Charging LiFePo4 (LFP) to 3.4V and 3.5V with and without Absorption. What a difference!

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With the new ZKE-Tech EBC-A40L tester, I'm learning already so much about the LiFePO4 chemistry. I jump right into the first test I always wanted to make for a long time.
What difference in capacity does it make if I charge my battery to 3.4V instead of 3.5V? Will absorption always charge to 100%? Many questions to answer and many tests to run... The results are quite interesting.

Specs of both testers:
ZKE-Tech EBC-A20 Charger and Tester:
Test Voltage: 0-30V
Test Current: 0.1-20A
Charge Voltage: 0-18V
Charge Current: 0.1-5A

ZKE-Tech EBC-A40L Charger and Tester:
Test and Charge Voltage: 0-5V
Test and Charge Current: 0.1 - 40A

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One of the most usefull videos I have ever seen on this subject. Actual evidence for the charge voltages instead of just opinion!

richardeccles
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A Note at 13:45 - "What am I doing here?"
You are educating me. I appreciate that.

Fantastic work. Please keep it up!

loganv
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Found your channel today, at Microcare we have been manufacturing solar equipment for 30 years. I really think you are doing great work for the industry, Thank you and well done

markstemmett
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i was wondering all the time "what is absorption?" "do i need absorption with my lifepo4 box?".
All my doubts are gone!
i dont have words to thank you Andy!

bbiero
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probably one of the most informative or educational videos on youtube that i've ever watched. ty very much for your time and effort.

StultusRex
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This video should be pinned and bookmarked by everyone just getting started in LiFePO4 battery charging. It’s so helpful to see those curves, and work through the differences between long absorption and faster charge times and how it does and doesn’t affect total charge effectiveness. Thanks so much for taking all that time to document these results! 🙏

pchris
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I really find your videos informative, and I appreciate the time and dedication you take, great to see you following the evidence instead of following the crowd, thanks Andy. You make it easier for us to follow the evidence as well👍👍

garycampbell
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Excellent testing! Next you need to run the same test at 3.375V, 3.35V, 3.325V, and 3.20V. You will find that the behavior begins to change at these lower voltages, even though they are still above the cell's nominal operating voltage. (And this is why 'Float' voltages are typically set between 3.35V and 3.375V... doing the least damage to the battery while still being able to support loads without having to drain the battery, which would cycle it unnecessarily).

You could even test 3.25V and 3.20V, but you will find that these voltages hit diminishing returns very quickly and just don't charge the cell up sufficiently.

For a 4-cell 12V battery:

3.20V is 12.8V <--- less typical and usually not all that useful.
3.25V is 13.0V <--- less typical.
3.30V is 13.2V <--- less typical but still useful in some situations.
3.35V is 13.4V <--- typical float + load-support voltage / trickle-charge voltage, etc. Still quite reasonable to use as a cell ages.
3.375V is 13.5V <-- typical charge controller float default, adds a little room to ensure reasonable operation as a cell ages.
3.40V is 13.6V <--- more typical if you intend to cycle the battery.
(higher voltages are more typical for bulk targets when charging at higher C rates, up to 3.65V / 14.6V when charging at 0.3C to 0.5C).

-Matt

junkerzn
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Very good information. At my home I am using a 12V LiFePO4 6ah battery as a DC backup for my home network. I have a simple power supply to both run the network equipment and float charge the battery and had been trying to determine what would be the best voltage setting to keep the battery fully charged but also not damage the battery. There are many articles which state that you should never float charge an LiFePO4 battery. However, a PowerSonic article stated that you can use 13.8V (equivalent to a cell voltage of 3.45V). Your testing shows that I should be fine by setting at 3.4V per cell (13.6V for the battery), so that's what I am now using. Excellent info! Thanks

fritsriep
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Thanks for these videos, when i first started using this chemistry battery/cells it was almost impossible to find the correct charging parameters. As we say in Jamaica, respect brother.

phillipchen
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This is one of the best video on Youtube explaining important of charge voltage. thank you very much.

