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

[Brucey]

So I tested one of my 12 year old never used A123 m1a cells and got 2.07 Ah / 2.3 = 90% SOH = 0.83% per year calendar aging. It measured 3.29V before charging = 30% SOC. I guess it was stored at 50% 12 years ago. That’s amazingly low self discharge rate.

That is impressive. Here's some other charts from the a123 Doc on their 20Ah pouches:, definitely looks like time and especially elevated temps take a toll.

 

[wpns]

@Will Prowse stated in one of his videos (I think) that he doesn't want to have to monitor his systems on a daily basis. I agree with that. I shouldn't have to monitor that closely if things are working as they are supposed to. Monitoring down the cell level shouldn't be required to keep the batteries healthy. The only way to monitor to that level is via the BMS Test software and then I'd need to keep a computer attached to the batteries.

Isn't there some simpler way? Shouldn't the BMS be doing a better job of balancing cells?

I’m with Will except I want to understand my batteries and the BMS well enough to know what’s happening and what good and bad behavior is and then let a computer (probably the Raspberry Pi inside one of my 18 KPV inverters) obsessively watch the batteries for me and let me know if something appears to be going wrong. Right now I’m in the first stages of figuring out what’s going on.

Too many examples here, and too many instances in real life of “black box“ batteries that just stopped working for no apparent reason. One of my neighbors finally cut open a battery that wasn’t working and discovered it had a crack in the bottom of the case and was half full of (salt) water. had I known that, I wouldn’t have spent a month trying to slowly charge it and wake it back up.

 

[wpns]

I’m not a sensitive person. It just annoys me when people disagree with what i say without making any effort to actually try to understand what i have said.

OK, but while I’m trying to understand, and I am grateful for your insights into LFP chemistry and physics, I’m not seeing your recommendations on what I should do.

Will has lots of opinions and recommendations, what are yours? Different opinions are always great, but “Will’s wrong” isn’t helpful when I’m trying to characterize my system and set notification limits that (hopefully) won’t trigger for years.

 

[JJJJ]

For day to day use when it comes to LFP, I can only say what I do: I don't go above 3.55V per cell (100% for all intents and purposes)

When I was doing cell testing it was interesting to note that the "bulk" of the amperage seems to reside between 3.3 and 3.4 volts. Yes, voltage tends to be linear but testing suggested that amperage was not. Charging between 3.3 and 3.4 took a lot of power. However once I hit 3.4 it was a fairly quick jump to top balance at 3.65.

Respect the 3.55 value. From my testing, there really doesn't seem to be that much power (amps) above that level. In my case when I had my Overkill battery set at the higher level, it created one or two runners. This was a pack that was carefully top balanced. They would constantly "hit the ceiling" and eventually ruined one of my BMS units. I have since replaced the BMS units and set my values to more conservative levels which enables me to get to float mode for the first time with the same cells.

 

[upnorthandpersonal]

Which part of cell imbalance in a pack doesn’t degrade cells don’t you understand?

Ok, you guys misunderstand each other. You're both correct.

If you keep the cells within typical charge parameters, there is no issue and the cell in the pack that reaches high voltage disconnect first will just limit overall capacity. However with a BMS that only balances while charging (like many in those cheap 12V packs), when you try to balance, it will cut off at high voltage, and do so many times while the same cell keeps hitting 3.65V and is potentially kept at this voltage for quite some time leading to this cell being overcharged before the balancer can make a dent.

So, in normal situations with good gear, not an issue. In situations where you have a crappy BMS (like Will points out is the case in those low cost 12V batteries) it can be an issue.

 

[Consumerbot3418]

Which part of cell imbalance in a pack doesn’t degrade cells don’t you understand?

Degradation would be understood to be irreversible, whereas imbalance can be reversed (with plenty of time or effort).

If it takes cutting open a sealed pack to restore balance, or months out of service on a trickle charger or power supply, then the distinction is basically academic.

 

[Suijkerbuijk]

Degradation would be understood to be irreversible, whereas imbalance can be reversed (with plenty of time or effort).

If it takes cutting open a sealed pack to restore balance, or months out of service on a trickle charger or power supply, then the distinction is basically academic.

No not.
If you use longtime a cell that is not operate on the volts it need
It have more cycle than a good cells that is good balance.
Than if stay more on lower volts it get a hit by the low cut off from the bms.

If you use the battery for the 100% settings from 2.5-3.65 range .
If you only use a parte like 60/70% that problem will not have the cells stay in some balance that the cycle are the same.

 

[Will Prowse]

Which part of cell imbalance in a pack doesn’t degrade cells don’t you understand?

You were the one making a false statement “imbalanced cells causes degradation”

I’m just correcting misinformation you posted on this forum, i haven’t watched any of your videos and judging from the quality of your advice here i’m not missing anything.

This thread was referencing my video and you didn't watch it? Ok I give up, I feel like I'm talking to a wall at this point

 

[Consumerbot3418]

No not.
If you use longtime a cell that is not operate on the volts it need
It have more cycle than a good cells that is good balance.
Than if stay more on lower volts it get a hit by the low cut off from the bms.

Meneer, I really appreciate your contributions to this forum, although it can be tricky to tease out your meaning sometimes. I think you’re saying this:

“No, that’s not correct.

If a cell operates outside its optimal voltage range for an extended period, it will experience more cycles than the other, better-balanced cells. This leads to accelerated wear on that cell.

If the cell stays at a low voltage for too long, it risks triggering the low-voltage cutoff from the BMS.”

It seems like an excellent point to me, and if true, even better refute to @toms’s claim “cell imbalance ≠ degradation”. Actually, he wrote this:

made no effort to understand that having imbalanced cells in a pack in a correctly functioning system is no issue.

If the system is functioning correctly, then cells wouldn’t drift far out of balance, and would come back into balance again on their own.

Badly imbalanced cells would only happen in a system that’s not functioning correctly, so what are we even talking about??!?

 

[Will Prowse]

Actually there's quite a few factors that create excessive cell drift over time. For example, excessive temperatures, high C rate loads or charging or mismatch cells in cheap budget batteries.

And then combine it with not charging up to a voltage that triggers the balance circuit, those cells are going to stay imbalanced for all time.

Also if an individual does not charge up to the balance circuit threshold, there will always be cell drift naturally over time. Some cells have a higher internal resistance, naturally. Those ones will give off more heat. The more you cycle, the more balancing required. I even said in my video that when I was running without BMS, I did not have to balance that often. But these packs are designed to last for decades, so you need to charge it above the balance triggering voltage. And preferably to 100% so it can balance faster.

I don't see how my point is not clear. The cells need to cycle together, balance, avoid excessive temperatures, and charge high enough to trigger the balance circuit. I still don't know what this guy's disagreeing with

 

[Will Prowse]

But the fact that he hasn't watched the videos makes me realize that he has no idea what I said. What information have I posted here on the forum that is wrong? Can you post it here? @toms

 

[AntronX]

@Will Prowse I understand that your videos are aimed at regular Joes out there but I also kinda don't like "always charge to 100%" and "capacity fade is too low to worry about" points. While 5 - 7% capacity fade per year may not be a big deal for $160 12v batteries applying this advice to $10k whole house system will end up causing double the rate of degradation which drastically changes the economics of battery storage for grid arbitrage use case (charge when power is cheap and discharge when expensive).

 

[Suijkerbuijk]

Meneer, I really appreciate your contributions to this forum, although it can be tricky to tease out your meaning sometimes. I think you’re saying this:

“No, that’s not correct.

If a cell operates outside its optimal voltage range for an extended period, it will experience more cycles than the other, better-balanced cells. This leads to accelerated wear on that cell.

If the cell stays at a low voltage for too long, it risks triggering the low-voltage cutoff from the BMS.”

It seems like an excellent point to me, and if true, even better refute to @toms’s claim “cell imbalance ≠ degradation”. Actually, he wrote this:


If the system is functioning correctly, then cells wouldn’t drift far out of balance, and would come back into balance again on their own.

Badly imbalanced cells would only happen in a system that’s not functioning correctly, so what are we even talking about??!?

Yes that is what i mean.
Thank you to explained more efficient than i can

 

[SolarCzar]

I agree that the theory of the 0%-100% charging cycle, but like someone else said on this thread, might be better to manage that more conservatively during the warranty period. I set my EG4 batteries to 5% after watching Will's video, as it made sense to me. Plus from a financial aspect, I was set at the default of 20% SOC cut-off and that 20% move to 5% based on my demand resulted in 1.25hrs additional battery usage = $0.79 day (5000 watts @ $0.158 kW) or $23.70 per month. It adds up. The temp turned cool (41º) during the night, and I saw the 5% degrade to 0% in the early hours. Assume it was the heaters kicking in. Don't know what the errors below mean, but will ping @EG4TechSolutionsTeam and see if they can provide some insight... I'd like to use all my battery, but don't know if the errors are a concern or just informational. Point being...I want to use all my battery but not at the risk of losing my battery due to BMS safety controls.

 

[wpns]

I agree that the theory of the 0%-100% charging cycle, but like someone else said on this thread, might be better to manage that more conservatively during the warranty period. I set my EG4 batteries to 5% after watching Will's video, as it made sense to me. Plus from a financial aspect, I was set at the default of 20% SOC cut-off and that 20% move to 5% based on my demand resulted in 1.25hrs additional battery usage = $0.79 day (5000 watts @ $0.158 kW) or $23.70 per month. It adds up. The temp turned cool (41º) during the night, and I saw the 5% degrade to 0% in the early hours. Assume it was the heaters kicking in. Don't know what the errors below mean, but will ping @EG4TechSolutionsTeam and see if they can provide some insight... I'd like to use all my battery, but don't know if the errors are a concern or just informational. Point being...I want to use all my battery but not at the risk of losing my battery due to BMS safety controls.

View attachment 256291

I tried taking my batteries down to 5% the other day, and it looked like they were falling off a cliff. While I did not get any battery disconnects, I have decided to leave the ChargeVerter cut in at 10%, and I set a non-silenceable alarm on my phone at 5%, which should (?) give me a half an hour to check for issues and/or fire up the generators.

 

[Starex]

What Will is sayings makes perfect sense if your controlling the charge and discharge rates and start with perfectly balanced nearly new cells, like in a bench test.
In real life you may not want to rely on his advice.

 

[Steve_S]

I tried taking my batteries down to 5% the other day, and it looked like they were falling off a cliff. While I did not get any battery disconnects, I have decided to leave the ChargeVerter cut in at 10%, and I set a non-silenceable alarm on my phone at 5%, which should (?) give me a half an hour to check for issues and/or fire up the generators.

Remember the normal LFP Voltage Curve.
Steep Fast Drop after you cross the 2.800-2.900 Volts per cell. The Infamous Cliff Fall.
Then the other side from 3.500 +/- to 3.650 is "Runner territory" where weaker cells to run to HVD.
AH between 2.500 to 2.900 and from 3.500 to 3.650 typically only represents about 2-4% of "Gross Capacity" (not net capacity which is the Working Voltage Range)
Depending on Cell Grade, Bulk, B or A etc the base Voltage where the cells drop or climb fast will vary.

I run a mix of EVE 280's from V1 to V3 and everything in between, including 2 franken-packs with V1 & V2 cells mixed together.
A Current JKBMS Inverter Model 2A Active Balancer (V15 HW).
The MOST they ever get out of balance is just at the point where Absorb transitions to Float. It is NEVER more than 0.020mv apart.
Within 15 minutes of FLOAT, All Cells in All Packs are within 0.005mv.
All the packs in the bank will remain that way till just a hair below 3.000 Volts per cell where they start to deviate a bit more again... By 2.800vpc, the max deviation may be 0.030 +/- 0.005 at which point they shutdown. Only gotten there during Thrash Tests, the bank never gets below 2.900vpc.

The Charge profiles, BMS settings I use at home and on systems I have installed out in the wild ALL perform pretty much identically and without issues. Some of those are heavy Loaders as well (1 Greenhouse & 1 saw mill).

I have active balancing start @ 3.42V. Bulk/Absorb run at 3.475vpc while Float runs at 3.435vpc. HVD is set to 3.510 and HVDRelease at 3.455 so the cycles stay tight & fast BUT due to my charge profile HVD never gets triggered.

Lastly, all of the above stays consistent regardless is the packs are at 15C/59F or 40C/104F temps. * Charging slows up a bit over 35C/95F.

A "Catch of sorts". All my packs are DIY. I have Bulk, B, A Grade cells (pending on pack & vintage). They have ALL been TOP-Charged to 3.650vpc @ Cell Level and allowed to charge until 1% of stated AH (2.8A for a 280AH cell), then "Set Balanced" all cells charged to same Voltage and allowed to balance between themselves before assembly. WEnsuring the Chemistry is fully activated and all available capacity is actually available.

This is My Setup & Settings which I have come up with over the years and it all works flawlessly without any concerns or regard. Each pack is assembled & built the same. All Heavy Cables etc are all exactly matched & to identical specs (length/gauge/nickel plated lugs etc). Granted I only have 1,960 AH in my Home Bank but it does exactly what it must and how it must.

Hopefully this is of use to some and good luck.
Just remember ONE THING, everything is Your Choice, Your Decision and ultimately Your responsibility for good or bad.
Most importantly, it is Your Wallet not the person who is giving you advice ! Your dog is the one running in the race, not theirs.

 

[JJJJ]

This is My Setup & Settings which I have come up with over the years and it all works flawlessly without any concerns or regard.

I have owned a number of cars over the years. Over the last 10 years I have developed a trusting relationship with my mechanic who also happens to be a neighbor and a friend.

Having said that, if there is a safety concern with my car, I can rest assured that my mechanic will point it out to me and fix the problem.

As shown in another thread, DIY is still alive and well. Those who embark on this direction can take years to develop their skills and their batteries are almost like one of the family. Much like my car which has 354,922 miles on it, I want to squeeze every last mile I can out of my batteries, calendar ageing aside. If that means adding another battery (which I just did) it isn't a big deal since I know the ins an outs of building and putting together one. We in DIY have a community who help each other with builds and repairs, hence the name of this forum. We may not agree on the BMS, or case, or even the cell used, but we do have something in common and that is getting our hands dirty while we learn the trade.

I personally have chosen more conservative settings for my cells. This has served my needs very nicely. As @Steve_S said so accurately, our wallets give the advice. I have built my system after carefully setting aside the funds over time and have built and added on as budgeting has allowed. If I were to buy an off the shelf battery, I might be tempted to run it for all it was worth, knowing that a replacement could be purchased in the future if needed with likely improved technology. Although, for me, probably not. I don't drive my car that way, I don't treat my body that way, and certainly not my batteries. But then this is the path I have personally chosen.

 

[Will Prowse]

What Will is sayings makes perfect sense if your controlling the charge and discharge rates and start with perfectly balanced nearly new cells, like in a bench test.
In real life you may not want to rely on his advice.

Controlling the charge and discharge? I have almost 200kWh of batteries I am cycling at various rates with multiple arrays all day. What are you talking about? Perfectly balanced cells? I even covered how budget packs come imbalanced from the factory. Hell even some server rack batteries. What in the world are you talking about

 

[Will Prowse]

I have owned a number of cars over the years. Over the last 10 years I have developed a trusting relationship with my mechanic who also happens to be a neighbor and a friend.

Having said that, if there is a safety concern with my car, I can rest assured that my mechanic will point it out to me and fix the problem.

As shown in another thread, DIY is still alive and well. Those who embark on this direction can take years to develop their skills and their batteries are almost like one of the family. Much like my car which has 354,922 miles on it, I want to squeeze every last mile I can out of my batteries, calendar ageing aside. If that means adding another battery (which I just did) it isn't a big deal since I know the ins an outs of building and putting together one. We in DIY have a community who help each other with builds and repairs, hence the name of this forum. We may not agree on the BMS, or case, or even the cell used, but we do have something in common and that is getting our hands dirty while we learn the trade.

I personally have chosen more conservative settings for my cells. This has served my needs very nicely. As @Steve_S said so accurately, our wallets give the advice. I have built my system after carefully setting aside the funds over time and have built and added on as budgeting has allowed. If I were to buy an off the shelf battery, I might be tempted to run it for all it was worth, knowing that a replacement could be purchased in the future if needed with likely improved technology. Although, for me, probably not. I don't drive my car that way, I don't treat my body that way, and certainly not my batteries. But then this is the path I have personally chosen.

How often do you hit LVD with your system?

 

[Will Prowse]

I have owned a number of cars over the years. Over the last 10 years I have developed a trusting relationship with my mechanic who also happens to be a neighbor and a friend.

Having said that, if there is a safety concern with my car, I can rest assured that my mechanic will point it out to me and fix the problem.

As shown in another thread, DIY is still alive and well. Those who embark on this direction can take years to develop their skills and their batteries are almost like one of the family. Much like my car which has 354,922 miles on it, I want to squeeze every last mile I can out of my batteries, calendar ageing aside. If that means adding another battery (which I just did) it isn't a big deal since I know the ins an outs of building and putting together one. We in DIY have a community who help each other with builds and repairs, hence the name of this forum. We may not agree on the BMS, or case, or even the cell used, but we do have something in common and that is getting our hands dirty while we learn the trade.

