behold, finally tabbed a battery..

[emaayan]

after getting my new iron (which is superior to my old one, i always though it just the that counted, but no), i finally think i managed to pin it down..

now if only i knew how to use my imax to see if it's actually still working..

 

[999zip999]

You can use a wet spronge to cool it down. The pos. end is where heat does the most damage and just over all heat is you biggest problem.

 

[liveforphysics]

When can's are soldered upon, you know you've decomposed and/or boiled the solvent locally touching the case in that area. If you're spending more than a couple seconds between start to finish on making this joint, you've got a strong likely hood of damaging the cell.

 

[wb9k]

What they said. Be VERY careful not to let the cell temp rise much at all. The entire soldering operation (at least on the cell itself) needs to be very quick. What type of solder are you using? Done any pull testing on the tabs to see how strong the joints are?

 

[wb9k]

One more thing---remember the can of these cells is strapped to the cathode. Make sure not to fold your anode tab over the corner of the cell body without additional robust insulation. With vibration and time, your tab could chafe through the PET sleeve of the cell, creating a dead short across the cell--and that's never any fun.

 

[cal3thousand]

Another reason why I think the eBay sellers offering custom pack welding are awesome.

 

[999zip999]

You should put a gasket under the pos. end befor you solder on the tab so the tab dosn't short on the case of the cell which is all and total Neg.all the way to the bottom.

 

[wb9k]

You should put a gasket under the pos. end befor you solder on the tab so the tab dosn't short on the case of the cell which is all and total Neg.all the way to the bottom.

Huh? It's actually the other way around. Anode is negative. The can is tied to the cathode, which is positive. There already is a gasket glued to the negative end of the cell to prevent contact there, but an additional gasket never hurts. The PET sleeve that covers the can (and outer edge of the existing gasket) isn't nearly as cut-resistant as the gasket. So, if your negative current carrier is going to be routed along the height of the can (something that really should just be avoided altogether in the first place), extra care is a must.

 

[999zip999]

O.K. A gasket ? yes or No ?

 

[wb9k]

It is. Those are Samsung cells, though. I have no idea if their can floats or is tied to one end of the cell or the other. The OP was using an A123 26650 which definitely has the can strapped to the cathode. We can't really make blanket recommendations that specific for all cells. It's important to know the cells you're using and understand how to manage whatever risks they present. My advice here was specific to A123 cylindrical cells.

 

[999zip999]

I get it. I looked at the pic. and now understand. Thanks . Daa.

 

[emaayan]

oh, so that's why a123rc placed that cardboard thingy under the tabs, but that would mean i have to cut down hundreds of circles from cardboard and glue them to the cell,

 

[wb9k]

oh, so that's why a123rc placed that cardboard thingy under the tabs, but that would mean i have to cut down hundreds of circles from cardboard and glue them to the cell,

Like I said, this is only something you have to worry about if your negative tab has opportunity to make contact with an unprotected part of the can.The plastic gasket on the negative end of the A123 cell is very robust, so you don't have to add paper gaskets unless you are looking to up the safety, which is already very good. Don't remove the existing gasket though!

 

[emaayan]

well i went in with an imax on one of them, completely discharged and charged them, i got 2124 mah, does that mean it's ok or i lost 150 mah?

 

[wb9k]

well i went in with an imax on one of them, completely discharged and charged them, i got 2124 mah, does that mean it's ok or i lost 150 mah?

What was the rate of the capacity test, and what were your exact criteria for defining 100% and 0% SOC? Any idea how old the cells are? Used or new?

 

[999zip999]

Thanks These is very good . Different angle of thought. More better.
Wb9k thamks for for the switch from pos. to neg.
Havent' held a A123 cyclinder and have learned.
Thanks.

 

[emaayan]

i gave it 2.3 ah, the cells are from 2011, new.

 

[etriker]

well i went in with an imax on one of them, completely discharged and charged them, i got 2124 mah, does that mean it's ok or i lost 150 mah?

Using the Hyperion 1420 to fully charge then discharge at 5 amps to 3.0v that is what good ones will do. 2100 to 2200 or so.

 

[etriker]

well i went in with an imax on one of them, completely discharged and charged them, i got 2124 mah, does that mean it's ok or i lost 150 mah?

What was the rate of the capacity test, and what were your exact criteria for defining 100% and 0% SOC? Any idea how old the cells are? Used or new?

Sorry for being mean.

Get a Hyperion 1420 and some cell logs, a big soldering iron and an old ebike with dead batteries cheap on craigslist and join the fun !

 

[wb9k]

well i went in with an imax on one of them, completely discharged and charged them, i got 2124 mah, does that mean it's ok or i lost 150 mah?

What was the rate of the capacity test, and what were your exact criteria for defining 100% and 0% SOC? Any idea how old the cells are? Used or new?

Sorry for being mean.

Get a Hyperion 1420 and some cell logs, a big soldering iron and an old ebike with dead batteries cheap on craigslist and join the fun !

I appreciate that etriker, and no hard feelings here.

I have a bunch of cell logs and a Turnigy FatBoy 8. I've been looking at doing a bike project for a couple years, but life and other projects (PHEV, home power systems, etc.) keep getting in the way. I'll take a look at the Hyperion for charging packs bigger than 8S.

 

[wb9k]

i gave it 2.3 ah, the cells are from 2011, new.

For 1C capacity test:

Float cell at 3.6V until charge current falls to C/20 (115 mA in this case) or less. Discharge at 1C until cell hits 2.0 V. If your discharge load does not adapt to maintain constant current, you'll need to do a little calculating. Main points are, capacity is found with a discharge test, and the cell needs to be properly topped off and then fully drained to get an accurate result.

 

[emaayan]

awesome, can you please explain it, in plain english to a moron who doesn't understand the meaning of "float" and "adapt to maintain constant current" ?

 

[dnmun]

it is what you needed to do to the original cells you cut out. there was nothing wrong with them. they just needed to balance.

 

[emaayan]

i didn't cut out any cells (yet), those were simply spare cells, as for the pack, i tried every combo they told me (and more) i tried charging them with a charger first and then charge each 8P pack individually by imax, i tried the other way around, it just made things worse, even dogman told me i apparently have a weak cell, and that i should either accept it, or surgery time..

 

[dogman dan]

From what I understood, that cell group continued to act up even after he manually balanced the pack. It may have been just one or two of the cells in that group that went bad though.

Rather than cutting hundreds of cardboard circles, what about cutting some cardboard strips, then securing them to the underside of the tabs with some shrink wrap? Or hot glue the cardboard to the cell under the tab, before soldering?