sameershinde
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All good Andy. It took me around a year of being off grid to learn what you have detailed and proved here. And it is always nice to see the proofs. A bit like your boat man example, I'm in the UK, the weather is often intermittent; I change the MPPT settings based on weather, need - when it is that week of sun and low power needs being able to set a 3.35-3.4v/cell charge makes me feel I'm protecting the battery, and increasing the lifespan of the battery. I'm sure I've read that avoiding higher voltages can increase the "at 80% capacity" cycles past 5000 even as high as 10, 000. For a solar system that's 25 years on the battery and panels, so worth knowing if you can lower the charge voltage and still have the system power what it needs to.

KevIsOffGrid
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This is a very good and valuable test! It shows a LFP cell can already be overcharged at 3.4V if you charge too long and with too little current. If you charge only to 3.4 and let it absorb its probably less stress for the cell. If you charge to 3.5 with a cutoff current high enough (about 0.02C) the cell will be fine but if you keep charging until 0.00xC you will most likely overcharge and damage the cell already a bit. A Voc (open circuit voltage) of 3.5 is already massive overcharging for one cell! You are more on the safe side with 3.4 or even 3.35V with absorption.

rilosvideos
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very intresting and lots of time to do the test.. One thing I think we forget sometime is most of the time you are not discharging to 2.5 per cell.. many people try to have enough capacity to power everything to where the discharge is only to 80 or 70% at lowest.. When are not having to recharge from 0 to 100% all the time the time to charge become less in theory.. one your 3.4 v test and 4 hrs abs time if you are only down to 3.2 or 3.0 v then recharge and abs time is lower.. This test has opened a lot of eyes i am sure on how to keep your cell going longer with less deteration.. THANKS mate..

carl
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This sort of stuff is fascinating to me even though I don't have any of this equipment and likely never will. You are doing things at a level of detail I don't think anyone else is on YouTube. Great stuff!

gumpster
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Hope it comes a new clip soon;)
I enjoy too see your clips not only for solar stuff but your seens of humor and your german english ;)👍
Every time I see a new post from you I put on the coffee and chocolate, big blanket and lay down on the sofa. I really enjoy and learn from you sir 👍😉
Best regards Morten from Norway 🇳🇴

mortendiysolarshinybilplei
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Great work Andy.
We’ve just been away in our caravan for a full month, where I typically charge to about 3.48v with no absorption time, using a Morningstar MPPT solar controller. We use the battery for everything if solar conditions are good- lighting, Sat Tv, fridge, microwave, air fryer, induction cooking, A/C reverse cycle heating, (a 2.5kW Panasonic inverter split system), electric blanket on a cold night, and even hot water for washing up and showers. I only use LP gas for cooking and hot water if solar conditions are not great, or if the conventional oven is needed.
(I bought my 4 x 400 Ah cells, and assembled my system in 2015.)
As it’s in a caravan, and we are not using it to live in full time, it hasn’t done a huge number of full cycles, probably equivalent to a hundred and fifty or so.

I did a discharge test on our last day away this trip, and found no evidence of degradation whatsoever even taking it down to just 10% SoC according to the Victron meter (360 Ah out of a 400Ah battery, of 4x Winston cells.) Battery voltage was still great on all four cells, and nicely balanced.

FutureSystem
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Thanks for your hard work on this. So the question becomes when in a pack with small cell differences how to change charge current based on the highest cell voltage. I look forward to your video on pack settings and why. I think we will see a new generation of charge controllers that interface with individual cell monitoring to really take advantage of this.

jasondevine
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Great great info.
This is EXACTLY what I've been curious about since you started messing with your Victron all those months ago!
Can't wait to see more testing.

TheComputerGuyDR
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Hi Andy, I have learned more from watching your videos than from any other source of information.
I am French and so my English is not really fluent, thanks to your accent and pronunciation I understand everything!
Unfortunately, I discovered your channel after ordering batteries and BMS... too bad for the discount but now I think I know how to set up my hybrid inverter.
Thanks again.

baygon
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