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Top Balancing "How to"

- OK

- But is there no risk? It will "float" without ever exceeding the target voltage (sorry, I have no knowledge in this area!)

- I speak french
Its added stress on the battery to leave it exposed to charge voltage longer than necessary to achieve full charge.
There is no consensus on just how bad that stress is though.
Pretty sure we have some french speakers here that could help explain.
Regardless of language you are asking good questions.
 
We have the understanding than an extra day "floating" at 3.5V is much less damaging than an extra day at 3.65
So long as you set a reliable CV/CC supply to your target voltage BEFORE connecting it to batteries, it should be safe sitting there charging for days, with you just checking it morning and evening.

That is simple to do, so no need to try to understand more complicated methods where you couldn't completely follow the explanation given in English.
 
We have the understanding than an extra day "floating" at 3.5V is much less damaging than an extra day at 3.65
So long as you set a reliable CV/CC supply to your target voltage BEFORE connecting it to batteries, it should be safe sitting there charging for days, with you just checking it morning and evening.

That is simple to do, so no need to try to understand more complicated methods where you couldn't completely follow the explanation given in English.
hello, after several days of rest, connected in parallel, I connected my cells with my home-made power supply. Currently I apply 3.50v to 3.3a (max of my power supply). Thanks for your help. I will come back to give you the result ...
 
Hello,

I'm topbalancing my 4 x LiFePo4 280Ah Varicore Cells at the moment.
I'm doing this with small SkyRC Charger. I configured it with the following parameters.
Voltage 3,65V
Max Charge Current 6A
ChargeMode LiFe
Cell Count 1S (Because all Cells are Parallel)

OK, I know that will take a long time to charge the cells to top. But the Voltage doesn't change. I think it should go up (slowly).
It stays exactly at 3.31

The Charger displays something between 1.5A - 1.7A at 3.65V
And this setup is already running for sometime so that the Charge displays the amount of 65Ah (16,25Ah each cell)
But if I check the Voltage at the busbars it is still 3.31V

What is my mistake?
 
And this setup is already running for sometime so that the Charge displays the amount of 65Ah (16,25Ah each cell)
But if I check the Voltage at the busbars it is still 3.31V

That 16Ah is less than 6% of the capacity of a cell. You're charging at a 0.0015C rate (1.7A for a total of 1120Ah with those 4 cells in parallel).
It is perfectly normal that you don't see any change in voltage. The curve is flat:
357200bc269bb450b52801de0e8c5c03.jpg

One thing I would do is make sure all your connections are good and you have proper cables. You should be able to push the 6A that the charger is capable of. If this is not the case and it's really at 3.65V, you have bad connections/cables.
 
Hello,

I'm topbalancing my 4 x LiFePo4 280Ah Varicore Cells at the moment.
I'm doing this with small SkyRC Charger. I configured it with the following parameters.
Voltage 3,65V
Max Charge Current 6A
ChargeMode LiFe
Cell Count 1S (Because all Cells are Parallel)

OK, I know that will take a long time to charge the cells to top. But the Voltage doesn't change. I think it should go up (slowly).
It stays exactly at 3.31

The Charger displays something between 1.5A - 1.7A at 3.65V
And this setup is already running for sometime so that the Charge displays the amount of 65Ah (16,25Ah each cell)
But if I check the Voltage at the busbars it is still 3.31V

What is my mistake?
New cells usually come roughly half full.
280 ah * 4 cells * .5 state of charge / 1.6 amps = 350 hours
 
Hello,

I'm topbalancing my 4 x LiFePo4 280Ah Varicore Cells at the moment.
I'm doing this with small SkyRC Charger. I configured it with the following parameters.
Voltage 3,65V
Max Charge Current 6A
ChargeMode LiFe
Cell Count 1S (Because all Cells are Parallel)

OK, I know that will take a long time to charge the cells to top. But the Voltage doesn't change. I think it should go up (slowly).
It stays exactly at 3.31

The Charger displays something between 1.5A - 1.7A at 3.65V
And this setup is already running for sometime so that the Charge displays the amount of 65Ah (16,25Ah each cell)
But if I check the Voltage at the busbars it is still 3.31V

What is my mistake?
No mistake, it will just take a couple of days to notice the voltage move up. They have a very flat charge curve.
 
OK, thanks for all the answers and you are all right. I didn't realized that the curve is sooo flat in this charging-state.
Thank you very much.

The wire cross section should be big enough. But could the croco clamps be a problem? What do you think?
 
OK, thanks for all the answers and you are all right. I didn't realized that the curve is sooo flat in this charging-state.
Thank you very much.

The wire cross section should be big enough. But could the croco clamps be a problem? What do you think?
What is the wire cross section?
Yes the crocodile clamps could be a problem.
Normally the leads that come with cheap bench power supplies are not fit for this application.
10 awg wire with ring terminals will probably cut your eta in half.
Have a look at this method https://diysolarforum.com/resources...ls-using-a-low-cost-benchtop-power-supply.65/
 
OK, thanks for all the answers and you are all right. I didn't realized that the curve is sooo flat in this charging-state.
Thank you very much.

The wire cross section should be big enough. But could the croco clamps be a problem? What do you think?
They are the most likely cause of less amps.
 
They are the most likely cause of less amps.

Which you can confirm with a voltmeter; measure voltage drop from supply terminal to cell terminal.
That should be near zero; if it is more like 0.1V, the leads are acting as a resistor.
If much voltage drop, that's why current is 1.5A instead of 6.0A and charging will take 4x as long.

You can also measure voltage between terminals of supply (see if they are same as supply setting) and see what voltage is across the batteries.
 
Hello, I'm still calling on you! My power has reached its target of 3.50v yet when I test the cells individually they are at 3.33v ... is this normal? thank you,
 
Hello, I'm still calling on you! My power has reached its target of 3.50v yet when I test the cells individually they are at 3.33v ... is this normal? thank you,

If the leads from your power supply to the battery are low quality and a high awg (like 18 awg) then there will be some voltage drop. Make sure the positive and negative leads are put on opposite ends of the battery.
 
Make sure the positive and negative leads are put on opposite ends of the battery.
I do not understand.

If the leads from your power supply to the battery are low quality and a high awg (like 18 awg) then there will be some voltage drop
Yes unfortunately the cables are thin!

But why does my DC power supply mark me 3.50v if in reality the cell pack is at 3.33v ??
 
I do not understand.


Yes unfortunately the cables are thin!

But why does my DC power supply mark me 3.50v if in reality the cell pack is at 3.33v ??

Go to this link:


On page 3, heading 4 Top Balancing your cells, see bullet point four.

The leads at opposite ends ensure that all the cells have the same access to the charge.
 
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