BYD BMS

[jasonhc73]

No, I don't have the ability to see individual cells...I bought the BYD in the big wheeled case with the BMS. The one will recently reviewed and then connected my same LV2424 to in another video shortly thereafter. This BMS cleary does something, but as far as I am aware, it doesn't give me a visual of what it is doing other than the sorta useless voltmeter on the box itself.

I have 3 of these for three separate LV2424 arrays:

BYD LFP 24V 5 kwh 200 Ah Battery Pack With BMS 130A LiFePO4

info@techdirectclub.com

www.techdirectclub.com

I think this is what's inside:

BYD LFP 8S BMS 24v LifePo4 130A with connection wiring for BYD Battery

info@techdirectclub.com

www.techdirectclub.com

The only monitoring I can do is through Watchpower, which I am grateful for and this guy (which hasn't been incredibly helpful yet):

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I can order the ISDT, but before I do I want to make sure it is not too impossible for me to actually connect it to my BYD. My batteries are not as accessible as yours because they are crammed into this box and closed up. I'm sure if I start tearing it down it won't go well and that I'll void whatever warranty I do have. I am thinking I should write Tech Direct and ask them if they can send me batteries that are balanced instead of whatever they sent me.

If you start at the first post in this entire thread, you will have listed out all the pieces you need to get at the wire connector.
TE made a very nice connector that connects to their black box of a BMS.

BYD BMS

A no cut, no splice, plug-n-play. It has a screen, Bluetooth, and more settings in the app than we know what to do with. Will already reviewed this BMS. The Inside wires: The Outside Wires: Conclusion: Molex Micro-Fit 3.0 430251000 10POS 3mm Molex Micro-Fit 3.0 or 1729521001...

diysolarforum.com

 

[heirloom hamlet]

Equal: By the way, here's part of my confusion. I have no idea what this means:
"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."
In order for this to make sense, we have to know if you are in Bulk, absorption or float, what the charge controller is inputting vs. what the load is - whether the load is coming from inverter AC or DC direct, what you mean by "30 to 50%" - How do you know you have 2kw available? State of charge derived from voltage readings is a moving target - and has to be defined based on careful repeatable readings. Sorry for my lack of understanding - but consider these as some readings;
(these are totally bogus numbers - just given as an example of the kind of valuable information to have at hand for evaluation)
24 hour cycle: Begin after a full charge (Charge to 27.4 or BMS disconnect)
Built in meter (at rest 24 hours): 26.5v (start)
Inverter output: 130w avg. for 3 hours (390wh)
Solar CC charge: 200w avg. for 7 hours (1400wh)
Built in meter (finish): 26.8
Built in meter (at rest 1 hour): 26.6
Built in meter (at rest 24 hour)s: 26.5
Start new cycle (adjust or keep charge time/voltage) and note measurements.
Only by measuring what goes in and what comes out will you have a sense of the state/capacity of your battery. Eventually you will create a set of charge/discharge parameters which will give you a steady reliable state.
Also, are your 3 units hooked up in parallel? Or are you doing these tests one battery at a time?
Best...

I'm sorry @GVSolar , I'm speaking in layman's terms and not using proper terminology, I'm sure. I was saying this: I had almost no output load from the array or the battery, only the LV2424 and a 4.5w LED bulb (equal to 30w incandescent) is using any power whatsoever. It was midday at the time, so I could test my 9 panel array and it was getting over 2kwh at that time. However, Watchpower was telling me that only 30 to 40 of those watts were being used to charge the BYD. 30 watts is, of course, almost nothing. So it was not even making a dent in the BYDs charging. Watch power would tell me that the battery was at 50% or less, and would even decline. That's all I was saying. It was before I clearly understood what you had diagnosed: That my cells were limiting what the BMS was allowing.

I have enough stuff here for 3 separate systems (for 3 micro cabins), but I've been doing these tests one battery at a time, individually.

