I have repaired a lot of these types of batteries using the method you used on the P103. I believe the reason the P104 didn't work was that you said you used protected cells. These batteries use unprotected cells, so the internal electronics on those cells will interfere with the operation of the cells in the pack. Another thing to consider is that you need to use the same types of cells with the same amount of capacity. The ones used with power tools have a low internal impedance and can supply large amounts of current. The ones used for lighter applications will have a higher internal impedance and when used in a power tool will not produce sufficient current and the voltage level will drop. I use a 3.7 ohm 20W resistor to test cells. This will draw about 1 amp. I measure the voltage with the cell under load and I expect the voltage to remain above about 3.8v loaded. The higher the voltage reading the lower the internal impedance and the better the cell is. I also have been able to revive cells that read 0 volts by temporarily connecting a zero volt cell in parallel with a good cell. The voltage will climb in the cell to be revived if it is able to be revived. I then place this cell in a single cell 18650 charger and let it charge. After charging test it for internal impedance as I just described. If it is good, then install it in a pack you plan to rebuild. 

Cool! I like the trial and error and then success. Thanks

Nice job. I enjoyed your humor!

Great Video, very impressed, slightly disappointed though ! as i have just thrown 4 of these batteries away !!, never mind. Thanks again

I don't see a problem with that. Looking at the circuit boards on both 1.4 and 2.6 AH batteries I see no differences. I did buy a reconditioned 4.2 AH battery from China that was in a 2.6 AH shell. But please bear in mind that there will be more heat produced from the cells if you work the battery hard. From my experience I use the Over capacity (you could say) battery in my lamp or smaller drills and pay attention to how warm it gets! Hope this helps?

Love our bench, looks just like mine

thank you answered most of my questions.  regards john

Like it. I'd always assumed the insides of the Lithium battery would be more sophisticated. Are those standard 18650 cells? I'm pretty sure the TEK4 4v battery is just a single 18650 cell too.

Did you try charging that one low cell? You must balance charge all cell's to same voltage in order for it to put out full 20 volts all together. Many times you will not need to replace a bad cell or low voltage cell. By charging it up by itself you might be able to revive it.

next time you might want to try removing the protection circuits on your Ultra fire batteries as I heard that they can sometimes stop the current if they were overloaded.

All of the cells were individually charged on a small RC balance charger before I Replaced the dud cell. This was the best I could do to match the cells. have you got any other tips on lithium cells as I'm thinking of building one for an electric bike project? cheers Pete