One use for salvaged laptop batteries - supercharged mattress inflater!

Batteries and Chargers Rechargeable Batteries
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not very flashlight related, but I know that there's a bunch of people on here, like myself, who compulsively salvage laptop batteries to add to their Smaug like pile of cells :) So when my wife bought a Coleman mattress inflater from a garage sale for $2 with what we found out later to be a duff battery, it was an obvious destination for some of my cell stash.

Original

pile of replacement batteries. I should have used matched cells (for reasons I'll get into later), but I wanted to keep my matched sets for some powertool packs I'm going to make.

getting wired up

all installed, with balance tap added. I tried a couple of times to add a 2S PCB, but managed to burn holes in both of them (literally, with magic smoke too), so that plan went in the circular file.

sealed up with voltage monitor velcroed on (I plan to use it on my powertool packs too)

balance charging (after I traced a charging problem to a reverse polarity protection diode in the +ve charge wire, grr)

and around 5min of blowing time later

:D

It's like a little shreaking mini-leaf blower. I don't know how much power the motor is consuming (or how long it'll last running at 7.4V!), but it pulls the voltage down on those cells something fierce. On the last mattress, the two banks were reading ~3.3V and 3.45V, yet when I recharged the battery I found that I'd only used 1500mAh of capacity. As total capacity is around 8Ah, that's some huge voltage sag for a 2S4P battery! The original set up must have used less than 6A continuous as that's what the switch is rated for, but the new set up must be pulling more than that.

Anyway, at the end it turned out to be a really fun project, even if it didn't feel that way during parts of it. It's also useful for doing model photoshoots (puffing up the model's hair) and chasing the kids around the house :)

2

love it, next is a brushless ducted fan for real horse power J)

3

Wow! Nice job!

4

that’s scary - I’m already worried about popping mattresses as it is! Found another use for it already - annoying the lab technician at work :slight_smile:

thanks!

5

great mod !

I hate that 6V lead acid batteries… laptop pulls rocks ! :smiley:

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Nice up-cycling job there !

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thanks! The wife was happy to find more space in the fridge salad draw too :slight_smile: I just remembered, the SLA battery had “1.25A initial current” written on it, so I must be pumping many times that through the motor - no wonder it spins so fast J) I might need to add some heatsinks to the switch now though…

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Its crazy how small that motor is inside there

Nice work.

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Nah, that motors huge, look up some of the small brushless rc motors, I had one smaller in diamter than a 1 pound coin, it spun a 3” prop at 46000 rpm and impressively destroyed my thumb when “interfered” with :open_mouth:

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well, it survived this weekend’s camping trip just fine, inflating and deflating 3 queen size mattresses (including one double thick one), plus topping up one of them periodically. It was pretty fun using it to help get a camp fire going too.

Unfortunately the 2 parallel banks aren’t well matched, as one pulls down much further than the other, so I may have to swap some cells around (mix the two banks) or rebuild it with some other cells. Then again, for how much it’ll get used, it’ll probably be fine just as it is. I just can’t get my head around how much current the motor must be drawing to pull the voltage on a 2S4P ~8Ah pack from 8V resting to 6V under load! When I recharged it, just over 2100mAh went in. Crazy stuff.

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Best mod I’ve read all year not flashlight related. Supercharged air mattress inflator. We all should have one. How many times have we pumped up air beds or the like by hand pump or even the 12 volt car blowers and cursed every minute as the air seemed to escape quicker than it goes in. l’ll take one.

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thanks MRsDNF! You can even use it for fire priming in glass blowing, according to my cousin-in-law :slight_smile: Postage would probably be prohibitive, but if you have one I’ll mod it for you :smiley:

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Theres another thought. Flame thrower. This gets better. I think its time for TexasPyro to step in. I’ll have to study up on the likes off multi batteries in series and parallel configuration as I dont understand it at all. Cheers.

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hmm, that’s stepping a little too far from the world of crazy into the world of missing fingers :slight_smile:

the series vs. parallel battery thing is pretty straightforward. You have as many batteries in series as you need for your source (6V motor in this case), then you add enough batteries in parallel to share the load. So if you have a tiny load, say 1A, then 2 cells in series (2S1P) is plenty. If you have a 10A load (which I have a feeling this is, if not more), that would demolish that battery and you’d get no usable runtime at all as it would pull the voltage down to 3V per cell in an instant. So then you add more cells in parallel until the current draw per cell is within the range it can cope with. So, in my case 4 cells in parallel isn’t enough share the load and the cell voltage sags badly, although one bank is far weaker than the other.

If I were to do it properly and actually spend money on something (gasp!), I’d use some high drain (20C+) li-po cells instead. Capacity might be a smidge lower than new li-ions, but usable capacity would be far higher and I’d need fewer cells.

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Thanks Mr muppet. I’ve just printed the explanation out as I will have to read it a 100 times for it to start making sense. I could keep masking questions but just not now. :slight_smile:

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I just found this old post but I think this is really nice work. I dont think you can make a mattress inflater supercharger like this

17

THX! Great mod.

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Yeap! Great mod. :nerd_face:

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I read this post some time ago. We don’t car camp too often, and as such our air mattress just sits for the most part. But we have a trip coming up in a couple weeks, so I decide to fool around with the air mattress pump. filling the air mattress with the shop vac takes about 27 seconds, but I’m not bringing that camping. First, I did a little test. 4 1.5V D cell batteries power my Coleman 4D pump. When the pump is on, best I can tell I get about 1.5V to the motor, and about 3A. It would work that way, but what’s the fun in that?

So I took a power tool cell I got charged to 4.0V, and put it in my single cell charger. Used some aluminum foil to create tabs, and connected the battery directly to the motor through short clip leads. The battery drops to about 3.3V, and delivers about 5A to the motor. Much faster. I’m sure I can make this even better, but I’ll likely just use it like this for the near term.

Can’t imagine putting two cells in series. I will likely try one of my new 30Q cells at some point to see how they do, as it seems like I could do better than a 0.7V drop in the cell. May be my setup also, who knows. Fun stuff though!

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Yeah, aluminium foil isn’t exactly the best way to connect them. :slight_smile: