General Category > Electric/Hybrid Car Conversion

Problem charging batteries via bms

<< < (2/3) > >>

TheKing:
These days it is very cold here, when it warms up I will work and plan to implement every part of your advice.
I'm going to use the solid bus bars between all the negative connections and wire them to the + terminals one cell at a time.
I hope everything will be fine. Very detailed and clearly stated by you. Thanks in advance
Regards,

TheKing:
Sun 14 h   Mon 19 h

3,52      3,355
3,44      3,355
3,48      3,355
3,37      3,355
3,5      3,356
3,48      3,356
3,37           3,356
3,33           3,356
            
27,49   26,844

Just inform you: In Sunday 14.00h start to balancing cells and after 29h at temp 1 C degree result is in second column. Is it logic ?  The sum of voltage looks with bigger difference than I expect! Cells are connected when the measure is made.
Your opinion ?
Regards,

Bikemad:
When energy is transferred from one cell to another there will be a certain amount of overall voltage drop due to thermal losses during the transfer process (in the bus bars, connecting wires and the cells themselves).
You also need to consider that some of your cells were previously overcharged, giving an exaggerated pack voltage to start with.

Please note that according to the LiFePO4 State of Charge curve shown below, a resting voltage of 3.35V per cell indicates that they are almost 100% charged, therefore all of the 8 cells measured still appear to be at a very good state of charge.  ;)



However, I am concerned that you have only shown 8 separate cell voltages when you're supposed to be balancing 16 cells.
You need to have all 16 cells connected in parallel simultaneously for a sufficient length of time to ensure that all 16 cells are perfectly balanced to the same resting voltage.
If you balance two halves of a single pack separately, the two halves could still be at significantly different voltages, and the entire pack would would not be balanced.

If you disconnect the cells and their individual measured voltages still vary considerably, you may have to leave them connected in parallel again for longer to ensure all of the cells are balanced as much as possible.

Alan
 

TheKing:
Hello,
I don't know why, it didn't give me a notification in my e-mail that there is a new post about me on the forum ... so now I accidentally saw it.
To tell you the truth, now I'm sorry why I didn't put all 16 cells together. I thought, of course, I will charge them 4 times with a 12 V charger, and the electric vehicle has 8 cells in the front under the hood and 8 under the back seat.
I think the front cells (not balanced) are lower or almost the same voltage without big difference. And if they are close to 3.350 then I will put all 16 together to balance for 2–3 days, so I can try them without topping up with a 12v charger.
If after 2–3 days of balancing the voltage is 3.30-3.35 then I will not charge them (which would be problematic to get the same voltage) ... but I will immediately try them on the vehicle without BMS.
Thanks again Sir, now the weather is much warmer, I can work outside Best Regards,

Bikemad:

--- Quote from: TheKing on February 16, 2023, 11:40:22 AM ---I don't know why, it didn't give me a notification in my e-mail that there is a new post about me on the forum ... so now I accidentally saw it.
--- End quote ---

The notification option appears to be turned Off by default, therefore it will need to be manually changed before future notifications will be sent:
Go to the Notifications page for your user profile and make sure the checkbox next to Turn notifications on when you post or reply to a topic is checked.
Then select whether you want the notification to be sent Instantly, Daily or Weekly etc. from the dropdown menu before selecting Only replies or Replies and moderation from the next dropdown menu.

Finally, you may also have to click the "NOTIFY" link in the tab at the top or bottom of this thread to make sure you receive future notifications. If it says "UNNOTIFY" in the tab instead of "NOTIFY", this may have been done automatically already.

Alan
 

Navigation

[0] Message Index

[#] Next page

[*] Previous page