BYD 24V LiFePo4 Battery Modules

[nwillitts]

Interesting. I've never seen it used off grid, but it does make sense. Even at ~100 volts I have to run pretty thick cable from the panels to the CC.

how thick and how far?

 

[steviep19]

how thick and how far?

I went a little overkill two pairs of 6awg wire 50 - 60 feet. each string is connected to 4x72 cell panels 2x2 for 72v - 90v, but when I originally ran the wire, I was using 3x72 cell panels per string for 100 - 120v

 

[GVSolar]

Better overkill than plain old dead.

 

[yocor103086]

New to the forum. Please correct me if this is not the proper place for this post.

David Poz generously sent me one of his BMU boards that he pulled from the BYD 24V Batteries he purchased from BatteryHookup so that I could try and get data from it. I was successful is pulling data from the unit using an Arduino board and CAN Bus adapter. At present I have decoded the cell voltages but without actually having the intended battery to test it on, I'm note sure what other data is available, I suspect it would also report back the temperature sensor readings if I had them hooked up.

Attached is a screen shot showing the raw CAN messages as well as the decoded cell voltages. If anyone with one of these batteries has any interest in taking this project further, I'd be happy to provide all the information I've gathered up to this point.

 

[maxx123]

New to the forum. Please correct me if this is not the proper place for this post.

David Poz generously sent me one of his BMU boards that he pulled from the BYD 24V Batteries he purchased from BatteryHookup so that I could try and get data from it. I was successful is pulling data from the unit using an Arduino board and CAN Bus adapter. At present I have decoded the cell voltages but without actually having the intended battery to test it on, I'm note sure what other data is available, I suspect it would also report back the temperature sensor readings if I had them hooked up.

Attached is a screen shot showing the raw CAN messages as well as the decoded cell voltages. If anyone with one of these batteries has any interest in taking this project further, I'd be happy to provide all the information I've gathered up to this point.

3.75 v seems very high for this type of battery

 

[yocor103086]

I didn’t have any LiFePo4 batteries to work with, so I just used 18650 cells I had lying around to test the board. The voltage being reported by the BMU is accurate.

 

[nwillitts]

bring it on please.i have 2 of the byd batts.
have an arduino laying around some where....

 

[yocor103086]

bring it on please.i have 2 of the byd batts.
have an arduino laying around some where....

Any Arduino should do, I used a Pro Micro and will reference those pins. You will also need to pickup a CAN Bus Adapter, I purchased one from Ebay.

Link: https://www.ebay.com/itm/Arduino-MC...var=660788208535&_trksid=p2057872.m2749.l2649

CAN Adapter to Arduino:
VCC >> VCC
GND >> GND
CS >> 7
SO >> 14
SI >> 16
SCK >> 15
INT >> No Connection

There is a jumper on the CAN adapter (J1) which connects a 120ohm termination resistor. This jumper should be installed.
You will then need to add a second 120ohm resistor to the last device on the CAN bus. The resistor will go between CANL and CANH.
To further explain, CAN requires two termination resistors, one on the first device on the Bus and one on the last device on the Bus. So, in your case you will have 3 devices on the Bus, Arduino CAN adapter, BMU1 and BMU2. Termination will be handled via J1 on the CAN adapter and the last device BMU2 will need a 120ohm resistor connected.

CN1 on the BMU board has 4 pins of interest. 2 are for an external 12vdc power supply, this supply powers the board and is necessary. The other 2 are for CANL and CANH.

CN1 on BMU to CAN Adapter:
CANL >> CANL
CANH >> CANH
+12V >> No Connection (Provide External 12VDC Supply to BMU Pulls Approx. 70mA @ 12VDC)
-12VDC >> No Connection



I'm assuming you still have the mating CN1 connector and can use that for making your connections.

On the arduino side you will need to install the MCP2515 CAN library. Then if you start with my sketch you can modify it to your liking.



The BMU uses the extended frame CAN Message format at 125KBPS, periodically the BMU sends out a message that contains a unique ID followed by 8 bytes of data.
The ID will be different for each BMU so you will need to identify that. In my case 0x8010 is the unique ID to each BMU then 219, 319, 519 and A19 indicate what data will be sent in the next 8 bytes.

Message 219 sends cell voltage. If the first byte is 0 then the next 6 bytes are voltages for Cell 8, 7 and 6. If the first byte is 1 then the next 6 bytes are voltages for Cell 5, 4 and 3. If the first byte is 2 then the next 4 bytes are voltages for Cell 2 and 1.
For Message 319 I think the first byte is maybe some type of heart beat. Seems to randomly toggle between 0 and 1. Other bytes are always 0.
For Message 519 I believe the first byte is a status byte. I've found it is always at 96 then goes to 112 if any one cell voltage drops below 1.5VDC. The other bytes in this message are always 0.
For Message A19 the second byte is always 3 and the others are 0.

I'm guessing if you actually have this BMU hooked up to the battery that you will see some extra data where I have 0.

If you have any questions along the way please feel free to just ask and I will help as much as I can.

Once you have it all wired up and my sketch loaded you should be able to open up the serial monitor and see this:



Under Unknown Message you should see the ID for your BMU. You will then replace all of my CAN ID checking with your specific data.
My sketch could be much more elaborate and automatically detect a BMU ID and start populating it's data, but right now everything is hard coded.

You may also find that you have some extra messages that I didn't have since you are actually connected to the battery.

 

[jasonhc73]

Any Arduino should do, I used a Pro Micro and will reference those pins. You will also need to pickup a CAN Bus Adapter, I purchased one from Ebay.

Link: https://www.ebay.com/itm/Arduino-MCP2515-CAN-Bus-Module-TJA1050-Receiver-SPI-Module-shield/391715195613?ssPageName=STRK:MEBIDX:IT&var=660788208535&_trksid=p2057872.m2749.l2649

CAN Adapter to Arduino:
VCC >> VCC
GND >> GND
CS >> 7
SO >> 14
SI >> 16
SCK >> 15
INT >> No Connection

There is a jumper on the CAN adapter (J1) which connects a 120ohm termination resistor. This jumper should be installed.
You will then need to add a second 120ohm resistor to the last device on the CAN bus. The resistor will go between CANL and CANH.
To further explain, CAN requires two termination resistors, one on the first device on the Bus and one on the last device on the Bus. So, in your case you will have 3 devices on the Bus, Arduino CAN adapter, BMU1 and BMU2. Termination will be handled via J1 on the CAN adapter and the last device BMU2 will need a 120ohm resistor connected.

CN1 on the BMU board has 4 pins of interest. 2 are for an external 12vdc power supply, this supply powers the board and is necessary. The other 2 are for CANL and CANH.

CN1 on BMU to CAN Adapter:
CANL >> CANL
CANH >> CANH
+12V >> No Connection (Provide External 12VDC Supply to BMU Pulls Approx. 70mA @ 12VDC)
-12VDC >> No Connection

View attachment 6180

I'm assuming you still have the mating CN1 connector and can use that for making your connections.

On the arduino side you will need to install the MCP2515 CAN library. Then if you start with my sketch you can modify it to your liking.

View attachment 6181

The BMU uses the extended frame CAN Message format at 125KBPS, periodically the BMU sends out a message that contains a unique ID followed by 8 bytes of data.
The ID will be different for each BMU so you will need to identify that. In my case 0x8010 is the unique ID to each BMU then 219, 319, 519 and A19 indicate what data will be sent in the next 8 bytes.

Message 219 sends cell voltage. If the first byte is 0 then the next 6 bytes are voltages for Cell 8, 7 and 6. If the first byte is 1 then the next 6 bytes are voltages for Cell 5, 4 and 3. If the first byte is 2 then the next 4 bytes are voltages for Cell 2 and 1.
For Message 319 I think the first byte is maybe some type of heart beat. Seems to randomly toggle between 0 and 1. Other bytes are always 0.
For Message 519 I believe the first byte is a status byte. I've found it is always at 96 then goes to 112 if any one cell voltage drops below 1.5VDC. The other bytes in this message are always 0.
For Message A19 the second byte is always 3 and the others are 0.

I'm guessing if you actually have this BMU hooked up to the battery that you will see some extra data where I have 0.

If you have any questions along the way please feel free to just ask and I will help as much as I can.

Once you have it all wired up and my sketch loaded you should be able to open up the serial monitor and see this:

View attachment 6182

Under Unknown Message you should see the ID for your BMU. You will then replace all of my CAN ID checking with your specific data.
My sketch could be much more elaborate and automatically detect a BMU ID and start populating it's data, but right now everything is hard coded.

