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Hopo28

Google Home Mini Battery Pack

by Hopo28 Feb 27, 2018
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NOt perfect, but it should work for most people

Just a FYI; there's no such thing as a 9800mAh 18650 cell.

The 18650 form factor tops out at 3000-3300, and that's only if you buy genuine Samsung, Sony, Panasonic or the few other very reputable manufacturers. The physical size of the cell is simply not able to hold more energy than that, it's the limit of the chemical's ability to store energy for the given size. Anything labeled over that is simply lying on the packaging to you so you buy them

You have have a sketch of the circuit diagram you could share do you?

sorry for not getting back to you sooner, yes, i have added a rough wiring guide to the thing files. I hope its clear enough, it was just a 5 min sketch.
All the parts are available from ebay.

OK got it printed and all fits fine. You were even so clever that you made the port hole so a USB C would not fit through.
So please share with us, what is your background in 3D modeling, and tell us how you did the measurements, etc., and anything
else you want to share with your fans!

Great idea. I have some extra batteries, and am printing up your design now. This will cost me almost nothing to make, but if I bought a factory made battery base it would cost more than the G mini did. Thanks so much for your design!

Great. Thanks for sharing. I’ve been looking for exactly that circuit, and it’s cheap! I printed this last night and it looks great. Nice work. I made a slight mod and raised the vertical ends at both ends the batteries, so I could put in a “bus” strip of copper for connecting the batteries. The batteries I’m using have a raised terminal on the positive end. Thanks again. Z

did you upload this somewhere?

Can I ask what circuit you used for charging this pack? I'm not very knowledgeable in charging circuit design. Is this an "off the shelf" circuit?

Thanks in advance.
PB

Yes, its an off-the-shelf unit, uses a TP4056 chip, i searched eBay for "charge protection board" to find it, this is the one: https://www.ebay.co.uk/itm/202372163920

very handy :-)

I'm thinking about the possibility of put a QI wireless charger for the battery pack at the bottom.

Its a good idea; I did that with a later stand i made (https://www.thingiverse.com/thing:2807221), it works pretty well.

If you put the pickup coil in the enclosure, make sure the bottom is as thin as possible to reduce the distance between coils.

Also be aware that QI charging can generate heat, it may be necessary to space the batteries away from the pickup coil to prevent them getting too hot.

Google Home Mini wireless charging battery-pack 45 degree stand
by Hopo28

how long do the batteries last?

I calculated about 5 hours+ playing music, I've never needed it to play for that long so far so Im not sure how long it will last in practice, but it managed 2 hours with no problem.
as tkmarsh said, take the ideal calculated values with a pinch of salt, 5-6 hours is a realistic expectation subject to the efficiency of your boost circuit and GHM volume etc.

Just checked the power consumption there, the Google Home Mini seems to use about 200-300mA while idle and about 400-500mA while playing some loud music. Although I'm only using a USB charger doctor, so the values are all over the place.

So if each of those cells is approx 1500mAh each, I think you'd get roughly about 9 hours of loud music and just over half a day of idling with 3 of them (4500mAh).

That's not really accounting for power losses and what not, so I'd take it with a bag of salt and assume a couple hours less maybe.

Not much of an answer, but I hope it helps some how.