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BYD packs — one year on — survey

BarkingSpider

Carbon Lifeform
Joined
Apr 14, 2020
Messages
440
Location
Silicon Valley, CA
HI, Im calling out to anyone that purchased the original 24v BYD packs. I bought 4 early this year (2020) and they seem to be holding up ok. They are definitely not the bargain they were when they first came out, as I can now buy way more new IifePo4 storage in 280ah cells from China, including shipping. Which I have done.

How are your BYD packs holding up?
How is the degradation?
What BMS did you use?
What issues have you encountered?
Did you swap them out for new cells?
Are you still happy with them?
Are they still relevant to you given the prices of new cells?

Let us know ... Thanks!
 
I'd be interested in this too. Maybe also include discharge rate, DOD, and charge cell or pack voltage?

Which cells # are you low or runners?
 
After going through 4 different BMS's I tossed them all.

I now only use an active balancer. The balancer is working flawlessly.
I only charge to 53.1 and discharge to 46.0.

The Active balancer is finicky and doesn't really like to stay connected to blue tooth. As long as it balances the bottom and top cells, I don't care!

Today I redid one wire harness.

The Active Balancer I use on eBay.

I charge from AC at only 2.5 amps per pack.
I charge from DC at whatever the sun will give it. I have it set to 20 amps max per pack, but I have never seen more than 8 amps per pack.

I can discharge at 20 amps per pack on occasion, but normally just 4 to 6 amps per pack.

End of cycle daily use (1 of 4):
2020-12-08 (4).png
Before the cycle use actually being solar charged:
Usually, at this time of day the pack is fully charged, however, I charged my Chevy Bolt EV this morning.
2020-12-08 (2).png
The "setup":
20201208_190023.jpg 20201208_185941.jpg

I have the massive thread for the "plug-n-play" connector. https://diysolarforum.com/threads/byd-bms.3034/
The connector part of the thread is perfect. Don't bother with the BMS, just go active balancer.

One of the only "minor" issues that I now have with these BYD's is that they have a lot of internal resistance(IR), see on the screenshots above. This active balance cannot balance if there is too much IR. Even though I have 2 amp active balancers, I can only have them set to maybe 1.3 amp. On occasion, even that is too much. So to keep from having to mess with them I set them all to 1 amp and that is working great.

After I switched off today's cycle, and returned to the grid for the night, this is what the packs show:

1607476532860.png

I did not check the meter I installed before for how many kWh of use this was, but this is 6 hours of 100% off-grid use. With 8 packs, I can get about 24 hours of use with no sun to recharge. If I have a good solar day to recharge, there really is no limit to how much I can be off-grid. But for now in early December, the sun is low and my off-grid panels are on a practically flat roof, maybe 5° slope.
 
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For me definitely more trouble than it's worth with the price now on new prismatic cells from China. For one, the weight makes it difficult to move around, and dealing with weak cells in the group is a pain.
I got 8 modules almost a year ago and I did parallel 4 modules at cell level following what David Poz did. That did help balancing out the weak cells a bit but I still can't get the pack to go above 54V without a significant runner topping out at 3.65V. I'm using Chargery 16T plus Deligreen active balancers and I'm getting about 22KWh for the 8 module pack. I have them cycle between 48V and 54V for a few months in the summer, and I did not see much degradation although I have not been tracking the capacity very closely.
 
All in all when it is said and done, I figure the BYD's are equivalent to about 80-100ah new cells.

It's amazing what has happened to the price of new LiFePO4 cells this year. I have 64 new 280ah cells floating somewhere in the Pacific now. I'll be going from about 14 kWh to about 57 kWh, and have fresh brand new cells for 2x what I paid for the BYDs.
 
I'm still in the assembly phase, but so far - I'm not very happy, but I have to go with what I've started since I can't afford to replace them. Having said that - for the price they're not a disaster either, just heavily used. I'm having pretty good luck un-shittying the modules by adding additional capacity to the weak cells. There's always at least one and usually two about 15-20AH low.
I'm overprovisioning the weak cells quite a bit by adding 30AH of capacity per cell with the idea that since the new cells have a much lower IR they'll be doing most of the work for short high capacity loads.

The modules usually test out at 2.9 to 3.1kwh with a couple in the 2.7-2.8 range and one at 3.2kwh - which I boosted to 3.7kwh with the extra capacity added.

P1030992.JPG
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Sorry for the messy basement, I have a lot of projects going on at once...
 
As for me, last year I bought 4 of the refurbished pre-built 24v BYD units w/BMS/case from TechDirect/Big Battery. They have performed beautifully - and have made power management in my off-grid home so much easier. Yes, they had less capacity than advertised (so BB sent the 4th one to me at no charge), but the units have shown remarkable stability and have out-performed my old Trojan lead acid bank in every way. Faster charging, deeper discharge, much greater capacity, and with no maintenance - all at a fraction of the cost of replacing my FLA bank with new cells. YMMV, but all in all, I have no real complaints. A great way to stick my feet in the LFP water with a shallow learning curve.
 

