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Large Portable DC Bank
#11
(06-22-2017, 11:43 PM)Dan Lim Wrote: If your activity is outdoor most of the time.... another alternative is to use a small foldable 70-80W Solar Panel USB charger... is light and portable.

It is alll indoor, the season starts in late Novembers and ends between April and June depending on how well they do. Thanks though!

(06-23-2017, 05:38 PM)John Wrote:
(06-22-2017, 04:26 PM)ridiculously_necessary Wrote: I am still short on cells, and time, at the moment. I have about 70 so far, and have two projects planned. For one, I want to build a high capacity portable charger. My daughter is involved in club volleyball and it is not uncommon to go 12 hours not being near a USB charger. I am looking into making a high capacity portable box, probably coming in around 80k mah. Just cause I can.

Check my thinking... I can wire this up, all positives, and all negatives, providing a bank wide voltage of 4.x. Then I want to locate some of those USB charger chips, around 10x and wire those up. Does anyone see a problem using this method? From what I can tell of those cheap single cell 18650 pocket chargers, they must step up the voltage of the battery to 5v at the cost of capacity? Then find a method to charge the bank as well. Are there any flaws to my thinking here?

Or....

Just get a bunch of these off of ebay.  I work with kids doing robotics.  I got 5 of these and I filled them with 2500 mah cells.  So I guess that I am at 50k mah...

They are easy to charge from any USB port.  And in a crunch I can just swap out flat cells for freshly recharged cells, giving and effective recharge time of 0 minutes.

http://www.ebay.com/itm/4-Slot-18650-Bat...2749.l2649

 



That is the exact unit I am currently using. I bought it to mess with before I got a nice charger that could convey voltage and capacity. I really like it, I lucked out on a salvage and found some 3500mah cells that now rate 3000mah. So I take it to all tournaments and camping. But it's only good for so many charges. My plan is to build a unit with several ports that the kids can charge their phones on, as well as parents cameras they are using to film.
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#12
So I am finally getting around to this! I could use some help selecting the USB-A portion though. There seem to be a ton of options, is there a preferred output module you all use? 2A or 3A out 5v? And is there a 2.x volt protection built in to them or do I have to do that with a separate module? Looking to have about 10 ports.
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#13
(04-24-2019, 05:38 PM)ridiculously_necessary Wrote: So I am finally getting around to this! I could use some help selecting the USB-A portion though. There seem to be a ton of options, is there a preferred output module you all use? 2A or 3A out 5v? And is there a 2.x volt protection built in to them or do I have to do that with a separate module? Looking to have about 10 ports.

Such a device is not going to be available. 10 ports from a 1p battery is going to be like 20a+, counting for boost as well. I would recommend building a 3S pack and bucking the voltage down. Most lighter socket style adapters will operate at 10v or even less.

I haven't seen a power bank with more that 4 ports. I don't really see much point either. Even my 6 Cell 15ah pack only has 2 ports.

Yes, I believe that all DIY USB power banks have under-voltage protection.
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#14
And even paralleled cells can/should get a BMS, its so cheap you should not go without. Its your last rescue against overvoltage and undervoltage, which would ruin all your cells and work in one go.
No Bank without BMS!

https://www.ebay.com/itm/10A-3-7V-PCB-BM...2367169597

Look for "BMS 1s". and you will get plenty in different fashions ( for 1 bank)

If you have 2 in serial search "...2s", 3 in serial "..3s", and 4 in serial.... Guess Big Grin .
1 kWp in Test
4 kWh battery target - plus Mobile Home battery
Ultra low cost
Electronics ? No clue. Am machinery engineer.
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#15
(04-26-2019, 02:37 AM)Geek Wrote:
(04-24-2019, 05:38 PM)ridiculously_necessary Wrote: So I am finally getting around to this! I could use some help selecting the USB-A portion though. There seem to be a ton of options, is there a preferred output module you all use? 2A or 3A out 5v? And is there a 2.x volt protection built in to them or do I have to do that with a separate module? Looking to have about 10 ports.

Such a device is not going to be available. 10 ports from a 1p battery is going to be like 20a+, counting for boost as well. I would recommend building a 3S pack and bucking the voltage down. Most lighter socket style adapters will operate at 10v or even less.

I haven't seen a power bank with more that 4 ports. I don't really see much point either. Even my 6 Cell 15ah pack only has 2 ports.

Yes, I believe that all DIY USB power banks have under-voltage protection.

Thanks, good to revisit. I was thinking of 36-49 cells, and that 20+a would be ok. But, no reason, I don't think, I wouldn't be able to go 3s. Reason for the number of ports is we could easily have 6-10 devices plugged in at a time.

(04-26-2019, 01:41 PM)Cherry67 Wrote: And even paralleled cells can/should get a BMS, its so cheap you should not go without. Its your last rescue against overvoltage and undervoltage, which would ruin all your cells and work in one go.
No Bank without BMS!

https://www.ebay.com/itm/10A-3-7V-PCB-BM...2367169597

Look for "BMS 1s". and you will get plenty in different fashions ( for 1 bank)

If you have 2 in serial search "...2s", 3 in serial "..3s", and 4 in serial.... Guess Big Grin .

That's the answer I'm looking for. So, would a BMS be wired between the charge, and discharge points? I wouldn't need one for each cell would i? Then one for each bank should I go 3s?
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#16
Well, do you need QC 3.0 operation?

I also think you should go either 1S, or 4S if you can.
The power of lithium ion is in our hands!
We'll show them what we're made of!
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#17
I personally use these $8.32 8 cell holders. It has a percentage readout, 1 amp & 2 amp USB, and two micro usb simultaneous charging ports. Edit: They are not easy to open back up so use good batteries.
I paired them with 2700mah fake LG HG2 cells to get a little over 21,600 mah. $21.16 for 10.


https://www.amazon.com/gp/product/B075N6...UTF8&psc=1

https://www.aliexpress.com/item/6pcs-lot...st=ae803_4
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