BYD BMS

[heirloom hamlet]

i have not but working on wiring up the setup soon maybe in a week or two. i was trying to get pointers from @jasonhc73 to see if i need to keep anything in mind as my setup will be similar but with 2 batteries to start with and 2 more coming in a few weeks.

I just got 3 of these with BMS, 3 separate arrays. So far, here are my compaints:
- My first unit's, first full charge/discharge test gave me 2.2kwh, a very far cry from 5.6kwh it was advertised. I realize that was the battery's original new mark, but they advertised "over 80%". That would be a minimum of 4.5kwh, less than half what was advertised, not even close. Not even sure what to say about that. Another test this week. Then the other two batteries.
- Easy to setup with Anderson connectors, but I have no idea what the BMS I supposedly paid for is doing, for the batteries or for me. Was I supposed to order something else from them that would actually allow me to monitor the batteries/cells?
- I got the AiLi monitor Will reviewed to give me some data at least. But hooking it up when the Anderson plug was used to connect to the battery is a curious thing. I literally have just shoved a little 16awg wire in with the connector for now.
I'm glad I came across this old thread from @jasonhc73 , and am trying to use it to add some insight or direction as I try to use the BYD BMS.
Why didn't I just order the batteries for much less, if the BMS does nothing?
What do I do with batteries that under-perform by more than half?
So far I'm a little frustrated with these things. They work, but miles from what was described and hoped for.

 

[jasonhc73]

I just got 3 of these with BMS, 3 separate arrays. So far, here are my compaints:
- My first unit's, first full charge/discharge test gave me 2.2kwh, a very far cry from 5.6kwh it was advertised. I realize that was the battery's original new mark, but they advertised "over 80%". That would be a minimum of 4.5kwh, less than half what was advertised, not even close. Not even sure what to say about that. Another test this week. Then the other two batteries.
- Easy to setup with Anderson connectors, but I have no idea what the BMS I supposedly paid for is doing, for the batteries or for me. Was I supposed to order something else from them that would actually allow me to monitor the batteries/cells?
- I got the AiLi monitor Will reviewed to give me some data at least. But hooking it up when the Anderson plug was used to connect to the battery is a curious thing. I literally have just shoved a little 16awg wire in with the connector for now.
I'm glad I came across this old thread from @jasonhc73 , and am trying to use it to add some insight or direction as I try to use the BYD BMS.
Why didn't I just order the batteries for much less, if the BMS does nothing?
What do I do with batteries that under-perform by more than half?
So far I'm a little frustrated with these things. They work, but miles from what was described and hoped for.

The best advise I have if you don't use the ANT-BMS is this.

Never charge more than 53.3V.
Never discharge lower than 50.4V

This voltage limits can easily be applied to all lifepo4 batteries. But is not at all much of a problem with new cells.

4 8 16
SOC Cell V 12V setup 24V setup 48V setup
100.00% 3.650 14.60 29.20 58.40
99.50% 3.450 13.80 27.60 55.20
99.00% 3.375 13.50 27.00 54.00
96.00% 3.363 13.45 26.90 53.80
90.00% 3.350 13.40 26.80 53.60
80.00% 3.325 13.30 26.60 53.20
70.00% 3.300 13.20 26.40 52.80
60.00% 3.275 13.10 26.20 52.40
50.00% 3.263 13.05 26.10 52.20
40.00% 3.250 13.00 26.00 52.00
30.00% 3.225 12.90 25.80 51.60
20.00% 3.200 12.80 25.60 51.20
14.00% 3.150 12.60 25.20 50.40
9.50% 3.000 12.00 24.00 48.00
5.00% 2.800 11.20 22.40 44.80
0.00% 2.500 10.00 20.00 40.00

 

[heirloom hamlet]

The best advise I have if you don't use the ANT-BMS is this.

Never charge more than 53.3V.
Never discharge lower than 50.4V

This voltage limits can easily be applied to all lifepo4 batteries. But is not at all much of a problem with new cells.

