8 cell power bank

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Asbestos
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8 cell power bank

Perhaps a noob question, perhaps not. I got 8 cells for one of those ebay usb power banks. I got 2800MaH cells
https://www.18650batterystore.com/collections/eve-18650-batteries/produc... and charged all of them in my Nitecore D4. Then I ran a load test and came out with 13.78 Ah. Now I understand that there are losses here. But here is how I figured things
each cell downrated to 2500MaH x 8 = 20Ah
Take off 15% for loss and I should be at at least 17Ah
Or am I wrong?
I tested the bank at about 1.6 amp draw.
TIA for any insight

I point to others in this group to justify how many flashlights I have.

Edited by: Asbestos on 09/15/2021 - 13:55
texas shooter
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As far as I know the best Chinese cells made in China are 2600 mah. Claiming 2800 mah could mean anything. Your measurements showed that you may have been ripped off. https://delongbattery.en.made-in-china.com/product/KNFEnoVSfHkp/China-Re... Read the product description “Normal temperature capacity:1800mah or customized”

chops728
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Are you talking about you’re only getting 13.78 AH through the Power Bank using a USB device —- That is about normal conversion up to 5v —- 60% / 70%

Asbestos
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Exactlyload test off the USB outlet. I did not figure the losses would be that high. I figured derate the cells to 2500 and then 15% but you are saying the loss is about 30% + that would definitely make sense of the numbers then.

I point to others in this group to justify how many flashlights I have.

chops728
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8 × 2.5 AH = 20 AH x 3.7v = 74 watt hrs

74 watt hrs / 5.1 v = 14.5 AH and with some loss 13.78 AH

The best I’ve ever gotten — I tested the cells and when I put them in the Power Bank — they converted to 70% of the cell capacity— that’s why people always get mad and say the capacity is low —most PB capacity rating is from the cells not the actual output

flydiver
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I’ve got a cheap 8-cell bank. The cells are tested in a pretty accurate discharge system. The capacity output is a lot less than I had hoped for.
OTOH, it IS a use for those cells that otherwise would get no use at all. So, there I am.

To Air is Human, to Respire….Divine.

Forsythe P. Jones
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Some time ago I found a site that tested a bunch of powerbanks and measured the conversion efficiency, and most of the better ones were above 80%. I thought I had noted the url but I can’t find it in my files. I might look for it again with web search. How did you do your load test? One issue is that most li ion chargers don’t use buck converters to go from 5v to 3.6v or whatever. They just dissipate the 1.4v difference as heat. So there is already around 25% loss right there.

The whole concept of powerbanks seems like a clunky artifact of almost all mobile phone batteries being sealed inside the phone these days. Otherwise you’d just swap charged cells into the phone. Sigh.

chops728
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Yep — Years ago the phone was as big as the Power Banks with interchangeable batteries

Now the phone is the size of the old battery and the power bank is the size of the old phones

I showed my granddaughter one of my old phones a couple years ago — she just laughed at how big it was — I laughed and said this was a smaller one of the time

ChrisGarrett
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Just get a decent battery bank like the Xtar PB2S and a quad of 21700s and keep them charged for emergencies.

I use 50Es in mine.

Chris

JagerLion
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texas shooter wrote:
As far as I know the best Chinese cells made in China are 2600 mah. Claiming 2800 mah could mean anything. Your measurements showed that you may have been ripped off.

I’ve found Molicel, DLG and BAK all test like any modern 3000 to 3500mAh cell at 1A, within ~5-8% of advertised capacity under my conditions anyway. Can’t speak to their longevity though.

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ChrisGarrett
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JagerLion wrote:
texas shooter wrote:
As far as I know the best Chinese cells made in China are 2600 mah. Claiming 2800 mah could mean anything. Your measurements showed that you may have been ripped off.

I’ve found Molicel, DLG and BAK all test like any modern 3000 to 3500mAh cell at 1A, within ~5-8% of advertised capacity under my conditions anyway. Can’t speak to their longevity though.

But that’s the 64 dollar question…how long do those Chinese cells last, before high I.R.s crap the bed?

Don’t skimp on lithium-ion ‘anything.’

Chris

JagerLion
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ChrisGarrett wrote:
JagerLion wrote:
I’ve found Molicel, DLG and BAK all test like any modern 3000 to 3500mAh cell at 1A, within ~5-8% of advertised capacity under my conditions anyway. Can’t speak to their longevity though.

But that’s the 64 dollar question…how long do those Chinese cells last, before high I.R.s crap the bed?

Don’t skimp on lithium-ion ‘anything.’

Chris

Agreed. I just bought a few of the cheapies when they were… cheap. For testing LVP, flashlight internal charging, things like that. GAs are still my go-to for actual use in non-monster flashlights.

I shoot magic into the darkness!

ChrisGarrett
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I’ve got the same one, but about 4-5 years ago. I think that mine states 6800mAh and that it uses LG/Samsung cells, but they are hardwired in.

I leave it at my gal’s place, so she can charge up her iPhone during a hurricane outage, which will work for her.

Good stuff, but I prefer to buy power banks with replaceable bateries.

Latest is the Xtar PBS 2 with LG 50Es and that will work for me in emergencies.

Chris

Perception
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ChrisGarrett wrote:
Just get a decent battery bank like the Xtar PB2S and a quad of 21700s and keep them charged for emergencies.

I use 50Es in mine.

Chris

This is what I do, I like it so much I’ll probably buy a second PB2S in the near future. I probably need to see if I can come by a few more 50Es first, finding those in stock is the hard part right now.

ChrisGarrett
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Perception wrote:
ChrisGarrett wrote:
Just get a decent battery bank like the Xtar PB2S and a quad of 21700s and keep them charged for emergencies.

I use 50Es in mine.

Chris

This is what I do, I like it so much I’ll probably buy a second PB2S in the near future. I probably need to see if I can come by a few more 50Es first, finding those in stock is the hard part right now.

If you have good cells, they’ll probably last longer than the PBS2.

Always have a spare, if my way of thinking.

Two is one and one is none.

Chris

texas shooter
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JagerLion wrote:
texas shooter wrote:
As far as I know the best Chinese cells made in China are 2600 mah. Claiming 2800 mah could mean anything. Your measurements showed that you may have been ripped off.

I’ve found Molicel, DLG and BAK all test like any modern 3000 to 3500mAh cell at 1A, within ~5-8% of advertised capacity under my conditions anyway. Can’t speak to their longevity though.

I’m going to concede to DLG and BAK making good higher capacity cells now. Molicel however gets much of it’s R&D from Canada.

Forsythe P. Jones
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I used to think the same way but it seems to me that preassembled powerbanks are generally cheaper and more compact than the raw cells would cost by themselves, at least from where most of us get our raw cells. I have an Aduro 30,000 mah powerbank that is pretty nice, supporting micro-usb/usb-A, usb-c, and Apple Lightning for both input and output. I don’t know if it does QC or PD. But it only cost $30 or so which would be $3 or $4 per cell not even counting the rest of the stuff, and I know it’s not going to pop open and dump cells all over the place

I’ve had terrible luck with single cell powerbanks but have done pretty well with the bigger ones.

TexasToasted
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Forsythe P. Jones
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Yeah PB2S is a 2 cell (2*21700 but still) rather than an 8 cell, Review here:

https://lygte-info.dk/review/Review%20Charger%20Xtar%20PB2S%20UK.html

ChrisGarrett
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Forsythe P. Jones wrote:
Yeah PB2S is a 2 cell (2*21700 but still) rather than an 8 cell, Review here:

https://lygte-info.dk/review/Review%20Charger%20Xtar%20PB2S%20UK.html

Yeah, but the operative concept is that their replaceable.

Fixed cells need to be topped up when the PB is depleted, so that was my point.

If one has a dozen 21700s at their disposal and a way to charge them up via solar, in a SHTF scenario, they’re golden.

Chris

chops728
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From being Subscribed to the Amazon Deals thread —through Vipon I have so many Power Banks —A couple yrs ago they had these Baseus PB going around —a 10AH for $10 that takes most all cables for charging and rather small for convivence — A 30 AH for $16 that has 2 USB outputs —this one is kind of big and heavy but it’s Legit —- I have several types that use cells in but I rarely use those

Right now on Vipon they have a couple cheap ones

Forsythe P. Jones
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Quote:
If one has a dozen 21700s at their disposal and a way to charge them up via solar, in a SHTF scenario, they’re golden.
If those are cells you have around anyway, then ok that makes sense. I guess I’d get a few if I had that many cells around. A dozen 21700’s is still 60ah of cells tops, though. Equivalent to two of those 30ah ready made powerbanks with built-in chargers if your solar stuff can produce 5 volts.

I dunno how this would come into play in SHTF. If your phone works then the SHTF can’t be all that bad. If the phone doesn’t work then you don’t need to recharge it and you probably have much more urgent concerns (food, water, sanitation) than recharging flashlights :(. A 20 watt folding backpacking-type solar panel and 1 or 2 powerbanks should be plenty to sustain several flashlights and radios and a couple of phones, with a little bit of frugal use and good weather.

The next important electricity consumer for most people in a power outage is probably a fridge, which uses maybe 2kwh a day. A dozen 21700’s doesn’t really help with that. You need several square meters of solar and a beefy powerwall to handle the starting surge, if not a gas powered generator.

