Renogy 100ah LiFePO4 Battery voltage

seattleStu

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Oct 22, 2021
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I bought a new 100 ah Renogy LiFePO battery over the summer. It didn't hold a full voltage after being fully charged. I would charge it fully to 13.9 v. Then it would sit for a day with nothing connected to draw, and it would be 13.23 v after 24 hours. According to the Renogy chart, this was 75% or so of a charge. Chart attached for reference. After many weeks (8 weeks?), and hours on the phone, Renogy picked up the battery for testing. They determined there was a problem, and sent me another battery!!
I charged it up to 13.9 v using a Noco Genius 5 charger. Then a few hours later, it started dropping, and in 24 hours, with nothing connected, it was at 13.24. Now I am thinking that I am doing something wrong.
Is this another faulty battery?
Is my testing with a multimeter wrong or off?
Is there another way to test that the battery is full, not at 70 or 80% right away?
Thank you for any help, I know enough to be confused, but not enough to be confident!

dod-chart.jpg
 

MisterSandals

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Is there another way to test that the battery is full, not at 70 or 80% right away?
I would try charging it a little higher and see if that makes any difference. Is there a reason you picked 13.9V? What does your battery documentation recommend?

Or, if there is a way to absorb at 13.9V I would try that. I am not sure if the Norco just stops at 13.9V or ??

Just a thought.
 
Last edited:

seattleStu

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Oct 22, 2021
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I would try charging it a little higher and see if that makes any difference. Is there a reason you picked 14.9V? What does your battery documentation recommend?

Or, if there is a way to absorb at 13.9V I would try that. I am not sure if the Norco just stops at 13.9V or ??

Just a thought.
The charger goes just above 14v, like 14.4 or so. But it soon drops lower.
 

mikefitz

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May 28, 2020
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How are you measuring voltage,? the meter may be slightly inaccurate.
Its normal for the voltage to fall on a resting battery, and will fall to around 13.4 volts. It will depend on temperature and the exact chemistry used in the battery.
The Noco Genius 5 charger is intended as a general purpose car battery charger and in my view is not optimal for a Lithium battery. Its advertised as suitable for lithium (if that mode is selected) charging to 14.6 volts, so I would expect to see the battery volts rise to near this voltage.
If you see the battery voltage rise above 14 volts you can consider the battery charged ( with a 5 A charge into a 100Ah battery).
You could measure the battery capacity. For a rough test apply a DC load that draws a known current, a car headlight bulb takes 4 amps. Measure how many hours it takes before the volts drop to 12.0 volts ( 10% capacity).
Each hour is 4Ah worth of capacity. Its not super accurate but will give you some idea on the battery performance.
( 90% of capacity should take almost 23 hours).

A more accurate test could be made with ,

DORK

Mike
 

seattleStu

New Member
Joined
Oct 22, 2021
Messages
3
How are you measuring voltage,? the meter may be slightly inaccurate.
Its normal for the voltage to fall on a resting battery, and will fall to around 13.4 volts. It will depend on temperature and the exact chemistry used in the battery.
The Noco Genius 5 charger is intended as a general purpose car battery charger and in my view is not optimal for a Lithium battery. Its advertised as suitable for lithium (if that mode is selected) charging to 14.6 volts, so I would expect to see the battery volts rise to near this voltage.
If you see the battery voltage rise above 14 volts you can consider the battery charged ( with a 5 A charge into a 100Ah battery).
You could measure the battery capacity. For a rough test apply a DC load that draws a known current, a car headlight bulb takes 4 amps. Measure how many hours it takes before the volts drop to 12.0 volts ( 10% capacity).
Each hour is 4Ah worth of capacity. Its not super accurate but will give you some idea on the battery performance.
( 90% of capacity should take almost 23 hours).

A more accurate test could be made with ,

DORK

Mike
Thank you! Here is my multimeter, it has been good so far.
1634943328050.png
Yes I have seen the Noco go above 14v, then rest, on Lithium battery mode.

thank you for the testing information.
 

Smokin

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Sep 8, 2021
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130
That battery is fine. Put it in service. My LifePO4 all 3 of them settle to 13.4 -13.3 after charge. That's how they are.
 
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