Removing Cell from a forklift pack?

evotech

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Nov 4, 2019
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So here is the deal. I have two banks of 24 2v tubular cells. One pack has a damaged cell at the end of the run. The question is this. If I remove that cell, should I also remove the corresponding cell in the other bank thus reducing the voltage to 46V. If I remove just the damaged cell, they will never equalize. Right? This is on a DC solar trailer with a midnite classic and 2 SMA inverters. PXL_20211115_155412396.jpg
 

Tecnodave

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Mar 22, 2021
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762
They will never balance with a different number of cells in each bank, The “short bank” will be over charged while the “full bank” will be undercharged. No easy answer to this dilemma. Cells can be replaced with that battery format but there is some removing the strap that connects the cells.

I have done it but it is not an easy task. Start with a carefully sized hole saw to cut out the connecting strap leaving a “battery post” . Connect new cell with liquid lead melted externally and poured into the gap between the battery post and the connecting strap. You will need to make some kind of “barrier” to keep the melted lead in the connection gap and not allow it to seep down to the plastic battery tops. cut pieces of insulating board is used in battery shops.

I have done time at a battery manufacturing facility so I do have experience here. Post some more details as to how this cell is damaged and I just may have a useable idea for you. Cell recovery is possible under some circumstances.
 

evotech

New Member
Joined
Nov 4, 2019
Messages
14
They will never balance with a different number of cells in each bank, The “short bank” will be over charged while the “full bank” will be undercharged. No easy answer to this dilemma. Cells can be replaced with that battery format but there is some removing the strap that connects the cells.

I have done it but it is not an easy task. Start with a carefully sized hole saw to cut out the connecting strap leaving a “battery post” . Connect new cell with liquid lead melted externally and poured into the gap between the battery post and the connecting strap. You will need to make some kind of “barrier” to keep the melted lead in the connection gap and not allow it to seep down to the plastic battery tops. cut pieces of insulating board is used in battery shops.

I have done time at a battery manufacturing facility so I do have experience here. Post some more details as to how this cell is damaged and I just may have a useable idea for you. Cell recovery is possible under some circumstances.
Thank you. I will get a pic up soon. I get that they will never balance, but what if I remove the corresponding cell in the 2nd bank and reduce the voltage to 46V? Is that a doable solution?
 

Tecnodave

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Mar 22, 2021
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762
Yes doable but limited by the low voltage cutoff of the inverter, The Classic is fully programmable and can do pretty much any battery voltage you want. I have extensive experience with the Classic but scant experience with the battery based SMA products.

Removing and replacing a cell is something only done in very expereinced battery shops. I cant recommend doing that unless you have a lot of “hands on” expereince. I have done it and it took hours to accomplish.

How is the bad cell damaged, is it external physical damage or a chemical imbalance?
 

Tecnodave

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Mar 22, 2021
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762
BTW......these appear to be flat plate cells as opposed to tubular cells, but the manufacturers name is “tubular“

Normally tubular cells are wound up with layers of plate and separators......done in some AGM cells
 

evotech

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Nov 4, 2019
Messages
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BTW......these appear to be flat plate cells as opposed to tubular cells, but the manufacturers name is “tubular“

Normally tubular cells are wound up with layers of plate and separators......done in some AGM cells
thanks for the help. After speaking with a forklift guy it seems like a big job as they weigh a ton and need a forklift or other lifting machine just to remove the old cell.
 

Tecnodave

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Mar 22, 2021
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762
Your forklift batteries are small and you do not need a forklift to lift out one cell......These cells are individually encased and can be replaced one cell at a time by removing the cell connector straps using the method I described. I replaced one cell in the middle of a 1300 a.h. 36 volt forklift battery which weighed more than a ton. I used a hole saw to cut out the connecting strap and asbestos sheet material to keep the molten lead from running through to the plastic battery top.

I did my stint in FLA battery shop at Alaska Husky Battery in Fairbanks, Alaska where we built batteries for the frigid far north so I do have real time experience in a high end Flooded Lead Acid battery manufacturing plant.
 

Porch

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Jan 17, 2021
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267
That battery reminds me of when I went to pickup my forklift battery from a warehouse almost in Mexico. They also rebuilt batteries in this place. There was so much acid on the floor, everyone was wearing flip flops and the hard forklift tires looked like melted rubber.
 

Tecnodave

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Mar 22, 2021
Messages
762
I would bet that you and I are the only persons on this site to even see those.....I did a stint at Alaska Husky battery in Fairbanks Alaska in the mid ‘60s to work my through University of Alaska, got my degree and moved on, cant remember how many batteries that i did that process on. Electrical Engineering was more fun than battery shop. Didnt mind the hot lead part but I hated the Sulphuric Acid......
 
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