PSOC definition

[evm1024]

Originally Posted by john61ct

That's circular. Most batt mfg spec in relation to endAmps.

Not really.

Sure the battery maker has to specify a 100% SOC point. And a 0% SOC point. This gives a capacity.

It is "easy" to say charge until the battery voltage reaches X volts and then hold that voltage until the charging current becomes Y current. And that makes a nice 100% SOC point. "Easy" to measure.

It is also very Lead Acid centric.

But it takes a long time in many cases. So in order to reduce the time to reach 100% SOC a user might (somehow, magic? I do know it is difficult) define their 100% SOC point as the point where the loss of battery life cycles due to under charging is a very (or just reasonably) small number.

This "point" could be measured by specific gravity, by voltage/tail current measurments or some other measurments.

I don't think that we know what the manufacturer of any given battery uses to specify their 100% fully charged state.

[thinwater]

If PSOC is a defined abbreviation, we should feel free to use it with ANY battery technology. It is just a term, like SOC. The mistake is attaching implications. For example, it may be harmless to Li and death to Pb, but that is separate from the use of the word. In fact, clear usage of the abbreviation makes descriptions of the difference more clear.


I think it is a useful term in all contexts, so long as the meaning is exactly what is says; cycling below full charge and nothing more. It should not carry baggage.

[Stu Jackson]

Could we not simplify this by including the type of batteries being discussed AND add the word "abuse" at the end, too, if applicable?


My FLA bank suffers PSOC abuse when I anchor out for a few days until I plug into shorepower because I don't have solar, only ICE, and only charge back up to between 60 and 80% every few days. In my case, only shorepower overnight will get me to 100% (absorbtion voltage to <2% C).


It appears from this and other recent threads on this interesting topic that LFP banks normally operate at PSOC all the time. Is it only the DOD that is an issue with them?

[tanglewood]

Originally Posted by john61ct

Let me also re-state my SoC terminology opinion.

The highest SoC point I ever want my bank to reach in daily use is how I define 100% Full.

That is what I want to see on my BM readout.

Example from leadworld:

We condition / equalize our FLA bank at 15.75V or even higher, maybe monthly, maybe more often.

This is a testing / maintenance protocol, not for daily use.

Just because we **can** go that high, push more AH in at that level, we know it would be harmful to longevity to do so in daily use.

If someone tries to say

you're only charging to 85% by stopping at 14.5V

Does that make sense?

No.

Paying attention to the vendor charge specs is fine if you only want the cycle lifetime they advertise.

Then **your** definition of 100% SoC can be

Hold V at 14.6 until amps trail down to .005C

or whatever.

My 100% is

Hold V at 13.8V until amps trail down to .03C

Likewise, I never let my bank go below 11.9V in daily use.

Thus that is **my** 0% SoC

And every bank from a quality vendor, that has been at or very close to their 20-hour AH rating.

So someone saying

you are using your bank at PSOC

or something nuts like

"20-80%" just makes no sense to me.

And by the way I actually discharge to 60-70% 99% of daily usage, only critical safety nav gear, mostly very low currents, are allowed to get anywhere near 12V.

John, Borrowing from the discussion about Float, and the newly adopted term "Standby Voltage" for LFP, let me propose some different terminology for what you are describing.


Perhaps we can call it an "Operational SOC" scale, where 0% SOC and 100% SOC are whatever operational min and max you select. And an Operational Capacity to represent the ah/kwh storage capacity given your SOC range.



Then we can distinguish it from a battery manufacturers SOC and capacity ratings, and not be talking across each other all the time when people talk about operating at 10% to 90% SOC, or 15% to 80%, or whatever. And if we wanted to be super explicit, we could even call it a Nameplate SOC and Capacity rating.

[tanglewood]

Originally Posted by evm1024

I agree fully.

The key here is that each of these use cases has a duration. (cycled between states or not enough time to fully charge)



It does not mean the current state of charge less than 100% SOC.

Well, it's good you have asked this, because I use the term differently, and will continue to do so.


