What would you do?

[native pepper]

That's .3 volts over the whole pack, not just one cell line and that has only occurred when there were no controls on the pack. If there is load on the pack, then all lines are virtually the same no matter the SOC.

[T1 Terry]

That's .3 volts over the whole pack, not just one cell line and that has only occurred when there were no controls on the pack. If there is load on the pack, then all lines are virtually the same no matter the SOC.

You have me totally confused now, it sounds now like you are saying you have 3 x 12v batteries connected in parallel with all the negative ends and all the positive ends linked but none in between?

T1 Terry

[SteveW]

You're confused Terry? You've just joined the club of people who have been confused for a long time. I wonder if it is all made up because the claims and contradictions seem to be circular.

[native pepper]

That's .3 volts over the whole pack, not just one cell line and that has only occurred when there were no controls on the pack. If there is load on the pack, then all lines are virtually the same no matter the SOC.

You have me totally confused now, it sounds now like you are saying you have 3 x 12v batteries connected in parallel with all the negative ends and all the positive ends linked but none in between?

T1 Terry

Not being technical at all, can understand how my explanations could be confusing to those who are used to technical jargon descriptions, been the butt of many laughs when trying to explain to experts how I see things and some times they confuse me. I'm not a very social or interactive person so have an expression problem, understand and except why. Re-reading some of my posts some times confuse me. Can't see how you get 3 batteries out of my quoted post, as there is no mention of anything like that. But if that's the impression I've given, I apologise for that. It may take me over an hr to write a post and sometimes many hrs, I can never understand the first draft.

I have 3 lifepo4 packs, all are for separate uses. The 120amp portable does get linked to either the house or bus packs sometimes, when we think we may not get enough sun for a few days and there is no wind, so the wind generator won't be contributing.

The .3v variation, means the combined variations across one series/parallel pack when it hits 14v and that has only occurred when there are no controls on the pack charging regime and that would be the maximum ever. That variation was on my portable pack, which has been the experimenter pack and has been subject to not that nice treatment when proving the system or changes, before they are used on the bus and house packs.

Have seen a few lifepo4 installs on the road that have to use globes to get cell lines down and they were using brand programmable chargers, some had set their upper cut off at 14.6v and 11v lower. That would have been a couple of years back. Expect when we head off next year we will run into the same people and they will have updated their system for a better outcome, as they learn and pool that learning with others.

[T1 Terry]

You're confused Terry? You've just joined the club of people who have been confused for a long time. I wonder if it is all made up because the claims and contradictions seem to be circular.

Well at least it's not being linked to the disciples of the lithium faith like other forums, so maybe it's secular as well as circular
I think it's just a matter of clarifying just what each of us mean, more misunderstandings than anything else, there will always be different methods used to reach the end result so it never hurts to look at other's methods and compare the good and the not so good about each method and from there it may be possible to fine tune each method rather than just making one method the right way and every other method the wrong way.

My way of looking at any system is to make it work independently at each level so the system truly has separate redundancies built in rather than a system that relies on something else functioning as we think it should to make it all work. The whole thing falls over if we got it wrong or simply didn't fully understand the data by not looking at anything that may have effected the data collected and therefore tainted the data. Unless all the data in is clean and all the data has been added, not just the bits that suit, the result can not match up between theory and the real world test results. If the two don't come up with the same result then some of the data on the theory side is wrong, then the real work starts trying to clean the data and make sure none has been left out. I avoid the use of add on items like balancers and equalisers during normal operation as they effect the clean data, if the result isn't what it should have been when you worked it out on paper then it's time to find out why, not look for a method to disguise it.
I guess that is the difference between hands on and theory based, the theory must match the result, not the result tampered with so it matches the theory

T1 Terry

[T1 Terry]

That's .3 volts over the whole pack, not just one cell line and that has only occurred when there were no controls on the pack. If there is load on the pack, then all lines are virtually the same no matter the SOC.

You have me totally confused now, it sounds now like you are saying you have 3 x 12v batteries connected in parallel with all the negative ends and all the positive ends linked but none in between?

T1 Terry

Not being technical at all, can understand how my explanations could be confusing to those who are used to technical jargon descriptions, been the butt of many laughs when trying to explain to experts how I see things and some times they confuse me. I'm not a very social or interactive person so have an expression problem, understand and except why. Re-reading some of my posts some times confuse me. Can't see how you get 3 batteries out of my quoted post, as there is no mention of anything like that. But if that's the impression I've given, I apologise for that. It may take me over an hr to write a post and sometimes many hrs, I can never understand the first draft.

I have 3 lifepo4 packs, all are for separate uses. The 120amp portable does get linked to either the house or bus packs sometimes, when we think we may not get enough sun for a few days and there is no wind, so the wind generator won't be contributing.

The .3v variation, means the combined variations across one series/parallel pack when it hits 14v and that has only occurred when there are no controls on the pack charging regime and that would be the maximum ever. That variation was on my portable pack, which has been the experimenter pack and has been subject to not that nice treatment when proving the system or changes, before they are used on the bus and house packs.

Have seen a few lifepo4 installs on the road that have to use globes to get cell lines down and they were using brand programmable chargers, some had set their upper cut off at 14.6v and 11v lower. That would have been a couple of years back. Expect when we head off next year we will run into the same people and they will have updated their system for a better outcome, as they learn and pool that learning with others.

This it bit I'm having trouble following, how is the 0.3v variation measured if it is not between either separate batteries within the pack or between cell groups within the pack.
I'll try another way, is the 12v battery built up from 3 equal capacity cells in parallel to build 3.2v packs and 4 of these linked together in series to build 12.8v
or
is each 12.8vv battery built up from 4 equal capacity cells connected in series and these 3 batteries connected in parallel?

T1 Terry

[SteveW]

Terry, henceforth you shall be known as Monica - the patron Saint of those seeking patience.

[Dot]

Terry, henceforth you shall be known as Monica - the patron Saint of those seeking patience.

No kidding Monica a saint

[grizzzman]

Dang Terry that's some good info there for sure! Now lets assume the cells are in balance. do you use a voltage or perhaps a SOC to bring charging back on?

Thanks

That is the whole point behind the long post, you can't assume they will be in balance at the top end of charging, SOC or battery voltage are wide open to creating a cell voltage run away so neither are suitable but battery voltage is a good primary control method. The battery protection control system must be cell voltage controlled, any other method is simply asking for trouble.

T1 Terry

Ok I can see that I am not being very clear. I apologize for that. My mind races and I don't type so fast. Let's try this again. I will have cellogs. (both s and m) on latching relays for high and low cut out duties. This should take care of any senior moments well I hope. My plan is to start with a 100 AH battery pack. I will run my FLA alongside and dedicate the LFP to inverter duties. It is likely that at first I will not charge the LFP while camping until I sort out equipment for charging. Terry you have talked of a management system you build and I am interested in that but I don't know if it is appropriate to discuss that in this forum? Okay, so I will ask my question again. When do you decide to "start" charging again after you have discharged it? At a SOC? or perhaps a voltage? With the idea that you want it topped off. (ya never know what the next day will bring)

Thanks

[grizzzman]

Double post