Large Portable DC Bank

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ridiculously_necessary

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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?
 
You should be fine using one of those 5v units you mentioned. Then just parallel a ton of cells together. You'll be wise to put a separate voltage meter to monitor low end voltage so you don't drain below 3v.
 
Toochi84 said:
You should be fine using one of those 5v units you mentioned. Then just parallel a ton of cells together. You'll be wise to put a separate voltage meter to monitor low end voltage so you don't drain below 3v.
Click to expand...

Good point, thanks! Those little chips probably contain a meter anyway, but, in either case, do you have any you recommend? Or would I be ok to just find any good inexpensive meter with good reviews?
 
Just remember that the more cells in parallel, the less mA each one will get. If your charger puts out 1A max, then with 10 cells each cell will get a max of 100mA. If you have 20 cells, each will only get 50mA. That equates to a longer charge time.
Also note it is not good practice to parallel the chargers as they are not in sync with each other. Meaning, with two chargers reading 1 cell, 1 charger may see 4.121V, the other charger may see 4.128V. This may not seem like a lot, but if the 2nd charger got the cells to 4.2V and shut off, the 1st charger will continue to pump power into the pack and essentially over charge the cells.

Or, another way to look at it:
Each charger charges at 1A. You put 5 chargers on the pack connected in parallel. You figure based on those numbers it will take an hr to charge (assuming you know the mAh of the pack). Well, as the pack is charged, the chargers will start shutting down at different times. Your charge time is not increased as they don't read the same voltage and as each charger shuts down, there's less amps going into the pack.

Just something to think about.
What pocket chargers were you referring to, btw. Are they TP4056 modules we've been using?
 
Toochi84 said:
You can get them for $1-$2each on eBay. Just search "mini digital voltmeter" make sure you find the one that has the adjuster pot on the back. The volt range should be 2.5-30 I believe

Example:
There are other colors around, just browse.

http://www.ebay.com/itm/New-ONE-Min...709055?hash=item283816c87f:g:55oAAOSwDrNZR1ru
Click to expand...

Thanks! This I assume just wires up between the batteries and the USB port/chips?

Korishan said:
Just remember that the more cells in parallel, the less mA each one will get. If your charger puts out 1A max, then with 10 cells each cell will get a max of 100mA. If you have 20 cells, each will only get 50mA. That equates to a longer charge time.
Also note it is not good practice to parallel the chargers as they are not in sync with each other. Meaning, with two chargers reading 1 cell, 1 charger may see 4.121V, the other charger may see 4.128V. This may not seem like a lot, but if the 2nd charger got the cells to 4.2V and shut off, the 1st charger will continue to pump power into the pack and essentially over charge the cells.

Or, another way to look at it:
Each charger charges at 1A. You put 5 chargers on the pack connected in parallel. You figure based on those numbers it will take an hr to charge (assuming you know the mAh of the pack). Well, as the pack is charged, the chargers will start shutting down at different times. Your charge time is not increased as they don't read the same voltage and as each charger shuts down, there's less amps going into the pack.

Just something to think about.
What pocket chargers were you referring to, btw. Are they TP4056 modules we've been using?
Click to expand...

I was going to eventually ask about parallel charging, so you are a step ahead thanks. I won't need to charge the bank quickly, so 1A is fine by me. I will have a minimum of a week to charge the bank, probably more.

If I wire up 10x USB ports, will they all be able to draw the max current they are designed for? I don't see why not until the bank voltage drops to the cutoff.

Yes, I have browsed those TP4056 but haven't looked in detail yet. Here is a link to one similar to what I talking about, figure one mini USB charging input, and 10 or so USB-A female for output. Haven't gotten far enough in my thinking to determine if I want to go from 1A to 2A on any of them.

https://www.walmart.com/ip/ALLPOWER...y-S7-S6-Edge-Note-5-HTC-One-Google-/165562997
 
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.
 
ridiculously_necessary said:
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?
Click to expand...

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-1865...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649


image_oygtgv.jpg


image_lgsdxj.jpg


image_jemyww.jpg
 
DanLim said:
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.
Click to expand...

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

John said:
ridiculously_necessary said:
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?
Click to expand...

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-1865...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649


image_oygtgv.jpg


image_lgsdxj.jpg


image_jemyww.jpg


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.
Click to expand...
 
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.
 
ridiculously_necessary said:
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.
Click to expand...

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.
 
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-P...ion-Lithium-LiPo-Battery-Cell-1S/322367169597

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 :D .
 
Geek said:
ridiculously_necessary said:
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.
Click to expand...

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.
Click to expand...

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.

Cherry67 said:
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-P...ion-Lithium-LiPo-Battery-Cell-1S/322367169597

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 :D .
Click to expand...

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?
 
Well, do you need QC 3.0 operation?

I also think you should go either 1S, or 4S if you can.
 
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/B075N6RKVR/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

https://www.aliexpress.com/item/6pcs-lot-LiitoKala-LG-HG2-18650-18650-3000mah-electronic-cigarette-Rechargeable-batteries-power-high-discharge-30A/32793701336.html
 
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