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Another Deep Cycle test on BYDs

jasonhc73

jasonhc73

Cat herder, and dog toy tosser.
Joined
Oct 1, 2019
Messages
1,921
Location
Wichita, Kansas
I just started a deep cycle on my BYD's


Duque thinks it's great, but, is this too far?

16S BMS with these settings:
CellLowProtect 2.60V
TotalVoltLowProtect 41.6V (16x2.6)
CellDiff Value to Start Balancing 0.02V
System Shut Down Cell Voltage 2.55V
Cell unit Voltage Gap protection 0.5V

MPP Solar LV5048 Inverter set to shutdown at 41.6V.
I have not run the packs below 48V yet, so this is new territory for me also.

Normal house usage, 11~13 amps(DC Battery) when the heater is going, 8 amps when the heater is off.

The batteries are in a cold garage, however, for this test, I have the house door open and it is indirectly heating it.

3 1/2 hours in and the kWh meter shows 3kWh used.
 
i have cycled mine twice.recharging now.my settings are -bulk charge 56v,float charge 54v,back to grid 50v,battery cut off 47.2v.max AC charging 60A.
what do you think?
 
nwillitts said:
i have cycled mine twice.recharging now.my settings are -bulk charge 56v,float charge 54v,back to grid 50v,battery cut off 47.2v.max AC charging 60A.
what do you think?
Click to expand...
How many banks do you have? 60amps is over 1C for two batteries, about .6C for 4 banks...
 
i have charge set at 60 max,test shows 15 amp when charging.i have 2 BYD's in series.60 too high?how about the other settings?bulk charge ok?
 
nwillitts said:
i have charge set at 60 max,test shows 15 amp when charging.i have 2 BYD's in series.60 too high?how about the other settings?bulk charge ok?
Click to expand...

I think the bulk is fine.

For the first few cycles, set the float to about 52V.
Just so you can see if the packs self discharges and where they get to their resting state. Normally LiFePO4's don't need to be "floated", RiGhT?

7kHw down, 9 hours of use. sitting at 51.2 V. So what's that C rate? (8 BYDs in 48V setup)

The "Max" setting is when you have solar panel engaged! The other setting is what you charge the packs from the grid/generator (A/C input).
 
For testing I have float set higher vs my bulk right now to keep the tested pack at 27.5 while some balancing goes on. Ive been mostly playing with my lowest pack. With balancing off float turns on and off every 5mims as the pack drops back down.
 
Uggghhh, this is taking forever. (8 or 9 amp battery discharge)

I'm going to put my car on the battery and just charge my car up at 32amps after this cycle. The EVSE has a kWh gauge on it. derp!
 
I'm adjusting the settings. :)

2.9V cell and 46.4V total cutoff

I've seen too many "active balancers" showing 2.9V is the Undervoltage Dormancy.

2020-02-15.png2020-02-15 (2).png
10 kWh into it. (11 hours)
IMG_20200215_002845742.jpgIMG_20200215_002849857.jpg
 
Last edited:
IMG_20200215_070640022.jpgIMG_20200215_070645263.jpg

This is all there is to get.
14 kWh.:mad:
2 cells ruined the entire party.
two at 2.900V. Most nearly all the rest about 3.170V
Cell Difference 0.230V, 0.151V, 0.136V, and 0.279V.

IMG_20200215_070701887.jpgIMG_20200215_070651571.jpg
IMG_20200215_070704693.jpgIMG_20200215_070712532.jpg
IMG_20200215_070723865.jpgIMG_20200215_070730802.jpg
IMG_20200215_070741264.jpgIMG_20200215_070749302.jpg
 
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jasonhc73 said:
Without a High Current Active Balancer.
View attachment 7374View attachment 7375

This is all there is to get.
14 kWh.:mad:
2 cells ruined the entire party.
two at 2.900V. Most nearly all the rest about 3.170V
Cell Difference 0.230V, 0.151V, 0.136V, and 0.279V.
Click to expand...
You should get another pack, split it down and use it to replace to two duff cells(use the two cells which most closely match your current pack), then build a 12v back up pack with the remaining cells for something else. That way your 'main bank' is as closely balanced as you could get it....much more capacity in the long run???
(just the thoughts of a newbie.....lol)
 
The BMS kicked in and did exactly what they are designed to do. Managed the system.
If you try to use these "very" used BYD's without BMS, you are walking on the thinnest of ice.

The end of the test...
This looks very much like the top of the steep slope that LFP cells have.
New-1.jpgNew-2.jpg
 
Solarfun4jim said:
You should get another pack, split it down and use it to replace to two duff cells(use the two cells which most closely match your current pack), then build a 12v back up pack with the remaining cells for something else. That way your 'main bank' is as closely balanced as you could get it....much more capacity in the long run???
(just the thoughts of a newbie.....lol)
Click to expand...
Cell 6 in pack 41
Cell 1 in pack 11

And here is the dismantling video (not at all an easy task)...
 
Last edited:
jasonhc73 said:
The BMS kicked in and did exactly what they are designed to do. Managed the system.
If you try to use these "very" used BYD's without BMS, you are walking on the thinnest of ice.

The end of the test...
This looks very much like the top of the steep slope that LFP cells have.
View attachment 7386View attachment 7387
Click to expand...
I cant believe anyone would risk using these without a BMS....they must be very confident in their abilities.
 
jasonhc73 said:
Cell 6 in pack 41
Cell 1 in pack 10

And here is the dismantling video (not at all an easy task)...
Click to expand...
Yes jason i see your issue....but if possible, without causing any damage, then you have to weigh that up against how long you expect to use them? If you envisage getting another 5 years out of them, then a couple of weekends spent on dismantle and re assembly, could be very productive. :)

The interconnectors in that video, dont look very substantial, but i guess getting them off is easier than if they were more substantial.
 
Last edited:
Solarfun4jim said:
Yes jason i see your issue....but if possible, without causing any damage, then you have to weigh that up against how long you expect to use them? If you envisage getting another 5 years out of them, then a couple of weekends spent on dismantle and re assembly, could be very productive. :)
Click to expand...
I am sure this is the very reason why the packs were taken out of service. They were used since at least 2012, nobody can provide an accurate date and use.
 
jasonhc73 said:
I am sure this is the very reason why the packs were taken out of service. They were used since at least 2012, nobody can provide an accurate date and use.
Click to expand...
Yeah, but the difference is, you are not looking for full capacity, you are happy with what they currently are and you are 'treating them nicely' now. Have you now arrested the degradation? Only time will tell.
 
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