It annoys me a bit that the PB2S isn’t a few mm longer and able to recharge protected 21700’s. I know that some lights use those and come with them. I have a Fenix light that came with a protected 18650, that won’t recharge in the original PB2/PB2C and also won’t fit in my D4v2. The light itself has internal USB charging but I made sure when I bought an external charger, that it would handle it (and protected 21700’s) anyway,

Another idea I’ve had is to dismantle power banks to extract the raw cells, since it’s cheaper than buying them. They wouldn’t be the high current cells used in enthusiast flashlights or in power tools though. At best they’d be good for rebuilding laptop packs.

ChrisGarrett
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Forsythe P. Jones wrote:
Quote:
If one has a dozen 21700s at their disposal and a way to charge them up via solar, in a SHTF scenario, they’re golden.
If those are cells you have around anyway, then ok that makes sense. I guess I’d get a few if I had that many cells around. A dozen 21700’s is still 60ah of cells tops, though. Equivalent to two of those 30ah ready made powerbanks with built-in chargers if your solar stuff can produce 5 volts.

I dunno how this would come into play in SHTF. If your phone works then the SHTF can’t be all that bad. If the phone doesn’t work then you don’t need to recharge it and you probably have much more urgent concerns (food, water, sanitation) than recharging flashlights :(. A 20 watt folding backpacking-type solar panel and 1 or 2 powerbanks should be plenty to sustain several flashlights and radios and a couple of phones, with a little bit of frugal use and good weather.

The next important electricity consumer for most people in a power outage is probably a fridge, which uses maybe 2kwh a day. A dozen 21700’s doesn’t really help with that. You need several square meters of solar and a beefy powerwall to handle the starting surge, if not a gas powered generator.

It annoys me a bit that the PB2S isn’t a few mm longer and able to recharge protected 21700’s. I know that some lights use those and come with it. I have a Fenix light that came with a protected 18650, that won’t recharge in the original PB2/PB2C and also won’t fit in my D4v2. The light itself has internal USB charging but I made sure when I bought an external charger, that it would handle it (and protected 21700’s) anyway,

Nobody runs protected cells in a power bank, frankly, as that’s noob stuff.

You’re putting a lot of faith in a generic ChiCom power bank with ChiCom cells of unknown quality.

If you want to replace things in a couple/few years, knock yourself out.

Chris

Forsythe P. Jones
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What can I say, if I have protected cells I want to be able to recharge them. Power bank is a separate issue I would agree. Protected is supposed to be preferable if you are using the cells in series because of the possibility of a dud cell getting reverse charged and igniting. I’d expect a 2 cell power bank uses them in parallel.

The next thing after 8 cell would be the kind of powerbank that can produce 120 vac. That might be less efficient but it is useful for lots of things. I wonder if it is possible to get those with replaceable cells, short of getting DIY powerwall-type stuff. There are some nice portable non-removable ones with around 300wh of cells (= 16× 21700 maybe), USB PD input and output, and MPPT solar controller built in. They are pricey but I’ve felt tempted at times.

Woot has a 200 watt portable solar thing for $300 today if anyone cares:

https://sellout.woot.com/offers/rockpals-200w-portable-solar-panel

That is way expensive compared to non-portable panels but it conveniently folds up, has some voltage conversion stuff, etc. It weighs 13.2 pounds apparently. I’d consider it if I had a legit use for it.

flydiver
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I’ve got 5 ready made powerbanks. ONE of them seems to have decent cells.
Of the half dozen (cheap) 1-cell PB I tried ALL were crap and died. I do have a more expensive one that is decent. I did my research on that one as it’s for hiking and needs to work reliably and still be small.
I MUCH prefer a good PB shell like the PB2S with replaceable cells. Better product, more personal control.

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Asbestos
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flydiver wrote:
I’ve got 5 ready made powerbanks. ONE of them seems to have decent cells. Of the half dozen (cheap) 1-cell PB I tried ALL were crap and died. I do have a more expensive one that is decent. I did my research on that one as it’s for hiking and needs to work reliably and still be small. I MUCH prefer a good PB shell like the PB2S with replaceable cells. Better product, more personal control.

Yeah I had 2 decent ones I got about 7 years ago one went missing and the other still works pretty well, since then I have bought a few and they have all sucked. I bought one of the “BYOB” ones off ebay because I had gotten ahold of a laptop that was less than a year old and had a bunch of cells . I liked it so much I got a few more Tried some more random laptop pulls and was getting about 3AH out of them. Not really worth the hassle

I point to others in this group to justify how many flashlights I have.