Changing Battery Charger Advice please

[Fat Albert]

Thanks for that every day is a school day and it again shows the benefit of being a member on here.

Just check the CBE516 manual and the switch mentions gel 13.8v or 13.5v for lead batteries. Not quite what I said regarding AGM. Don’t like to push out duff gen.

 

[treblid]

the long absorption phase on Gel is not good for Lithium and the float of 13.8v is too high. It would be better set to Lead Acid then the charge voltage is 14.1v & Float 13.5v also ther absorption phase is shorter 1½ hours.

LiFePo4 batteries can stay at 14.4V for long periods? Why are the absorption phase and float phase so important??? Technically you do not need a float phase.

 

[Lenny HB]

LiFePo4 batteries can stay at 14.4V for long periods? Why are the absorption phase and float phase so important??? Technically you do not need a float phase.

Far better to charge at 14.2v rather than 14.4v with a normal LA charger with an absorbtion phase that holds at over 14v is not good for Lithium.

Litithium chargers normally charge to 14.2v then drop to a 13.5v float, Lithium don't need a float but it means that when on EHU the power used is supplied by the charger rather than the battery.

Raul will be able to give a better explanation.

 

[treblid]

Far better to charge at 14.2v rather than 14.4v with a normal La charger with an absorbtion phase that holds at over 14v is not good for Lithium.

I agree that 14.2V removes the risk of over voltage protection coming in but 14.4V is fine if correctly regulated. Holding at 14.2V or 14.4V is not a problem? Do you have a technical reference to why it is an issue?

Litithium chargers normally charge to 14.2v then drop to a 13.5v float, Lithium don't need a float but it means that when on EHU the power used is supplied by the charger rather than the battery.

So 13.8V would not be a problem?


I do not wish to be pedantic but I see so much information quoted in various places that contradicts and technically does not stack up against the science.

 

[Raul]

LiFePo4 batteries can stay at 14.4V for long periods? Why are the absorption phase and float phase so important??? Technically you do not need a float phase.

Not healthy to keep them pinned so high at 14.4v. There is little room for imbalance or voltage calibration errors,
Absorption phase is important as to not keep them at high voltage for to long unnecessary, but just enough to give it a chance to balance the cells. A single cell does not need any absorption phase,, a pack does, so the lower ones catch up.
Float, it should be just that : free floating, nothing in -nothing out. To achieve that, hou dial a float voltage thats capable to feed the loads but not to charge. But also high enough so you don't discharge either. The 3.375v its a good middle ground to keep the cells charged and free floating.

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[Raul]

I agree that 14.2V removes the risk of over voltage protection coming in but 14.4V is fine if correctly regulated. Holding at 14.2V or 14.4V is not a problem? Do you have a technical reference to why it is an issue?

So 13.8V would not be a problem?


I do not wish to be pedantic but I see so much information quoted in various places that contradicts and technically does not stack up against the science.

Yes, float at 13.8v its not float anymore, you are charging, check with a clamp meter.

 

[treblid]

Not healthy to keep them pinned so high at 14.4v. There is little room for imbalance or voltage calibration errors,

Agreed. But technically through a good quality charger 14.4V is fine.

To achieve that, hou dial a float voltage thats capable to feed the loads but not to charge.

Yes, float at 13.8v its not float anymore, you are charging

Why would it be charging? If you have 13.8V or 14.4V across the battery it would be charged to this level and stop taking any more current (unless balancing the cells).
Other equipment and devices will run on this voltage and not take energy from the battery (unless the discharge is higher that the chargers current rating).

 

[Raul]

Agreed. But technically through a good quality charger 14.4V is fine.


Why would it be charging? If you have 13.8V or 14.4V across the battery it would be charged to this level and stop taking any more current (unless balancing the cells).
Other equipment and devices will run on this voltage and not take energy from the battery (unless the discharge is higher that the chargers current rating).

I will let you research and find out for yourself, lifepo4 does not suppose, and does not need a float charge. In fact you want the charger off after CV stage. that’s default charging characteristic method CC-CV and off.

 

[treblid]

I think this is a good practical summary for choosing the correct Float Voltage on a charger for a 12V LiFePO4 battery:

13.6V float is good if you're supporting loads. It's a little high for just holding there with no load, so 13.4V is recommended.

13.8V is a bit high - that can actually fully charge a LiFePO4 and 13.2V might be a little low if you do have active loads - the battery will dip down before full charging kicks back in.

 

[Raul]

I think this is a good practical summary for choosing the correct Float Voltage on a charger for a 12V LiFePO4 battery:

13.6V float is good if you're supporting loads. It's a little high for just holding there with no load, so 13.4V is recommended.

13.8V is a bit high - that can actually fully charge a LiFePO4 and 13.2V might be a little low if you do have active loads - the battery will dip down before full charging kicks back in.

I agree with the above, I may add, the 13.5v it’s plenty for sustaining loads, but the 13.6v it’s second best alternative.
I know ppl that fully charge (absorb) with 13.8v, no rebulk for the day, and float at 13.4v. All in static setup but with large capacity.

I personally use 14v absorb 13.5v float in the van

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