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geekhack Community => Other Geeky Stuff => Topic started by: suicidal_orange on Sun, 04 October 2015, 15:30:46
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I have a pair of Sennheiser MX-W1 earbuds which take a rechargeable 3.7v 12.5x5mm 40mah Li-ion button cell battery, but one of the batteries barely holds a charge and you can't buy replacements.
(http://images10.newegg.com/ProductImageCompressAll300/26-106-220-09.jpg)
I'm thinking that if I wired up a bigger 3.7v battery it could be attached to discretely hook over my ear, and I'm pretty sure that they wouldn't notice the extra capacity during discharging (feel free to correct me!) but I'm not so comfortable about not burning out the recharge circuit which would probably kill everything given how small it all is.
Does anyone know what it would do if I were to connect a 600mah 10440 battery to a recharge circuit designed for a 40mah battery? My searching only reveals hundreds of people trying to sell me batteries which is not useful!
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someone correct me if im wrong but, i feel like your only obstacle is fitting the 600mah battery. It would in theory pull the same amperage as the 40mah.
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Thanks, you sound about as confident as I am - not quite enough to just do it but seriously tempted.
All it needs is to solder wires to the tabs the button cell connects to and a bit of filing to the plastic case to let them in/out. The 600mah battery is as long as the earpiece so no way it's fitting inside! Not even sure it's worth going that big as the earpieces will outlive the transmitter, but they look safer to put behind my ear than the dodgy looking DIY helicopter ones from China :))
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Is this the wrong size? http://www.batteryspace.com/li-ion-rechargeable-2032-button-cells-lr2032-3-6v-40mah-20d-x-3-2mm-0-14wh-0-012---un-38-3-passed.aspx
Or would one of these fit in? https://www.sparkfun.com/products/11316
Anyhow, you're fine charging a larger cell from that circuit, they limit the charge current, so it will take a lot longer to charge, but it should work fine.
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Thanks Oobly
The first you linked is 20mm and the second 16mm and not round so not going to fit the 12.5mm hole. One factory made these batteries and when they went out of business Sennsheiser (big headphone company) just discontinued the model rather than finding someone else to make them, people have been looking for years without luck so external is the only option.
When you say a lot longer is it just going to charge at, say, 10mah per hour so double the capacity will take take twice as long?
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Utterly off-topic from the question asked in the first post, but if an electrical engineer is reading this:
Can a 12V DC power supply be used to charge an auto battery, albeit very slowly?
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it's probably going to fall out of your ear.. much too heavy..
the older cells are probably just wearing out, if you get new cells, the new cells will / should last much longer.
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it's probably going to fall out of your ear.. much too heavy..
the older cells are probably just wearing out, if you get new cells, the new cells will / should last much longer.
If they made them I would buy them! I've just found some 12.5x2mm but they're only 12mah so even with two stacked up that's quite a cut in capacity.
Pretty sure if I loop the wires over the top of my ear it will stay put...
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it's probably going to fall out of your ear.. much too heavy..
the older cells are probably just wearing out, if you get new cells, the new cells will / should last much longer.
If they made them I would buy them! I've just found some 12.5x2mm but they're only 12mah so even with two stacked up that's quite a cut in capacity.
Pretty sure if I loop the wires over the top of my ear it will stay put...
it might stay on when you're sitting at the chair, but when you start moving about, up and down stairs, etc, that's when the momentum might become too much.
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Utterly off-topic from the question asked in the first post, but if an electrical engineer is reading this:
Can a 12V DC power supply be used to charge an auto battery, albeit very slowly?
My guess is that, without any current limiting circuitry, the power supply would burn out/fuse out because the battery would try to draw too much juice.
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To my knowledge the limiting factor is voltage. The current will determine how fast the charge cycle is,but the voltage will control what you are charging the cells to essentially.
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Thanks Oobly
The first you linked is 20mm and the second 16mm and not round so not going to fit the 12.5mm hole. One factory made these batteries and when they went out of business Sennsheiser (big headphone company) just discontinued the model rather than finding someone else to make them, people have been looking for years without luck so external is the only option.
When you say a lot longer is it just going to charge at, say, 10mah per hour so double the capacity will take take twice as long?
You're welcome.