4 8 16
SOC Cell V 12V setup 24V setup 48V setup
100.00% 3.650 14.60 29.20 58.40
99.50% 3.450 13.80 27.60 55.20
99.00% 3.375 13.50 27.00 54.00
96.00% 3.363 13.45 26.90 53.80
90.00% 3.350 13.40 26.80 53.60
80.00% 3.325 13.30 26.60 53.20
70.00% 3.300 13.20 26.40 52.80
60.00% 3.275 13.10 26.20 52.40
50.00% 3.263 13.05 26.10 52.20
40.00% 3.250 13.00 26.00 52.00
30.00% 3.225 12.90 25.80 51.60
20.00% 3.200 12.80 25.60 51.20
14.00% 3.150 12.60 25.20 50.40
9.50% 3.000 12.00 24.00 48.00
5.00% 2.800 11.20 22.40 44.80
0.00% 2.500 10.00 20.00 40.00

So for me with my single 24v battery setup, would those figures change to:
Never charge more than 26.7
Never charge less than 25.2 ?
So what in the world did I pay for with these built-in "BMS"?
Seems like I could have just gotten 6 BYDs for nearly the same price and had twice the storage...and just kept within these parameters then.

 

[jasonhc73]

So for me with my single 24v battery setup, would those figures change to:
Never charge more than 26.7
Never charge less than 25.2 ?
So what in the world did I pay for with these built-in "BMS"?
Seems like I could have just gotten 6 BYDs for nearly the same price and had twice the storage...and just kept within these parameters then.

Exactly:

Lithium Iron Phosphave Charge Range

Sheet5 Lithium Iron Phosphate Charge Voltage Range (LiFePO4) What to charge your cells/batteries/packs to. (SOC),Never More than,3.650,Shown is the "FLAT CURVE" of LiFePO4 cells/batteries/packs. What to not discharge past. (DOC),Nominal,3.200,The steap parts on the left and the right are the "Le...

docs.google.com

 

[heirloom hamlet]

Exactly:

Lithium Iron Phosphave Charge Range

Sheet5 Lithium Iron Phosphate Charge Voltage Range (LiFePO4) What to charge your cells/batteries/packs to. (SOC),Never More than,3.650,Shown is the "FLAT CURVE" of LiFePO4 cells/batteries/packs. What to not discharge past. (DOC),Nominal,3.200,The steap parts on the left and the right are the "Le...

docs.google.com

Thanks.
Jason, can I ask you an insanely stupid question, but one I don't have an answer to none-the-less.
HOW do I not allow the battery to charge any higher than 26.7 or lower than 25.2?
Is that something that can be done through the LV2424?
Right now, when the sun is blazin', the display on the BYD might read as high as 27.4 or so. And a guy on here the other day said to never do a capacity test UNLESS it was at least 27.4. So confused.

 

[jasonhc73]

Thanks.
Jason, can I ask you an insanely stupid question, but one I don't have an answer to none-the-less.
HOW do I not allow the battery to charge any higher than 26.7 or lower than 25.2?
Is that something that can be done through the LV2424?
Right now, when the sun is blazin', the display on the BYD might read as high as 27.4 or so. And a guy on here the other day said to never do a capacity test UNLESS it was at least 27.4. So confused.

In my LV5048 I set the bulk and float charge. I am pretty sure you can do the same with the LV2424.
If you don't have the Watchpower app, on the panel settings.
Program 26 and Program 27 on the LV5048.
Program 29 is Low DC cut-off voltage.

 

[heirloom hamlet]

In my LV5048 I set the bulk and float charge. I am pretty sure you can do the same with the LV2424.
If you don't have the Watchpower app, on the panel settings.
Program 26 and Program 27 on the LV5048.
Program 29 is Low DC cut-off voltage.

Thanks Jason. Mine was not showing some of those options. So it turns out I had an older version of watch power and once I figured out how to get the newest version of watch power installed I had those options available to me. Question: could you screen capture your main watchpower screen for me so that I can see your stats there also?

 

[jasonhc73]

Thanks Jason. Mine was not showing some of those options. So it turns out I had an older version of watch power and once I figured out how to get the newest version of watch power installed I had those options available to me. Question: could you screen capture your main watchpower screen for me so that I can see your stats there also?

 

[heirloom hamlet]

Thanks man!
Jason, do you know why sometimes my PV Input watts will plummet from 1.7kw to like 40w for no reason. The sun is only more clear and intense than a moment ago, yet watts drop completely off. Voltage stays the same or increases. It's happening right now.
It also seems to stop feeding the battery its charge, although the battery is far from full and the sun is booming.

 

[jasonhc73]

Thanks man!
Jason, do you know why sometimes my PV Input watts will plummet from 1.7kw to like 40w for no reason. The sun is only more clear and intense than a moment ago, yet watts drop completely off. Voltage stays the same or increases. It's happening right now.
It also seems to stop feeding the battery its charge, although the battery is far from full and the sun is booming.

Mine does that also.

I think when my batteries are charged, the mppt shuts down the panels.

I notice every time I try another setting, the PV input restarts and ramps up the watts slowly.

 

[heirloom hamlet]

Mine does that also.

I think when my batteries are charged, the mppt shuts down the panels.

I notice every time I try another setting, the PV input restarts and ramps up the watts slowly.

It was just treading water after changing those settings, pulling around 30 watts...it would never have charged the battery that way. I literally had to kill the BYD breaker so it would allow the wattage to be shared with the battery. Although it still isn't right. Watts went up ten times to 350-400w... But my multimeter says the array is pulling as much as 2kw. Maybe a setting is off or this thing is busted. I know it is capable of being right, I've seen it at times.
Also funny, the charge light is constantly on, implying a full charge. But the LCD little icon is pumping between half and full. Odd.

 

[GVSolar]

Your built in BYD BMS may be shutting off charge as well. Mine does whenever single cell voltage exceeds 30v. This can happen well before the pack voltage on the external voltmeter shows a high charge (because of out-of-balance cells). My pre-built when close to a full charge can shutoff with the voltmeter as low as 27.4. That "usable capacity" reference of 27.4 was to enable you to see what the limits of your AHours could be (discharging to =/- 23.5). You'll need to find your own balance between high charge & low discharge (longevity vs. usable capacity).

 

[heirloom hamlet]

Your built in BYD BMS may be shutting off charge as well. Mine does whenever single cell voltage exceeds 30v. This can happen well before the pack voltage on the external voltmeter shows a high charge (because of out-of-balance cells). My pre-built when close to a full charge can shutoff with the voltmeter as low as 27.4. That "usable capacity" reference of 27.4 was to enable you to see what the limits of your AHours could be (discharging to =/- 23.5). You'll need to find your own balance between high charge & low discharge (longevity vs. usable capacity).

Response to the first part: That makes perfect sense.
Response to the second part:
30 Volts in a single cell!? Aren't they each supposed to be limited to 3.75!?
Response to the third part:
Ugh. How? I'm so screwed, I should have never bought all this stuff.

 

[GVSolar]

Response to the first part: That makes perfect sense.
Response to the second part:
30 Volts in a single cell!? Aren't they each supposed to be limited to 3.75!?
Response to the third part:
Ugh. How? I'm so screwed, I should have never bought all this stuff.

Don't despair. It takes a while to get charge settings right. I have been messing around with my bank for nearly a month - adjusting charge specs - and i am just now getting it about where I want it. A couple of things to understand:
The BMS shuts off to protect you from overcharging. That's a good thing.
My mistake in syntax: 30v = 3.75 x 8. That's why the BMS is shutting off - at least one cell hit that voltage. (see attached TechDirect BMS specs)
I'm not sure which "voltmeter" you are referring to: if it is the built-in one it will show a voltage drop as the BMS shuts off - but if it is still receiving a charge from the Charge controller it will shoot back up showing a higher charge. Then the BMS shuts off again - and the situation repeats. The solution is to drop your charge voltage down until the battery is receiving a "full charge" (defined by you) without shutting off the BMS.
One possible suggestion: Go to a no float system: charge to x volts (maybe 26.8 or 27v) then no float until the battery hits the recharge voltage (which you will need to set in your charge controller) then the battery will run back up to 27v (rinse, repeat, rinse, repeat).
All of these things depend on the size of the loads you have vs. the amount of solar charge (plus time of sun). Also how fully charged the battery is when you begin charging each day.
Set some very conservative charge/discharge specs - observe and note the voltage and charge times - and you'll find a happy medium. Much depends on the careful programming of your charge controller.
And by all means, read a lot about charging lifepo4 batteries - and also general knowledge of battery bank wiring. (You might want to post a wiring diagram of your setup - people like Jason will be able to help you more)
Best of luck.

