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Cheap 4kwh LiFePO4 batteries from Battery Hookup

The batteries are still a great deal at 3kw. What worries me is how fast it drops from there. Will they still be working ok in a year, two years, three years?

What I have been finding out recently with my older lithium batteries is they no longer can handle high charge rates once the cell capacity starts noticeably dropping (to 75-80%), and trying to charge them anywhere near 1C has killed a few of my cells, even though those cells could handle 15C charging when new.

I know most here think lithium batteries are magic and will last forever. But what I'm finding out is that when the manufacturers say their "end of life" is X years, but they'll still have 80% life left...it really means at that age they can no longer handle high currents without failing. Might not be a problem in a low draw application like Jason's...but be careful using them anywhere near rated draw/charge rates. I found all it takes is one "fast charge" to kill an already failing cell. Now i have a bunch of battery packs I have to rip open and swap out cells. :(
 
HMR said:
"BYD has an external control box for the built in BMS so that it can talk to SMA and other inverters/chargers via rs485/CAN. These BYD modules are the first gen version as far as I can tell. MFG date is gonna be around 2013 I would guess. This is for the 2.0 version https://www.cclcomponents.com/byd-b-box-battery-management-unit "

Thanks for this link, Picasso. I did a quick search beginning with this information. Confusion: all I found refers to BY 2.5 Kwh modules, not the 5.6 nominal KwH modules we are buying. Is this version 1 vs version 2? Most interesting is that Victron has linked up with BYD to provide access to the interal BMS. See: https://www.victronenergy.com/live/battery_compatibility:byd_b-box . Notice the very informative wiring diagram contained on this site for an entire BD - Victron system. Can someone with more knowledge than myself analyze this new information? Q. Can we use the Victron link with our batteries to use the installed BMS directly without having to remove it and rewire? Q. Does the wiring diagram look good for putting an entire small home system together?
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I believe the Victron link is for the B-Box. These modules (I think) came out of some kind of mass transit vehicle. The B-Box is meant for datacenter applications.
 
shorawitz said:
I believe the Victron link is for the B-Box. These modules (I think) came out of some kind of mass transit vehicle. The B-Box is meant for datacenter applications.
Click to expand...
Yeah, we've heard all kinds of rumors about the origin of these batteries. My original reason for spending time on this issue was to find a user's manual of some kind or official spec sheet from BYD. That quest was a dead end. So now we are just experimenting directly with these batteries to learn about them first hand.
 
SolarRat said:
The batteries are still a great deal at 3kw. What worries me is how fast it drops from there. Will they still be working ok in a year, two years, three years?

What I have been finding out recently with my older lithium batteries is they no longer can handle high charge rates once the cell capacity starts noticeably dropping (to 75-80%), and trying to charge them anywhere near 1C has killed a few of my cells, even though those cells could handle 15C charging when new.

I know most here think lithium batteries are magic and will last forever. But what I'm finding out is that when the manufacturers say their "end of life" is X years, but they'll still have 80% life left...it really means at that age they can no longer handle high currents without failing. Might not be a problem in a low draw application like Jason's...but be careful using them anywhere near rated draw/charge rates. I found all it takes is one "fast charge" to kill an already failing cell. Now i have a bunch of battery packs I have to rip open and swap out cells. :(
Click to expand...
Most of the spec sheets we have seen for these BYD batteries list 100 A as max charge and discharge rate. Sometimes one sees 200 A. Given your experience, any opinion on what would be a maximum comfortable charge and discharge rate for these batteries?
 
HMR said:
Yeah, we've heard all kinds of rumors about the origin of these batteries. My original reason for spending time on this issue was to find a user's manual of some kind or official spec sheet from BYD. That quest was a dead end. So now we are just experimenting directly with these batteries to learn about them first hand.
Click to expand...

I gotta say, this forum is much more useful than the DIY FB page. I too was hoping to get some info on these. I have done some serial interface programming before in C++, and was hoping to figure out the protocol. I think though that the factory boards are externally powered. I haven't had time to play with them much, so I was going to take the easy way out (see David Poz's video) and use my own BMS. I've been flip-flopping on 8S || 16S since I have mine in series for 48V. I wasn't sure how the other batteries would be affected (or affect the lone one) if I use 8S and only one pack shuts down. I haven't been as adventurous as jasonhc73. I have 8 of these, but I only put 4 in production at a time. I've been swapping them in/out to test them while I get some use from them in my off-grid scenario.

I currently have manual switches per pair, but I guess I could add a relay to take them out of production as needed from the BMS.
 
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HMR said:
Most of the spec sheets we have seen for these BYD batteries list 100 A as max charge and discharge rate. Sometimes one sees 200 A. Given your experience, any opinion on what would be a maximum comfortable charge and discharge rate for these batteries?
Click to expand...

For years I've been charging most of my cells at about half of the rate of the "standard charge" the manufacturer lists and other than the usual slow gradual decrease in capacity I never had a problem. I recently (past few months) started experimenting with charging at the standard charge current (most are 0.5C standard charge) or higher, and that is when I started having problems with the packs staying in balance, with some cells never reaching near the desired charge voltage and the balance charger no longer being able to balance. Same thing happened with my 6 year old quality Q30 18650's when I bumped them up to 0.5c, some are pretty much toast now.

I think it's trial and error and a guessing game. The BYD's MAX charge is 0.5c, so standard is probably 0.25C (50a)? I'd certainly approach or exceed that with caution. Keep in mind the battery is no longer a 200ah battery, at 3kw its more like a 125ah battery. So 0.25C would now be more like 30 amps...so that would be MY upper limit, until others do some more experimenting anyway ;).

Also, it would be helpful to know it the BYD's listed charge rate is the limit of the cells, or the limit of the stock BMS....
 
SolarRat said:
For years I've been charging most of my cells at about half of the rate of the "standard charge" the manufacturer lists and other than the usual slow gradual decrease in capacity I never had a problem. I recently (past few months) started experimenting with charging at the standard charge current (most are 0.5C standard charge) or higher, and that is when I started having problems with the packs staying in balance, with some cells never reaching near the desired charge voltage and the balance charger no longer being able to balance. Same thing happened with my 6 year old quality Q30 18650's when I bumped them up to 0.5c, some are pretty much toast now.

I think it's trial and error and a guessing game. The BYD's MAX charge is 0.5c, so standard is probably 0.25C (50a)? I'd certainly approach or exceed that with caution. Keep in mind the battery is no longer a 200ah battery, at 3kw its more like a 125ah battery. So 0.25C would now be more like 30 amps...so that would be MY upper limit, until others do some more experimenting anyway ;).

Also, it would be helpful to know it the BYD's listed charge rate is the limit of the cells, or the limit of the stock BMS....
Click to expand...
That is very useful advice. Thanks a lot of amps.
 
HMR said:
I am gradually beginning to understand my BYD batteries. A big thank you to all the diysolarforum members for all the information you have provided me and in particular to Jasonhc73 for his practical input and solid understanding. I especially find his recent post at: https://diysolarforum.com/threads/lifepo4-voltage-chart.3156/ extremely valuable.

After 3 discharge/charge cycles of my first battery I was able to discharge 2.94 KwH/ 116 Ah and charge back up 3.19 KwH/ 120 Ah using a shunt meter as my measuring device and the ToolkitRC balancing charger charging at 5 amp for 33 hours. After 24 hours rest, this first BYD battery settled at 26.59 v with cells ranging between 3.31 – 3.33 and a delta of 21 mV. During charging the cells sat between 3.31 and 3.33 for the majority of the time. Getting to 3.31 was quick and getting to 3.38 – 3.55 when battery was full was also quick. I am seeing a gradual increase in capacity especially on the 3rd discharge/charge cycle.

I performed my first charge cycle of my second battery. Starting data: 24.14 V; 2.95 – 3.09 cell V; delta V = 14 mV. This time I charged at 10 amp. The battery was full 10 hours later. Ending data: 27.6 V; 2.64 Kwh/ 99 Ah; 3.39 – 3.56 cell V right after charging; delta V = 170 mV. After a few hours I expect the cell voltage and delta to drop.

