Top Balancing "How to"

[benja.min47]

This is normal.

Okay. Even if there's nothing plugged into it? In this case it becomes very difficult to balance them !! ?? When I think that when I received them they had 0.01v difference ... I should have connected in series !!! At what voltage can we estimate that it is normal 3.55v? Thank you all for the help you give me, I'm so afraid of doing anything stupid !!!!!

 

[HRTKD]

Ben, ease up on the exclamation points!!!

No, just because the voltage differential was miniscule, that doesn't mean the cells were closely balanced already. The Top Balance method is the safe way to go.

 

[upnorthandpersonal]

Even if there's nothing plugged into it? I

Yes.

In this case it becomes very difficult to balance them !!

No, at that stage they are balanced. You can do this for each cell, charge to 3.6V, wait for the current to settle, repeat with other cells. They are all balanced after that even if the voltage drops.

 

[upnorthandpersonal]

When I think that when I received them they had 0.01v difference ... I should have connected in series !!!

Stop looking at the voltage. Again, repeat after me: stop looking at the voltage. Voltage is not an indicator for anything outside the knees.

Look at the graph (for a 12V battery, but doesn't matter):

You can not determine the state of charge by looking at the voltage when this sits at 3.3V per cell. It's flat. Once cell could be at 30%, the other at 60% and you wouldn't know. This is what balancing is about: bring them to the same state of charge. The only way to do that is to either completely charge them to within the upper knee (top balance), or discharge to the lower knee (bottom balance).

In our case we opt to top balance because cells will spend most of their time there, but I digress. In any case, you can see in the graph that the only place where you can use voltage and current to determine state of charge is in those knees. Now, if you charge each cell to 3.6V or thereabout, you can see that the current will taper off and the cell is 'full'. Self discharge is negligible. Do this with each cell (or all at once in parallel) and you can know for sure each cell is 'full' - i.e., balanced. Just because the voltage drops a little (which is normal for the chemistry) does not mean that the cell is somehow 'less full'.

 

[Gauranga108]

Hi I just received my 32 eve cells and want to top balance. I have read the pdf and watched wills video, I just have one question. If I am using the step by step method and only using a power supply could I set the power supply voltage to the highest voltage (in my case 32v) which will allow for the PS max current of 10.10amps. I would obviously keep a close eye and monitor cells with multimeter at the terminal heads. Once I reach 3.4 at the cells I would then reduce the voltage to a safer 3.65. The reason being even if I set this ps to 3.65v it is only charging at 3.2amps. Currently my cells are 3.304 and at that rate for 32 cells it may never finish. I do have the ability to set up with in series, with a 16s Daly bms as stated in the pdf where I get up to almost full charge. If this sounds crazy to you all please let me know, I just had my reason as to why this would be simpler but can definitely go the pdf route as posted by snooker.​

 

[Gauranga108]

Edit: auto correct snoobler

 

[HRTKD]

Hi I just received my 32 eve cells and want to top balance. I have read the pdf and watched wills video, I just have one question. If I am using the step by step method and only using a power supply could I set the power supply voltage to the highest voltage (in my case 32v) which will allow for the PS max current of 10.10amps. I would obviously keep a close eye and monitor cells with multimeter at the terminal heads. Once I reach 3.4 at the cells I would then reduce the voltage to a safer 3.65. The reason being even if I set this ps to 3.65v it is only charging at 3.2amps. Currently my cells are 3.304 and at that rate for 32 cells it may never finish. I do have the ability to set up with in series, with a 16s Daly bms as stated in the pdf where I get up to almost full charge. If this sounds crazy to you all please let me know, I just had my reason as to why this would be simpler but can definitely go the pdf route as posted by snooker.​

Yeah, that's crazy. Don't do it. Patience is critical. 32v would likely damage 3.2v cells in parallel.

 

[Just John]

Hi I just received my 32 eve cells and want to top balance. I have read the pdf and watched wills video, I just have one question. If I am using the step by step method and only using a power supply could I set the power supply voltage to the highest voltage (in my case 32v) which will allow for the PS max current of 10.10amps. I would obviously keep a close eye and monitor cells with multimeter at the terminal heads. Once I reach 3.4 at the cells I would then reduce the voltage to a safer 3.65. The reason being even if I set this ps to 3.65v it is only charging at 3.2amps. Currently my cells are 3.304 and at that rate for 32 cells it may never finish. I do have the ability to set up with in series, with a 16s Daly bms as stated in the pdf where I get up to almost full charge. If this sounds crazy to you all please let me know, I just had my reason as to why this would be simpler but can definitely go the pdf route as posted by snooker.​

Sounds like you might want to invest in some real cables instead of the alligator clips that come with the supply. I don't have any problems pushing full amps, but I use 10 gauge wire and crimp ring terminals and never have a problem. Charging in series with a BMS is a good idea, what will you charge them with in "production". A 30v power supply won't charge 16 cells in series.

 

[Gazoo]

Hi I just received my 32 eve cells and want to top balance. I have read the pdf and watched wills video, I just have one question. If I am using the step by step method and only using a power supply could I set the power supply voltage to the highest voltage (in my case 32v) which will allow for the PS max current of 10.10amps. I would obviously keep a close eye and monitor cells with multimeter at the terminal heads. Once I reach 3.4 at the cells I would then reduce the voltage to a safer 3.65. The reason being even if I set this ps to 3.65v it is only charging at 3.2amps. Currently my cells are 3.304 and at that rate for 32 cells it may never finish. I do have the ability to set up with in series, with a 16s Daly bms as stated in the pdf where I get up to almost full charge. If this sounds crazy to you all please let me know, I just had my reason as to why this would be simpler but can definitely go the pdf route as posted by snooker.​

I think the cables that came with your PS might be crap and there are many posts confirming the same problem you have.

Get some bigger cables (at least 12 AWG) and ring terminals. Your power supply should be able to charge with the voltage set to 3.65 volts and be able to output the full 10 amps, or very close to it. Is it in CC or CV mode? It should be in CC mode. Also it's important to set the voltage of the PS before connecting it to your cells.

I tried the step method and it didn't work for me. Any voltage under 3.5 volts and the current was too low. So I went straight to 3.65 volts and waited 4+ days for my 8 EVE cells to parallel top balance using 12 amps.

Since you have 32 cells it would take 16+ days to parallel top balance them.

 

[upnorthandpersonal]

The reason being even if I set this ps to 3.65v it is only charging at 3.2amps.

As others have said, your cables and/or connectors are crap. Use ring terminals, and decent size wire and you should see your 10A at 3.6V. Do not use higher voltages, you will regret this.

 

[Gauranga108]

Thanks for the replies, I am just about to make my own cords for my ps with 10 gauge and ring terminals I will let you know.