But tomorrow I am going to do my best to set up a table and all three LV2424 units right next to each other so that I can show you guys, and monitor them simultaneously. That seems like it will save me a ton of time in the long run. Each LV2424 will be connected to its own Tech Direct BYD (with their installed BMS) and each will be fed by it's own 1500w 112.8v 24.8a solar panel array. I'll post a few pics of the layout when I have it looking nice enough.

Your sample data will prove to be very helpful. I will no doubt go back to your and @jasonhc73 recent instruction a hundred times. But I will do my best to follow, where my experience and common sense let me do, well, I don't know what I can do about that. Maybe @Will Prowse will even see something that is relevant enough to the masses to address.
It still bugs me a little that Tech Direct would not do active cell balancing before sending them out, as they just connected and charged for their BMS, and boxed these things up. If the customer already had their BMS installed when it arrived, why would they expect to have to tear what was just installed apart in order to connect things that would help them to force their new battery to work right. It is bizarre to me. But maybe I'm missing something or just don't know enough about this field yet.

 

[heirloom hamlet]

If you start at the first post in this entire thread, you will have listed out all the pieces you need to get at the wire connector.
TE made a very nice connector that connects to their black box of a BMS.

BYD BMS

A no cut, no splice, plug-n-play. It has a screen, Bluetooth, and more settings in the app than we know what to do with. Will already reviewed this BMS. The Inside wires: The Outside Wires: Conclusion: Molex Micro-Fit 3.0 430251000 10POS 3mm Molex Micro-Fit 3.0 or 1729521001...

diysolarforum.com

I'll open it up in the morning. Are you saying you would recommend I order the new BMS, take out Tech Direct's, and follow your instructions to make and connect the new one?

 

[jasonhc73]

I'll open it up in the morning. Are you saying you would recommend I order the new BMS, take out Tech Direct's, and follow your instructions to make and connect the new one?

Or splice into their wire connector.

BYD LFP 8s Wiring Harness Adapter

info@techdirectclub.com

www.techdirectclub.com

I would use their connector with a M/F Dupont jumper wires. Then wire in your ISDT or other BMS to the jumper wires. They already made the connector, it works fine.

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[heirloom hamlet]

Or splice into their wire connector.

BYD LFP 8s Wiring Harness Adapter

info@techdirectclub.com

www.techdirectclub.com

I would use their connector with a M/F Dupont jumper wires. Then wire in your ISDT or other BMS to the jumper wires. They already made the connector, it works fine.

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Okay. Do I select 40Pcs, 120Pcs or 240Pcs?

 

[jasonhc73]

Okay. Do I select 40Pcs, 120Pcs or 240Pcs?

You need 9 per battery.

Go with the 400 pack. ?

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200 x 6cm Black Breadboard Jumper. 200 x 6cm Red Breadboard Jumper. Internal copper wire x 5. Color : Black & Red.

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[heirloom hamlet]

You need 9 per battery.

Go with the 400 pack. ?

400 pcs 6cm Breadboard Jumper Cable Dupont Wire Electronic Wires Black Red Color | eBay

200 x 6cm Black Breadboard Jumper. 200 x 6cm Red Breadboard Jumper. Internal copper wire x 5. Color : Black & Red.

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400?! 9 per cell? So confused. But okay, if you say so. Do I have to order that harness from TD or do I already have that?

 

[jasonhc73]

Take the lid off the battery and look at it before you do anything else.

 

[GVSolar]

I'm sorry @GVSolar , I'm speaking in layman's terms and not using proper terminology, I'm sure. I was saying this: I had almost no output load from the array or the battery, only the LV2424 and a 4.5w LED bulb (equal to 30w incandescent) is using any power whatsoever. It was midday at the time, so I could test my 9 panel array and it was getting over 2kwh at that time. However, Watchpower was telling me that only 30 to 40 of those watts were being used to charge the BYD. 30 watts is, of course, almost nothing. So it was not even making a dent in the BYDs charging. Watch power would tell me that the battery was at 50% or less, and would even decline. That's all I was saying. It was before I clearly understood what you had diagnosed: That my cells were limiting what the BMS was allowing.

