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Why your outdoorsy friend suddenly has a gummy bear power bank

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Re: Why your outdoorsy friend suddenly has a gummy bear power bank

#131

Post by MobiusHorizons »

mbesto wrote: post #113
MobiusHorizons wrote: post #100

Earlier quoted context omitted.

Battery capacity is always measured in amp hours not watt hours, because it’s telling you more than just capacity. The rating is a measure of how many amps the battery can emit continuously for one hour. You can estimate how long the battery will last at different loads, but it won’t match up 1:1 because of efficiency differences depending on how fast the battery is discharged, and if it has a chance to recover betwe…

> The rating is a measure of how many amps the battery can emit continuously for one hour. This is absolutely not true at all. 'Ah' is a measure of capacity and 'amps' is a measure of current. Batteries typically have three measurements: nominal voltage, capacity (Ah or mAh), and rated continuous current (amps). > watt hour measurements are path dependent Watt hour is a normalized measurement of the battery's capacit…

Batteries have different capacities at different C rate discharge. 1C is the amperage listed as the battery amp hours, but at higher discharge, batteries have a lower capacity. Some batteries handle higher discharge better than others (closer to the rated capacity). You can of course estimate the battery capacity in watt hours, but it’s not how the battery is classified (eg in a data sheet)

Re: Why your outdoorsy friend suddenly has a gummy bear power bank

#132

Post by [deleted] »

ashdksnndck wrote: post #127
trenchpilgrim wrote: post #115

Earlier quoted context omitted.

You put them under your sleeping bag and they make your sleep way warmer than if your sleeping bag is directly on the tent floor. https://www.nemoequipment.com/collections/sleeping-pads

That the purpose of the sleeping pad is characterized as thermal performance and not comfort is proof that I am not capable of the ultralight mindset.

[deleted]

Re: Why your outdoorsy friend suddenly has a gummy bear power bank

#133

Post by MobiusHorizons »

mattmaroon wrote: post #121
MobiusHorizons wrote: post #100

Earlier quoted context omitted.

Battery capacity is always measured in amp hours not watt hours, because it’s telling you more than just capacity. The rating is a measure of how many amps the battery can emit continuously for one hour. You can estimate how long the battery will last at different loads, but it won’t match up 1:1 because of efficiency differences depending on how fast the battery is discharged, and if it has a chance to recover betwe…

I can see why you would think that, but no, that’s not the case. My RV battery is 200aH but can discharge at 380 amps and drain itself in well under an hour. (That’s a peak rate which it cannot sustain for long enough to discharge itself but it can still be well above 200 the entire time.) Most lithium batteries can drain themselves much faster than an hour.

I understand that. What I’m saying is that the capacity is different depending on how quickly you drain it. Different battery construction can mitigate this effect to a higher or lower degree, but the battery is rated for 200A discharge in one hour. At 380A you will get less total watt hours out of the battery than you would at 200A, ie it will discharge in less than the 31.5 minutes you would otherwise expect.

Re: Why your outdoorsy friend suddenly has a gummy bear power bank

#134

Post by MobiusHorizons »

wkat4242 wrote: post #108
MobiusHorizons wrote: post #100

Earlier quoted context omitted.

Battery capacity is always measured in amp hours not watt hours, because it’s telling you more than just capacity. The rating is a measure of how many amps the battery can emit continuously for one hour. You can estimate how long the battery will last at different loads, but it won’t match up 1:1 because of efficiency differences depending on how fast the battery is discharged, and if it has a chance to recover betwe…

Ah does not mean it has to be discharged over exactly one hour in some test. It's simply a unit just like kWh. And most batteries are not optimised for one hour discharge. There's batteries with insanely high C-rates for delivering a lot of power quickly, discharging in 10 minutes. And some with really low that can standby for years. They'll still indicate the Ah capacity the same way.

The C rate still comes from the amp hour number on the battery. I’m aware you can discharge faster or slower than that, but the capacity measured will not be the same

Re: Why your outdoorsy friend suddenly has a gummy bear power bank

#135

Post by wkat4242 »

pcmaffey wrote: post #66
dole wrote: post #62

Earlier quoted context omitted.

Worse question: who’s got a hn frontpage/grease monkey/ai assisted subscription service to replace the main links with the archives?

