Low Budget Lifepo4 Experiences anyone?

[s/v Jedi]

No, a battery is cells connected in series, not in parallel. When you have a 25Ah 12V battery, it has 6 cells of 25Ah in series. When you have a 100Ah battery then you still have 6 cells in series but they are 100Ah each.

Lithium arrangements with cells in parallel means you can’t monitor individual cells anymore and parallel cells can be at different SOC (it’s a given that they are, the question is how much and for top quality cells it will be the busbars, terminals and cables that make the big difference).

[newhaul]

Originally Posted by s/v Jedi

No, a battery is cells connected in series, not in parallel. When you have a 25Ah 12V battery, it has 6 cells of 25Ah in series. When you have a 100Ah battery then you still have 6 cells in series but they are 100Ah each.

Lithium arrangements with cells in parallel means you can’t monitor individual cells anymore and parallel cells can be at different SOC (it’s a given that they are, the question is how much and for top quality cells it will be the busbars, terminals and cables that make the big difference).

Yes lead based but lifepo4 it is 4 cells.

[CaptainRivet]

think we might have a failure of terminology => true but this is around for years and a domain expert must know

I’m using INDIVIDUAL CELLS . My question was given the only arrangement for me with 100Ah cells is too arrange them as 3P4S => well no you mean 4S3p

A 3P4S arrangement is equivalent to three sets of 4 cells connected in parallel , ie three “batteries “ ( on the basis that a battery is a collection of cells ) =>
Wrong it means 3 cells parallel into one block and then 4 of these blocks in series

Hence I fail to see how there is any practical difference between a bank arranged as 3P4S and 3 “ batteries “ of 4 cells in series.
=> see above and test it yourself. There is no real difference when you have 12 perfect and 100% equal cells but that doesn’t exist. If you get Winston high end cells you are close but then you use 4 1000AH cells in series and are done. But your budget 100AH cells are far from that…so are my Grade A and factory matched Lishen cells but they are only 1600Euro for 840AH compared to 4600 for 4x700AH Winston at my doorstep.

Perhaps this might be called 4S3P => that’s what you mean

I’m not disagreeing with you that 3 cells paralleled then in 4 series is a good idea.=> best with Budget cells

With my config every cell is capable of being individually monitored with interference. => yes monitored but the weakest cell defines the whole bank.

In any parallel configuration load ( or discharge ) balances as a function of relative resistance. Resistance of a battery increases as it discharges hence load currents redistribute as SOC falls => that’s wrong, first the load gets spread evenly between the 3 batteries, then the weakest cell defines the whole bank as the one battery with the weakest cell drops the most in an high load event because this cell has no other parallel cell to share the load and the BMS of the one battery just tries to compensate that and eventually puts even more load on the weakest cell in a high load event. I don‘t know if that’s scientifically correct explained but that’s what happens in real life.
And I tortured many cells doing car stereo and saw how they behave. my buddy runs a corvette Z06 with 10000W stereo and a 7lV8 of an 6 cell 40AH LTO battery and that works since 2,5years.

I’m not an electrical engineer I’m an electronics engineer ( that’s my specialist degrees ) with domain experience in handheld Li battery equipment. => well handheld and a boat is different cup of tea…and Li chemistry

[goboatingnow]

I should say I’m well aware of the debate over parallel first or series first battery construction with some ( often bms makers ) expressing doom over series first constructions. But each has trade offs.

[Simi 60]

Originally Posted by CaptainRivet

I can just highly recommend to put a shunt on your minus 24V main busbar and really measure what’s really going through your whole system. It must be much more Amps then you post, if it’s what you see something fouls the measures.
You have a massive system and a lot of power hungry 240V stuff.
4 fridges/freezer 240V that switches on at the same time will definitely bring your inverter near its limits and your current above 200A and then the 1800W heater switches on powered by solar, here we go 300A+
Plus all the other gear…and it happens rarely but does and that’s what you minimum spec it for plus a safety margin.
In the galley no microwave, no mixers, icemakers or other 240V stuff…?
Everything that passes through your system does go through the main fuse that also protects the house bank, doesn‘t matter if it’s supported by solar and not going purely of your house bank.

I assume you have separate banks for your bowtrusters and anker windlass.

So many wrong things in this ^^^^^^^
You say my inverter can't run the gear we have yet it has been doing it with ease every day for 5+ years.
I think you need to go back and look at it again