Charging voltage

slowbutsure · Mar 25, 2024

Hi

I have 16 cells to make up 14.2kw as a lithium battery. Anyone know what the charging voltage should be? Thanks.

brandonboosted · Mar 25, 2024

slowbutsure said:
Hi

I have 16 cells to make up 14.2kw as a lithium battery. Anyone know what the charging voltage should be? Thanks.

Assuming your talking lifepo4 most guys run 55.2 (3.45 per cell) for absorption and 54 float. Hopefully this answers your question.

timselectric · Mar 25, 2024

brandonboosted said:
Assuming your talking lifepo4 most guys run 55.2 (3.45 per cell) for absorption and 54 float. Hopefully this answers your question.

That's just barely touching the upper knee.
Those cells aren't getting any useful balancing.

slowbutsure · Mar 25, 2024

timselectric said:
That's just barely touching the upper knee.
Those cells aren't getting any useful balancing.

You think it should be higher?

sunshine_eggo · Mar 25, 2024

It depends on how the charger is configured. If you can program the absorption time to a fixed 2 hours or more, then 3.45V is likely adequate if your BMS can be configured to balance in that range.

If your charger just runs up to 3.45V and then stops, that's pretty turdy.

3.40V may be adequate with a 5 hour absorption as I demonstrated here:

battery achieved 99.7% SoC with 0.02C tail current @ 3.40V/cell (13.6V).

timselectric · Mar 25, 2024

slowbutsure said:
You think it should be higher?

Absolutely
Useful balancing starts at 3.45v/cell. (Minimum 3.4v/cell)
55.2v is the lowest I would float at.
And bulk should be 55.5v .
Personally I charge at 57v bulk and 56v float.
But not everyone wants to, or can go that high.

slowbutsure · Mar 25, 2024

I’m not asking for what the voltage is for when it’s fully charged. I want the charging voltage.

timselectric · Mar 25, 2024

sunshine_eggo said:
turdy

He he
He he

sunshine_eggo · Mar 25, 2024

slowbutsure said:
I’m not asking for what the voltage is for when it’s fully charged. I want the charging voltage.

This indicates you really don't have a basic understanding of charging LFP.

You can charge at any voltage you want to. The results will be different for every voltage. You probably need to clarify your intent.

slowbutsure · Mar 25, 2024

sunshine_eggo said:
This indicates you really don't have a basic understanding of charging LFP.

You can charge at any voltage you want to. The results will be different for every voltage. You probably need to clarify your intent.

My friend, was that necessary? It gets a bit old this “I’m an expert and you don’t know what you’re talking about.” But if it makes you feel important or better about yourself then you do you.

sunshine_eggo · Mar 25, 2024

slowbutsure said:
My friend, was that necessary? It gets a bit old this “I’m an expert and you don’t know what you’re talking about.” But if it makes you feel important or better about yourself then you do you.

Yes. It was. This sort of statement:

slowbutsure said:
I’m not asking for what the voltage is for when it’s fully charged. I want the charging voltage.

is nonsensical.

Why do you want a "charging voltage?"

To fully charge your battery or something else?

slowbutsure · Mar 25, 2024

sunshine_eggo said:
Yes. It was. This sort of statement:

is nonsensical.

Why do you want a "charging voltage?"

To fully charge your battery or something else?

Because my inverter has a setting for it. Regardless, no it wasn’t necessary. You can contribute and be helpful if you want to, or say nothing. But to be insulting is not one of those two options.

sunshine_eggo · Mar 25, 2024

slowbutsure said:
Because my inverter has a setting for it. Regardless, no it wasn’t necessary. You can contribute and be helpful if you want to, or say nothing. But to be insulting is not one of those two options.

Why does your inverter have a setting for it?

slowbutsure · Mar 25, 2024

sunshine_eggo said:
Why does your inverter have a setting for it?

I have no idea. It’s currently set to 55 and when the battery is charging it does so at 55v. It stops charging when the battery can sit at 54.1v.

sunshine_eggo · Mar 25, 2024

slowbutsure said:
I have no idea. It’s currently set to 55 and when the battery is charging it does so at 55v. It stops charging when the battery can sit at 54.1v.

Why do you charge it?

slowbutsure · Mar 25, 2024

sunshine_eggo said:
Why do you charge it?

Why do I charge the battery? Is that your question?

sunshine_eggo · Mar 25, 2024

slowbutsure said:
Why do I charge the battery? Is that your question?

Yes. You don't care about fully charging it, so why are you charging it, i.e., why are you asking about a charging voltage at all?

gotbeans · Mar 25, 2024

slowbutsure said:
You think it should be higher?

Recommended Charge Profile for DIY LiFePO4 Batteries Sticky Post

12V 4S LiFePO4 Battery w/ BMS: Absorption: 14.5V Float: 13.6V Inverter Cut-off: 10.7V-12V (depending on size of load and voltage drop etc) 24V 8S LiFePO4 Battery w/ BMS Absorption: 29V Float: 27.2V Inverter Cut-off: 21.4V-24V 48V 16S LiFePO4 Battery w/ BMS Absorption: 58V Float: 54.4V...

diysolarforum.com

slowbutsure · Mar 25, 2024

sunshine_eggo said:
Yes. You don't care about fully charging it, so why are you charging it, i.e., why are you asking about a charging voltage at all?

Dude, my friend just died, my house builder just ran off with my money, my father is dying and my marriage is falling apart. Do me a favour and go and troll someone else.

crossy · Mar 25, 2024

Let's try a different tack.

Which inverter do you have?
Which BMS do you have?
Do you have inverter - BMS communications connected and enabled?

"Charging voltage" per-sé doesn't really have any meaning as your pack will be charged in constant-current mode for most of the time, only when approaching full does the voltage come into the equation.

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