You may also find that you have some extra messages that I didn't have since you are actually connected to the battery.

That's all you can get from the BYD BMS? Just the V's? I thought for sure there would be some temp numbers coming in. Do you have access to the pins that the rest of wires connect to on the 32pin POS connector? I think after the 8 easy V ones, there are only 10 others used.

I have a few arduinos also maybe take a crack at this, did you just use breadboard jumpers to tap the connects?

I already just bypassed it all and went with an external 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

 

[Maast]

New to the forum. Please correct me if this is not the proper place for this post.

David Poz generously sent me one of his BMU boards that he pulled from the BYD 24V Batteries he purchased from BatteryHookup so that I could try and get data from it. I was successful is pulling data from the unit using an Arduino board and CAN Bus adapter. At present I have decoded the cell voltages but without actually having the intended battery to test it on, I'm note sure what other data is available, I suspect it would also report back the temperature sensor readings if I had them hooked up.

Attached is a screen shot showing the raw CAN messages as well as the decoded cell voltages. If anyone with one of these batteries has any interest in taking this project further, I'd be happy to provide all the information I've gathered up to this point.

If you're anywhere near Tacoma WA you're welcome to come on by and futz around with mine. I gotta bent wing and could use the help moving them around anyway

 

[yocor103086]

That's all you can get from the BYD BMS? Just the V's? I thought for sure there would be some temp numbers coming in. Do you have access to the pins that the rest of wires connect to on the 32pin POS connector? I think after the 8 easy V ones, there are only 10 others used.

I have a few arduinos also maybe take a crack at this, did you just use breadboard jumpers to tap the connects?

I already just bypassed it all and went with an external 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’d guess there is more data than just the voltages. But that’s all I hooked up to the board. Not sure what pins are for the temperature sensors or what type of sensor they are using. If you can determine that for me I'll get some similar ones and hook them up.

I suspect my board isn't balancing because I don't have the temperature sensors hooked up. Maybe some of the data indicates when it is balancing a cell? I don't know.

Yes, you can just use breadboard jumpers to tap the connectors. I only had a couple at the time so I ended up soldering to test pads on the board.

I see this not as a replacement for an external BMS but rather an easy way to gather the data from all of your BMU's into one central location. From there you could do whatever you want with it, data log it, display it, text or e-mail alerts to your phone, etc. Keep in mind once you have an Arduino on your CAN network you could also pass any of that data on to another device that talks CAN as well, such as a charge controller.

 

[yocor103086]

If you're anywhere near Tacoma WA you're welcome to come on by and futz around with mine. I gotta bent wing and could use the help moving them around anyway

Unfortunately not. Ohio is home for me.

 

[nwillitts]

yocor-fabulous job.

 

[ytwytw]

After several cycles, I am getting 198Ah out of a single BYD pack

I am happy with it

 

[nwillitts]

excellent news,ytwytw.

 

[Delmar]

How many amps can you pull? Was seriously considering a pair for my 48V golf cart. The motor when cruising pulls around 25A however can peak at 100A+ when accelerating. I have read the BYD cannot handle 100A+ for long. Or maybe is a BMS issue. My UPSverter will only pull around 30A for backup power.

 

[ytwytw]

How many amps can you pull? Was seriously considering a pair for my 48V golf cart. The motor when cruising pulls around 25A however can peak at 100A+ when accelerating. I have read the BYD cannot handle 100A+ for long. Or maybe is a BMS issue. My UPSverter will only pull around 30A for backup power.

My setup is a stationary solar storage, so that most of the time is less than 40A
Which BMS are you using?
My ANT BMS can do 100Amp no problem, but not for too long

 

[Darkstar]

After several cycles, I am getting 198Ah out of a single BYD pack

I am happy with it

View attachment 7190

Which supplier did you purchase them from?

 

[nwillitts]

Which supplier did you purchase them from?

he got them from techdirect.same as me.i have 2 in serial right now,been off grid in my cabin all day,very little sun today.they are wired to a MPP LV5048 and they handle every thing i throw at them.air fryer,mini split,55 inch tv,gaming PC,security cams.speakers,lights.no problems.

 

[GVSolar]

As you know, there’s been a great deal of discussion about the actual useful capacity of these used BYD 24v batteries. Perhaps this post will be informative. Please forgive the lousy formatting - I took my notes in a word processor, not a spreadsheet.

Here are the basic breakdowns of the charge/recharge cycles that I used to “wake up” my Tech Direct/BYD units. I repeated the same charge/discharge cycle three times with varying depths of discharge.

First I charged each unit separately to an equal voltage of 26.3. Then I individually charged all three units with an 800w LFP Charger (23 amp average charge) - to an equal voltage of 28v (that’s the BMS cutoff). I then connected all three units in parallel - and discharged them all to 24 volts using a 500 watt heater. I then recharged them again to 28volts.

Round ONE Charge to 28v
(A/B/C Combo) Lifepo4 Charger Profile 800w LFP Charger17.2 hoursR1
(Battery B’s meter shows .1 less voltage than reading taken at terminals)
TIME CHARGE Current CHmeter BATT A BATT B+.1 BATT C
1/24/20 DC bulk 23a/b/c 26.7 28.0 27.9 28.0

First Discharge to 24v:
Round One Discharge (A/B/C Combo) to 24v
TIME DISCHARGE Current METER BATT A BATT B+.1 BATT
1/29/20 END 18.1 amps 24.0 24.0 23.8 23.9
TIME Capacity Energy METER Time Int R Ext R
2:09 END 315 AH 8.14 kwh 24.0 17:12 hrs 216 mOhms 1.4 Ohms

Recharge again to 28V (BMS cutoff):
Round TWO Re-Charge to 28V
(A/B/C Combo) Lifepo4 Re-CHARGE Profile 800w LFP Charger14:35 hours R2
TIME CHARGE Current CHmeter BATT A BATT B+.1 BATT C
1:35 pm DC 621w 23a/b/c 27.2 27.5 28*cutoff 27.5
(A/B/C Combo) Lifepo4 METER PROFILEwith LFP Charger ReCharge #2 to 28v
TIME Capacity Energy Meter Time Int R Ext R
1/31/20 @ rest for .5 hour
2:30pm start 0 wh 23.8 0 min 155mOhms 1.1Ohms
1:35pm 326 AH 8.68 Kwh 27.5 14:35 hr 0 mOhms 1.2 Ohm*

My second discharge was to 23.5 volts:
Round Two DISCHARGE TEST to 23.5v – three hours rest
(A/B/C Combo) Lifepo4 METER PROFILE500w approximate discharge
TIME Capacity Energy METER Time Int R Ext R
2/3/20 reset AH reset wh 2.2 0 min
4:30pm 0 AH 0 wh 26.7 start 68 mOhms 1.4 Ohms
1:54 END 319 AH 8.23 kwh 23.5 17:14 hrs 246 mOhms 1.3 Ohms
(A/B/C Combo) Lifepo4 DISCHARGE Profile#2with Inverter & Heater (Bmeter)
TIME DISCHARGE Current METER BATT A BATT B+.1 BATTC
2/3/20 @ rest - 3 hrs (small) 26.7 26.6 (7) 26.7
1:54 END 17:14 hrs 18.1 amps 23.5 23.4 23.4-3 23.4

Recharge again to 28V (BMS cutoff):
Round THREE Re-Charge to 28V
(A/B/C Combo) Lifepo4 ReCharge Profile800w LFP ChargerR3
TIME CHARGE Current CHmeter% BATT A BATT B+.1 BATT C
2/5/20 @ rest for .5 hr 23.6 23.6 (7) 26.7
14.52 min 622 watts 27.8 28* 28*cutoff 28*OVER
TIME Capacity Energy Meter Time Int R Ext R
2/5/20 @ rest 1/2 hr (meter on) 178 mOhms 1.1 Ohms
1:52pm 333 AH 8.85 Kwh 27.8 14:52 hr 0 mOhms 1.2 Ohm*

My third Discharge was to 23 volts:
(A/B/C Combo) Lifepo4 DISCHARGE Profile#3with Inverter & Heater (Bmeter)
TIME DISCHARGE Current METER BATT A BATT B+.1 BATTC
2/8/20 @ rest 3 hrs (small) 26.7 26.6 (7) 26.7
6:00pm start 500w nom 26.7 26.6 26.5 26.6
11:55 END 17:55 hrs 420 watts 23.2 23.2/1 23.0 23.1
DISCHARGE TEST – Round THREE 3 hours rest
(A/B/C Combo) Lifepo4 METER PROFILE500w discharge
TIME Capacity Energy METER Time Int R Ext R
2/8/20 reset AH reset wh 26.8 0 min
6:00pm 0 AH 0 wh 26.8 start 71 mOhms 1.4 Ohms
11:55 END 322 AH 8.32 kwh 23.2 17:55 hrs 263 mOhms 1.3 Ohms

After the next 28v recharge I’ll prepare the batteries for service in my main system. My home is completely off-grid (30+ years) - looking forward to finding out how these batteries perform in a real world situation.