Let's say the originals are 40mAh and have a 1C charge rating. That means they can take a minimum of 1 hour to fully charge with the charger supplying a maximum of 40mA charge current. At 40mA charge current a 600mAh cell will take 600/40 = 15 hours to charge. If the original cells were only rated at 0.25C or the charger were designed to keep well within the cell ratings and took 4 hours to charge, the charge current would be around 10mA and it would take 60 hours to charge a 600mAh on that.
You could also get a separate charger for the 600mAh cells and use a removable plug so you can charge them quicker if it's inconvenient to leave them charging for so long. I have a range of different cells and packs for my hobbies (from 1 cell 120mAh to 4 cell 2200mAh) so I have one of these: http://www.hobbyking.com/hobbyking/store/__5548__IMAX_B6_50W_5A_Charger_Discharger_1_6_Cells_GENUINE_.html
Can be used for any type of rechargable (LiIon, LiPoly, LiFe, NiCd, NiMH) up to 6 cells. Includes discharge and cell balancing and is affordable, but needs an external DC power supply to power it.
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The "good" remaining battery takes about an hour to charge but who knows how full it's getting. Overnight would be acceptable but 15 hours is really pushing it, and that's best case scenario...
Between your explanation of li-ion charging and tp4's concerns over weight issues I think 10280 (around 200mAh according to wikipedia) would be a good compromise. I can't actually find any in the UK but will continue searching :)
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These little guys are 50mAh, 18x14x5.6mm and 1.67g in weight with the cell itself being 13.8x13.8x5.6:
http://www.indoorflyer.co.uk/fr-50mah-cell-116-p.asp
http://robotbirds.com/catalog/product_info.php?cPath=63_412&products_id=3012
Still won't fit inside the units, but light and small.
These may be a handy form factor for you, they come with a connected socket: http://www.hobbyking.co.uk/hobbyking/store/__34650__Turnigy_nano_tech_130mah_1S_25_40C_Lipo_Pack_Kyosho_Eflite_Parkzone_UK_Warehouse_.html
These connectors plug into them: http://www.hobbyking.co.uk/hobbyking/store/__31812__2_Pin_6_x_Pico_Plug_Charging_Set_Eflite_compatible_UK_Warehouse_.html
Anyway, let us know how the project goes.
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Ooh random sizes... very nice, thanks :D
I'm liking the look of these (http://www.hobbyking.co.uk/hobbyking/store/uh_viewItem.asp?idProduct=37550) as round would be more comfortable behind the ear but they've only got one in stock in the UK. The ones you linked with higher capacity and a connector are tempting and I sat on the page so long a popup appeared offering a discount (on a £0.90 product :)))
Will have a proper look tonight with the aim of getting this done over the weekend, seems a waste to only buy a couple of batteries from such an interesting looking site!
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You could also try over on candlepowerforums.com. CPF is to batteries what GH is to keyboards.
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I'm not sure that this topic is still actual) I found that item - lir1254:
aliexpress.com/item/2-lir1254-3-6/32837502625.html
Now I use 2x lir1220, want to order this batteries.
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Thanks Haier. The LIR1254 worked perfectly. Well had to cram in a little. After the 1st time, was easy to put in and take out.
I also bought LIR1220 but didn't test, look to be same diameter as the LIR1254 but probably needed to drop in 2 or 3 to make to allow them to stay in and fit. The LIR1254 only needed 1 battery.
But yeah finally get to use these, first time since 2013.... No one probably uses these anymore.... I had a set I bought back in 2013, that came 1 battery dead. At time replacement battery were no longer in production and were out of stock everywhere. So it just sat there unused. Very glad to get these up and running. Bulkier than more recent wireless earbuds. And probably not as great sounding either, but always loved how these looked. Thanks again
I'm not sure that this topic is still actual) I found that item - lir1254:
aliexpress.com/item/2-lir1254-3-6/32837502625.html
Now I use 2x lir1220, want to order this batteries.
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Wow, here's a blast from the past!
Having chosen my batteries many years ago I opened the box to find both earpieces were missing. I still have the box containing everything else but the earpieces themselves have not appeared...
Belated thanks to Haier, and glad to see at least one pair was saved by this thread :thumb: