battery capacity huge lifepo4 vs small power banks

Ian0

Joined Aug 7, 2020
6,735
This huge Dakota lifepo4 is 7 aH battery
https://www.amazon.com/gp/product/B00PG5I8EE/ref=ox_sc_act_title_3?smid=A20YSPW1I1I0OV&psc=1

while this small power bank is a 20 aH battery unless my math is wrong.
https://www.amazon.com/gp/product/B07YPY31FL/ref=ox_sc_act_title_16?smid=ATVPDKIKX0DER&th=1

Where am I going wrong in my understanding here? Thanks for any help.
The first on is 12V and the second one is 5V. So the energy stored in the first is 84Wh and the energy stored i n the second is (hypothetically) 100Wh.
Then there's the problem of credibility.
If anything is quoted as being umpteen thousand milliamp hours instead of simply quoting it in Amp-hours, BE VERY SUSPICIOUS!
The first also may be full of air, as it looks as though it has been designed to replace a 12V 7Ah sealed lead-acid battery.
 

Marley

Joined Apr 4, 2016
489
The first one is obviously designed as a drop-in replacement for a standard 12V 7A/h lead-acid battery. Looks a bit suspicious to me. The method of charging a Li-Ion battery is totally different to lead-acid so I can't see how you could simply replace one technology with another.
 

MisterBill2

Joined Jan 23, 2018
13,841
What I see is that with the small battery pack is fundamentally A LIE!! The added zero and the invisible decimal point make it a 2 amp hour battery pack, believable for a cell phone application.
And note that the 7AH battery has a charger available, which is handy because the charger for a lead battery of any type is not suitable for a lithium battery of any type. So there is a mechanical fit but an electrical misfit. And I doubt that the touted warranty is actually valid.
 

Tonyr1084

Joined Sep 24, 2015
7,210
I am also suspicious of the 5V pocket power pack. It says it has power for 7 days without knowing how heavy the user may use it. I bet I could deplete it in a few hours of use. Let alone 7 days.

Also agree with Marley about the difference in technologies. Lead Acid (or SLA's {sealed lead acid}) batteries are very forgiving when charging them. They don't require specific currents for specific periods of time whereas Lifepo's require a specific charge profile. Simply slapping one in place of another is a recipe for disaster.

Let the buyer beware!
 

Tonyr1084

Joined Sep 24, 2015
7,210
Quick comment on links:
https://www.amazon.com/gp/product/B00PG5I8EE/ref=ox_sc_act_title_3?smid=A20YSPW1I1I0OV&psc=1
and
https://www.amazon.com/gp/product/B00PG5I8EE/ref=ox_sc_act_title_3
is the same thing. Everything including the question mark and after is there for tracking purposes. Now that I clicked on your links I'm going to be getting ads for batteries that I don't necessarily want or need.

When I post a link I always sanitize it by removing everything from the question mark on back. That way if someone clicks on a link I post they're not inundated with advertisements they didn't want.
 

Thread Starter

Newusaa

Joined Mar 4, 2018
15
I am also suspicious of the 5V pocket power pack. It says it has power for 7 days without knowing how heavy the user may use it. I bet I could deplete it in a few hours of use. Let alone 7 days.

Also agree with Marley about the difference in technologies. Lead Acid (or SLA's {sealed lead acid}) batteries are very forgiving when charging them. They don't require specific currents for specific periods of time whereas Lifepo's require a specific charge profile. Simply slapping one in place of another is a recipe for disaster.

Let the buyer beware!
I’m not so sure about this but I think the main problem people have with the lead acid is when you run a fish finder from it, it goes below the fishfinders required amps long before the battery is drained. Whereas the lifepo4 will keep that amperage available till near the end. I’m really hand waving but that was my understanding
 

Ian0

Joined Aug 7, 2020
6,735
I’m not so sure about this but I think the main problem people have with the lead acid is when you run a fish finder from it, it goes below the fishfinders required amps long before the battery is drained. Whereas the lifepo4 will keep that amperage available till near the end. I’m really hand waving but that was my understanding
How much current does a fishfinder require?
 

Tonyr1084

Joined Sep 24, 2015
7,210
Two things here; first you can't run a fish finder on 5V. Second, if your fish finder DID operate on 5V I don't think you're going to see it run for seven hours. This is one of those situations that backup my statement about having the ability to drain a battery faster than they say you can. The ONLY situation where you could get seven days of safe power (see cut-n-paste below) assuming the claim of 20Ah is real, the numbers work out like this:

22.5W ÷ 5V = 4.5A. Maybe it can deliver 4.5A. But to last seven days - you'd draw no more than 26.9mAh constant draw. In other words you could light a small LED steady for seven days but charging phone after phone after phone, assuming you take one off the minute it reaches full charge and plug a second one on, it's not going to last seven days.

