Please help

To charge 4 of them off a 12v charger you would have to hook them in series.

Here is a picture of a LiFePO4 pack configured to be 12v.

LiFePO4 Prismatic Battery: 12.8V 60Ah (768Wh, 100A rate )

May I ask why you need to charge 4 of your cells in a 12v configuration? And are you using a charger for LifePO4 batteries or is it a standard lead acid 12v charger?

 

Presumably Minn_P is trying to correct an imbalance problem? This is one of the ways, to use a standard 12V charger for a one-off. Most lead acid 12V charge to 13.8V, which is 3.45V per cell. It's not an everyday long term solution, but it works well to bring some cells to rough balance so that a BMS can do the rest.

The main aspect to get correct is connecting your black lead to the negative terminal of the cell at the bottom (i.e. #1) and the red lead to the positive terminal of the cell at the top (i.e. #4).

 

Hi Minn_,
I would suggest that if you need to ask this question you probably should not be doing this yourself.

My suggestion is to find some help from some one that can take a DVM and trace out your string of cells and get the charger connected in properly.

Also many 12v chargers put out 15v-16v or even as high as 18v. This is OK but you really need to be sure that the charge is stopped when any cell goes to a high voltage and be aware that this will happen all of a sudden with no warning. You can read 3.35v for several hours and then that cell can jump to 4+v in just a matter of minutes when it hits full capacity.

Thanks,
Dan