Using inverter for TV during 8 hour power cut

Forums › Home Workshop DIY › Using inverter for TV during 8 hour power cut

Reanalyse

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Ultimate Geek

#300718 29-Sep-2022 20:49

Hi All

We have a scheduled 8 hour power cut coming up in a few days, and as I have a spare new car battery was planning to use an inverter to keep the power on the TV.

Looking to purchase a basic Jaycar model https://www.jaycar.co.nz/150w-450w-12vdc-to-240vac-modified-sinewave-inverter/p/MI5300 to keep the TV on.

Power draw for the Panasonic 43" looks to be ok.

Are there any fishhooks I should be aware of.

Thanks and Regards

mattenz

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Master Geek

#2975012 29-Sep-2022 21:16

I doubt that you'll run a TV for eight hours on a car battery.

lxsw20

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#2975060 29-Sep-2022 21:19

You'll also likley kill a cell in the battery if it's not deep cycle, they are not designed to be drained like that.

pih

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#2975076 29-Sep-2022 22:13

I've found on lower end models you should take the 150W (450W peak) with a grain of salt. If your draw is likely to be over 100W, go for the next model up. And yeah, you'll probably need a bank of 3-5 batteries for 8 hours of comfortable TV, not one.

Linux

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#2975077 29-Sep-2022 22:17

You should be using a deep cycle battery

gzt

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#2975078 29-Sep-2022 22:18

I have almost no experience with inverters. It says modified sine. Laptops yes because it an adaptor charges a battery. TV who knows imo far more sensitive.

neb

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#2975100 30-Sep-2022 00:19

gzt: I have almost no experience with inverters. It says modified sine.

Just avoid modified sinewave anything. "Modified sinewave" is a stepped square wave, and in cheap and crappy inverters tends more and more towards a pure square wave as the battery runs down. There's really no reason to still have square-wave inverters nowadays.

Edited to add: Just had a look at the Jaycar link, a $45 inverter is not going to be a good one. It'd be OK for feeding a resistive load (e.g. a heater, fridge, etc in a camper van which it looks like this is designed for), but for an inductive or capacitive load you're going to dissipate a lot of energy as heat since the load is designed for 50Hz, not the higher-order harmonics delivered by the square wave. At best this will affect their operation, at worst it can destroy them.

Dynamic

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#2975191 30-Sep-2022 08:02

I've got a fairly quiet 700w digital inverter generator you can borrow if you can get to my lockup just off Lincoln Road. It's backpack sized. You would need to re-fuel it after 3 hours. It runs my 290l fridge just fine in a power outage.

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Mehrts

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#2975603 30-Sep-2022 17:11

Is is essential to have the TV running during this outage?

neb

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#2975605 30-Sep-2022 17:17

Mehrts:
Is is essential to have the TV running during this outage?

Are you kidding? There's a Duck Dynasty marathon on, this is more important than silly stuff like keeping the fridge running.

shk292

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#2975665 30-Sep-2022 20:35

Mehrts:

Is is essential to have the TV running during this outage?

That was my thought - just run TVNZ+ or whatever on a tablet or something. Seems a lot of work to cater for an 8 hour power outage, assuming it's a one-off

Ge0rge

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#2975690 30-Sep-2022 22:26

Linux:

You should be using a deep cycle battery

Depends on the size of the battery, and the intended depth of discharge.

In this proposed case, even a deep cycle battery would experience damage.

Scott3

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#2975698 30-Sep-2022 23:42

I'll run the numbers some numbers.

Lets assume the car battery is a smallish one at 45Ah. with 50% intended depth of discharge. That 270Wh of storage.

lets assume 32" LCD drwaing say 50 watts (A lot of variation here, could be anywhere between 20 and 100W).

Say 90% inverter efficiency = 4.86 hours.

I can't comment on if the modified sine wave will run a TV fine. Have run my laptop on modified sine before. everything worked fine except the track-pad, which went haywire (I disabled it and used an a mouse). The Jaycar site lists most TV's as suitable.

neb

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#2975701 1-Oct-2022 02:00

An update in my earlier comments, here's a video of someone comparing "simulated sinewave" inverters with a true sinewave one:

The... garbage coming from the squarewave inverters is truly scary. It's not even a proper square wave, it's a pulsed square wave which really going to mess with any modern APFC power supply because of the amount of time it spends at zero power. So not only are they not even remotely a sinewave, they're not even a square wave, they're a pulsed square wave with massive overshoot and thus lots of high-order harmonics. Short of pathologically bad circuits designed to kill devices it's hard to think of a worse output waveform than this.