

I push my battery bank hard to an extent, but I'm not foolish with my money long term either.

 

[jimf909]

Thanks. I feel so stupid on this forum. Seems like there is a ton of shit I don’t know/understand.

No need to feel stupid. There is a LOT to learn and like anything it takes time to synthesize the information. On top of it there is a some gray with some of the topics and opinions, code and interpretations vary. In some things the facts are immutable.

Reading the all of the manuals is good starting point (sadly, some manuals aren't awesome). Ask questions to the mfr. and here on what isn't clear (sadly, sometimes the mfr. or posts here are unclear or wrong). Go to beginners corner to see what people are asking. I find that's a good place to learn.

I've got some years of experience and know some stuff and am a total n00b with other stuff. Knowledge takes time to build.

 

[Zwy]

No, the BMS is inside the Big Battery box and it is monitoring the individual cells. Unless you are using communication cables from inverter to batteries the only thing the inverter knows about is the DC bus voltage to both batteries. I do think if any of the responses to you have been confusing the bits about "don't go over 3.xx" cell voltage" are not helpful for you because you are not (from what I've seen) changing the settings in your BMS (those are usually locked out to most users anyway).

The very responses stating to go to higher bulk and float are the confusing responses. There is no need to go there.

Relying on a BMS to disconnect with high cell voltages that should not be reached on a daily basis is just asking for trouble. The Up In Smoke forum contains more than just a few cases of cell damage from excess voltage, fires, failed BMS's, bloated cells, take your pick.

Do what you want with your batteries, but I won't let you tell someone inexperienced to do something that could cause them to post in The Up In Smoke forum.

 

[ksmithaz1]

NO THAT IS TOO HIGH !
58.0V = 3.625 Volts per Cell ! DON'T !
56.0V = 3.500 Volts per Cell and that is MAX for a Working Battery Pack.
Even then, this is still considered Aggressive hence why a Majority of longterm LFP users will not go over 3.450 Vols per cell or 55.2 Volts for Bulk/Absorb and Float at 55.00V or 3.437Volts per cell.

The ONLY TIME to charge Battery cells to 3.6## is to Top Balance or after longterm storage ONLY !!!
This is also stated in many manufacturers spec sheets.

Not according to manufacturer... They spec even higher.

SKU:	AKONG-48150-G1
System Voltage:	48V
Nominal Voltage:	51.2V
Chemistry:	LiFePO4
kWh Capacity:	15kWh
Ah Capacity:	300Ah
Charging Voltage Range:	55.6 - 58.0V
Max Charge Voltage:	58.8V
Operating Voltage Range:	47.2 – 58.8V
Suggested Low Voltage Cutoff:	47.2 – 50.8V
BMS Cutoff Range:	42 – 47V
Cell Configuration:	16S 2P
Max Continuous Discharge Current:	150A
Max Continuous Power:	7500W
Max Discharge Peak Current:	350A (6 Seconds)
Max Charge Current:	90A

 

[New England Rhinoceros]

My batteries read in millivolts, as we speak I’m charging and all of the cells read 3400. I assume that to be 3.4v. I have changed my charge settings to 55.2v bulk and 55.0v float like Steve S had suggested, I’d rather err on the side of caution than not. If my system fails I’m completely dead in the water. The nearest utility is 2/10 of a mile away and the power company wants $15k for temporary power. That was 18 months ago, since then the utilities have gone up.

 

[Zwy]

Not according to manufacturer... They spec even higher.

SKU:	AKONG-48150-G1
System Voltage:	48V
Nominal Voltage:	51.2V
Chemistry:	LiFePO4
kWh Capacity:	15kWh
Ah Capacity:	300Ah
Charging Voltage Range:	55.6 - 58.0V
Max Charge Voltage:	58.8V
Operating Voltage Range:	47.2 – 58.8V
Suggested Low Voltage Cutoff:	47.2 – 50.8V
BMS Cutoff Range:	42 – 47V
Cell Configuration:	16S 2P
Max Continuous Discharge Current:	150A
Max Continuous Power:	7500W
Max Discharge Peak Current:	350A (6 Seconds)
Max Charge Current:	90A

And you charge yours to?

 

[New England Rhinoceros]

No need to feel stupid. There is a LOT to learn and like anything it takes time to synthesize the information. On top of it there is a some gray with some of the topics and opinions, code and interpretations vary. In some things the facts are immutable.

Reading the all of the manuals is good starting point (sadly, some manuals aren't awesome). Ask questions to the mfr. and here on what isn't clear (sadly, sometimes the mfr. or posts here are unclear or wrong). Go to beginners corner to see what people are asking. I find that's a good place to learn.

I've got some years of experience and know some stuff and am a total n00b with other stuff. Knowledge takes time to build.

My manuals are crap and the “help desk” phone line at Shop Solar is considerably less than desirable and anything BUT helpful.

 

[DIYrich]

My battery setting is set to "USE" which I believe is user defined. My default battery equalization is set to disabled but the very limited manual with my inverters says I can set this value, (program 30) to enable battery equalization if my batteries are set to USE.

What values would you recommend? I'm at my wits end here and have a LOT of money in this system.

I would do one cycle to 58.0v. Your batteries seem to need power and a reset. The BMS will protect the battery. After that, do whatever Steve suggests.

 

[DIYrich]

I also suggest adding a shunt, like victron smart shunt, so you can get more detail on the battery.

Also, ask shop solar if the bms has an app.

 

[smr.ruby]

My batteries read in millivolts, as we speak I’m charging and all of the cells read 3400. I assume that to be 3.4v.

Yes 3400mV is 3.4V. And the fact that they are all equal that high on the charge curve is good, that means they are pretty well balanced. I kind of doubt your system is anywhere near "failure" you just need to 1) get them fully charged and I believe 2) you still need to figure out why you are using more power than you expect? Refrigerator? 12V power supply on the RV? For context I run a similar RV setup and on a cold night (25F) I can use about 6KWH over a ~20 hour period that is cloudy in the evening and dark at night - just on a little bit of TV time and continuous cycling of the heater fan and with the refrigerator running from 120v (not propane).

 

[Steve_S]

There is a reading on my batteries on the status screen that says BmsSat: 0000
What does that mean?
Also, are my inverters also my BMS?

A BMS (Battery Management System) is contained within the battery packs. It is the Guardian & Manager simply put.
It ensures that batteries are not Over/Under charged by enabling/disabling those functions.
Some can balance cells Passively or Actively, others may not at all.
They will also prevent cells from charging outside of proper operational temps.

An Advanced BMS with communications ability can interact with Inverters or AIO (All in Oners). of course there are dependencies.

 

[ksmithaz1]

Thanks. I feel so stupid on this forum. Seems like there is a ton of shit I don’t know/understand.

Never confuse ignorance with stupidity. The former is easily correctable, stupidity would be staying ignorant and not asking questions. Take your time sift thru the reponses, you'll get the enlightenment you need.

The values you spec seem to be within the boundaries of their published specifications, but there are going to be folks here that have their own ideas on what is appropriate for the various chemistries of batteries. 10K FT view, the bottom line is your 'Big Battery' (all of these batteries have something) has a 'BMS' inside that tries to control the individual cells and make sure they charge evenly. You generally have two voltages spec'd, a 'float' voltage and a 'Bulk or charge' voltage. The former is where you just leave it, think 'trickle charger' for you car battery. The latter is a number you can use to make it charge faster, and you will want to hold it there for a time, as the BMS will use the additional voltage to bleed power from one cell to another so the individual cells all have the same state of charge (SOC), ie the voltage level will be the same for each battery.

So what the battery geeks are taking about is optimizing the values and time that work best for the batteries. If the batteries get out of whack, ie with wide variances in voltage, it causes issues because the cells are in series and it becomes difficult to accurately figure out the SOC, then the BMS will shut things down before it should. This gets more complicated when you run two in parallel, as the battery units may also vary slightly, and the overall objective is to minimize the variances across the board.

(I'll defer back to the battery geeks from here)...

 

[DIYrich]

Does your inverter tell you how much power is being sent to loads?

 

[smr.ruby]

I also suggest adding a shunt, like victron smart shunt, so you can get more detail on the battery.

Also, ask shop solar if the bms has an app.

These are great and I recommend too. But if you are in a pinch and don't have one OP should consider watching the battery discharge rate (amps) and going around messing with various loads: turn everything off and make sure amp draw is limited to inverter standby. then turn on only the TV. then only the refrigerator. etc etc. the amp meters in the BMSs are usually pretty good too.

 

[ksmithaz1]

He is only changing the inverter settings anyway. The BMS is going to control the charge situation as long as the inverter is providing more voltage than the BMS needs it isn't going to impact the battery. 58v at the inverter doesn't translate to 3.625v/cell because the BMS is just going to disconnect from the supply when it sees fit. Personally I run my inverters at 56.4 for all bulk and float and the BMS's take care of the rest. 58 is high but with ANY decent BMS it won't cause problems because even with a 56v setting the BMS will disconnect when it needs to . The risk of running 54v float charge though is that his BMS is never resetting to 100% because the inverter is not giving the BMS enough voltage to ever see an OV situation or whatever triggers it to "decide" the batteries are 100% and re-calibrate. That is likely why he is seeing the SOC reading be way off.

Especially with two batteries without really good data communication between batteries and inverter there is no guarantee that they both need the same voltage at the same moment in time (to come to full charge) so better to run it a bit high and let the batteries do what they are supposed to for themselves.

How exactly does the BMS kick in and prevent you from overcharging the batteries? The ones i've seen have a relay, and it should be on when the battery is "ON". There are two voltages in the inverter settings because the inverter/charger is supposed to be monitoring the voltage to the battery. It is supposed to attempt to provide the bulk voltage to the batteries. When the voltages reaches that threshold, it is supposed to drop the voltage to the batteries to the float voltage. If you set the float voltage too high you will cook your batteries. If your inverter/charger can communicate with the inverter then it can tell the inverter what voltage it would like to see, but the BMS has no way I am aware of to control the voltage it is passing thru. The nice part about BMS communication with the inverter is that it can actually request an appropriate voltage based on what it is seeing at the cell level.

 

[Steve_S]

Not according to manufacturer... They spec even higher.

SKU:	AKONG-48150-G1
System Voltage:	48V
Nominal Voltage:	51.2V
Chemistry:	LiFePO4
kWh Capacity:	15kWh
Ah Capacity:	300Ah
Charging Voltage Range:	55.6 - 58.0V
Max Charge Voltage:	58.8V
Operating Voltage Range:	47.2 – 58.8V
Suggested Low Voltage Cutoff:	47.2 – 50.8V
BMS Cutoff Range:	42 – 47V
Cell Configuration:	16S 2P
Max Continuous Discharge Current:	150A
Max Continuous Power:	7500W
Max Discharge Peak Current:	350A (6 Seconds)
Max Charge Current:	90A

Sorry but I am going to be terribly BLUNT on this.
Far too many battery pack sellers will use the ALLOWABLE VOLTAGE range in their specs which is terribly wrong... Even with perfectly matched cells, stuff WILL get awry past the working curve. This is just the way it is.

Nominal Cell Voltage is ALWAYS STATED AT 3.200 Volts for Standard LFP. Dead Centre of the Working Range which is 3.000-3.400 YES that Very Flat voltage curve. IF Nominal Voltage was stated as 3.075 that would put it dead centre of 2.500-3.650.

EVE, CATL, LISHEN and all the others producing Standard LFP, test & validate the cells to deliver their stated AH from the WORKING RANGE and not the allowable.

Confusion Source: quite often, "shifty" vendors flogging great market cells will say they are rating the cells from testing BUT from 3.650 down to 2.50. Customer get's them, charged to 3.450 and tests to 3.000 and get's "maybe" 80% of spec'd AH. It's happened a LOT and a lot of folks here have hit that... Again why some of us tell folks to get A-Grade Matched & Batched with Factory Reports only.

Finally, we have people here using every conceivable "assembled retail battery" out there pretty much (for this class of gear). A great many have just followed the "label" charging to 3.65 etc etc... They hit problems, we troubleshoot, they finally get to reasonable, proper conservative charging profiles and POOFDAH the Problems go away... time & time & time again... BTW: it gets exhausting !

There are links in my signature & several TECH threads I've written over the years for folks here... Have at it and Good Luck.

 

[ksmithaz1]

And you charge yours to?

I don't DIY/fiddle with my batteries or inverter settings. I let the battery BMS to inverter communications handle it. Thus far it seems to provide expected results. Based on my polling data I have seen as much as 57v in the last 30 days...(purple)