  • INIU Portable Charger, 22.5W 20000mAh USB C
    • ✅【7 Days of Safe Power】Enjoy a full week’s worth of charging capacity with the airline-approved 20000mAh power bank.
    • ✅【Charge Your iPad Pro up to 34% in 30 Mins】Most power banks in the market cannot charge your iPad or charge at a snail’s pace. However, INIU with 22.5W high-speed output can charge all the existing iPad even the newest one at FULL speed.

I'm guessing it can charge your iPad from zero to 34% in 30 minutes. Then it's done charging anything because it's depleted.

In short what we're saying is that you have to see ads for what they are - an attempt to get you to buy their product. I've seen so many deceptive ads that make a statement that contains no facts or figures. Just comments that make you come to the conclusion that theirs is the best when that's not what they are saying at all. One recent ad that pops into mind is "My A1C was here, and now it's here" as the actress lowers her hand from one elevation to another. The consumer assumes it means her A1C was lowered significantly, when what they really said was nothing at all. Here to here has no frame of reference so you have to draw a conclusion. If you're a sufferer of diabetes type 2 you WANT to believe in it and will ask your doctor to prescribe it. I have no idea if it will work or not. But there's no imperial evidence offered. In other ads their claims are outright deceptive, as it appears this one probably is. I can't say it truly is deceptive, but I have enough experience to question whether they're being truthful or not.

Oh; and "Airline Approved"? Airlines don't approve batteries, the FAA is the one who regulates batteries. Right there there's a deception. A clearly false statement.
 

Irving

Joined Jan 30, 2016
3,192
Couple of points. A 7Ah SLA means it will produce 350mA (7/20) for 20h from 100%SOC to 10%SOC. At 100%SOC its output voltage will be 13.6v, at 20%SOC its 10v for a new battery - you cannot get the last 10-15% as the internal resistance is too high unless you're only taking a few milliamps. This is called the 20h rate, or C-rate. The nominal voltage is 12v so its better described as 0.35 * 12 * 20 = 84Wh. If you discharge it at 1A it'll lose 5 - 10% capacity due to internal losses, mainly heat, so it'll be more like 76-80Wh. As the battery ages its capacity drops. For a battery continuously operated at 2 - 3C that can mean a loss of 40% in 2 - 3years.

A lot of the 'power pack' suppliers ignore the 20Ah convention hence the fanciful figures. I have a pack here that is 3 x 3.7v lipo pouches at nominally 8800mA. That's 11.1v nominal * 8.8Ah = 97Wh at the 1C rate, or 440mA. It has a 5v output using a buck converter with a 2A current limit, so nominally a 10W charger. At 80% efficiency that's 12.5W input on average or about 3C giving a nominal capacity of around 80Wh typical or about 8h charging time - and in fact I can charge my phone twice from a fully charged pack. It was advertised as 5v 24000mAh or 120Wh! They simply added the 3 8800mAh together and knocked 10% off, which is meaningless. And that's one of the better ones!

Re charging a 12v lifepo4 pack from an SLA charger. It can be, and is, done with some internal circuitry. The SLA charger will produce typically 300-400mA for a 7Ah pack (1C charge rate) at a constant voltage of 14.4v, expecting the charge current to drop to about C/10 within 12hours and then switch to a maintenance voltage of 13.6v typically to keep the pack topped-up against self-discharge.

A lifepo4 drop-in replacement needs 4 x 3.6v = 14.4v at a constant current which of course will be limited by the SLA charger so the lifepo4 pack will charge slower than a proper life charger would operate (3 - 5C is common) and can't get to 3.6v per cell as there isnt enough headroom so will typically cell balance at 3.5v giving a maximum of 95-97%SOC. But a lifepo4 will be <10% at full discharge and still giving 11+ volts.
 

ThePanMan

Joined Mar 13, 2020
522
At 100%SOC its output voltage will be 13.6v
Disagree. 13.6 (13.8) volts is the float charge. A 12V SLA fully charged voltage will be typically 12.6V resting (after 12 hours). Nominal voltage is 12V. Perhaps you mistyped. But I've never seen a car battery or SLA resting at 13.6V.
 

Ian0

Joined Aug 7, 2020
6,735
Disagree. 13.6 (13.8) volts is the float charge. A 12V SLA fully charged voltage will be typically 12.6V resting (after 12 hours). Nominal voltage is 12V. Perhaps you mistyped. But I've never seen a car battery or SLA resting at 13.6V.
I tested a batch of new SLA batteries which arrived last week. They were all at 13.1V, and they had definitely been resting for more than 24 hours as they arrived by 3-day carrier. I've never found one as high as 13.6V.
 

BobTPH

Joined Jun 5, 2013
6,095
The power banks typically quote the Ah as that of the 3.7V battery, not the 5V output. So the Wh is Ah x 3.7, not 5. But that is probably exaggerated as well.
 

Irving

Joined Jan 30, 2016
3,192
Disagree. 13.6 (13.8) volts is the float charge. A 12V SLA fully charged voltage will be typically 12.6V resting (after 12 hours). Nominal voltage is 12V. Perhaps you mistyped. But I've never seen a car battery or SLA resting at 13.6V.
Correct, that was a typo, should have been, as @Ian0 said, around 13.1v. Thats typical for eg an MK gel, but the Odessey pure-lead AGM deep discharge are often a little higher.
 

Reloadron

Joined Jan 15, 2015
7,088
Of minor difference is a 7.0 AH 12 Volt SLA battery weighs in around 8.0 Lbs (3.62 kg) while the LiPo replacement comes in at 2.15 Lbs (0.97 kg) or about 1/4 the weight while the size is the same so plenty of air in the box. This is not unusual. Harley Davidson offers a LiPo replacement battery for my bike which is same size as original SLA battery and 1/4 the weight. Oh yeah, in the small print you need to replace the charging system or really bad things will happen. They passed around a demo battery at one of my chapter meets. Only after I questioned charging did the rest of the story come out. :)

Now as to the second link?
"INIU Portable Charger, 22.5W 20000mAh USB C in & Out Power Bank Fast Charging, PD 3.0+QC 4.0 LED Display Phone Battery Pack Compatible with iPhone 14 13 12 Pro Samsung S21 Google LG iPad Tablet, etc".
I have my doubts as to the 20 AH rating even at the reduced voltage. While it is true that Lithium Polymer batteries can deliver power vs. weight like we have never seen before I just have a problem with the 20,000 mAH claims. Does have a pretty faceplate meter. :) The suggested charger looks to be a simple wall wort so I assume much like my phone charger the charge control is handled onboard much like my phone. I am just having a hard time getting past the 20 AH.

Ron
 

Tonyr1084

Joined Sep 24, 2015
7,210
They were all at 13.1V
Can't argue with imperial data.
as @Ian0 said, around 13.1v. Thats typical for eg an MK gel, but the Odessey pure-lead AGM deep discharge are often a little higher.
When I think of LA batteries I go back to what I learned back in the 80's, that each cell is 2.1V. Six cells comes to 12.6V, and I've never plucked a car battery off the shelf or tested resting voltage that was higher than 12.6V.

MK gel? One I'm unfamiliar with. I'm sure by now things have changed and someone has managed to find a way to pack more energy into the same space. Maybe even dropped a pound or two here and there. In the world of batteries I'm pretty basic. Li-Ion's and Li-Po's are still somewhat new to me. Li-Fe-Po's - well, I've heard of them. Even watched some YouTube's on them. And that is ALL I know about Lifepo's.
 

Irving

Joined Jan 30, 2016
3,192
Of minor difference is a 7.0 AH 12 Volt SLA battery weighs in around 8.0 Lbs (3.62 kg) while the LiPo replacement comes in at 2.15 Lbs (0.97 kg) or about 1/4 the weight while the size is the same so plenty of air in the box.
Good point, and not a minor one. Nobody sane (IMHO!) would drop a 7Ah LiFePO4 in place of a 7A SLA, since you could easily drop an 18 or 20Ah Li pack in the same space and it'll weigh less still.

But there are other advantages: My wheelchair packs 8 x 3.6v 200Ah LiFePO4 cells giving 5.3kWh of which 80% is usable in the same space as 2 x 60Ah 12v SLA giving 1.5kWh, of which 60% is usable. and about 2/3 the weight. 5000 recharge cycles v 400, 10y life v 18mo, Initial cost £1200 v £450, but total cost over 10y £1200 v £3,150...

MK gel? One I'm unfamiliar with
The MK or the gel? MK are a US manufacturer. They make both gel and AGM SLA - basically gel has the electrolyte mixed with silica to form a gel squeezed between thin lead alloy plates tightly wound in a spiral per cell. AGM (absorbent glass mat) has it held within a matrix of glass strands. Both represent a 'dry' lead-acid battery. The gel is generally better (lower resistance) for peaky loads and multiple recharge cycles while AGM handle deep discharge better. Odessey batteries are a form of AGM but use 99% pure lead flat plates with electrolyte pads between them packed linearly. They are more expensive and difficult to manufacture but produce a superior battery with the best characteristics of both the gel & AGM types.
 
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