Lab power supply as charger

[Deere John]

Got inspired by another thread and bought myself a better lab PSU with CC/CV setting. Current one I have is 30V/5A but as I need 42V that was not unfortunately not enough. So, after some serious googling I found the Korad lineup, same one sells at Farnell as "Tenma" brand, or Elfa/Distrelec as "RND Lab" brand, or Velleman brand also. So I thought it felt quite safe buying the original Korad.

Choice fell on this 60V/5A model Korad KA6005P that is programmable, you can connect it through USB to your computer to control it or monitor to create your own charging curves. Also one neat feature is the five presets. I currently have M1 at 38V/3A and M2 at 41V/3A. Storage charge (~70%) and full charge (~90%).

It comes in various packages, I took one which have a load of extra cables and adapters, DC-plugs for anything you can imagine:



Started up and connected to my external charge monitor and my multimeter:




And finally, storage charging one battery pack here at 38V/3A:



Seems to work just fine, it makes some noise though. Otherwise fine

 

[Deleted member 4366]

Where did you get it from?
How much did you pay?

 

[Deere John]

Where did you get it from?
How much did you pay?

Aliexpress, I paid $146

 

[Deere John]

Have now tried data logging, first attempt was hard because program language was chinese but I asked seller and got an english version. So now it works perfectly. Really neat with computer control, you can control everything except main power on/off. There is also more advanced control with scripting and such but that is beyond my ambition now


Tried to ride my new battery pack until BMS shut down because of low voltage (but last bit was gentle ride on first assist level). And then charge until 41.0 Volt that I always do (not 42.0 V like the standard charger). Charge current 3 A and sample rate 1 read/s.

Measured with Fluke multimeter before and after and got: 32,75V / 40,92V.

So here is the graph, don't know what happened when reaching set voltage level and the PSU goes over from CC to CV. Will try some more and see if it behaves more as it should (like a straight line up to 41).
(you get a CSV-file that you need to put in a spread sheet to get this fancy graph).

 

[chris_n]

Surely if you don't charge it fully the battery will go out of balance as the bms will never. The group of cells that power the bms will always be lower than the rest and over time will drift so far that you are over charging the rest.

 

[Deere John]

Surely if you don't charge it fully the battery will go out of balance as the bms will never. The group of cells that power the bms will always be lower than the rest and over time will drift so far that you are over charging the rest.

Not sure I understand what you mean. The BMS is powered by the main battery pack power and not single cells. The balance wires each comes from one of the serial branches.

 

[Nealh]

The bms only balances in the final stages of charging 41v is a bit too low for the balance function to work properly unless it is an intelligent bms that can be programmed or is pre- programmed.
My LG intelligent charge system on the Swizzbee is programmed to max 41.5v for balancing.
Balancing won't happen correctly until the bms sees 41.5 - 42v so every now and then it might be worth doing a full charge to prevent cells straying.

 

[chris_n]

Not sure I understand what you mean. The BMS is powered by the main battery pack power and not single cells. The balance wires each comes from one of the serial branches.

The balance wires do come as you say from all of the serial branches but most of them are just for measurement not to actually power the 'brains' of the BMS. The power for the brains normally only comes from one set of cells not the whole 36/48v pack.

 

[GLJoe]

The balance wires do come as you say from all of the serial branches but most of them are just for measurement not to actually power the 'brains' of the BMS. The power for the brains normally only comes from one set of cells not the whole 36/48v pack.

Just wondering - does anyone have a link to a circuit diagram/article on typical BMS design?

 

[Deere John]

The bms only balances in the final stages of charging 41v is a bit too low for the balance function to work properly unless it is an intelligent bms that can be programmed or is pre- programmed.
My LG intelligent charge system on the Swizzbee is programmed to max 41.5v for balancing.
Balancing won't happen correctly until the bms sees 41.5 - 42v so every now and then it might be worth doing a full charge to prevent cells straying.

ok, that might be something to think of. But since it is 5 cells in parallell wouldn't they balance each other? But I guess that could work bad when pack is old.

Best would be a Smart BMS of some kind, a colleague has one with BT connectivity so he can monitor/program by his cell phone

 

[chris_n]

ok, that might be something to think of. But since it is 5 cells in parallell wouldn't they balance each other? But I guess that could work bad when pack is old.

Best would be a Smart BMS of some kind, a colleague has one with BT connectivity so he can monitor/program by his cell phone

The whole parallel group goes low together. No need for a smart BMS just make sure you charge fully occasionally.

 

[Nealh]

The five cells in P will all remain balanced as very little amps travel between each cell as long as the P connection is secure, we know this because of the thin sense wires used for the bms.

The unbalancing comes about in the series connections this is where the big amps rush form one to another.

BMS are cheap a few £££'s to £30, a smart programmable bms/bluetooth is about £100.

 

[awol]

Best would be a Smart BMS of some kind, a colleague has one with BT connectivity so he can monitor/program by his cell phone

I use a Neptune15 BMS, you can set the charge and discharge limits to what you want so can set it to balance at 4.1v per cell if you wanted and has bluetooth connectivity

https://www.speedict.com/

 

[Deere John]

I use a Neptune15 BMS, you can set the charge and discharge limits to what you want so can set it to balance at 4.1v per cell if you wanted and has bluetooth connectivity

https://www.speedict.com/

seriously nice BMS! whish I had those one in all my packs