You are describing PSOC as a behavior, and more particularly as a negative behavior.


I don't use that way at all. I use it literally, to describe a battery's state of charge at an instant in time, as anything less than 100% SOC. It's a state of being, not a behavior, just as 50% SOC is a state, not a behavior. Operating at a PSOC is a behavior involving batteries at a PSOC. Never charging to anything other than a PSOC is a behavior that is detrimental to LA, and favorable to LFP.



So I think it means exactly what you don't think it means. Who ever thought a common language could be so confusing.

[Maine Sail]

PSoC (Partial State of Charge) is usually followed up by: Cycles, Cycle, Cycling, Use, Operation, Interval, Walk-Down, Applications etc.

Originally Posted by Trojan Battery

"Consistent PSOC cycling is harmful to the battery and leads to significant reductions in cycle life."

eg; PSoC-Cycling, PSoC-Operation, PSoC Walk-Down, PSoC Interval

It simply means is the battery is never fully recharged before being discharged again.

In the case of PSoC Walk-Down it means the battery looses a bit more usable capacity with each continual PSoC cycle away from a 100% recharge. If a full charge is not attained within a reasonable time frame the capacity loss from these PSoC cycles can become permanent.

A PSoC Interval is the number of PSoC cycles you go between 100% recharges. For lead acid batteries the PSoC interval should be kept as short as possible.

PSoC can also be followed up by the term "window" meaning your PSoC discharge floor to top charge point eg; My PSoC-Window is 50% SOC to 85% SOC or 50% to 90% SOC etc...

Early on in the white papers that shed light on PSoC, Sandia National Labs called this DSoC or "deficit state of charge cycling" or "DCC" Deficit Charge Cycling. It means the same exact thing as PSoC-Cylcling in that the battery never receives a full recharge before being discharged again.

[john61ct]

Originally Posted by evm1024

I don't think that we know what the manufacturer of any given battery uses to specify their 100% fully charged state.

Wut? [emoji2957]

I would never buy nor recommend a battery from a mfg that did not make such basic info very easy to obtain.

Literally dozens of good vendors I have the info in my notes, or can pick up the phone and talk to an knowledgeable tech support engineer with that information at his fingertips.

Including variations for special circumstances.

I can't express my feelings about your not knowing that.

Maybe you should read some past threads here.

Not really.

> It is also very Lead Acid centric.

Yes, that is the topic here.

> But it takes a long time in many cases.

It takes what it takes, sorry no magic. 2-3 times a week is "good enough to avoid the effects of PSOC.

Except Firefly, much longer periods in between without loss of capacity.

[john61ct]

Originally Posted by Stu Jackson

Could we not simplify this by including the type of batteries being discussed AND add the word "abuse" at the end, too, if applicable?

Sure, plenty of examples above.

But Abuse is IMO best for extreme, obvious damage done within months.

The difference between the coddling that gets 13 years vs the "normal" 3-5 years is a lot of grey.

PSOC issues for those.

As I said over thousands of threads in dozens of forums this is the only context in which the term has ever come up.

Until RR's blather caused us to recoil in horror.

[john61ct]

Originally Posted by Stu Jackson

In my case, only shorepower overnight will get me to 100% (absorbtion voltage to <2% C)

To the extent you get back to shore within a week, over all your cycles PSOC is the minority case then not really abuse IMO.

You may even get above average lifespan if the other factors are better.


> It appears from this and other recent threads on this interesting topic that LFP banks normally operate at PSOC all the time.

They should only be Full for a short time, tgat is the ideal.

Some users feel just a few days is OK.

I try to keep it to minutes or hours.

> Is it only the DOD that is an issue with them?

That is not a major issue, long as you don't often go much under 12V.

For example compared to avoiding the shoulders by keeping voltage below 3.5Vpc.

Also, going dead flat or charging while too cold can turn them instantly and irreversibly into scrap.

I've periodically posted an LFP summary blurb, if you've seen that, covers most points I believe.