I have enough stuff here for 3 separate systems (for 3 micro cabins), but I've been doing these tests one battery at a time, individually.

But tomorrow I am going to do my best to set up a table and all three LV2424 units right next to each other so that I can show you guys, and monitor them simultaneously. That seems like it will save me a ton of time in the long run. Each LV2424 will be connected to its own Tech Direct BYD (with their installed BMS) and each will be fed by it's own 1500w 112.8v 24.8a solar panel array. I'll post a few pics of the layout when I have it looking nice enough.

Your sample data will prove to be very helpful. I will no doubt go back to your and @jasonhc73 recent instruction a hundred times. But I will do my best to follow, where my experience and common sense let me do, well, I don't know what I can do about that. Maybe @Will Prowse will even see something that is relevant enough to the masses to address.
It still bugs me a little that Tech Direct would not do active cell balancing before sending them out, as they just connected and charged for their BMS, and boxed these things up. If the customer already had their BMS installed when it arrived, why would they expect to have to tear what was just installed apart in order to connect things that would help them to force their new battery to work right. It is bizarre to me. But maybe I'm missing something or just don't know enough about this field yet.

@jasonhc73 is way smarter than I am - but - I think you need to slow down.
From my reading of your explanation above I'm not sure you ever discharged enough amps/energy to make a dent in your battery. (4.5w is nothing up against one of these BYDs) And the entire charging process depends on the charge parameters that have been set on your charge controller and your inverter. Bulk=? Absorb =? (for how long) Float = ? Battery AH = ? Example: Many charge controllers stop charging as soon as the charging amps reach 2% of the battery rating. So if you rated the battery at 200ah the CC would stop charging as soon as the amps necessary to hold absorb reached 4 amps - which would happen in no time at all if you only discharged 4.5 watts. A 2kw array in full sun would do that in less than a minute. As to the "Watchpower" - it's analysis of your state of charge is only as good as the numbers you put in to program it... and those may be suspect at this point.

You can tear deep into the case if you want to - and I intend to do so myself at some point (with ONE of my units) but only after I have them settled into a conservative charging regimen that meets my needs.

I don't mean to discount your abilities at all - but I suspect that building out a custom interface at this point - when you are still learning the basics - is not in your best interest. Just my 2 cents.

Meanwhile, I suggest taking a picture of how you have one system wired - also of your charge controller settings - and any other settings you have programmed into the inverter - and post them for analysis. @jasonhc73 will have a good idea about the MPP - I do not. I highly respect his judgement. But I truly suspect something else is going on here.

As always, my advice is free - and worth what you paid for it. Good thoughts, sir.

 

[Will Prowse]

Don't open the case, the cells need compression. Don't do it.

The cells do not need active balancing. Hook up a LiFePO4 8S or 16S BMS (1/2 packs), and cycle it. It will balance it as much as it can in a few cycles, and you are done.

No need to see individual cell voltages. The BMS that comes with the ready built unit works great. Just connect BMS and cycle it.

If you want to see the condition of your pack, build your entire system and do a single capacity test. Cycle it a few times and test again. If the capacity results look good, no need to check anything. Keep using it.

 

[Will Prowse]

These packs won't balance until you hit the balancing voltage threshold. So be sure to charge your BYD packs to 29 volts(3.625V for each cell). And cycle down to 23-24V. Repeat this over and over.

If you want to cycle up to 90% SOC, use a shunt and set absorption manually. Thats the best method. Dont set absorption manually till you cycle it a few times.

 

[heirloom hamlet]

These packs won't balance until you hit the balancing voltage threshold. So be sure to charge your BYD packs to 29 volts(3.625V for each cell). And cycle down to 23-24V. Repeat this over and over.

If you want to cycle up to 90% SOC, use a shunt and set absorption manually. Thats the best method. Dont set absorption manually till you cycle it a few times.

Okay. Are you saying I can use Watchpower to try setting "Bulk" to 29v and the "Float" to 23 or 24v?

 

[heirloom hamlet]

Don't open the case, the cells need compression. Don't do it.

The cells do not need active balancing. Hook up a LiFePO4 8S or 16S BMS (1/2 packs), and cycle it. It will balance it as much as it can in a few cycles, and you are done.

No need to see individual cell voltages. The BMS that comes with the ready built unit works great. Just connect BMS and cycle it.

If you want to see the condition of your pack, build your entire system and do a single capacity test. Cycle it a few times and test again. If the capacity results look good, no need to check anything. Keep using it.

When I first got them I took my first ready built unit and charged it until full, I believed it was full anyway. The LV2424 light had been solid green for days. I tried to do everything just like in your video. I used a heat gun to discharge and measured. Only got 2.2kwh. I was disappointed, but wanted to try again.
That's when I started noticing the low input rate, built-in BMS was slowing the CC's roll. It seems it won't charge ever. The second battery with built-in BMS behaves the same. I have a third I haven't cracked yet. I have been using the same LV2424 all along (I have 3).
So, I want to keep charging and discharging, testing (before I complain to Tech Direct) but it seems I can't. I've tried lots of the guy's settings, don't change much.
I don't really want to see the condition of the packs or monitor cells, I just want them to work, honestly Will. If in 3 to 5 years I need to upgrade to higher tech more pricey storage at that time, fine and good.
I am confused though. You say "just connect a BMS and cycle" but I thought I had a connected BMS in my built-ins. Are you saying add a different one? Or am I not connected to and using the one I have? Whatever the case, cycling is what isn't happening cause they aren't really charging.

 

[jasonhc73]

When I first got them I took my first ready built unit and charged it until full, I believed it was full anyway. The LV2424 light had been solid green for days. I tried to do everything just like in your video. I used a heat gun to discharge and measured. Only got 2.2kwh. I was disappointed, but wanted to try again.
That's when I started noticing the low input rate, built-in BMS was slowing the CC's roll. It seems it won't charge ever. The second battery with built-in BMS behaves the same. I have a third I haven't cracked yet. I have been using the same LV2424 all along (I have 3).
So, I want to keep charging and discharging, testing (before I complain to Tech Direct) but it seems I can't. I've tried lots of the guy's settings, don't change much.
I don't really want to see the condition of the packs or monitor cells, I just want them to work, honestly Will. If in 3 to 5 years I need to upgrade to higher tech more pricey storage at that time, fine and good.
I am confused though. You say "just connect a BMS and cycle" but I thought I had a connected BMS in my built-ins. Are you saying add a different one? Or am I not connected to and using the one I have? Whatever the case, cycling is what isn't happening cause they aren't really charging.

I used my packs without any BMS at all for about two weeks.

I set the charge on the MPP Solar to a voltage and let it charge, then used the battery.

BMS can only do two things, open the circuit (disconnect the battery) and add a small resistive load to try to discharge the highest voltage cell.

Set the MPP Solar to bulk charge.
Set the MPP Solar to float charge at the nominal voltage.

These packs do not behave anywhere near like NEW cells. These are VERY USED.

If you don't have a kWh meter showing you from full charge to where ever your battery disconnects (FULL to EMPTY), the real kWh capacity is merely a guess.

 

[heirloom hamlet]

I used my packs without any BMS at all for about two weeks.

I set the charge on the MPP Solar to a voltage and let it charge, then used the battery.

BMS can only do two things, open the circuit (disconnect the battery) and add a small resistive load to try to discharge the highest voltage cell.

Set the MPP Solar to bulk charge.
Set the MPP Solar to float charge at the nominal voltage.

These packs do not behave anywhere near like NEW cells. These are VERY USED.

If you don't have a kWh meter showing you from full charge to where ever your battery disconnects (FULL to EMPTY), the real kWh capacity is merely a guess.

I do have a kwh meter. The problem is, when I implement all these ideas, I don't see a change in behavior. By behavior, I mean the CC or the BMS is not allowing the battery to charge at any reasonable input. No matter what, within minutes, the batteries (any and all of the 3) are getting 30watts from my panels and aren't doing jack squat. They don't charge up. Says they are, but hours and days pass and still are the same.

 

[heirloom hamlet]

These packs won't balance until you hit the balancing voltage threshold. So be sure to charge your BYD packs to 29 volts(3.625V for each cell). And cycle down to 23-24V. Repeat this over and over.

If you want to cycle up to 90% SOC, use a shunt and set absorption manually. Thats the best method. Dont set absorption manually till you cycle it a few times.

I used the Watchpower software this morning to set the CC to Bulk 29 and Float 24. It didn't charge. By the end of the day it gave me Fault #4 Battery Voltage Too Low. It was like 25. I shut the battery breaker off to shut it down.
Yesterday I tried the 26.4/24.4 range. Nothing.
Day before 27.4/25.6 range. Nothing.
I will post a picture of all my settings tomorrow. Maybe I have something totally unrelated to Bulk/Float settings that is messing everything up.
I will also connect to different LV2424s, I have 3 of them. Maybe the one I've been using is busted. I don't think so, but it's worth a try as troubleshooting goes. I won't change any of the stock settings right away just to see.
Something is wrong. They don't charge. How can J possibly test their capacity, or even play with charge settings if they never charge in the first place?

 

[GVSolar]

Is it possible your recharge setting (the voltage at which a recharge cycle begins) is set too low? I'm not familiar with the MPP (or Watchtower) but my Schneider Conext system has a recharge setting for both the CC and the inverter - as well as a bulk termination setting - all of which can affect if and when charging will recommence.

 

[heirloom hamlet]

Is it possible your recharge setting (the voltage at which a recharge cycle begins) is set too low? I'm not familiar with the MPP (or Watchtower) but my Schneider Conext system has a recharge setting for both the CC and the inverter - as well as a bulk termination setting - all of which can affect if and when charging will recommence.

Hmm, good question. This is Jason's screen capture, but these are some of those possible settings.

 

[heirloom hamlet]

Is it possible your recharge setting (the voltage at which a recharge cycle begins) is set too low? I'm not familiar with the MPP (or Watchtower) but my Schneider Conext system has a recharge setting for both the CC and the inverter - as well as a bulk termination setting - all of which can affect if and when charging will recommence.

So here is 9am. These are the current settings, current status, and how the array is currently performing. Sad.

 

[GVSolar]

Hi Equal...

So here is 9am. These are the current settings, current status, and how the array is currently performing. Sad.

Hi Equal... Sorry I can't make heads or tails of that data - too small to read. And my lack of knowledge where the MPP is concerned makes me kinda useless - i.e.. I've no idea what "sbu", "power saver mode" and "back to discharge voltage" means... Best to ask Jason or post another thread with all these issues. I still believe something is up with the settings... but I just can't help. Sorta like mac vs. pc... if you own a mac and someone asks you about Microsoft settings you're screwed.

 

[heirloom hamlet]

Hi Equal...

Hi Equal... Sorry I can't make heads or tails of that data - too small to read. And my lack of knowledge where the MPP is concerned makes me kinda useless - i.e.. I've no idea what "sbu", "power saver mode" and "back to discharge voltage" means... Best to ask Jason or post another thread with all these issues. I still believe something is up with the settings... but I just can't help. Sorta like mac vs. pc... if you own a mac and someone asks you about Microsoft settings you're screwed.

I appreciate all your help. But man, if you can't make heads or tails of it, how on Earth am I supposed to? But I am starting to think its the settings, too. Thanks for everything brother. I wish I knew if Will was telling me to hook up another, different BMS, or if he was saying to utilize the one I have more fully. Somehow.

 

[GVSolar]

It's not likely the BMS is your problem... like you said, it's probably settings. I have the same BMS, as does Will. @Will Prowse is very willing to be helpful - try sending him some mail directly. In fact I wrote to him asking for help with your issues (and a few other folks with pre-built BYDs). That's one reason he reached out on this thread. And he's very familiar with MPPs.
Pictures are helpful, especially with wiring. Wish I could be more so.

 

[heirloom hamlet]

It's not likely the BMS is your problem... like you said, it's probably settings. I have the same BMS, as does Will. @Will Prowse is very willing to be helpful - try sending him some mail directly. In fact I wrote to him asking for help with your issues (and a few other folks with pre-built BYDs). That's one reason he reached out on this thread. And he's very familiar with MPPs.
Pictures are helpful, especially with wiring. Wish I could be more so.

I'm going to call Tech Direct and ask them for direction using their BMS. I think Will has got bigger fish to fry.
Man, you've been over the top helpful. We may not have cracked the code yet, but I've learned a ton and am in a much better position to take the next steps and keep learning. I'm determined to harness the Sun's powers and use it to change the world...or at least make lights, fans, phones and a small refrigerator operate.

 

[GVSolar]

Stay steady. You'll get there. Good thoughts.

 

[heirloom hamlet]

Conclusion:

Molex Micro-Fit 3.0
430251000 10POS 3mm Molex Micro-Fit 3.0
or
1729521001 Micro-Fit TPA Receptacle Housing WITH Micro-Fit Terminal Position Assurance (TPA) Retainer

Molex
4303000001 12" PRE-CRIMPED Molex Jumper Wires
or Crimp your own wires
Micro-Fit 3.0 Crimp Terminal, Female


TE Connectivity AMP Connectors
1318772-2 12POS 2.2MM Tyco Electronics Header
1318745-2 32POS 2.2MM Tyco Electronics Header

Dupont Wires
Female to Female Jumper Cables

The Male to Male jumper cables, sort of work, but are very loose. If you are comfortable with them, you do not need the TE connectors.

The Molex connector on the BYD fan panel:
The connector has pretty much no standard on the backside. I have 3 different ways it is wired on my BYD batteries. Use the jumper cables to the outside panel.

The only thing that is standard, is the fan 24V position on the far left.
24V R B B B B
24V R B B B B
or
24V B B B B R
24V B B B B R
(nevermind this, just look at the pictures a few posts after this)

It's just a color and a connector. Connect the jumpers so the Molex Connector on the outside is
_ 7 5 3 1
_ 8 6 4 2


Wires on the battery side on my BYD's are the same for all 8.
- - - 7 5 3 1 ---------
- - - 8 6 4 2 ---------

Jason, is it a lot of trouble to dumb what I would need to purchase down for me (in order to do what you did here)?

I am doing a return with Tech Direct of my three BYD with pre-built BMS batteries. The AC capacity tests I have repeatedly done on them vary, but the worst are only getting 1.4 kwh, and the very best 2.6 kwh. Not good enough. So, they are going back and instead I will get two BYDs like yours for each of my 24v systems and connect them in parallel. So I need to connect my own BMS like what you did here.

My trouble is, I'm not super clear what to order, even after thoroughly going through all of your amazing details in this thread. Maybe it is only because some of the links no longer work like you originally intended. Also, some different options are given.

I am not concerned about saving a couple of dollars, I'm interested in saving time and avoiding unnecessary headaches.

So, for me to do just one of my systems (that is, two paralleled BYDs and your same BMS), following your instructions, exactly which connectors and pre-crimped leads should I buy?

As for which BMS I should choose on eBay, it seems for my 24v system which will never pull more than 20 amps, the "7s to 16s 100a with LCD" option should be more than adequate, agreed?