Portable phone charger using RC lipos?
 

Hi Everybody

Long time no post.

I have a question and I think you guys have the knowledge to answer it.

I want to be able to plug some of my lipos into a bec and plug them into my phone so I can basically have a portable charger for my phone. What I would like to have though is a low voltage cutoff and maybe even a fuse. Anyone know of a small bec that has a low voltage cutoff built in or a separate cutoff that I could use?

Note to castle. Add a low voltage cut off to your becs. I know it would be dangerous in RC use but just add lots of warnings or difficult to switch on.

I think I've seen something at HobbyKing like that. But it was just a buzzer/light, not a true cutoff. What you want is something that will literally cut power and external LVCs simply output a neutral throttle signal.

Also, just about all USB chargers need the "programming" pin tied to ground to tell the phone to charge. The chargers specific to each phone has the appropriate resistor built into the molded plug. If you use a normal USB computer cable, the computer (via the driver) tells the phone to charge. Using a normal USB computer cable hooked to 5v won't put most devices into charging mode by itself. I hope all that made sense.

For that to work at all, you would have to plug it into the throttle channel. Either that, or just sound a buzzer (better option IMO).

I believe something from this page will answer part of your Equation.

http://www.all-battery.com/protectiv...terypacks.aspx

One problem I see is, you need to regulate the amperage output from your charging device.

The cellphone contains the actual charging circuit. The power supply is voltage regulated and only current limited by the USB spec of 500mA.

Most of the wall chargers are 1A so they exceed the usb spec. I have a couple of regulators already so all I really need is a LVC. Looking at the Tenergy website I can't seen to find a cut off that cuts off at 9 volts.

My phone uses a standard micro usb plug to charge. Thinking about it now you mention it the easiest thing to do would be to copy the wiring in my car charger. So if that has extra pins grounded I will do the same.

Well, it's not that easy. See, a normal USB cable has 4 wires: +5v, ground, data+, and data- (the data lines are balanced). And it has a shield, which is tied to the metal plug case. But the micro plug itself has a fifth contact, which doesn't have an associated wire in the cable. That contact is left "floating" in a computer USB cable, but in a brand-specific charger, that contact has a resistor tied to the ground wire - and that is done INSIDE the plug molding (surface mount).

For computer USB cables, that 5th contact is left floating, but the computer sets the data+/- lines in such a way (via the driver) to tell the phone to charge.

In stand-alone chargers, there is only 5v and ground wires that go to the plug. The data+/- contact are either floating or resistor set to something (essentially not used), and the 5th contact is tied to a resistor.

The easiest thing would be for you to just get another charger. Unless of course, you can carefully remove the plug molding and add the required itty bitty surface mount resistor between the programming pin and ground.

In the past, I had a mains charger that stopped working. So, I cut the wire and re-used the connector end, which has the programming pin set. Then it was just a matter of using any regulated 5v source.

http://www.ladyada.net/make/mintyboost/

I have one myself, I'm currently using a Tenergy 6600mAh 1S LiIon with a built in PCB board..
Thing rocks!
I can get a good 4-5 charges on my iPod, and 1-2 on my phone on a single charge!
Instead of the two double AA's, I soldered up a JST connection, and hooked the battery into that connection.

I'll grab some pictures afterschool today..

cheaper to just buy them.

this way you have a Solar Lipo charger.
i got 5 and Thay work good for all types of things.
and if you want more power just change out the Lipo cell for a larger one
mine are now 6800mAh

if you look you can get them for low as $6.00 a pop free S/H as i did.

http://66.116.138.89/ebay/crystal_sell/ESOLARC7S.JPG

http://cgi.ebay.com/USB-Solar-Batter...item1e5d6656f5

Or

http://cgi.ebay.com/Solar-Power-Port...item3f04469537

Most definitely very cheap to buy prebuilt, I assume it charges the LiPo inside so you could use it w/o sun?

Building it yourself kind of gives you that "I MADE IT!" feeling.. Once I whipped out my Altoids charger during school one day to help a teacher charge up his phone, everyone stared in awe..

Kinda makes you "cool". :P

This was kind of the plan. I was going to cut up a cable/charger as i bought a whole bunch of them so I could have chargers everywhere. I bought a few too many so giving one the chop is no worries.

Those prebuilt things are good but ordering stuff is effort and I have to wait for ages being here (Aus) and by the time it turns up I will have lost interest. I do like Rawfuls little setup but there is still no lvc and I cant use the hundreds of batteries I already have.

Last night while I was putting my bike away I saw my bike light batteries. I have a few of these and normally I only use one at a time. The big thing about these is that they have a LVC built in. BOOYAA. Now I can do a MacGyver and combine everyday house hold items to build a bomb, I mean phone charger. Double BooYah. It isn't perfect as I won't be able to use my RC batteries but I have enough batteries for my bike light to keep my phone charged for a few days so I think I'll be OK.

you can charge it by usb to

Hmm, there really isn't a LVC; but the battery will auto-cutoff if you just pick up a cheap PCB...
Anyways, do make a new thread with your new project when it's finished!