LiFePO4 Charge rates

dane

dane

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Hi,

Following the sudden and unexpected early death of my AGM leisure battery, I have bought a Poweroad 100AH LiFePO4 battery (wasn't first choice, but was the correct physical size, price seemed good for Li and in stock!). But the way my chargers are behaving is making no sense not me, based on a very quick bit of reading. Are they behaving correctly?

Victron 12v 15amp charger. It's probably about 5 years old and predates the bluetooth connectivity. I have set to Li-Ion. I disabled the solar charger. Seemed to go straight to absorption, but charging in the mid 13v range at around 5a. Both seemed low? Expectign 14.2v. Switched it off when it dropped into float mode.

I then enabled my solar charger. Victron 15/75, latest firmware. Changed settings to default LiFePO4 settings. This charger has stayed on bulk, giving 13.5v and as many amps as it can (up to about 7a. It's only 160w of panels, on a changeable day, on a drive sloping away from the sun). But it has been doing this all afternoon yesterday, never falling into absorption.

Which seems odd, given the 12v charger thought the battery was charged?

Should I have left the chargers on AGM?

Thanks for any info,
dan
 
Is it a Poweroad Infinty or a Base. If it is an Infinty you can check the SOC with the Bluetooth App.
The batteries seem to be shipped with around 50% charge - which is pretty standard for Lithium.
The profile I saw when charging various examples of these batteries was quite a bit different to what you are used to with the Lead batteries.
With Lead, you get the voltage going up to 14.4V or whatever you select, and the current then gradually declining as the last 20% or so of the battery is charged.

With the battery you have, I would expect you will get the voltage at a much lower level - around that mid 13V you mention but taking a full current. Then when the battery is very close to full, only then does the voltage start to ramp up to the 14.2V the Victron Li-on is set at and the current then rapidly declines to nothing. I saw it went from a constant 30A (it was a 30A charger) down to 0A in under 10 minutes.
This was the pattern I observered with 3 different Poweroad LiFePO4 batteries and the total Ah (current over time) was just as I would have expected.

HTH.

Your 15A charger only supplying 5A seems low. How are you determining that current? Not in night mode (that halves the output)?
 
Thanks Wildebus. It's the Base. The Infinity would have been my preferred choice, but not in stock.

Thanks for the description, that sets my mind at ease. It is certainly what I am seeing from the solar controller. If it had of been at 50% on delivery, I make that around 640wh that needs replenishing, solar has done 340wh so far, but I don't know what the 12v charger did. voltage has been slowly creeping up through this morning so I will continue to monitor that.

I will take a look at the 12v charger, it does have a slow mode but the manual says lights will flash when in this mode. My lights are solid.

Thanks for the info,
dan
 
dane said:
Thanks Wildebus. It's the Base. The Infinity would have been my preferred choice, but not in stock.

Thanks for the description, that sets my mind at ease. It is certainly what I am seeing from the solar controller. If it had of been at 50% on delivery, I make that around 640wh that needs replenishing, solar has done 340wh so far, but I don't know what the 12v charger did. voltage has been slowly creeping up through this morning so I will continue to monitor that.

I will take a look at the 12v charger, it does have a slow mode but the manual says lights will flash when in this mode. My lights are solid.

Thanks for the info,
dan
Click to expand...
This is a graph of the charge pattern I got ... I thought the voltage would have raised earlier than it did I have to say, but it was the identical charge pattern on three different Poweroad Infinity Batteries so that says to me it is as designed. I would assume the Base would be the same
1620639399394.png
 
That's really useful. I am seeing a slow increase in voltage, so looking good. Going to have to take a look at the 12v charger, something very odd going on with that.
 
Due to the vagaries of solar, my charge curve didn't look quite as stable as that, but it followed the pattern and has now moved through bulk, absorption and is now in the float phase.

Thanks for the info, it allowed me to stop worrying that I was about to set my little van on fire :)

Out of interest, what have you set the tail current to in the BMS? I've gone with 1% for now, so 1amp.
 
dane said:
Due to the vagaries of solar, my charge curve didn't look quite as stable as that, but it followed the pattern and has now moved through bulk, absorption and is now in the float phase.

Thanks for the info, it allowed me to stop worrying that I was about to set my little van on fire :)

Out of interest, what have you set the tail current to in the BMS? I've gone with 1% for now, so 1amp.
Click to expand...
I am guessing when you say BMS you are meaning BMV (Battery Monitor)?
I have a pretty unusual setup so I wouldn't go for my settings :D

Be worth while watching a couple of videos to help you with the fine tuning:
first this one

I haven't seen this next one but could be worth watching as pretty new.
 
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