Propulsion & house LFP bank

[aybabtme]

What's the expected outcome you folks hope to get out of this discussion about where to measure voltage and what voltage will be measure at a battery poles if an infinite set of parallel chargers is involved? Would a separate thread perhaps help?

[StuM]

Originally Posted by aybabtme

What's the expected outcome you folks hope to get out of this discussion about where to measure voltage and what voltage will be measure at a battery poles...

Hoping to get people to understand post #65 and why it's inefficient to parallel chargers without some sort of combined controller.
Unfortunately, it takes a lot of repitition and further explanations to convince some people about basic physical truths.

[Q Xopa]

Originally Posted by aybabtme

Per the lithium cells spec sheets (all chemistries) charging should stop not when a voltage is reached but when the current drops to a specific value (e.g 100mA), after the voltage was reached. That is for a standard charge regiment.

Hmmm this is not what I have read from trusted sources.

Can you supply where/ which Lithium manufactures spec sheets, you are getting this please?

[StuM]

Fat fingers/typo/brain f*rt: repitition -> repetition.

[PaulCrawhorn]

Originally Posted by aybabtme

charging should stop not when a voltage is reached but when the current drops

My point is that is a wrong interpretation if the specs.

"Should" for what reason?

"Can", yes, the spec sheet's job is to give maximum and minimum parameters.

The system designer's job is to ensure operation WITHIN those ranges.

Stresses occur, lifespan and reliability suffer as min/max are approached.

Do not approach them without good reason.

Going from 95% capacity utilisation to 99% is not a good enough reason to impose those stress factors.

[Dirk01]

Originally Posted by Q Xopa

Hmmm this is not what I have read from trusted sources.

Can you supply where/ which Lithium manufactures spec sheets, you are getting this please?

The statement about the float-voltage and dropping charge current is correct. The cut off charge current depends on the size of th battery @ a given voltage. Ask PHILTAO. He'd developed the best BMS I know.

Cheers
Dirk

[newhaul]

Originally Posted by Dirk01

The statement about the float-voltage and dropping charge current is correct. The cut off charge current depends on the size of th battery @ a given voltage. Ask PHILTAO. He'd developed the best BMS I know.

Cheers
Dirk

At the extreme ex ppl sense of service life personally other than 5he initial and Angel if needed top balance I never charge above 3.55v pc. Or 14.2v on my system with float at 13.8v

Any higher any your into the knees . if you need that extra ah then you need a bigger bank

[Catapault]

Originally Posted by newhaul

At the extreme ex ppl sense of service life personally other than 5he initial and Angel if needed top balance I never charge above 3.55v pc. Or 14.2v on my system with float at 13.8v

Any higher any your into the knees . if you need that extra ah then you need a bigger bank

Agree totaly, the amount of actually energy in that knee is tiny compared to the rest, esp vs the impact on battery health.

3.55vpc (14.2v) is what I plan to use as max charge for normal operation. and may even consider slightly lower yet.

13.8 (3.45vpc) float though seems a little high to me, I was planing to use 3.4vpc (13.6v) , and possibly 3.35vpc (13.4v) as recomended by https://marinehowto.com/lifepo4-batteries-on-boats/
- Also noting the term he uses is standby voltage, as it is not technically 'floating' at 100% SoC, but float is still the term the charger uses/place to put in the value !.

(for Ref: I'm refering to a bank of 4 x 400AH Winstons, which will become 12 x 400AH winstons next year, 12v nominal)

[newhaul]

Originally Posted by newhaul

At the extreme ex ppl sense of service life personally other than 5he initial and Angel if needed top balance I never charge above 3.55v pc. Or 14.2v on my system with float at 13.8v

Any higher any your into the knees . if you need that extra ah then you need a bigger bank

My tablet and my fat fingers I have to decipher this.

It should read : at the extreme expense of service life. Personally other than the initial ( and annual if needed) top balance I never charge above 3.55v pc or 14.2v on my system with float setting at 13.8v .

The rest is readable.

[newhaul]

Originally Posted by Catapault

Agree totaly, the amount of actually energy in that knee is tiny compared to the rest, esp vs the impact on battery health.

3.55vpc (14.2v) is what I plan to use as max charge for normal operation. and may even consider slightly lower yet.

13.8 (3.45vpc) float though seems a little high to me, I was planing to use 3.4vpc (13.6v) , and possibly 3.35vpc (13.4v) as recomended by https://marinehowto.com/lifepo4-batteries-on-boats/
- Also noting the term he uses is standby voltage, as it is not technically 'floating' at 100% SoC, but float is still the term the charger uses/place to put in the value !.

(for Ref: I'm refering to a bank of 4 x 400AH Winstons, which will become 12 x 400AH winstons next year, 12v nominal)

Just checked and my "float setting is at 13.6v

All settings are personal to you and your bank. 13.6v. For me because I don't use much power and I want my bank to be basicly full when I stop getting solar input at the end of the day.

[Q Xopa]

Originally Posted by Catapault

Agree totaly, the amount of actually energy in that knee is tiny compared to the rest, esp vs the impact on battery health.



3.55vpc (14.2v) is what I plan to use as max charge for normal operation. and may even consider slightly lower yet.



13.8 (3.45vpc) float though seems a little high to me, I was planing to use 3.4vpc (13.6v) , and possibly 3.35vpc (13.4v) as recomended by https://marinehowto.com/lifepo4-batteries-on-boats/

- Also noting the term he uses is standby voltage, as it is not technically 'floating' at 100% SoC, but float is still the term the charger uses/place to put in the value !.



(for Ref: I'm refering to a bank of 4 x 400AH Winstons, which will become 12 x 400AH winstons next year, 12v nominal)

Agreed, anything higher than 13.68v it is still theoretically overcharging is still possible with a low enough current.