I personally have chosen more conservative settings for my cells. This has served my needs very nicely. As @Steve_S said so accurately, our wallets give the advice. I have built my system after carefully setting aside the funds over time and have built and added on as budgeting has allowed. If I were to buy an off the shelf battery, I might be tempted to run it for all it was worth, knowing that a replacement could be purchased in the future if needed with likely improved technology. Although, for me, probably not. I don't drive my car that way, I don't treat my body that way, and certainly not my batteries. But then this is the path I have personally chosen.

If you live in a place where electricity is even moderately expensive, using your whole battery will speed up payback period before the calendar aging causes capacity fade over time. If you think with your wallet, using your whole battery today makes the most sense.

And if you're off-grid and hitting LVD daily, you need more batteries.

My advice assumes you calculated your system correctly and rarely if ever hit 0%. But if there is an emergency, use it. It won't hurt anything. And calendar aging is degrading your capacity every single second of every single day. Regardless of how you use the battery

 

[Starex]

Controlling the charge and discharge? I have almost 200kWh of batteries I am cycling at various rates with multiple arrays all day. What are you talking about? Perfectly balanced cells? I even covered how budget packs come imbalanced from the factory. Hell even some server rack batteries. What in the world are you talking about

200kWh? That’ almost enough to power 20 average size homes. Where the hell is all that power going?
I’m guessing you have an equally large panel array?
I’m only bringing up charge rate because you conditioned your argument based on a .1C rate in a previous post.
If you read the post by Mckravits he showed mathematically that low soc %’s will drop battery voltage and increase current as soc % goes down when powering an inverter.
I’m beginning to suspect that you’re not really reading anyone’s post. Or perhaps just enough to insult them.
Look Will, you’re a very smart guy, I’ll give you that, but there many smart people on your forum. Your argument on this topic seems to fly in the face of common sense and many manufactures recommendations.
Most people’s post on this topic have been enlightening and offered as suggestions not marching orders.
Can we all just respect everyone and let them operate their systems as they see fit?

 

[Hedges]

200 kilo watt HOUR of battery storage.

A home could use 30kWh or 100kWh of power in a day.
200kWh would be enough for two days without sun.

Add an EV, drive 3 hours away and back, and 200kWh would let you charge it overnight.

Units matter.

 

[Will Prowse]

200kWh? That’ almost enough to power 20 average size homes. Where the hell is all that power going?
I’m guessing you have an equally large panel array?
I’m only bringing up charge rate because you conditioned your argument based on a .1C rate in a previous post.
If you read the post by Mckravits he showed mathematically that low soc %’s will drop battery voltage and increase current as soc % goes down when powering an inverter.
I’m beginning to suspect that you’re not really reading anyone’s post. Or perhaps just enough to insult them.
Look Will, you’re a very smart guy, I’ll give you that, but there many smart people on your forum. Your argument on this topic seems to fly in the face of common sense and many manufactures recommendations.
Most people’s post on this topic have been enlightening and offered as suggestions not marching orders.
Can we all just respect everyone and let them operate their systems as they see fit?

Common sense and you don't know what a kWh is? These responses in the last couple days are making my head spin. And I've been saying the same thing over and over again for the last couple years now. Where were you when I drew these conclusions with test data and study references? Yes of course everyone can do whatever they want. I have my recommendations that I'm sharing, and I back it up with my logic and evidence. Did you even watch the videos?

 

[Will Prowse]

200kWh? That’ almost enough to power 20 average size homes. Where the hell is all that power going?
I’m guessing you have an equally large panel array?
I’m only bringing up charge rate because you conditioned your argument based on a .1C rate in a previous post.
If you read the post by Mckravits he showed mathematically that low soc %’s will drop battery voltage and increase current as soc % goes down when powering an inverter.
I’m beginning to suspect that you’re not really reading anyone’s post. Or perhaps just enough to insult them.
Look Will, you’re a very smart guy, I’ll give you that, but there many smart people on your forum. Your argument on this topic seems to fly in the face of common sense and many manufactures recommendations.
Most people’s post on this topic have been enlightening and offered as suggestions not marching orders.
Can we all just respect everyone and let them operate their systems as they see fit?

Watch the video: