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Will Prowse says charging 0%-100% daily is a non-issue for lifepo4 battery longevity. Thoughts?

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Speng

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Check timestamp 3:35

I've just placed an order for 2x 280Ah packs with PACE bms, and opted for 2 DALY external active balancer units.
Manufacturer told me charge 20%-100%. I thought they mistakingly said 100% and meant 80%.
General consensus has been to keep 20%-80% for longevity.

Will here says this is a misconception and charging/discharging 0%-100% all the time is fine.

Thoughts?
 
My thinks is easy .

Bms is nog make for daily use for 100% .
The mosfets have a big ampère to disconnect or connect .
And that will kill the bms after years .

So for my self a bms is only if the go wrong to protect the battery.
Even lifepo4 cells company advice to use 80% of the battery for optimal use.
That is lower than the bms settings.

You can read that information by the cell company.
 
Suijkerbuijk said:
My thinks is easy .

Bms is nog make for daily use for 100% .
The mosfets have a big ampère to disconnect or connect .
And that will kill the bms after years .

So for my self a bms is only if the go wrong to protect the battery.
Even lifepo4 cells company advice to use 80% of the battery for optimal use.
That is lower than the bms settings.

You can read that information by the cell company.
Click to expand...
EVE states a recommended scope of SOC of 10%-90%.
www.evlithium.com

EVE LF280K 3.2V 280Ah LiFePO4 Prismatic Battery Cell

Factory sale grade A prismatic cells lifepo4 3.2v 280ah battery for energy storage and power lifepo4 battery
www.evlithium.com
 
1) While battery under warranty, I'd do what's necessary to maintain that.
2) Otherwise, I charge to 100% every day that's possible with solar.
3) The low end is always the conundrum for me. Am I worried about going own to low single digits for battery longevity? NO (so I agree with Will, and note that he has much more experience than me in this area). But I don't want to get into the habit of going too low, because I don't want batteries to get too low when I'm away from home (say, traveling for a week or two) and find that the BMS has shut things down. So, I have a warning set for 20% SOC and will fire up the generator at that point, more for having a wide margin of system safety (power stays on with time to react if a problem occurs, such as a generator that doesn't start) and not out of fear of harming the battery.
 
Madcodger said:
1) While battery under warranty, I'd do what's necessary to maintain that.
2) Otherwise, I charge to 100% every day that's possible with solar.
3) The low end is always the conundrum for me. Am I worried about going own to low single digits for battery longevity? NO (so I agree with Will, and note that he has much more experience than me in this area). But I don't want to get into the habit of going too low, because I don't want batteries to get too low when I'm away from home (say, traveling for a week or two) and find that the BMS has shut things down. So, I have a warning set for 20% SOC and will fire up the generator at that point, more for having a wide margin of system safety (power stays on with time to react if a problem occurs, such as a generator that doesn't start) and not out of fear of harming the battery.
Click to expand...
It's straight from China. 10 years warranty. Not sure how much I could actually rely on that warranty, lol.
Thank for your further insights. I do agree. The sellers themselves said 20%-100%. I'd be happy with 80% capacity (22kwh), so that's not an issue. Just trying to see what the general consensus is regarding these things. Andy too has stated on YouTube that because of the very flat charging/discharging curve, you can go about 5%-95% without dropping down/spiking up in the curve...
 
if you plan a system with "three days of autonomy", it is pretty hard to to run the ESS from 0-100 % "daily" .
I have no issue using the 'whole' capacity of the packs, and don't care about "warranty" - most of my packs are DIY, and I doubt the factory packs warranty is worth a Dime.
What is "daily" use - depends a lot on weather and loads being used.
In summer it can be normal to run 70 % - 100% most days, and drop down to 30%-70% during a week of poor weather.
In winter it can be normal to run 30%-60% daily, and top up a bit from chargeverter at night to make up from short-fall of solar that day.

I set my low cut off at 10% - just to have something left if needed - but have only seen once that the system ever hit that low value - gotta keep an eye on the Official Solar Tester sometimes. :ROFLMAO:
 
OffGridForGood said:
if you plan a system with "three days of autonomy", it is pretty hard to to run the ESS from 0-100 % "daily" .
I have no issue using the 'whole' capacity of the packs, and don't care about "warranty" - most of my packs are DIY, and I doubt the factory packs warranty is worth a Dime.
What is "daily" use - depends a lot on weather and loads being used.
In summer it can be normal to run 70 % - 100% most days, and drop down to 30%-70% during a week of poor weather.
In winter it can be normal to run 30%-60% daily, and top up a bit from chargeverter at night to make up from short-fall of solar that day.