My experience clearly shows: (1) repeated cycling of the BYD batteries increases storage capacity up to some as yet unknown steady state level. I will continue to cycle until I observe no more increase in capacity at which point I will report the final capacity of my BYD batteries. (2) The limiting factor at each charge cycle is how rapidly or slowly the cells reach their voltage maximum. My charger is set for a maximum cell voltage of 3.55 V and begins to diminish the amps from about 3.5 V upwards. This behavior is constant through all cycles. The variable is the number of Ah the cells can soak up before they top off at 3.5 v. So far those Ah numbers have been increasing at each cycle. BatteryHookUp reported achieving 4 - 4.5 KwH capacity in their sales literature so this is my goal. If I cant reach that, how much capacity should I be satisfied with so I feel that I got my money's worth?
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With great embarrassment, I have to announce that my post yesterday (1/22/2020) used inaccurate data and therefore the conclusions based on that data are WRONG! In my first two cycles of my first battery, I used a PZEM--015 shunt meter with a 300 amp shunt. I had no idea the meter that came with the shunt was preset to match with a 100 amp shunt, not the 300 amp shunt I ordered. I realized midway through that something was wrong but did not know what. I switched to my old standby 100 amp shunt and immediately saw the correct numbers. I did not understand my mistake until this morning reading the MAAST thread on making a DIY single cell LiFePO4 tester. It can be found here . GMS ran into the same problem and SCClockDr pointed out the place in the manual that shows how to correct that setting. So here are the revised data:
Battery #1:
Cycle 1: charge = 3.54 KwH / 133 Ah; discharge: 2.76 KwH / 110 Ah
Cycle 2: charge = 3.18 KwH / 120 Ah; discharge: 2.94 KwH / 116 Ah
Cycle 3: charge = 3.19 KwH / 120 Ah; discharge: to be determined
Battery #2:
Cycle 1: charge = 2.64 KwH / 99 Ah; discharge: to be determined
New Conclusion: based on these numbers, the jury is till out whether I am gaining any capacity with increased cycling. The degree of cell discharge will affect the amount of charge it will accept upon recharge. I will add that variable in my next post showing more cycling results so that all the relevant data is available for analysis. I just wanted to get this quick post out so that everyone will realize that the data in my previous post are wrong.
 
Keith C said:
If you were off with your shunt by 300% shouldn't the results be more screwed up than what we saw?
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You are absolutely right. The first cycle of the first BYD battery were taken with the 300 amp shunt and showed a discharge of 1.18 KwH/44.5 Ah. The charging uptake was 919 KwH/36.5 Ah. At this point my anxiety level was really high thinking that my batteries were a complete failure. But I had a nagging feeling something was wrong because the charging amps that the Balance Charger claimed to be sending to the battery through the shunt meter was only a third of what the shunt meter was showing was going into the battery. So I tried again. Charging uptake showed 1.06 KwH/30.9 Ah on the shunt meter. At this point I smelled a rat. So I put my old trusty 100 amp shunt meter in place of the 300 amp shunt. The discharge recorded 2.94 Kwh/116 Ah. I was delighted to see this improvement, but here is where I screwed up.
I still did not realize that the difference in readings was completely a mathematical one due to not setting the 300 amp shunt meter correctly. I ASSUMED that whatever had happened the batteries showed an improvement in capacity due to the cycling I was doing (which was what I was expecting). My mistake was reporting that belief. In fact, I just finished my 4th cycle: discharge was 2.87 KwH/114 Ah. Charge up was 3.08 KwH/116 Ah. So it appears that after 4 discharge/charge cycles, correcting for instrument error, there has been no significant change in battery capacity. After a few more cycles of my second battery and testing various SOC levels (ie 80/20; 90/15) will pull it all together and present the data and conclusions. Then I will be ready to move on to the next step.
Have you Keith done a capacity check on your BYD batteries? Have you seen anyone report findings like I have done? I was expecting a lot of forum members to be reporting their results by now.
 
HMR said:
Have you Keith done a capacity check on your BYD batteries? Have you seen anyone report findings like I have done? I was expecting a lot of forum members to be reporting their results by now.
Click to expand...
I can't speak for the others, but I've been delayed a lot because I had to deal with a death in the family and all the paperwork, and I fell off the back of a dump trailer and badly hurt my arm and can't even pick the things up for now. And I was going at a snails pace anyway because I work graveyards and only get a couple of hours a day at most for projects before I have to go silent to not wake up my wife.

Also, I think people just dont want to take the time to do detailed testing, they just want to plug it in and go.
 
i have not placed the batts in their permanent location yet,can not run any good tests here,all my heavy draw stuff is 60 miles away.
 
Mine are being trickle charged, slowly by a small solar panel. I am organizing what I can to add more solar, and get them charged quicker.

But my business just eats all my time.
Busy is good, but it is difficult to find time for projects.
 
Thanks for all the responses for my query. I am so sorry Maast for your accident. A friend of mine just suffered a similar injury and just got done with surgery. No fun at all. Hope you get better soon. Also I understand deeply the desire just to get going and use these things. Nwillits and Supervstech: I completely empathize with your situation. I am retired and can just spend my time where my fancy takes me. However, I am such a newbie to solar and batteries, I have to take it one step at a time otherwise I feel lost. I was just hoping someone on the forum could contest or corroborate my findings. These BYD batteries of mine are essentially 3 KwH / 110 Ah batteries -- not by any stretch of the imagination the 4 - 4.5 Kwh / 180 Ah batteries that were advertised by BatteryHookUp.com. These findings obviously have huge implications for how many batteries I need in order to put together my small cottage power supply.
 
Well, HMR, I hope your next test goes well, because I have three of them (TechDirect BYD built units) - and I was hoping for 4kw per as well. Mine should be fully installed in an off-grid home in about two weeks. Doing the charge/discharge regimen with limited sunlight this week. Either way I'll be glad to get the FLA out of my basement crawl space...
 
My plan is to attach a drock shunt meter to track the Wh charge and discharge once I have fully top balanced the pack.

I have a 12000 btuh minisplit just sitting, waiting to hook up.
If it sips power too slowly, I may tie in a 36000 model...

I only have a 2400W inverter, so I cant just hook up a heat strip and blower
 
HMR said:
Have you Keith done a capacity check on your BYD batteries?
Click to expand...

Sorry HMR, but as you can see by how long it's taking me to even respond that I'm being shellacked by work at the moment. I'm a consulting EE and one of my biggest clients had the entire center burn out of their factory, Fourteen fire trucks 20 hose lines, and a never shut-off two and a half inch 3psi gas line made quite the mess.. :/ They're struggling to get production going again... I'm struggling to get half a dozen custom, hand made machines with melted controls running again...

I eat dinner with my 8 BYD batteries watching me every night. I think they're either snickering or laughing at me.

I cannot bring myself to hack all the connectors so I can plug an ISDT into them to see where they're at. I'm going to instead layout a board that you unplug the existing BMS cables out of and plug this board in and it feeds the 8 cells to the front panel connector. Then I make one cable that mates with the front connectors on the BYD and the other end plugs into the ISDT.

Of course I then start pondering just making a BMS plug-in replacement for the BYD BMS. Sigh.
 
My three TD assembled/BYDs also stopped charging @ approximate 28v (BYD meter) on the lifepo4 charger. Finally got enough sun to work on the charge/discharge cycle. Made sure the three were cutting off individually at about the same voltage as well as in parallel mode. (It looks like the internal BMS and not the charger is cutting them off). Then hooked them back up in parallel to do a discharge cycle (slowly, as i'm using a cheap 24v 3000w inverter that will only push 500watts at a time). They are hooked up to a AH & Kwh meter so I should get a pretty good idea of capacity at a defined lower voltage.
This would be much easier if I installed them into my full system, but I wanted a good baseline before they go into service. Any further word from others?
 
Keith C said:
Sorry HMR, but as you can see by how long it's taking me to even respond that I'm being shellacked by work at the moment. I'm a consulting EE and one of my biggest clients had the entire center burn out of their factory, Fourteen fire trucks 20 hose lines, and a never shut-off two and a half inch 3psi gas line made quite the mess.. :/ They're struggling to get production going again... I'm struggling to get half a dozen custom, hand made machines with melted controls running again...

I eat dinner with my 8 BYD batteries watching me every night. I think they're either snickering or laughing at me.

I cannot bring myself to hack all the connectors so I can plug an ISDT into them to see where they're at. I'm going to instead layout a board that you unplug the existing BMS cables out of and plug this board in and it feeds the 8 cells to the front panel connector. Then I make one cable that mates with the front connectors on the BYD and the other end plugs into the ISDT.

Of course I then start pondering just making a BMS plug-in replacement for the BYD BMS. Sigh.
Click to expand...
You only have to read the first post now for the BMS plugs I have sourced...

diysolarforum.com

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 diysolarforum.com

For the 1st 6 weeks, I've been charging all 8packs, 48v setup at 20 amps. Now I charge at 40 amps.

I bulk charge at 56.0V(3.5V per cell) and float at 53.0V.

As soon as bulk charging completes the voltage of the entire battery drops to 52.9 within 10 minutes. Then the entire battery either sits idle or gets 2 amps of charging from the MMP Solars.

Normally LiFePO4s do not need float charging. BUT these are very used and need some kind and gentleness in their twilight years to come. I expect they have worked the full 3000 cycles they are warranted for. I expect they will self-discharge to a low voltage, mine all arrived 23.3V or 23.6V.

The low voltage cutoff on the BMS's is 47.2. The Inverter is set to battery cut-off at 47.0, and back to grid at 48.0. I only run these off-grid, so kind of moot.

I have only ever discharged 3 times to less than "nominal" voltage.

The largest load I have presented to the battery(16S4P) is 92 amps discharge. According to BYD that would be about a .2C load on each cell.

I have the BMS set with the physical cells are 200AH, I usually use 27AH to 29AH of the entire battery during the 7 hours of use.

I have no concern for the 0°C charging, all are kept indoors.
 
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