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By the way, I use very conservative specs: 27.1 charge, 26.7 float, 26.4 recharge. My charge rates vary from .1C to .25C on average. The batteries have worked so well in my AC/DC coupled system that I am adding a mini-split heat pump this week.
 
All in all when it is said and done, I figure the BYD's are equivalent to about 80-100ah new cells.

It's amazing what has happened to the price of new LiFePO4 cells this year. I have 64 new 280ah cells floating somewhere in the Pacific now. I'll be going from about 14 kWh to about 57 kWh, and have fresh brand new cells for 2x what I paid for the BYDs.
I hope they were not on that container ship that lost containers overboard:

 
My BYD packs are showing no noticeable degradation.

Individual cells paralleled, No BMS, 5A active balancer. I rely on inverter LVD for low voltage protection and my charge controller for high voltage protection. It's a 48V nominal system.

Would not go the BYD route again though. new EVE cells are the way to go, from every angle...
 
For me definitely more trouble than it's worth with the price now on new prismatic cells from China. For one, the weight makes it difficult to move around, and dealing with weak cells in the group is a pain.
I got 8 modules almost a year ago and I did parallel 4 modules at cell level following what David Poz did. That did help balancing out the weak cells a bit but I still can't get the pack to go above 54V without a significant runner topping out at 3.65V. I'm using Chargery 16T plus Deligreen active balancers and I'm getting about 22KWh for the 8 module pack. I have them cycle between 48V and 54V for a few months in the summer, and I did not see much degradation although I have not been tracking the capacity very closely.
I've got Deligreens QNBBM-8S Active Balancers and like them (no BYD packs) but Chargery's Passive Balancing is OFF, it's not good with the Active Balancers.
 
I've got Deligreens QNBBM-8S Active Balancers and like them (no BYD packs) but Chargery's Passive Balancing is OFF, it's not good with the Active Balancers.
I came to the same conclusion and turned off balancing on Chargery after a few cycles.
 
I have five of them in parallel in a stand-by system, so they don't get cycled very often. They have not degraded much in the time that I've had them. Get an honest 650 Ah (130Ah each) out of this from a 40A discharge from 26.6v to 24.4v. They settle to 26.6v after a charge to 28.0 with a 15A exit. My 'usual' range is 26.6v to 25.2, which is roughly 80% of the SOC range.

My Bulk Charge voltage is set at 28.0v to prevent a a couple of cells from climbing past 3.6 well before the others. As long as I enter Absorption there, the cells seem to behave. My low end voltage is gated by one cell that dives off of a cliff before the rest. I could take the time to weed out the bad cells or patch them with augmented cells, but I really don't care that much....

I use an SBMS0 as a BMS which looks after the climbers and the jumpers.

I use a Samlex Evo 2224 to manage the stand-by aspects. Part two of this project is to integrate my SCC and power my Home Office from the sun as much as possible. I built this for fun and education, I don't rely on it or need it.

I am happy with the purchase. I did get a substantial refund from the seller to make up for erroneous capacity claims which makes this a decent value in my book.
 
I am finding my BYD's to be very stable after doing the fused cell interconnects and headways, packs stay within 50mv on the knees... I have been running the cells between 3v-3.4v per cell, and pull +-20 kwh daily..

The main thing I find with these byd's is that they need time at absorption voltage..and it's just not worth trying to charge to 3.65v to pickup a extra 5ah when, they will get to the same state of charge with added absorbtion time..

Would buy again or go CALB cells
2 x 8s qnbbm
Jkbms
 

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I am finding my BYD's to be very stable after doing the fused cell interconnects and headways, packs stay within 50mv on the knees... I have been running the cells between 3v-3.4v per cell, and pull +-20 kwh daily..

The main thing I find with these byd's is that they need time at absorption voltage..and it's just not worth trying to charge to 3.65v to pickup a extra 5ah when, they will get to the same state of charge with added absorbtion time..

Would buy again or go CALB cells
2 x 8s qnbbm
Jkbms
Off with your head with that copper pipe usage! (I use it also, we are doomed). .?

End of the cycle today and sitting at 0.004V difference on my problem set, managed with the active balancer at only 1 amp.

Take notice hat how much more resistance my balancer has compared to yours. That is what happens when I use the BYD traced lines and plug and play with my harness. If I took the time to put the balance leads directly to the cells I'm sure I'd have a lot more balance amperage capability.
 

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Off with your head with that copper pipe usage! (I use it also, we are doomed). .?

End of the cycle today and sitting at 0.004V difference on my problem set, managed with the active balancer at only 1 amp.

Take notice hat how much more resistance my balancer has compared to yours. That is what happens when I use the BYD traced lines and plug and play with my harness. If I took the time to put the balance leads directly to the cells I'm sure I'd have a lot more balance amperage capability.
jasonhc73,

Love your setup that's really impressive. I've had the same good experience with mine. I've seen no degredation after having my BYD packs for almost a year. That screenshot of the battery voltages, is that from the Jkbms? I like that output view of voltages.
 
Does anyone have pictures of paralleling the individual cells for two units? I watched several videos, but I am still not 100% clear on the process. I have two units coming that I would like to parallel to get what I am hoping will be about 24v 200AH total storage (anything more would be gravy).
 
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