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silvestro avatar image
silvestro asked

LiFePo4 battery - 0.1A-0.2A maximum charge current, and that only over 14.5V

Hello community, I looked through many of the threads here and learned a lot (thank you!), but did not manage to find exactly a solution to the situation I am currently facing. The most similar thread being this one:

https://community.victronenergy.com/questions/174754/lifepo4-skipping-bulk-phase-going-to-absorption.html

But in that thread, neither solar charging nor wall charging works, which seems plausible. In my case, one of the two works, the other not.

I have the following setup:

- Inexpensive LiFePo4 100Ah battery with BMS

- Victron IP65 12/10 blue smart charger

- Victron BMV712 smart battery monitor

- Inexpensive solar panel with PWM charge controller

In the beginning, everything worked well and I did a full charge/discharge/charge cycle with the new battery (it performed well, 104Ah drawn). But since some time now, the battery does not seem to charge any more. It sits around 13.1V-13.2V volts and works fine when used with 12V loads as well as with a 1000W inverter no problem. Charging from solar seems to work good enough, during wintertime 1.5A-2A charging current and I brought it from 13V to 13.2V. But the problem is loading from a wall socket. No matter what I do, the charging current is 0A.

The IP65 12/10 charger quickly jumps from bulk to absorption charge, the voltage stays at 14.2V, but the current stays at 0A. Checking with the BMV712, it also shows 14.19V and 0A current. When I unplug the charger, the battery voltage quickly drops back to 13.1V-13.2V. When I connect the charger again, it quickly goes to 14.2V / 0A.

I tried a different, cheaper charger, with the same situation - the charger tries to charge for a very short time (goes to 14.2V), but then after split second thinks the battery is full and goes to 0A and stops charging (back to 13.2V).


So my question is, I guess: is the battery broken? Or am I understanding something fundamentally wrong on how charging is supposed to work?

I really don't understand why solar charging works, but wall charging doesn't. Any input is highly appreciated!

battery chargingLithium Battery
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ingo21 avatar image ingo21 commented ·
are you trying to solar and wall charge at the same time?
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silvestro avatar image silvestro ingo21 commented ·
No, I tried one or the other so far. But I can try both at the same time as well!
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ingo21 avatar image ingo21 silvestro commented ·

both at the time is probably not good the two chargers my confuse each other about the voltage. that is why i was asking.

is the solar charger completely disconnected ( all cables off ) when you try the wall charger?

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silvestro avatar image silvestro ingo21 commented ·
Yes, everything disconnected. Still finishing my build, so I can connect everything separately. I have tried just the battery + wall charger, and also inside a setup with charger - BMV712 - battery.
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snoobler avatar image snoobler ingo21 commented ·
both at the same time is a non-issue.
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snoobler avatar image snoobler snoobler commented ·
Is there an inline fuse between the IP65 and the battery. If so, check to see if it's blown.


"inexpensive" LFP battery that has sat may be triggering over-voltage protection due to cell imbalance.


Set absorption to 0.2V above battery voltage and see if it will charge.

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silvestro avatar image silvestro snoobler commented ·
Thanks for the suggestion! There is currently no fuse, as I am connecting the charger directly to the battery (or directly to BMV712 when testing different things).


Could you explain the "0.2V above battery voltage"? Do you mean 0.2V above the resting voltage (currently at ~13.1V) or above the voltage when charging (currently set at 14.2V by default, also tried 14.4V)?

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snoobler avatar image snoobler silvestro commented ·

Charger should always be connected to the load side of the shunt opposite the battery, or the shunt can't see the current.

By 0.2V higher, I mean if battery is at 13.4, set charger to 13.6 and see if you can get current to flow.


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silvestro avatar image silvestro snoobler commented ·
Yes, battery side of the shunt only connects to the battery. Charger is connected to the load side.


I tried setting absorption voltage to 13.3V (battery was sitting at 13.1V without load), nothing happened.


However, the battery manufacturer just suggested me to try charging with 14.6V (even though their manual says maximum charge voltage 14.5), so I set the absorption to 14.6. Now the charger shows 0.1A output and the shunt even says 0.11A current! Looks like some progress, but still, the current is very low.

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silvestro avatar image silvestro snoobler commented ·
Interesting - setting absortion voltage to 14.5V shows some current: going back and forth from 0A to 0.1A on the charger side. However, the smart shunt still shows 0.00A input. (for this test I connected charger - shunt - battery on the negative side, positive side directly connected)


I also tried setting the absorption voltage to 13.3V, nothing changed.

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snoobler avatar image snoobler silvestro commented ·
It may be that the battery is severely imbalanced, and the BMS is triggering cut off. I didn't consider this because you indicated you could still get charging from solar, and that shouldn't be the case. If the BMS is triggering charge protection, no charger should work.


Ensure that the current you are seeing isn't a result of a draw on the system. The shunt showing 0 indicates 1) charger current is feeding some other part of the system or 2) the current is below the threshold of the shunt. IIRC, the default is 0.1A. You might want to adjust this down.


If you let cheap LFP batteries sit, they will inevitably go out of balance and must be held at elevated voltage to permit the BMS to balance the cells.


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1 Answer
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silvestro answered ·

Thank you for the answers so far. Some updates/recaps:

  • charging the battery with 14.6V does actually put some current through. The charge current ranges from 0.1A to 0.2A, but never goes higher. This is why the solar charger also worked, since I set it for test purposes to 14.6V
  • everything below 14.5V does not charge (0A)
  • when I disconnect the battery from the charger, it quickly goes back to 13.3V. Originally, I started the experiments at 13.1V, and managed to trickle charge until 13.3V, but is is a very slow process
  • to "force" the 14.6V I set the Absorption and Float voltage of the custom charge preset to 14.6V. When I start a new charge cycle, the charger first enters Bulk mode for ~2 minutes, then goes to Absorption, where it stays for 30 minutes. Then it goes into Float for 4 hours, after that into Storage. So in total ~4,5 hours of constant 14.6V charging
  • one theory is (thanks snoobler) that the cells are somehow imbalanced, and that holding the battery at elevated voltage may fix the problem - not sure if this is realistic
  • still, I don't know what happened, the first charge cycles were totally normal, but at one point this problem started to occur. Maybe it has to do with an inverter load? Maximum I tried was 500W (with a 1000W inverter), which seemed to be handled completely fine by the battery

If anyone has any ideas left, I would be very thankful. The battery manufacturer is so far giving underwhelming support...

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snoobler avatar image snoobler commented ·

If the cells are imbalanced, holding at elevated voltage will help them balance.

The immediate drop to 13.3V is odd. I would expect a gentle settling with a lot of time between 13.8 and 13.3V.

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silvestro avatar image silvestro snoobler commented ·
Thanks for your replies so far, I have changed the thread title so it better fits the new information I have received. I have the impression that charging the battery with 14.6V for a longer period slowly improves the situation - just now I managed with a whopping 0.3A! :D

I now also tried reducing to the normal Victron Li-ion charging profile (14.2V), and now it charges with 0.1A-0.2A - that is definitely new and did not happen some days ago.

Still, this is not normal as ideally it would charge with much more current.

Also, I just counted the duration of the voltage drop - measuring with a multimeter directly at the battery terminal while charging gives 14.33V, I detach the charger, the battery takes ~2.5 seconds to drop to 13.35V, and stays there...


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snoobler avatar image snoobler silvestro commented ·
sounds like a faulty cell or BMS
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