[RE-wrenches] Portable power station for surge loads

Sun Mar 22 08:19:52 PDT 2026

Love to see it Ray
I have used an Electrocalc calculator for years & the results seem overly conservative not that that is a bad thing at low voltages. But dam quick.
Sent from my iPad

On Mar 21, 2026, at 9:59 PM, David Coale via RE-wrenches <re-wrenches at lists.re-wrenches.org> wrote:

Hi William,

Thanks for the summary.  I have been collecting information on 120-volt induction cooking solutions, which are listed below.  Most of these are probably too big for an ADU, but this is what I have so far

David

Induction cooktop info

The best portable one-burner induction cooktops:
https://www.nytimes.com/wirecutter/reviews/best-portable-induction-cooktop/

Copper induction range with a battery – only 120-volt outlet required:
https://copperhome.com/products/charlie

Impulse induction cooktop only with a battery – only 120-volt outlet required:
https://www.impulselabs.com/

Electra stove with a battery
https://cleantechnica.com/2025/11/25/electra-just-made-switching-to-induction-as-easy-as-plugging-in-a-toaster/

On Sat, Mar 21, 2026 at 8:38 PM William Miller via RE-wrenches <re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>> wrote:
Thanks everyone for the input.  Here are answers to some of the questions:

I have a heat gun that runs right at 1300 watts (10.8 amps).  I made before and after voltage measurements and got 6.5% voltage drop.  (124 VAC versus 116 VAC).

My spreadsheet predicts 3.4% VD.  There are some Polaris splices that might contribute to the overall resistance.

My plan would to power only the cooktop with the integrated inerter/battery/charger unit, if this becomes the decision.

I like the all in one unit because I don’t want the complexity and foot-print of separate inverter and battery array.  This ADU is a rental and the owners are elderly and need plug and play simplicity.

We could bump the circuit to 240 VAC, or higher, for that matter.  However there is an off-grid home in the middle of this feeder that taps off 120 VAC very occasionally to get through cloudy/low hydro days.  Then we would need three transformers.

I did recall that there are induction cooktops with batteries built in .  I need to research that more thoroughly.

Still pondering.

William

William Miller
Miller Solar
www.millersolar.com<http://www.millersolar.com/>
CA License C-10 77398

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org<mailto:re-wrenches-bounces at lists.re-wrenches.org>] On Behalf Of Ray Walters via RE-wrenches
Sent: Saturday, March 21, 2026 6:20 PM
To: re-wrenches at lists.re-wrenches.org<mailto:re-wrenches at lists.re-wrenches.org>
Cc: Ray Walters
Subject: Re: [RE-wrenches] Portable power station for surge loads

I remember doing some measurements on a long wire run, and being surprised that the actual voltage drop was much less than the calculations.  That's when I found a small note at the bottom of the NEC Table 8 conductor properties used for official VD calculations.   The resistance is listed at 167 F (75C), so if you use the adjustment equation in Note 2, it is much less VD, and corresponds to reality.  For underground conductors, I might use 25C.  Use common sense.

The formula is R2=R1 (1+ a(T2-75))

I made a spread sheet about 15 years ago, that uses that formula for doing wire sizing.  Happy to share, if anyone is interested.

Ray Walters
Remote Solar
On 3/21/2026 3:21 PM, Jay via RE-wrenches wrote:
Are you trying to run the whole house or just the burner?
I’m also curious about how you calculated the VD. I ran it on a few programs and it came up much less VD. I’d go direct or try the load and measure the VD. It won’t use the full power for long. Or at least when I use my induction top it takes so short to bring anything to a boil, after that it’s turned down.
Lots of options.

On Mar 20, 2026, at 11:23 PM, William Miller via RE-wrenches <re-wrenches at lists.re-wrenches.org><mailto:re-wrenches at lists.re-wrenches.org> wrote:

Friends:

A long-time client has an ADU 755 conduit feet from the main house.  They started off-grid but they are now grid connected.

In 1999 we pulled a 120 volt feeder of #1 aluminum to the ADU.  This provides about 10 amps at 5% voltage drop.

This client wants to abandon a propane cook-top in the ADU in favor of an induction cook-top (indoor air pollution as a consideration).  A sample two burner induction cook-top is 1800 watts--too much power draw for this feeder.

I was wondering if a portable power station rated at enough power to run the induction cook-top might solve this problem.  The 10 amp power feed can charge the power station at (hopefully) an acceptable amperage over an extended time period and the power station can provide enough surge power to run the cook-top intermittently.

I see the Bluetti AC500, for example, can be adjusted to draw no more than 10 amps when plugged into AC.  Unfortunately this charge rate, when running at the full 10 amps, allows little overhead for other loads.  I presume this 10 amps draw is only 10 amps when the internal battery is fully discharged.  Maybe other units can charge at a lower rate.

Have any of you tried this?  Any input is appreciated.

William

William Miller
Miller Solar
www.millersolar.com<http://www.millersolar.com/>
CA License C-10 77398

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