Andy's Postbag and random ebay links

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RogerClark
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Re: Andy's Postbag and random ebay links

Post by RogerClark » Tue Feb 06, 2018 7:39 pm

I have both the cynlindrical and the rectangular ( flat ) style of batteries from laptops.

I presumed it was just the shape that was different.

The rectangular ones where easier to work with, as they had smaller interconnecting straps, and hence were easier to cut apart.

Drill power packs are much more difficult to extract the batteries from. In fact I have not managed it yet.

I will need to search the net looking for tutorials and methods to extract the batteries, as they are firmly welded in at each end by straps as wide as the battery :-(

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ahull
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Re: Andy's Postbag and random ebay links

Post by ahull » Tue Feb 06, 2018 9:29 pm

I just dive in with the tin snips, while wearing gloves.. my main safety precaution is to do this outdoors in case I need to throw an angry hissing spitting battery pack a safe distance away. Safety squints might also be a good idea, but I tend to rely on my reading glasses, which I need anyway to ensure I only remove the metal straps and none of my precious digits. Only being able to count up to nine is too high a price to pay for a bunch of rechargeable batteries. ;)

Proceed as follows. Wear gloves. Cut the straps at a convenient point to liberate all of the cells, while avoiding as much as possible the embarrassment of welding the tin snips to the battery by shorting anything out, then grab each of the still welded stubs of strap with a pair of long nosed pliers, and roll it up towards the weld, a bit like opening a sardine can. Once you have it rolled back to the spot weld, then use excessive force to break the weld, continue rolling to the next spot weld, rinse repeat. Most packs only have a couple of small spot welds per tab. Oh.. and did I say wear gloves.. 'cos not only can you burn your hands with red hot batteries, chop off your digits with tin snips, but you have the added peril of ripping your hands apart with razor sharp bits of freshly cut scrap metal. Driving yourself to casualty with blood dripping from the end of one you recently severed piggies is not a good way to spend a Saturday night.

The sharp metal is by far the biggest hazard, LiPos actually take a lot of abuse before they get really angry and catch fire or explode. Despite my best efforts, the most impressive thing I've managed to do so far is inflate a pouch cell like a balloon, having previously left it outside in sub zero temperatures, completely discharged (to <0.5V). Despite charging it at a very low current (around 100mA) it was not happy, and slowly inflated as I was watching. Needless to say I cut the power and flung it outside, but it did nothing else dramatic after that, even when I subsequently stabbed it with a box cutter and proceeded to do an autopsy on it.
- Andy Hull -

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RogerClark
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Re: Andy's Postbag and random ebay links

Post by RogerClark » Tue Feb 06, 2018 10:09 pm

Andy

Thanks for the tips.

Doing it outside on a concrete floor with eye protection and wearing thick gloves sounds a good idea
I some knife proof gloves, designed for fishing, which I think may serve the purpose, and if not I have some old leather motorcycling gloves.

I have tin snips, but I was hoping to re-purpose the whole battery pack from the drill as it has a self contained charger / battery management board, which could come in handy.

So I may need to develop an alternative approach

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Re: Andy's Postbag and random ebay links

Post by ahull » Tue Feb 06, 2018 11:40 pm

RogerClark wrote:
Tue Feb 06, 2018 10:09 pm
Andy

Thanks for the tips.

Doing it outside on a concrete floor with eye protection and wearing thick gloves sounds a good idea
I some knife proof gloves, designed for fishing, which I think may serve the purpose, and if not I have some old leather motorcycling gloves.

I have tin snips, but I was hoping to re-purpose the whole battery pack from the drill as it has a self contained charger / battery management board, which could come in handy.

So I may need to develop an alternative approach
I've seen a couple of 3d printed adapters to allow battery packs from brand A tool to be used on brand B, so that might be the way forward, print an adapter plate to let you connect the thing to whatever your project requires (XT-60 lipo plugs or whatever).

Here is an example of the sort of "thing" I'm talking about -> https://www.thingiverse.com/thing:19806

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- Andy Hull -

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RogerClark
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Re: Andy's Postbag and random ebay links

Post by RogerClark » Tue Feb 06, 2018 11:47 pm

Interesting...

Actually, I found that a LiPo power pack, which someone had thown away, into the recycling , worked OK on a different drill that I already have

The problem is that 2 of the 4 cells in the lipo pack are dead

But I have 2 spare cells

So I was hoping to repair the LiPo pack (from the recycling) and use it in my old drills . I think technically there are not exactly the same voltage, but the drills seem to be able to withstand mild over-volting.

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Re: Andy's Postbag and random ebay links

Post by ahull » Wed Feb 07, 2018 12:01 am

You could go down the route of building your own spot welder, but I suspect that way madness lies.

You could *carefully* (and I do mean carefully) drill out the spot welds to the depth of the metal straps with a Dremel and a sharp bit, this should allow you to pop out the duff cells (assuming the geometry of the pack allows). I don't need to remind you not to puncture the cells. Dead or alive, they still contain major quantities of angry pixies surrounded by interestingly inflammable (or flammable, depending on which flavour of English is favoured in the part world you are from) electrolyte.

Then *quickly* solder the new ones in place of the old ones. This means.. lots of flux, and use your biggest battleship capable soldering iron, and leaded solder (lower melting point) to tin everything first, then quickly sweat them together with the iron. What could possibly go wrong?! ;) Besides you got the pack for free, and everyone needs a little LiPo related peril in their lives every so often.

- Andy Hull -

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Re: Andy's Postbag and random ebay links

Post by RogerClark » Wed Feb 07, 2018 12:07 am

I was considering using the dremmel angle grinder disk to cut through the straps, as I can do that a bit away from the batteries

Then solder the new cells in place using thick wire.

Over a short distance e.g. 1 to 2cm I don't think the volt drop even at 20A should be that bad.

The worst case is those cells get less hammered than the others

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Re: Andy's Postbag and random ebay links

Post by mrburnette » Wed Feb 07, 2018 3:52 am

Most older packs use nickel straps spot welded to the cells. When possible, I use tin snips to cut the strap in half. I have old straps from dead packs and use a short piece to solder a bridge between the replacement cell. Nickel solders very well.

If needed, nickel plated steel strips can be easily purchased from eBay. Big budget folks can buy solid nickel straps.

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Re: Andy's Postbag and random ebay links

Post by RogerClark » Wed Feb 07, 2018 6:12 am

Thanks Ray

I've noticed that the straps seem to be solderable on most of these battery packs. Its just that they suck away a lot of heat.

I have a lighter fluid powered soldering iron that I sometimes use for this, as kicks out loads of heat ;-)

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Re: Andy's Postbag and random ebay links

Post by mrburnette » Wed Feb 07, 2018 3:31 pm

I have a lighter fluid powered soldering iron that I sometimes use for this, as kicks out loads of heat ;-)
Obviously, we missed out on Elon's big sale of high-temperature soldering tools ...

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