DIY battery longevity
- Thread starter Subdood
- Start date
Zwy
Emperor Of Solar
It will meet capacity, however you will find one that usually is a runner at the top or bottom.
High temperature combined to fully charged state is the worst combination for li-battery lifetime.
scubadoo
Solar Enthusiast
Cycle counts for partial daily draws? I have serious doubts about accurate counting via any method.
Our battery is now approaching 3800 days of supplying somewhere in the region of 115Ah or 1.5 KWh overnight while the sun does not shine.
Someone else is welcome to perform any cycle maths.
Our 4 cell 300Ah Sinopoly LiFePO4 battery pack has now survived 10 years of full time travel both powering the motorhome and starting the 3.9l turbo diesel engine often multiple times a day.
I perform an annual C/10 capacity test each November. Converted to Ah the capacity has reduced from the original 315 to just 299. I expect a few more years of usable life.
Our battery is now approaching 3800 days of supplying somewhere in the region of 115Ah or 1.5 KWh overnight while the sun does not shine.
Someone else is welcome to perform any cycle maths.
Our 4 cell 300Ah Sinopoly LiFePO4 battery pack has now survived 10 years of full time travel both powering the motorhome and starting the 3.9l turbo diesel engine often multiple times a day.
I perform an annual C/10 capacity test each November. Converted to Ah the capacity has reduced from the original 315 to just 299. I expect a few more years of usable life.
HighDesertOffgrid
Solar Addict
- Joined
- Sep 15, 2022
- Messages
- 628
What is considered high temperature?
Why does my EG4-LL-48V V2 manual recommend to charge to 100% for long term storage then?
hwy17
Anti-Solar Enthusiast
EG4 is more concerned with the battery self discharging into over discharge than the minor degradation of storing at full charge. So putting into storage at 100% gives the longest possible storage time without catastrophic destruction. Maybe 1-2 years.
That users concern about storing at full charge is stronger than the community consensus though, which is more like it's not as ideal as 20-80%, but not that bad.
Anything above 25 degrees C has some effect but even 40 degrees is tolerable if you avoid 100% charge levels for extended perioids.
See page 5.( or the original references) https://hv.diva-portal.org/smash/get/diva2:1766051/FULLTEXT01.pdf
below 25 cel and 80% SOC should give you 10-20years lifetime with good cells.
But as usual predicting anything to 10 or 20 years is not that easy, especially when we have B-C-D grade chinese cells instead of premium Sony cells.
robot_zombie
New Member
- Joined
- Sep 22, 2022
- Messages
- 68
I built a battery around 15 months ago, from CATL 302AH cells (remarked QR, B grade likely), still flat as etc no change there, has around 320 cycles on it (by the JKBMS). chg to 3.47-3.49 VPC @ max 100A in or out. Still running well, I do have one cell that has developed a slightly different vibe, its always the highest on charge and lowest on discharge, but doesn't deviate significantly at the bottom or top. No problems with balance or anything like that over the time, I have logged all the data so far, the voltage at DOD 10% is a little lower than it was initially, something like 50-60 mV. Ie, initially, 10% would be around 3.08-3.1, now 10% is around 3.01 - 3.02. Recharge from this level still sucks up 280-285aH. The cells initially tested 299-302aH (to 2.6V) I guess it might have lost 2-4%. Reasonable, lets see how it keeps truckin....
Subdood
Photon Wrangler
Thanks that's very useful info.Cycle counts for partial daily draws? I have serious doubts about accurate counting via any method.
Our battery is now approaching 3800 days of supplying somewhere in the region of 115Ah or 1.5 KWh overnight while the sun does not shine.
Someone else is welcome to perform any cycle maths.
Our 4 cell 300Ah Sinopoly LiFePO4 battery pack has now survived 10 years of full time travel both powering the motorhome and starting the 3.9l turbo diesel engine often multiple times a day.
I perform an annual C/10 capacity test each November. Converted to Ah the capacity has reduced from the original 315 to just 299. I expect a few more years of usable life.
About to enter the fifth year on two of my packs. Not sure about the exact cycles, but they've been powering my house 24/7. I rebuilt them last year to put them in a different housing. No swelling, capacity about 267Ah from the 280Ah spec. I reported it here:
LiFePO4 cells in use since 2020. Bloating? Capacity?
As some of you may know, I'm in the process of moving my batteries into a new enclosure. Reasons: it's more organized, space is better optimized, and I can add more batteries more easily later if needed. This is the first time I took these apart since I built them somewhere early 2020. I bought...
diysolarforum.com
Note, those definitely weren't 'Grade A' - they were 100 Euro including shipping/taxes back in 2019.
In the datasheets, cycle life is stated being 0% - 100%.
Subdood
Photon Wrangler
Another BMS question. When looking at them I see a continuous and peak rating. What's a good rule of thumb for a particular rated cell? Say what would be the best BMS for a 280Ah battery? Maybe 250A continuous and 300A peak? 200A/250A?
Why push it. If you need the power: build two packs, put them in parallel and draw half the current.
Subdood
Photon Wrangler
I probably don't have room in my closet for two batteries, plus I'm cheap..so I was just inquiring about what one battery would require.
Cells can handle 1C continuous, so with 280Ah cells you can pull 280A out of them. At 48V, that's about 13kW.
Your BMS would of course also have to be able to handle this.
Zwy
Emperor Of Solar
It comes to $0.10/watt at the price I paid. Biggest concern I would have right now is shipping costs could drastically change overnight. Second concern will be what cells will be sold when basement bargain prices come into play. Manufacturers like EVE could stop production and try to clear out any inventory. This was similar to during covid, the available cells tended to be lower quality.
Hey my no grade dirt cheap Chinese cells seem to be holding up better than the dirt cheap AGM batteries I used to buy. Likely the dirt cheap BMS I put with them will fail first. I trust chemistry over electronics.
Cycle counts for partial daily draws? I have serious doubts about accurate counting via any method.
Our battery is now approaching 3800 days of supplying somewhere in the region of 115Ah or 1.5 KWh overnight while the sun does not shine.
Someone else is welcome to perform any cycle maths.
Our 4 cell 300Ah Sinopoly LiFePO4 battery pack has now survived 10 years of full time travel both powering the motorhome and starting the 3.9l turbo diesel engine often multiple times a day.
I perform an annual C/10 capacity test each November. Converted to Ah the capacity has reduced from the original 315 to just 299. I expect a few more years of usable life.
My 16 cells 200Ah sinopoly are different,
All cells aged differently.
The worst cell only has 115Ah.
Removing it from the pack and stick with 15 remaining cells......
Until I noticed the second worst cell only has 140Ah while the rest have 160-165Ah......out of the 200Ah specification....so, there is that....
Cells were installed back in year 2019 with SPF5000ES (replaced with SPF6000ES now), when installed at the time, those cells had 185-190Ah......
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