He have a bunch of Gen 1 batteries that are about 5 years old and can’t hold much of a charge anymore. Given the Gen 2 battery delays, we are in a tight spot for batteries that work come the fall. We wanted to see if anyone has successfully opened up the rechargeable batteries and swapped out the battery pack with a new one and were able to reuse? The disclaimer, this is for practicing only. We have opened three of the battery packs without breaking the case and have the tools to solder and do whatever. So curious if anyone has had success doing this, things to look out for, specific battery pack order, ect. (I searched the forum for past posts and didn’t see anything, but also assume I am not the first one to ask / try this)
I think a safer, and ultimately more flexible, solution would be to buy some IQ AA battery holders. There’s a good choice of rechargeable AA batteries (including Li-ion) available now.
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But where is the fun in that, lol.
But on a serious note, the problem with that is given the amount of batteries we’re going to have (I think we have at least eight batteries to swap), we will then have to go by a bunch of chargers to keep those battery circulating versus just using the existing vex chargers for the rechargeable batteries that we have now. Then you have to factor in kids are going to lose batteries, well because kids are kids.
Basically we are at the point where we’re going to try it with one first no matter what and see what happens. So really looking for pointers or gotchas from anyone who is done this so far. As I said, we have all the tools and skilled adults to accomplish this, So really would have to be talked off the ledge of why we shouldn’t.
Below is the battery pack that we purchased that we’re going to test out on one first.
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This will be interesting to follow. Please report back your results.
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Not really sure why doing rechargeable individual AA battery in an approved case is such a big deal. It’s all off the shelf stuff.
OK, it’s your $250 IQ brain to cook.
… with an abundance of common sense too!
@SCFarrell is saying Jump, Jump, Jump 
While this fits your use case, it doesn’t fit anyone else and it’s got a danger factor involved of shorting a fully charged battery pack down. I always twitch at danger things (bottle rocked launchers, Este rocket launchers, spinning an RC prop up to 10,000 RPM with VEX motors and gears, etc) in the name of “science”.
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What @Foster may have meant is use appropriate PPE, the engineering process, document your process and findings.
This isn’t some magical IED, replacing cells is done all the time and is a business for many. It isn’t legal for competition, but, in my opinion, there is nothing wrong with a competent person doing this on a practice battery.
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Please don’t post any details or pictures on the forum. We do not need a 13 year old trying to do this and getting it wrong. There is at least one sensor in the pack the charger needs to read, and it has only been tested with the batteries we use.
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No, what @Foster ment was don’t do this. Taking apart prepackaged battery packs is hard. They are welded with harder metal straps. Which means taking them apart is harder than you think. As @jpearman noted there are sensors taking stock of the battery, they expect certain types of cells.
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Wondering if instead it would be worthwhile to harvest any good cells from the battery pack for use in other projects?
If that is the position, feel free to remove the rest of the replies in this thread and post that it isn’t within the allowable use case of the program. (Including this post)
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Yes, posting any details here would be a bad idea for kids to try and will not post anything else here.
Yes opening the battery packs would be bad for anyone to try and there are risks. That said, If you are interested in how this turns out, you can DM me and can provide updates offline on how this turns out.
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Not going to recommend that. If you are desperate for a battery, grab the $10 case a 6 AA batteries and use that. Frankenmashing battery packs is not recommended.
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While trying to rebuild the IQ Gen 1 battery pack is a bad idea, trying to rebuild the packs on the V5, EXP or IQ Gen 2 batteries is a REALLY bad idea.
IQ Gen 1 uses NiMH cells, which have much lower energy density, but are more forgiving of mechanical abuse.
V5, EXP and IQ Gen 2 all use some variant of lithium cells. If you are trying to open a battery pack with lithium cells and manage to puncture one of the cells, it can quite literally burst into flames (while spewing highly toxic fumes).
LiFePO4 does NOT fail in this manner. (the chemistry of v5, and likely IQ gen2)
Sweeping statements about Lithium chemistries is not accurate in this instance. Older Lithium tech did show this type of failure mode, but implying that all Li-ion batteries will fail this way is disengenous.
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LiFePO4 cells are certainly much less likely to fail in a dangerous fashion than Li-ion. Poking a hole in it or slicing it open is still likely to lead to a BAD outcome.
I am not trying to say that lithium batteries are unsafe. I am simply saying that poking, prying and cutting around lithium cells is a bad idea. Most (if not all) of the safety systems built into lithium batteries assume you haven’t physically poked holes in them…
When used correctly, lithium cells and batteries have become quite safe. They are just less tolerant of abuse (this is part of the reason for rules about NOT using the wrong battery charger, as some lithium chemistries REALLY don’t like being charged wrong).
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