Top Balancing "How to"

[HRTKD]

Yes i know that but i was talking about the voltage on the power supply that is also dropping over time. Is this normal ?
Initially, it was set on 3.6v. Now it is 3.55v

Leave it alone. It knows what the target voltage is, as long as you set it for constant voltage. The leads are to be connected after the settings are in place. Also, the wires that came with the power supply are notoriously wimpy. Creating your own set of larger gauge wires with ring terminals often results in faster charging.

 

[Hedges]

What is the current limit setting?
If impedance of load changed over time (cheap alligator clip started to make better contact), current would increase. If it reached limit, voltage would drop.

Alternatively, cheap supply drifts in accuracy.

 

[crozen]

What is the current limit setting?
If impedance of load changed over time (cheap alligator clip started to make better contact), current would increase. If it reached limit, voltage would drop.

Alternatively, cheap supply drifts in accuracy.

I cranked the current to the max. It is a 10A bench power supply, brand new.

 

[crozen]

Leave it alone. It knows what the target voltage is, as long as you set it for constant voltage. The leads are to be connected after the settings are in place. Also, the wires that came with the power supply are notoriously wimpy. Creating your own set of larger gauge wires with ring terminals often results in faster charging.

OK.
I now made my wires. I used 4mm² (about AWG 11) and much bigger clamps ?
Let's see now.

 

[HRTKD]

I would have put ring terminals on both ends, ditching the alligator clamps.

 

[crozen]

Now the power supply is on CC for the same cell. Why ? Charging at 10A constant.
The cell is now 3.34v under charging.

 

[HRTKD]

Are you using a digital volt meter to confirm the voltage at the cell terminals?

 

[crozen]

Are you using a digital volt meter to confirm the voltage at the cell terminals?

Yes.

 

[HRTKD]

Your power supply is set to constant current. It should be set to constant voltage. Crank the current all the way up, then set the voltage and it should switch to constant voltage. Disconnect the cables while doing that.

 

[crozen]

Your power supply is set to constant current. It should be set to constant voltage. Crank the current all the way up, then set the voltage and it should switch to constant voltage. Disconnect the cables while doing that.

I did this.
It was on CV but when i plug the cables on the cells, it automatically switch to CC.

 

[Just John]

Your power supply is set to constant current. It should be set to constant voltage. Crank the current all the way up, then set the voltage and it should switch to constant voltage. Disconnect the cables while doing that.

Trying to remember, long time since I used a similar supply.
Disconnect from battery. Use your meter to adjust voltage to 3.65v, then connect back to battery and adjust current to max.
I think if the voltage is different enough, constant current light should remain lit until you get the cell charged enough to display 3.65v on the display, then should switch to constant voltage and amps drop. Voltage on battery will be different, don't adjust voltage after setting it, just let it taper amps until it drops below 1.

 

[crozen]

Trying to remember, long time since I used a similar supply.
Disconnect from battery. Use your meter to adjust voltage to 3.65v, then connect back to battery and adjust current to max.
I think if the voltage is different enough, constant current light should remain lit until you get the cell charged enough to display 3.65v on the display, then should switch to constant voltage and amps drop. Voltage on battery will be different, don't adjust voltage after setting it, just let it taper amps until it drops below 1.

Yes i'm not touching anything when it is connected.
According to this chart, it seems that i'm in stage 1. Wonder why it was on CV before i changed the wires.

 

[HRTKD]

Trying to remember, long time since I used a similar supply.
Disconnect from battery. Use your meter to adjust voltage to 3.65v, then connect back to battery and adjust current to max.
I think if the voltage is different enough, constant current light should remain lit until you get the cell charged enough to display 3.65v on the display, then should switch to constant voltage and amps drop. Voltage on battery will be different, don't adjust voltage after setting it, just let it taper amps until it drops below 1.

Long time for me also. I have a picture of my power supply (30v/10amp) with the constant current light on. As I recall, that happened ONLY because I had bumped the current knob on accident. Taking the picture alerted me to the problem. Good thing I noticed it too as the voltage swung up above what I wanted.

 

[Hedges]

The earlier dip in supply voltage display probably just a variation in reading accuracy.
The 3.5A vs. 10A is due to voltage drop in wires previously. Now it is working correctly.
As batteries get full, supply should switch from CC 10A to CV 3.65V

But, probably best to reduce current setting first, "derate" before the supply dies on you.

Your DMM is even cheaper than your supply.
Looks like a free one from HF. Mine didn't last.

 

[crozen]

The earlier dip in supply voltage display probably just a variation in reading accuracy.
The 3.5A vs. 10A is due to voltage drop in wires previously. Now it is working correctly.
As batteries get full, supply should switch from CC 10A to CV 3.65V

But, probably best to reduce current setting first, "derate" before the supply dies on you.

Your DMM is even cheaper than your supply.
Looks like a free one from HF. Mine didn't last.

I think as you. Now with the good wires, the power supply will switch by itself on CV when the cell is almost full.
The fan starts and stops every 10 sec ? I will reduce a little bit the current to prevent its death.
It is running 2 hours now at 10A, the cell is only at 3.37v. It means it took 20Ah and not event finished. What a huge difference between the cell that triggered the BMS and this one Totally unbalanced.

Yes it is a cheap DMM, 10 bucks ? but it is good for my needs. I'm using it since 7 years.

 

[Just John]

Yes i'm not touching anything when it is connected.
According to this chart, it seems that i'm in stage 1. Wonder why it was on CV before i changed the wires.

Because the garbage wires supplied with the power supply insert too much resistance.

 

[Just John]

I think as you. Now with the good wires, the power supply will switch by itself on CV when the cell is almost full.
The fan starts and stops every 10 sec ? I will reduce a little bit the current to prevent its death.
It is running 2 hours now at 10A, the cell is only at 3.37v. It means it took 20Ah and not event finished. What a huge difference between the cell that triggered the BMS and this one Totally unbalanced.

Yes it is a cheap DMM, 10 bucks ? but it is good for my needs. I'm using it since 7 years.

I tested that supply (ok, one that is identical internally) and it has no problems with 100% over its full range.
If it makes you feel better, then turn the amps down to 8, but really shouldn't be a problem.

Cheap power supply for top balancing (tested and works well).

First, a link to the cheapest 30 volt, 10 amp supply I could find on Amazon. There are others on occasion that go on special for a dollar or two less, but this one is pretty consistently the cheapest I could find. https://smile.amazon.com/gp/product/B07512KQDW/ An alternative that is not as...

diysolarforum.com

Nothing wrong with cheap if it works the way it is intended to be used.

 

[Gazoo]

I think as you. Now with the good wires, the power supply will switch by itself on CV when the cell is almost full.

That is correct. Once the PS voltage reaches 3.65 volts, or very close to it, the PS should switch to CV mode and then the amps will begin to drop. Easy peasy. Still keep an eye on the cell voltages.

 

[crozen]

That is correct. Once the PS voltage reaches 3.65 volts, or very close to it, the PS should switch to CV mode and then the amps will begin to drop. Easy peasy. Still keep an eye on the cell voltages.

I put the voltage limit on 3.60v. Is it fine to keep that for top balancing ?

 

[Just John]

I put the voltage limit on 3.60v. Is it fine to keep that for top balancing ?

Should work fine.