And then open them in reader mode.

That would be so amazing. But there's the edge case that the page is not archived yet. Though admittedly that'll be very rare for paywall links on HN.

Re: Why your outdoorsy friend suddenly has a gummy bear power bank

#136

Post by trenchpilgrim »

ashdksnndck wrote: post #127
trenchpilgrim wrote: post #115

Earlier quoted context omitted.

You put them under your sleeping bag and they make your sleep way warmer than if your sleeping bag is directly on the tent floor. https://www.nemoequipment.com/collections/sleeping-pads

That the purpose of the sleeping pad is characterized as thermal performance and not comfort is proof that I am not capable of the ultralight mindset.

I spent time in India as a kid sleeping on the hard floor of my grandmother's home. Maybe my sense of comfort is different IDK, but I don't consider a pad essential on a warm night

Re: Why your outdoorsy friend suddenly has a gummy bear power bank

#137

Post by invalidator »

thegrim33 wrote: post #48
cenamus wrote: post #5

20Ah for 23 bucks? Seems like it's almost too good to be true. Wouldn't surprise me if it was just half that, would explain the price and weight.

Man it drives me crazy when people/products use Ah instead of Wh as a way to specify battery "capability". Without knowing more details about the battery, "20Ah" alone does not convey enough information to determine how long the battery could power a given load for. If I need to power a 100 watt lightbulb, will a 20Ah battery power it for an hour? 10 hours? 10 days? No way to know. Wh is the unit of stored energy, Wh…

There's a technical reason for it: the voltage sags when the battery is discharged quickly. Ah is relatively constant, but Wh decreases significantly with faster discharge rates, so it can't specified as a single figure.

Re: Why your outdoorsy friend suddenly has a gummy bear power bank

#138

Post by eichin »

int_19h wrote: post #83
JohnFen wrote: post #56

Earlier quoted context omitted.

Paper is very heavy. Even if you just carry a single map, you could likely save much of an ounce by trimming the borders.

And then there are things such as maps printed on silk...

... and tyvek (no idea if that wins on weight, but they're disproportionately durable)

Re: Why your outdoorsy friend suddenly has a gummy bear power bank

#139

Post by Fricken »

heelix wrote: post #8
cenamus wrote: post #5

20Ah for 23 bucks? Seems like it's almost too good to be true. Wouldn't surprise me if it was just half that, would explain the price and weight.

I'll find out if this is true. Hiking buddy of mine pointed it out on Friday, so got one on the way. Was $18 when he called it out, $23 by the time I ordered. Apparently they have a bunch of random stuff like this. They must have some outdoorsy folks in marketing.

Some endurance athletes do love their gummies. I'm not one of them.

Re: Why your outdoorsy friend suddenly has a gummy bear power bank

#140

Post by mbesto »

MobiusHorizons wrote: post #131
mbesto wrote: post #113

Earlier quoted context omitted.

> The rating is a measure of how many amps the battery can emit continuously for one hour. This is absolutely not true at all. 'Ah' is a measure of capacity and 'amps' is a measure of current. Batteries typically have three measurements: nominal voltage, capacity (Ah or mAh), and rated continuous current (amps). > watt hour measurements are path dependent Watt hour is a normalized measurement of the battery's capacit…

Batteries have different capacities at different C rate discharge. 1C is the amperage listed as the battery amp hours, but at higher discharge, batteries have a lower capacity. Some batteries handle higher discharge better than others (closer to the rated capacity). You can of course estimate the battery capacity in watt hours, but it’s not how the battery is classified (eg in a data sheet)

Sort of. C rate discharge is just another (confusing) way of state CDR. You might as well just say the CDR in amps. C rate is really just to give a comparison on battery chemistries to illustrate how performant different chemistries can deliver power at a normalized value (to illustrate how the battery chemistry could in theory scale up)

For example, 1C is rated continuous discharge amps, which means a 1C rated battery will provide 1 * Ah. So if a 20,000 mAh battery is rated for 20,000 mAh @ 1C, it will (in theory) discharge 20,000 mAh at 20A in one hour.

> You can of course estimate the battery capacity in watt hours, but it’s not how the battery is classified (eg in a data sheet)

You're right but this is irrelevant because real life usage highly varies. Data sheets are just guides.

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