17 Comments
author

Last year I did a direct comparison between a portable 12-volt DC compressor fridge/freezer running directly from a battery vs an inverter and PWM power supply. I can post that tomorrow if you all like.

Expand full comment

Is there a list that shows which commonly available generator is and is not a pure sign wave generator?

Expand full comment

Mike, I know generators without a pure sine wave is bad for your electronics. I have a laptop i wish to protect. It's power supply appears to convert 120V AC to various DC voltages to keep my laptop's battery charged. Should I be more concerned for my power supply than my laptop?

Expand full comment
Jan 12, 2023·edited Jan 12, 2023

Aren't electric blankets nothing more than dead shorts being used to produce heat?

Expand full comment
author

Not dead shorts, but basically big resistors.

Expand full comment

Mike -- google search "12 volt DC mattress pads. That brought up some at Walmart, (which surprised me, cozywinters.com for truckers, and lots more.

Expand full comment
author

I just looked at your link, and their 12-volt DC mattress pad draws 75 watts, so it will drain most of a 100 amp-hr battery in 8 hours. Watts is watts, the voltage really doesn’t matter….

Expand full comment

Many electric blankets and mattress warmers are made to run on 12 volt DC, and this saves a lot of power.

Expand full comment
author

The ones I’ve looked at draw 50 to 75 watts. As noted in my article a 100 amp-hr lead/acid battery only has around 600 watt-hrs of available energy. So 600 watt-hrs / 75 watts = 8 hrs to 50% SoC.

Expand full comment
author

Steve,

I haven’t found any Full or Queen size electric blankets that run on 12 volts DC, only leg warmers. Please post a link if you know of a specific product.

Expand full comment

many electric blankets and mattress warmers are made for 112 volt DC power and use far less than using inverter on AC warmers. Also no magnetic fields generated for those concerned about that with AC blankets.

Expand full comment
founding

Mike, I would enjoy seeing your comparison on 12 VDC fridge/freezer. I have a ARB fridge/freezer that I mostly use for 4 wheeling in the back of my Jeep. I do sometimes use it in the M/H on the 120VAC while on the inverter!

Also would be great to know how much that M/H heater fan draws for each cycle!

Thank you

Snoopy

Expand full comment

Great info as always. You mentioned the gas furnace typical in RV's but you did not mention the numbers related to it. So, How much power does a typical gas furnace blower use?

Expand full comment
author

I’ll have to check, but IIRC it’s around 8 amperes or so…

Expand full comment

Is there a DC blanket available and would that make a difference in power usage?

Expand full comment

Lots of 12v stuff available in the OTR trucking industry. Try Rainey's for all the trucking accessories you could ever want. (Not affiliated)

Expand full comment
author
Jan 11, 2023·edited Jan 11, 2023Author

But watts is watts. There will be some advantage to powering many devices directly from 12 volts DC, but unfortunately 12 volt heating appliances with the same wattage as their 120 volt versions will deplete the batteries nearly as rapidly, with perhaps a 10% advantage by eliminating the inverter losses.

Expand full comment