Can somebody please give me all the inns and outs about repacking my laptop battery. What kind of Spot/resistance welder do i require? Is there a special welder for lithium ion batteries? What are the proceedures for this welding and safety tips? all info is gladly welcome as i am just learning my way around this new hobby and lastly were are the places i can purchase this equipement.
What make/model laptop? Where do you plan to get the replacement cells?
I ask because the Li-ion battery in my ThinkPad is toast and I am considering building an NiMH pack. Todays NiMH cells are pretty close in capacity to the factory Li-ion pack and are a whole bunch cheaper.
I have been considering making some sort of holder into which I could just pop in standard AA cells.
You can simply scrape/sand the terminals and wash off with alcohol and take a high-wattage soldering iron and solder to the terminals. Don't use a low-wattage iron as it will require you to leave it on the terminals too long and it will harm the battery. In other words, get on and get off quickly.
Building a holder is fine as long as excellent contact is made to large-area electrodes and not some pin point.
I'd ask myself the charging current and the internal electronics needed. In most battery packs now are two or more IC's that talk to the computer when beat upon the head and provide charging rates based on real time feedback.
I thought a picture was in the current issue of design news -
Ive got an acer laptop i want to repack, aswell as my nokia 3310.As to youre question of where i am going to get my replacement cells i dont know yet, but im browsing the net to see where i might find them.Prefrably lithium cells.
I've been messin around with this for a couple of years. I've never had a really successful repack experience, but I've been using surplus cells. There are MANY more issues than you'd imagine in repacking battery packs.
Where are you gonna get the cells? If you find a place that will sell you a few Lithium Ion cells at a reasonable price, please let me know. Make sure you get the right Kind of cells. There are at least two types in popular use. You MUST get the right one for the battery monitor chip that's in the pack or you may explode the battery and your laptop and maybe yorself. The laptop manufacturer nor the pack vendor nor anyone else is gonna help you figure this out because of the liability issues.
I once blew up a NiMH pack. Managed to get the thing out of the laptop before it exploded. If I hadn't been wearing glasses, I'd be typing this on a braille computer.
During the transition from NiMH to Li-Ion, there were laptops that could accept either pack. My Toshiba 2100 and 400CDT are such animals. BUT, the internals of the pack are different. You CANNOT put a different type of cell from what was originally in the pack.
Depending on how smart (or dumb, depending on your viewpoint) the battery protection and charge control circuits are, you can make them go brain dead by disconnecting the cells. Some have said you can hook up an external supply to the controller while you replace the cells, just don't let the voltage go down. I've got a pair of Gateway packs that went flat and now won't charge. They'll run the computer just fine if charged externally, but they don't have the secret password that the laptop needs to allow them to charge. Anybody got info on packs for Gateway Solo 2100?
How do you hook them up? Soldering on cells is a no-no. First, the cells will barely fit in the pack. Even a tiny lump of solder will make them too tall to fit back in the plastic.
There's a vent that is supposed to prevent explosion if overcharged. When you heat the top of the cell, you're likely to damage the vent. If the cell doesn't fail immediately, it will fail later as it dries out. Yes, people will tell you they've done it successfully. I've done it hundreds of times myself on surplus ten-cent cells that I put in stuff I didn't care much about. Reliabiltiy was not high.
Spot welding is the way to go. I tried building one out of a microwave oven transformer. Worked...sorta...but was not repeatable. Capacitive discharge is the way to go. I managed to get a Unitek 125 for $15 and built the series head for it. At 80 joules, the spot welds are very nice. Then you have to have something to weld. .005" Nickel strip isn't easy to come by in small quantities. I found a bin of surplus battery tabs but the only other place was Batteries Plus. They took pity on me and sold me a foot of the stuff for a buck.
So, if you have lots of free time on your hands and a LOT of packs to rebuild, go for it. If your time has ANY value at all and you only need one pack, go buy a new one off ebay.
I'd be glad to discuss this further...I have lots of free time ;-)
Just remember that the different battery types - Li-ion, NiCd, NiMH, etc. all have unique charging currents and limit in-rush currents..... Not a simple swap.
I'd be sure to take apart the old one and see what is there - and buy the same or buy a charger for that type of battery. The latter is likely what you need to do. I don't like NiCd for anything anymore - the other two are just fine - fuel cell better, just not there yet. But I thought I saw one at Fry's the other day - a play with one type.
I am aware of this. My laptop is an IBM ThinkPad 385XD that was available with either NiMH or Li-ion. There are a mess of contacts between the computer and the battery pack. If I can't find any documentation, I'll dismantle the dead Li-ion pack and see what is there.
An alternative plan is to make a holder for AAs and use a separate charger. This would have the advantage of being able to have more than one pack.