Sprinter-Forum    
 

Go Back   Sprinter-Forum > Sprinter-Based RV's & Conversions > Sprinter RV's & Conversions Talk

Sprinter RV's & Conversions Talk Common features found in Sprinter RV's and Conversions.


 
Thread Tools Display Modes
Old 11-13-2019, 04:55 PM   #31
OrioN
2008 2500 170" EXT
 
OrioN's Avatar
 
Join Date: Sep 2007
Location: Vancouver, BC
Posts: 10,233
Thanks: 565
Thanked 2,521 Times in 1,843 Posts
Default Re: Dual-Purpose Batteries for high-draw applications?

Quote:
Originally Posted by GSWatson View Post
It’s not like I have the whole setup just for coffee.


Cheers,
Greg
There are herbal teas too.
OrioN is offline   Reply With Quote
Old 11-13-2019, 05:56 PM   #32
elemental
 
Join Date: Jul 2017
Location: USA PNW
Posts: 407
Thanks: 171
Thanked 257 Times in 174 Posts
Default Re: Dual-Purpose Batteries for high-draw applications?

Quote:
Originally Posted by dynaco1 View Post
Given the same amount and temperature of tap water, wouldn’t an 800W water kettle take twice the time but the same amount of power to boil the water as does a 1600W kettle
To answer your question directly, yes... and at the same time, no.

Yes: The same amount of energy is required to heat a fixed quantity of water from one particular temperature to a second higher particular temperature no matter whether the energy is applied at an 800W/second rate or a 1600W/second rate, so the 800W kettle requires the same amount of power as a 1600W kettle, at 1/2 the rate, expended over twice the time. Theoretically, in an ideal world.

No: In the case of an electric water kettle drawing power from a lead acid battery storage system, given the same physical wiring, battery storage, etc., a higher current draw results in more losses in the system delivering the power to the kettle that heats the water than a lower current draw. The biggest practical loss may be the one mentioned by john61ct, Peukert's law. Simply put, the usable energy storage capacity of lead acid batteries depends on the discharge rate; higher discharge rates lower the usable energy storage capacity. So using the 800W kettle to heat the water reduces the usable energy stored in a lead acid battery system by less than using the 1600W kettle (but takes twice as long). Practically, in the real world.

Assuming, of course, that the rate of loss of heat energy from the system during the heating period isn't high enough to make a significant difference over the increased time required. I.e., that both the 800W kettle and 1600W kettle have decent insulative qualities and/or that the quantity of water is small enough that the desired increase in temperature can be achieved in a relative short period of time.
__________________
--
2017 Sprinter 2500 170 Crew OM642 5-speed auto with Adventure Wagon interior&MOAB
elemental is offline   Reply With Quote
Old 11-13-2019, 06:07 PM   #33
elemental
 
Join Date: Jul 2017
Location: USA PNW
Posts: 407
Thanks: 171
Thanked 257 Times in 174 Posts
Default Re: Dual-Purpose Batteries for high-draw applications?

If one has time to kill, one can be even more efficient with this 1200ml DC electric kettle. 120 Watts on 12VDC (so only 10 amp draw)... but it takes 45 minutes to boil 40 fl. oz. of water (probably from "room temperature" and not a typical morning wake up van interior temperature in chillier ambient temperatures). I'm using my propane stove, since I don't otherwise need an inverter.
__________________
--
2017 Sprinter 2500 170 Crew OM642 5-speed auto with Adventure Wagon interior&MOAB
elemental is offline   Reply With Quote
Old 11-13-2019, 07:10 PM   #34
Midwestdrifter
 
Join Date: Sep 2013
Location: Charlotte NC
Posts: 10,413
Thanks: 2,025
Thanked 6,860 Times in 4,332 Posts
Default Re: Dual-Purpose Batteries for high-draw applications?

I'm probably guilty of using them interchangeably in common conversations, but power does not equal energy. Energy is power over time, power is an instantaneous measurement. Watt-hours is energy, watts is power.

So heating the water takes the same energy, but when you halve the power, you double the time.
__________________
2004 T1N | Overland Conversion in Process Completed...For now... | 187,000 miles | 140" | High Roof | My Build Thread
Another Random Blog | http://VagariesAbound.blogspot.com
Midwestdrifter is offline   Reply With Quote
Old 11-13-2019, 11:46 PM   #35
richard cabesa
 
Join Date: Jan 2017
Location: Santa Barbara
Posts: 273
Thanks: 17
Thanked 153 Times in 84 Posts
Default Re: Dual-Purpose Batteries for high-draw applications?

Quote:
Originally Posted by NBB View Post
All in - the most expensive cup of coffee ever.

What about a Jet Boil?
I LOVE my jet boil !!!


I have a propane stove in the RV and I still take the Jet Boil for coffee.

It IS the one pot that you have to watch it boils so quick
__________________
Graphite Dave's old rig
richard cabesa is offline   Reply With Quote
Old 11-14-2019, 12:57 AM   #36
elemental
 
Join Date: Jul 2017
Location: USA PNW
Posts: 407
Thanks: 171
Thanked 257 Times in 174 Posts
Default Re: Dual-Purpose Batteries for high-draw applications?

Quote:
Originally Posted by Midwestdrifter View Post
I'm probably guilty of using them interchangeably in common conversations, but power does not equal energy. Energy is power over time, power is an instantaneous measurement. Watt-hours is energy, watts is power.

So heating the water takes the same energy, but when you halve the power, you double the time.
I used power in the colloquial sense at one point in my answer, the same as it seemed to be used in the original question. Had I been more on the ball, I might have made the same point as you have here in the interest of being totally clear and been more careful in my own language as well.

Thanks!
__________________
--
2017 Sprinter 2500 170 Crew OM642 5-speed auto with Adventure Wagon interior&MOAB
elemental is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT. The time now is 09:18 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2019, vBulletin Solutions, Inc.