[john61ct]

Originally Posted by john61ct

And by the way I actually discharge to 60-70% 99% of daily usage, only critical safety nav gear, mostly very low currents, are allowed to get anywhere near 12V.

Just realized I did not specify that 60-70% is SoC, not DoD.

[Stu Jackson]

Originally Posted by john61ct

Sure, plenty of examples above.

1 But Abuse is IMO best for extreme, obvious damage done within months.

>>>>>>>>>>>>>>>>>>>>>>

2 Until RR's blather caused us to recoil in horror.

1 Good point


2 I got a "friendly be-nice" message from a moderator for my tongue in cheek letter to Mr. pResident on that thread. I enjoyed writing it, though.


Maine Sail's description answers it all, doesn't it?


Per my last post here, I operate in a PSOC interval and window, but fully recharge within no more than four or five days of operation for my FLA house bank, which should eliminate or reduce walkdown.


Did I get that right?

[Olddan1943]

Side Note: About 10 years ago, I needed some sheet lead. Took me a while but I finally found one out west. I paid a premium for the lead. I was told, this was the last lead smelter in the US. The EPA was forcing this one to close.
I'm not sure where the lead comes from now.

[evm1024]

Originally Posted by john61ct

Wut? [emoji2957]

I would never buy nor recommend a battery from a mfg that did not make such basic info very easy to obtain.

Literally dozens of good vendors I have the info in my notes, or can pick up the phone and talk to an knowledgeable tech support engineer with that information at his fingertips.

Including variations for special circumstances.

I can't express my feelings about your not knowing that.

Maybe you should read some past threads here.

Not really.

> It is also very Lead Acid centric.

Yes, that is the topic here.

> But it takes a long time in many cases.

It takes what it takes, sorry no magic. 2-3 times a week is "good enough to avoid the effects of PSOC.

Except Firefly, much longer periods in between without loss of capacity.

Don't misunderstand. I am sure that they all specify where their design 100% SOC is.

And I would expect them to specify the relevant industry standards which apply.

I'm not so sure they are willing to state how they test internally. At least not unless they are making batteries that meet some (for example) mil spec. that requires it

As an example of what I mean looking at the Trojan T-105 spec pdf I see that they state various capacities and other parameters. But I do not see any statement that says as measured in according with XXXX.

[evm1024]

Originally Posted by Maine Sail

PSoC (Partial State of Charge) is usually followed up by: Cycles, Cycle, Cycling, Use, Operation, Interval, Walk-Down, Applications etc.



eg; PSoC-Cycling, PSoC-Operation, PSoC Walk-Down, PSoC Interval

It simply means is the battery is never fully recharged before being discharged again.

In the case of PSoC Walk-Down it means the battery looses a bit more usable capacity with each continual PSoC cycle away from a 100% recharge. If a full charge is not attained within a reasonable time frame the capacity loss from these PSoC cycles can become permanent.

A PSoC Interval is the number of PSoC cycles you go between 100% recharges. For lead acid batteries the PSoC interval should be kept as short as possible.

PSoC can also be followed up by the term "window" meaning your PSoC discharge floor to top charge point eg; My PSoC-Window is 50% SOC to 85% SOC or 50% to 90% SOC etc...

Early on in the white papers that shed light on PSoC, Sandia National Labs called this DSoC or "deficit state of charge cycling" or "DCC" Deficit Charge Cycling. It means the same exact thing as PSoC-Cylcling in that the battery never receives a full recharge before being discharged again.

Thank you , exactly.

Operation where you never receive a full recharge... by design or by fault.

[evm1024]

PSOC operation is the likely mode of operation for LiFePO4 in (at least my) boats.

1) Charge to some set point

2) use the bank for some number of days where solar etc is used to up the SOC as it can.

3) if at some point we get too low in SOC due to lack of solar (capacity or sun) then use ICE to charge to the set point (or some larger SOC)

4) at some time when we think that out battery monitor is no longer accurate enough recharge to the set point and start again.

This graph is from a different paper but does show PSCO draw down and the like.