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Author Topic: 5V supply help needed  (Read 4313 times)
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must not be using the meter properly, but i doubt it, it worked fine on testing a 5V fan, but not usb.  I'll try again, I'm going to cut a new cable, should eliminate potential error
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ok, so I tested most of my parts, used datasheets for the rest, if everything pulls peak power its close to 1950mA, but not everything will be at peak at the same time, if ever, closer "run values" are more like 1400, if the main processor stays running full steam and everything else settles.
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Sounding like a pretty good size battery. I'd design for at least 2A and an 8-hour runtime, to give some headroom and allow for battery aging. Total energy the battery needs to deliver to the 5V load is 80Wh. Assuming a 3.7V LiPo, that'd be about 21.6Ah. Then figuring 90% efficiency for a boost converter to bring it up to 5V and we're at just slightly over 24Ah. Time to start studying datasheets for batteries, charge controllers, and boost controllers/regulators.
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Thanks for adding that up for me.  I'll start digging more in depth, I'll post what I find.
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So I'm thinking in the first wave of searching, 8 of these should meet those requirements.  Hooked up in parallel should give me 24AH.
http://www.batteryjunction.com/ultrafire-brc-18650.html

I'm still looking for smaller or flatter, but those are a good first round pick i think.

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So I'm thinking in the first wave of searching, 8 of these should meet those requirements.  Hooked up in parallel should give me 24AH.
http://www.batteryjunction.com/ultrafire-brc-18650.html

I'm still looking for smaller or flatter, but those are a good first round pick i think.

I am certainly not an expert on Lithium batteries, but I think there are some considerations when connecting them in parallel. Note the comment on the cells above:

Quote
These fully protected cells simplify usage with their integrated PCB. Perfect for your single cell application these cells are not for pack building as doing so will defeat the PCB protection which is matched to the correct voltage on a single cell. If you are building a pack please choose one of our other cells and the appropriate PCB.
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DOH, i definitely missed that, well, at least I've found "pack friendly" 2.6AH in the same size.
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So just to make sure I'm understanding this, if I use something like this:
https://www.sparkfun.com/products/8483

and hook up say, 10 of them, in parallel, then a single charge circuit would be sufficient?  I'm also looking at several of the 18650 style batteries, quite a capacity to reach, I'm trying to get around 20AH at a minimum, but reaching the goal would be even better.
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 How about a USB power pack? They come in all shapes and sizes and put out voltage on a USB port.

Here is just an example. http://www.ebay.com/itm/5000mAh-2-USB-output-Power-Bank-External-Battery-Pack-for-ipad-iphone-Mobile-/270988783171?pt=PDA_Accessories&hash=item3f1830ae43
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So just to make sure I'm understanding this, if I use something like this:
https://www.sparkfun.com/products/8483

and hook up say, 10 of them, in parallel, then a single charge circuit would be sufficient?  I'm also looking at several of the 18650 style batteries, quite a capacity to reach, I'm trying to get around 20AH at a minimum, but reaching the goal would be even better.

Like the others, they may not be designed to be used in parallel. I took a quick spin through the datasheets, both for the battery and for the built-in protection circuit and didn't find them very enlightening. Unfortunately, like I said, I'm not a Lithium battery expert. Maybe someone else on the forum can chime in here. I'd be very careful to use them properly and charge them properly.
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Cycle, that's what I have, if you scroll up I explained my reasons for wanting my own circuit.  Jack thanks for the help.  I'll keep an eye out to see what else I can find, I'm hoping for a single cell or dual at most, but that's almost impossible.  If only nimh or nicad were as light and had the capacity of lithium ;D
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Found it, I'm bad at all the mumbo jumbo, but these are made for pack building, I just need to design a charge circuit

http://www.batteryjunction.com/tenergy-18650-tab-2600.html
http://www.tenergy.com/30005

I'm guessing I still need a protection circuit for each cell though right?
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  From what I have read..... The main thing to worry about with Lipo batteries is overcharging and under charge.  With that information, you could have wires going to positive and negative to each cell to monitor the voltage of the individual cells. Then, use your Arduino or a ATTiny84 to measure the voltage and turn the charger on and off or turn off the load on the battery.

 As far as short circuit protection is concerned I would use a cheap glass fuse or whatever is handy.

Those PCB protection devices found in your link would get pricey if you plan to make a lot of these battery packs. On the other hand, it may be a wash if you have to make additional circuits to do the same job.
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So I've found the battery, but I'm still a little confused on how to hook up teh charge circuit when building a pack.  Do I only need one MCP73843? Or is that all together teh wrong IC for this?
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