I set my low cut off at 10% - just to have something left if needed - but have only seen once that the system ever hit that low value - gotta keep an eye on the Official Solar Tester sometimes. :ROFLMAO:
Click to expand...
Nice! I'm planning to automate everything in Home Assistant. And perhaps with a dynamic contract, load from grid to inject later on when price is higher if profitable. My solar setup will be 10 panels of 440Wp probably. And my inverter is capped at 120A charging & discharging current (DEYE SUN 5k-SG04lp1). The batteries will have PACE 200A BMS, but obviously inverter 120A is the limiting factor there.

Warranty is from Chinese factory indeed. 8000 cycles or 10 years, whichever comes first. But I too don't put too much trust in this warranty.
 
below 18% gives me the heebie-jeebies, I could go to 10% but not past that. I just don't have the need with my capacity.
So how many at least reach the balancing voltage of 3.45 or higher per cell on the charge side?
 
ricardocello said:
I ran mine down until the BMS cut out a couple months ago during an outage.
First and only time I expect to do that.
Learned a lot about where my low cutoff voltage settings needed to be.
Click to expand...
Under load the voltage will sag, and this could trigger a low voltage shut down (by BMS settings) before you hit the low SOC value.
This is one reason I built the ESS bigger, it reduces the sag-voltage considerably to have 8 packs or more, as each only supplies a portion of the load.
 
OffGridForGood said:
Under load the voltage will sag, and this could trigger a low voltage shut down (by BMS settings) before you hit the low SOC value.
This is one reason I built the ESS bigger, it reduces the sag-voltage considerably to have 8 packs or more, as each only supplies a portion of the load.
Click to expand...
It was overnight so the loads were very light, so the sagging was minimal.
However, I definitely need and want more battery!
 
A combination of inductive loads and voltage sag generally takes out my inverter between 10-15%. I have, on occasion, manually power cycled the inverter to bypass recovery voltage, and once all 4 parallel bms' did enter LVP.

I do charge to 100% daily if possible and use 50-90% depending on external variables.

I believe Will's point was not to promote using 100% of the battery daily, but to clarify that it isn't a big problem if you do.
 
Last edited:
Is it better to charge batteries once per day or multiple small charges? I'm on a free nights plan, charge my batteries up at night at least once. But during the day when I have excess solar, the batteries also get charged (when they probably don't need to). Is this a big deal? I don't see any settings on my 18kPV to stop that if I wanted.

Also after reading this, I've changed my SOC charge limit to 100% instead of 80%.
 
Others can (and will) chime in but doing the 20-80% charge is supposed to be better (as I read) for longevity
BUT
I find it unbalances the crap out of the cells if you don't get either a top or bottom charge & balance. I have been using top more often to afraid to venture into the dark depths of 0 SOC.
 
sunshine_eggo said:
HOW you charge to 100% matters too. A long slow charge at 3.45V/cell will have a higher cycle life than fast charges to 3.65V/cell.

Victron actually publishes varying cycle life vs. DoD on their LFP batteries.


View attachment 255002

Maybe they pulled it out their butt. Maybe it's based on testing.
Click to expand...
I made this chart a while back. Time for public opinion on it. For what I have learned since then I would have added 55.2 for 3.45 balance on it as optimal charge voltage.

1731255551331.png
 
If you don't charge close enough to 100% often enough, balancing can't occur. You will end up with diverged SoC between cells which will reduce accessible capacity. You should be able to learn by cell voltages near 100% SoC whether they are staying balanced.

Discharging to LVD by BMS would be inconvenient. Better to shed less important loads earlier, keep the lights on.

3000 or 6000 cycles daily is 8 or 16 years. Good chance something fails, possibly takes out the batteries, before cycle life is up. Use 'em while you got 'em.

Having batteries at elevated temperature while near 100% SoC is expected to shorten life.
Lower SoC like 30% to 50% is what is recommended for long-term storage and shipping.

In use, best I think to reach near 100% (or whatever high level you charge to based on voltage) just before you start discharging. So reduced charge rate may be better than hitting 100% by 10:00 AM. Except, in times of poor weather you may not have sun all day.
 
I'm on Will's side, and have always advocated to use 100% of the battery. Charge to 3.55v/ cell with enough time to balance.

I have enough battery capacity to never get below 50% now, but I would routinely take my batteries below 3v/ cell In the past.

"I bought the whole battery, I'm gonna use the whole battery"
 
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