Ontopic The new car-seching thread

[Domon]

got plenty of those around, been running reserve capacity calculations for a 50ah or so battery and it looks like 2ish hours is doable, but would deeply discharge the battery, which is not great for lead acid.

looks like there are some Lipo batteries that can do continuous discharge of about 10 amps without melting, that could be a good choice as well. Way lighter too.

 

[Domon]

I assume portable? How much recharge time between sessions?

as much recharge time as needed between 2 hour sessions.

 

[wetwillie]

If ya'll had to run a 12v, 8a load for about 2 hours in the most lightweight way possible how would you do it.

Big deep cycle lead acid battery? Small engine with a 12v dc step down?

Bonus points if you can do it with something less than 20lb (probably not possible)

Your 20 lb. limit is the sticking point. 40 lbs would make it no sweat. gee is right - the 50 ah would be close to flat.

 

[gee]

If ya'll had to run a 12v, 8a load for about 2 hours in the most lightweight way possible how would you do it.

Big deep cycle lead acid battery? Small engine with a 12v dc step down?

Bonus points if you can do it with something less than 20lb (probably not possible)

8A load x 2 hours = 16aH.
20aH 12V LiFePO4 will do it, 5.8 pounds.

Amazon product ASIN B07X523S96

 

[Domon]

lipo stuff is getting really good, and cheap

Amazon product ASIN B07X7MD2JK
that should last for 2 hours, without nasty discharge effects and only weighs 4lbs

 

[Domon]

b10 by 2 seconds by gee. Came to the same conclusion.

 

[wetwillie]

8A load x 2 hours = 16aH.

Amazon product ASIN B07X523S96

That math is way off. You didn't use/apply Peukert's Law, a 20AH won't really do it.. As capacity decreases, the rate of discharge accelerates. Simple multiplication doesn't cut it.

 

[Domon]

That math is way off. You didn't use/apply Peukert's Law, a 20AH won't do it.. As capacity decreases, the rate of discharge accelerates. smfh

not on lifepo4 it doesnt. that only applies to lead acid.

 

[wetwillie]

not on lifepo4 it doesnt. that only applies to lead acid.

I understand the sudden plummet after the steady voltage(silver oxides do similar). 20ah leaves no margin of error on time or load. Even for lifepo4. You'll need 2.5 hours minimum to recharge.

 

[Domon]

all those lipo based batteries have a built in BMS (battery management system) that will shut them off before they get unpleasant.

 

[wetwillie]

all those lipo based batteries have a built in BMS (battery management system) that will shut them off before they get unpleasant.

And hence you may find yourself without even a drop of juice extremely suddenly and without much warning. Maybe go 30ah and have less worry.
*I have to argue this shit, same as you guys. We could try unity

 

[Domon]

2 hours included a 30-50% buffer already you really think im the kinda guy thats not gonna build that in?

 

[wetwillie]

2 hours included a 30-50% buffer already you really think im the kinda guy thats not gonna build that in?

mmmm, well.
Where is this bufffer - on your load, your time? Did you mention this?
Do I think you might be gaslighting?

 

[wetwillie]

Alternate answer - insufficient data provided in original query.

 

[Jehannum]

mmmm, well.
Where is this bufffer - on your load, your time? Did you mention this?
Do I think you might be gaslighting?

hydrogen gas isn't a concern with Lifepo4 batteries, and hardly a consideration even in lead-acid batteries anymore

 

[Mr. Argumentor]

That math is way off. You didn't use/apply Peukert's Law, a 20AH won't really do it.. As capacity decreases, the rate of discharge accelerates. Simple multiplication doesn't cut it.

Are you gonna tell domon he doesn't know how to skin a human body next?

 

[wetwillie]

Fine - I give. And yes, I know I was a bit dick. Sorry @Domon

 

[wetwillie]

You know, I actually like you folks. Not many places have this level of slapstick and brain cells.

 

[Domon]

Fine - I give. And yes, I know I was a bit dick. Sorry @Domon

I have no emotions to be offended, and will always provide fact-based evidence that I am correct. It is of no consequence if you disagree

 

[gee]

That math is way off. You didn't use/apply Peukert's Law, a 20AH won't really do it.. As capacity decreases, the rate of discharge accelerates. Simple multiplication doesn't cut it.

For the LiFePO4 package we put in the YEAH BUOY!, their capacity is 90% of rated when discharged at a 1C discharge rate.
Their 100% capacity is stated at 0.2C discharge rate.

Normally people go for the lead package, because shipping lithium batteries over a certain size by air is problematic.