 

[heirloom hamlet]

Don't despair. It takes a while to get charge settings right. I have been messing around with my bank for nearly a month - adjusting charge specs - and i am just now getting it about where I want it. A couple of things to understand:
The BMS shuts off to protect you from overcharging. That's a good thing.
My mistake in syntax: 30v = 3.75 x 8. That's why the BMS is shutting off - at least one cell hit that voltage. (see attached TechDirect BMS specs)
I'm not sure which "voltmeter" you are referring to: if it is the built-in one it will show a voltage drop as the BMS shuts off - but if it is still receiving a charge from the Charge controller it will shoot back up showing a higher charge. Then the BMS shuts off again - and the situation repeats. The solution is to drop your charge voltage down until the battery is receiving a "full charge" (defined by you) without shutting off the BMS.
One possible suggestion: Go to a no float system: charge to x volts (maybe 26.8 or 27v) then no float until the battery hits the recharge voltage (which you will need to set in your charge controller) then the battery will run back up to 27v (rinse, repeat, rinse, repeat).
All of these things depend on the size of the loads you have vs. the amount of solar charge (plus time of sun). Also how fully charged the battery is when you begin charging each day.
Set some very conservative charge/discharge specs - observe and note the voltage and charge times - and you'll find a happy medium. Much depends on the careful programming of your charge controller.
And by all means, read a lot about charging lifepo4 batteries - and also general knowledge of battery bank wiring. (You might want to post a wiring diagram of your setup - people like Jason will be able to help you more)
Best of luck.

I can't thank you enough. I have the $40 AiLi Battery Monitor that Will reviewed not long ago as well as the one on the BYD box. Also, yesterday I finally got the most up-to-date version of Watchpower monitoring things from a laptop.
My setup diagram of my battery bank wouldn't be very exciting...it is a single BYD with the BMS so it's in that big white box with wheels. Without tearing it apart you can't really see anything in there. A guy did a YouTube teardown of one.
So I am pretty sure I followed you fully before and around this: "Go to a no float system: charge to x volts (maybe 26.8 or 27v) then no float until the battery hits the recharge voltage (which you will need to set in your charge controller) then the battery will run back up to 27v".
What I did yesterday is what Jason seemed to recommend: I set the Bulk Charging V to 26.7 and the Float Charging V to 25.2. Are you saying that I should set that first figure higher, say 27.4 and then lower on the Float (or set to 0) and sit there with it at 1pm when the sun is kickin'? Observe and note it climb to and to allow that 27.4 voltage (or even higher?) and then notice when it starts to gradually taper the watts it allows and that voltage down down down? Am I following? What would I do then, on the other side of it's tapering down?

 

[GVSolar]

I can't thank you enough. I have the $40 AiLi Battery Monitor that Will reviewed not long ago as well as the one on the BYD box. Also, yesterday I finally got the most up-to-date version of Watchpower monitoring things from a laptop.
My setup diagram of my battery bank wouldn't be very exciting...it is a single BYD with the BMS so it's in that big white box with wheels. Without tearing it apart you can't really see anything in there. A guy did a YouTube teardown of one.
So I am pretty sure I followed you fully before and around this: "Go to a no float system: charge to x volts (maybe 26.8 or 27v) then no float until the battery hits the recharge voltage (which you will need to set in your charge controller) then the battery will run back up to 27v".
What I did yesterday is what Jason seemed to recommend: I set the Bulk Charging V to 26.7 and the Float Charging V to 25.2. Are you saying that I should set that first figure higher, say 27.4 and then lower on the Float (or set to 0) and sit there with it at 1pm when the sun is kickin'? Observe and note it climb to and to allow that 27.4 voltage (or even higher?) and then notice when it starts to gradually taper the watts it allows and that voltage down down down? Am I following? What would I do then, on the other side of it's tapering down?

Keep it simple. Go with Jason's figures, observe carefully and then adjust up or down as the situation requires. The battery will fill faster when not under load, and slower when used. Note the results over time and different charging voltages. What is key is to understand the difference between bulk, absorption and float as it applies to LFP batteries (used in the case of the BYDs) and your particular charger and BMS. I'm not familiar with your charger (I believe Jason is) and how it regulates CC/CV - so I suggest you ask him. Give it time and study - things have a way of working out. Best...

 

[heirloom hamlet]

@jasonhc73 Do you have any additional insight on how I can balance these BYDs I bought? I have tried you suggested voltage but soon, they just stop pulling any significant wattage. It's there to use, but some cells must be maxed out and the controller quickly tapers off and shuts things down.

@GVSolar has been over-the-top helpful, but he says he just isn't particularly experienced with our controllers.
I am putting into practice the best way I know how, what he has advised, but I am not really seeing any changes in function at all.

No matter the settings or usage load (almost zero, a 30 watt LED bulb and the controller itself), it just shuts down to like 30w on my 2kw of available power. The battery doesn't ever charge at 30w, not past 30 to 50%. Who knows how accurate that even is.

When I put it under a 1300w 8.5a heater load it can runs because the power is there from the sun, and the battery charger may kick up to 300w, and when the sun declines you can imagine it quickly brings that battery to ground zero.

I'm reading and reading, thinking and thinking, but these boxed units are tough to apply much of what I'm finding because they are so unique. I have three, they all behave the same. Half charge, taper down, settings don't seem to matter. At least not the novice way I have modified them and monitored. Any additional ideas or direction is appreciated. I'm sorry to take so much of both of your time.

 

[heirloom hamlet]

@jasonhc73 @GVSolar Is this guys video from about a month ago insightful? You may have already seen it. If you have time and haven't already, read some of the back and forth in the comments and replies.

My batteries are basically, on arrival, getting what these guys seem to be getting...about half of the as advertised performance (and that based on the distributor's 80% promise). Now, these review guys all bought the raw batteries, and have the luxury of doing active cell balancing and testing. I bought their "With BMS" units and they are not as test and tinker friendly as in those reviewer's cases.

 

[heirloom hamlet]

@jasonhc73 @GVSolar @Will Prowse If they were going to sell these this "With BMS" way, at a higher price tag, should they not have balanced the individual cells first, and tested them for plug and play performance, so that the boxed batteries and BMS worked as advertised? A person shouldn't have to expect to tear them apart and force them to work as advertised, if that is even possible, when they were just supposedly custom assembled in this way?
The clear nature of these boxed up, with BMS, units is that they are supposed to be fairly plug and play. This is anything but that. At least to me, I realize I'm super new to the game and may be thinking like a typical consumer. If I'd known that these units would have the same shortcomings and DIY demands, not any more plug and play than the plain batteries, I at the very least would have purchase them plain and saved funds or gotten more. It's the same work, in fact more, this way. You can probably tell I'm really disappointed and frustrated. Is my thinking off in this world? Be honest, you can tell me if it is.

By the way, they are capable of sending these batteries out in pretty good working order. I bought from Tech Direct, not Battery Hook Up. But regardless, seems to me that the with BMS units should have recently gone through this from the distributor.

 

[jasonhc73]

@jasonhc73 @GVSolar @Will Prowse If they were going to sell these this "With BMS" way, at a higher price tag, should they not have balanced the individual cells first, and tested them for plug and play performance, so that the boxed batteries and BMS worked as advertised? A person shouldn't have to expect to tear them apart and force them to work as advertised, if that is even possible, when they were just supposedly custom assembled in this way?
The clear nature of these boxed up, with BMS, units is that they are supposed to be fairly plug and play. This is anything but that. At least to me, I realize I'm super new to the game and may be thinking like a typical consumer. If I'd known that these units would have the same shortcomings and DIY demands, not any more plug and play than the plain batteries, I at the very least would have purchase them plain and saved funds or gotten more. It's the same work, in fact more, this way. You can probably tell I'm really disappointed and frustrated. Is my thinking off in this world? Be honest, you can tell me if it is.

By the way, they are capable of sending these batteries out in pretty good working order. I bought from Tech Direct, not Battery Hook Up. But regardless, seems to me that the with BMS units should have recently gone through this from the distributor.

The guy in the video is still only playing around in the extreme bottom end of the charge of the cells.

He ought to put the packs on a float charge and just get every cell to 3.2V. Until that happens those bottom feeder cells are way past the point of usability.

He isn't really giving the float a chance to absorb when the cells are lower than 2.9V.

This is where taking the cover off and putting a single cell charger directly on the bottom cells will help.

The other way to get those very low cells up with the rest of the good ones is to do what DavePoz did and put every cell in parallel and passively just wait for a couple weeks until every cell is the same level.

Bulk charge to 53.3, float it at 52.9. And just sit there and wait while in float.

The overall voltage read at the big terminals is the AVERAGE of the cells. Those extremely low cells will take the voltage eventually. But don't forget, when there is a cell way lower than the average, there has to be some way more than the average.

If his(YouTube video) "dead cells" truly were dead they would not charge at all. They are taking charge. The cells just need a lot more juice and time.

52.9V = 3.309V per cell.

Lithium Iron Phosphave Charge Range

Sheet5 Lithium Iron Phosphate Charge Voltage Range (LiFePO4) What to charge your cells/batteries/packs to. (SOC),Never More than,3.650,Shown is the "FLAT CURVE" of LiFePO4 cells/batteries/packs. What to not discharge past. (DOC),Nominal,3.200,The steap parts on the left and the right are the "Le...

docs.google.com