Pismo/ Wallstreet battery cells

[beachycove]

Are the battery cells in Pismo/ Wallstreet batteries matched in any way with the battery controllers? In other words, is there any point in re-celling a main battery with different capacity cells?

 

[Franklinstein]

Apple really doesn't publish any technical information in that detail, which is a shame for old machines that are hard to equip with proper replacement parts.

Anyway, some people have had success recelling with higher capacity batteries where others have failed even replacing with identical batteries. It's kind of a craps shoot with those things. As to whether the "intelligent" portion of the battery is trained to run with certain cells or not, I am unable to say.

 

[Bunsen]

Don't recell a LiON or LiPo battery. You're taking your life in your hands, unless you really know what you're doing. The smarts in there stop them asploding in your lap.

 

[Da Penguin]

The controllers will handle different capacities. Lots of people have re-celled these batteries before. But these people also know what is going with these things very well.

They can be very dangerous, as bunsen said, so I would recommend against it as well.

TBird

 

[tomlee59]

The controllers must be matched to the batteries, particularly in a lithium-ion pack. More than with any other battery chemistry, lithium-ion requires very special handling to avoid overcharge (and over-discharge). If you change the cell type, you will make erroneous the controller's assumptions about what electrical terminal behavior corresponds to a given charge state. This could be Ghostbusters bad.

If you can find cells with the same ratings as the original, and you still want to proceed with a recelling operation, it isn't particularly hard, but you must observe a couple of rules to ensure safety:

1) Never short the cells.

2) Make sure that you connect the cells exactly as in the original (you knew that, I know).

3) Do not solder the cells. Use a spot-welder to connect the tabs together. Lithium-ion cells are exceptionally intolerant of heat.

If the cells were ever over-discharged, some controllers will set a nonvolatile bit to prevent recharge. Even after recelling, the controller may refuse to initiate a charge cycle. If none of this deters you from recelling, and you get stuck at this point, post again, and I'll outline a "CPR" procedure (it is a bit scary).

 

[macintoshme]

I wonder if you could (i know you guys will hate this) super glue the tabs, then use conductive paint to connect the tabs? so no soldering or spot welding needed?

 

[Franklinstein]

If the cells were ever over-discharged, some controllers will set a nonvolatile bit to prevent recharge.

Is that why bunches of these stupid LiIon batteries won't recharge after a very long period of disuse? I know lots of my NiMH and NiCD batteries won't recharge because they've leaked or something, but that's typically obvious from either bulging cases, corrosion, or goo all over everything.

If the LiIon cells haven't burst all over the place, what exactly happens if one tries to recharge an over-discharged battery (assuming that the controller doesn't prevent it)?

 

[tomlee59]

I'm sure equill will be able to provide a great deal more about the chemistry, but it is my understanding that over-discharge is dangerous because conductive filaments can form in that condition, and short across the cell. Charging a lithium-ion cell that has these filaments will result in a fair amount of heat generation, which for Lion cells is a Very Bad Thing.

The threshold for determining if an over-discharge has occurred is necessarily set to a safe value, but such conservative controllers will prevent you from ever using that battery again, even if it is actually salvageable.

 

[beachycove]

Thanks for the advice.

The reason for asking was simply that I have a Wallstreet battery with newish cells in which, however, I believe the controller to have failed. It came recently from China, it charged fine maybe 5 times, and then, it went stone dead. The fault could be the cells, but my bet is on the electronics.

I also just bought a reasonably mint Pismo with a dead battery, and so I idly wondered about transplanting those already-welded cells from the Wallstreet battery into the Pismo battery.

It seems that it is both dangerous to do this (which I knew, but not that it was seriously dangerous) and electronically ill-advised also (which I suspected), so I will not go there. I have instead ordered a new Pismo battery. I may, however, still try "resuscitating" my dead Wallstreet battery with those new cells by transplanting the controller from a dead battery into it. Fingers crossed, as you never know your luck....

I used the old Wallstreet intensively for several years and have been a big Wallstreet fan ... until I started playing with the Pismo. I'd never had the pleasure before, but the Pismo really is a lovely PowerBook. I think it is going to become my new travelling companion. I even prefer the Pismo's keyboard — not the usual view on the two machines.

 

[Bunsen]

I wonder if you could / super glue the tabs, then use conductive paint to connect the tabs?

You could probably make up a mix of conductive paste with superglue, or preferably a two part epoxy. Thermal paste is often mixed with glue to mount heatsinks.

I found a photographic guide to recelling a Lombard/Pismo battery.

Note though:

Two Years After Doing this Battery Replacement
It has been about two years since I replaced the cells in two Pismo battery packs. These batteries did not last as long as they should have. One pack is completely dead now, and the other only lasts about 30 minutes. I suspect that there is something that needs to be reset when the cells are replaced, but I'm not sure.

 

[Bunsen]

I found a seller in the US who has lithium cells with built in protection circuits. I think 18650 and 4/3A are the same - I remember I found him while looking for cells from my own Lombard. They're only 2200mAh though, and no solder tabs. Cheap though.

Conductive glue with strips should work, or if the image above is correct, maybe they can just drop in. Maybe. I am not a battery expert.