Thursday, December 8, 2022

RVelectricity – Just Ask Mike (J.A.M.): How many batteries are in a tank of propane?

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Welcome to my J.A.M. (Just Ask Mike) Session, a weekly column where I answer your basic electrical questions. If you’re a newbie who’s never plugged in a shore power cord (or ask – what’s a shore power cord?), or wonder why your daughter’s hair dryer keeps tripping the circuit breaker, this column is for you. Send your questions to Mike Sokol at mike (at) noshockzone.org with the subject line – JAM. Today I discuss the energy in a tank of propane compared to batteries.

I found that question over on the Rockwood Facebook group, and saw that Tony Barthel was quoting a number I must have told him about the amount energy in a tank of propane compared to a 100 aH battery.

At the time I pulled a number out of my head, which was a bit of a SWAG (scientific wild-a** guess) since I already knew the energy equivalent of a gallon of propane, but I never showed my work. So let’s see what Tony said that I said, and we’ll find out if I knew what I was talking about or if I’m actually full of bologna…

Dear Tony Barthel,

My husband and I were talking about which method is the best for heating water for dishes, showers, etc. (for the purpose of the question, imagine you have full hookups).

We’ve gone back and forth on this topic so decided we would take a poll and see the opinions of those in this group…

Thanks! —Stacy

Depends on so many factors including where you like to camp, what your expectations are and that sort of thing. For boondocking there’s almost no choice – use your propane.

When on full hook-ups, use electric. When in a hurry and on full hook-ups, use both.
Propane has more energy than the electricity available on 30 amps (depending on what-all’s running) so you will get hot water faster using it.

Mike Sokol said that a single 20 lb. tank of propane has as much energy equivalent as one hundred 100Ah batteries. Wow. —Tony Barthel

Tony was right in quoting what I told him, so I’m not full of bologna! My calculations show that a 20-lb. or 5-gallon (which is actually 4.7 gallons) tank of propane does contain the equivalent energy of around one hundred 100aH batteries. It’s 101 batteries, to be exact!

Here are my calculations, in case you want to win a bar bet!

• 1 Gallon of Propane = ~27 kWh (Kilowatt Hours) of electrical energy
• So 4.7 Gallons of Propane = 127 kWh of electrical energy
• A 100Ah battery x 12.5 volts = 1.25 kWh of energy
• So 127kWh / 1.25kWh = 101 Lithium batteries that can be discharged to 0% SoC
• Or 202 Lead Acid batteries that should only be discharged to 50% SoC

Oh, most learn-ed one. How much would all those batteries weigh?

• One 100Ah Lithium battery weighs around 30 lbs.
• So 101 Lithium batteries would weigh 30 x 101 = 3,030 lbs.
• One 100Ah Deep Cycle Lead-Acid battery weighs around 70 lbs.
• So 202 Lead-Acid batteries would weigh 70 x 202 = 14,140 lbs.
• A 5-gallon propane tank with the same energy weighs 35.8 lbs.

I’ll take that Guinness now!

OK, everyone. Remember that electricity is a useful and powerful force, so we all need to pay attention to safety precautions while using it.

And yes, a properly poured Guinness is my favorite beer, so you can always buy me one at a bar and I’ll be a happy guy!

Let’s play safe out there….

Send your questions to me at my new RVelectricity forum here.

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

You don’t want to miss Mike’s webcasts on his YouTube channel.

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California Travel Videos
1 month ago

The wise analyst always begins with “It depends…”
While a ratio based on the constant number 27 is no doubt accurate based on a set of assumption, interestingly the derivation is based on 91,500 BTU (1 gallon of propane) = 27 kWh, or 1 Watt = 3.4 BTU/hr.

So I’d add that “it depends” on one’s APPLICATION such as heating, electricity production, e.g., generator losses from an efficiency perspective to “do work.” For instance a propane clothes dryer works about 25% faster than its electric counterpart. Of course, depending on which way one is inclined to go, the respective manufacturer will promote positive attributes based what they are selling. In their grocery list, they will champion the environmental impacts, net weight, space, noise, fuel storage longevity, possible risks of explosion, initial capital and ongoing maintenance costs, longevity, possible condensation, carbon emissions, toxicity, etc. Uh now, what was the original question LOL!

Happy trails and good luck.

California Travel Videos
1 month ago

So when we are boondocking and riding our 2 ebikes, each with 750 Watt batteries that have a slooow charge cycle of 4-6 hours, I certainly am not going to run our 3K Onan generator all day and our four 100 Watt solar panels won’t cut it either. So I have two 1K Ecoflow Delta storage/inverters that contain rapid charge/discharge Lithium cells. I can run our Class C Sprinter diesel an hour and have the alternator connected to a 2K inverter which can quickly charge the two Ecoflow 1K storage units that can then slowly charge the RadPower ebike batteries, run our laptops, etc. Bottom line, I can’t see running a noisy generator long periods, especially at night to meet our power requirements. Plus, if we’re already driving on the road, our Sprinter is already running. (and yes, I’m aware of the double DC to AC conversion power losses)

Of course, I’d love hear what works best for others…

Cheers, Michael

Mike Sokol
1 month ago

The act of energy mining, production, distribution, storage and conversion has always been an expensive and dirty proposition with huge environmental impacts.
TANSTAAFL (There Ain’t No Such Thing As A Free Lunch)!

Dave
1 month ago

Mike, When you need another challenge, it would be interesting see how electric VS LP gas compare when efficiency (or lack of) are taken into account on say an RV propane furnace VS a portable electric heater or RV water heater LP gas VS electric. I suspect LP gas will still be a winner, but when you figure electric heat is 100% efficient compared to an RV LP gas furnace with is probably 60% efficient it would be good to know.

Mike Sokol
1 month ago