Some very general observations:
As you can see, the recorded battery capacity rose in each charge/discharge cycle – obviously because of the constantly increasing depth of discharge/recharge. Whether that will represent a general increase in capacity over time remains to be seen.
As an approximate average, I would rate the usable capacity of these three TD/BYDs at 110AH/2.95kwh each, or 330AH/8.85kwh total.

Not bad for a 4-6 year old battery of unknown heritage... and for the money, an excellent bargain (assuming at least another 5 years of good service). A comparable Battleborn battery bank would have been triple the cost. For the AES/Discover Batteries – five times the cost. Of course, then I would have the peace of mind given by a 10 year warranty (but not nearly the same learning curve/fun). And I genuinely prefer the form factor of these refurbished units – especially their well-built roll-a-round cases.

How the TD built-in BMS will perform over time remains to be seen. Because the TechDirect BMS has no cell level monitoring I elected not to push my discharge tests any lower than 23.0v. Only time will tell how the batteries respond to the constant usage (and varying charge/discharge rates) of off-grid living, but overall I am satisfied with the current usable capacity of these TechDirect units.

Some people have reported higher total AH/Kwh; I suspect that is the result of active balancing at cell level with an outboard BMS - and possibly an earlier generation of BYDs that were capacity tested before sale.

One other note: As expected, a charge from 27 to 28 volts took less than 30 minutes – and the last half-volt happened in less than 5 minutes. That sudden uptick/dropoff would occur in discharge as well – something to be keenly aware of when I program my final solar charging parameters.

If you have a meter setup that allows for it, the battery’s internal resistance seems to be an excellent indicator of actual SOC. During my charge cycle IR would end at damn near zero and begin at something close to 180 mOhms. The reverse is true for the discharge cycle – ending IR was at about 263 mOhms at 23v. In the midzone (where there is very little voltage shift) keeping an eye on that internal resistance reading could be very helpful in determining true SOC.

As always, your mileage may vary downhill in a tailwind. Hope some of this was helpful, and best to all.

 

[ytwytw]

Which supplier did you purchase them from?

I got from battery hookup, the first batch that saying 4.5kWh

I am doing less than 0.2C for charging & discharging, and I did heat up the battery pack, so YMMV

It’s always possible that the BMS isn’t reporting the correct capacity, I would need to buy a battery capacity but hard to get one in Canada (or very expensive)

 

[Mouse]

can anyone identify this P2 connector on the BYD BMS? For those interested, this gives the battery voltage with ground on the rightmost pin followed by the eight cells starting with cell 1. The left most 4 pins appear to be full pack voltage.

 

[ytwytw]

testing full capacity of my BYD pack again with hall effect sensor
only able to measure 3.925 kWh out of the pack

and I know the hall effect sensor isnt as accurate as the one Will has (10% higher than my other clamp meter)

so it's about 3.53kWh available to use

Looks like the Ant BMS measurement isnt correct as I hoped (it says capacity is 198Ah, but actual kWh isnt matching Ah number)

Did I miss something? or I did the math wrong? Or Ant BMS isnt giving out the correct number?

Buying another shunt meter on amazon and waiting for delivery, hope to able to measure correct Current/Power so that I can get correct power usage.

 

[Darkstar]

View attachment 7546
can anyone identify this P2 connector on the BYD BMS? For those interested, this gives the battery voltage with ground on the rightmost pin followed by the eight cells starting with cell 1. The left most 4 pins appear to be full pack voltage.

There was a fellow on Youtube I think that was using that connector for cell monitor and / or bms.

 

[Picasso]

That connector is for a balancing add on board. Some BYD's had them some didn't. A or P in serial number on bms box. You can use the BYD BMS to read voltage and temp. Is a post here with decoding to read the CAN. the user @yocor103086 posted some info on it.