this post was submitted on 15 Aug 2023
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I'm tired of buying a new 12 V battery every 1-2 years. I have about 4 small (rated ~ 300 W [not VA]) UPSes with 7 Ah, 12 V, maintenance free batteries.

I'm thinking about replacing them with one, powerful unit. But the more powerful the unit, the more it costs - non-linear.

Do you have experience with some DIY solutions? Like 12V DC to 230V AC inverter, battery charger, some UPS controller (simple relay?)?

Or maybe you have some other idea that is cheap(ish)?

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[–] xtremeownage@lemmyonline.com 7 points 1 year ago (2 children)

I built a homemade one. 2.4kwh of capacity.

Should be good for a few decades easily.

Wouldn't call it cheap. But, it will be around for 15 or 20 years.

https://xtremeownage.com/2021/06/12/portable-2-4kwh-power-supply-ups/

[–] TheWiseAlaundo@lemmy.whynotdrs.org 1 points 1 year ago (1 children)

Man. That AIMS low frequency inverter is nice.

I actually bought one of those cheaper Chinese pure sine wave inverters, but found that they don't run motors/power tools that well. The surge current demand just exceeds anything they can provide. They're great for resistive loads like PCs/LEDs/Hotplates, but if you wanted to run a table saw or something the AIMS is the only way.

[–] xtremeownage@lemmyonline.com 2 points 1 year ago

Cheaper or not, isn't a huge factor.

My really expensive sol-ark 12k cannot start my 110v air-compressor.

The issue is, the rated L.R.A. ie, locked rotor amps, how much current it takes to get it started.

My A/C motor, for example, uses around 20 amps @ 240v when running, ie ~5,000w. However, its L.R.A, is 112.0 amps @ 220v, ie- (24,640 watts). Which is more than the peak load my 12k inverter can handle. So- if you tried to start it on the inverter, well, it doesn't work.

https://static.xtremeownage.com/blog/2023/off-grid-ac/

The same principle applies to anything with a motor.

You have to evaluate the L.R.A. Remember, if you have say, a 5,000watt RMS inverter, which can handle a 10k peak- its not going to be able to start something that has a 14,000 startup draw.