I could use some advice about a 12VDC to 120 VAC inverter project:

[meep]

the marine (hybrid) was a good move. Functionally, you could have also parallel’d a starter battery in to handle the current, but it would be susceptible to discharge stress as the pack as a whole dropped into deeper discharge - the deep cycle(s) would be fine with it but the starter battery would groan.

the marine batteries are a hybrid, which also can be compromise. they give up some depth of discharge for additional burst current. IIRC the typical rule of thumb for a marine battery is down to 50%, whereas a good deep cycle can dig as low as 20%. Starter batteries are happiest, generally, when not brought below 80%.

 

[JHZR2]

I can’t help you with brands of inverters, but I’d echo the idea of using a robust UPS with external batteries.

Since this is a mission critical situation set up two sets of big Ah batteries, and swap over to the second when necessary. Have a rate capable charger for the banks that can be switched between them.

The car thing in a pinch sounds interesting, but if I was really serious about that and the mission critical nature I’d probably buy a hybrid and tap into the hv battery. Otherwise I’d probably look at the two battery bank setup and use the car to charge the other bank as needed.

 

[JHZR2]

I occasionally get HF emails, and got one that had new items. For whatever reason this caught my eye:

3000 Watt Continuous/6000 Watt Peak Pure Sine Wave Power Inverter

Amazing deals on this 3000W/6000W Pure Sine Wave Inverter at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

What is interesting and caught my eye on the email was the automatic transfer switch. So it looks to me like you could use this almost like an UPS and have some peace of mind…. And have it be connectable to your car when the situation demands it.

It’s HF and brand new so who knows if you really want to push it with a mission critical application like yours. I suspect most all of this sort of thing is made in China. What you need to identify is what variant is most reliable. Still can’t help you there, but the built in transfer on this is interesting. Who knows if it is “no break”…

 

[meep]

I occasionally get HF emails, and got one that had new items. For whatever reason this caught my eye:

3000 Watt Continuous/6000 Watt Peak Pure Sine Wave Power Inverter

Amazing deals on this 3000W/6000W Pure Sine Wave Inverter at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

What is interesting and caught my eye on the email was the automatic transfer switch. So it looks to me like you could use this almost like an UPS and have some peace of mind…. And have it be connectable to your car when the situation demands it.

It’s HF and brand new so who knows if you really want to push it with a mission critical application like yours. I suspect most all of this sort of thing is made in China. What you need to identify is what variant is most reliable. Still can’t help you there, but the built in transfer on this is interesting. Who knows if it is “no break”…

I want this to be a good product so badly.

 

[DuckRyder]

+1 on Samlex. Don Rowe is a good supplier.

You'll need to provide adequate power cables for the load of course.

 

[sky jumper]

I occasionally get HF emails, and got one that had new items. For whatever reason this caught my eye:

3000 Watt Continuous/6000 Watt Peak Pure Sine Wave Power Inverter

Amazing deals on this 3000W/6000W Pure Sine Wave Inverter at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

What is interesting and caught my eye on the email was the automatic transfer switch. So it looks to me like you could use this almost like an UPS and have some peace of mind…. And have it be connectable to your car when the situation demands it.

It’s HF and brand new so who knows if you really want to push it with a mission critical application like yours. I suspect most all of this sort of thing is made in China. What you need to identify is what variant is most reliable. Still can’t help you there, but the built in transfer on this is interesting. Who knows if it is “no break”…

I have several "all in one" inverter/charger/auto transfer switch units --- Tripplite APS2012, the "utility" version of it, and a cheap offshore model. I no longer use them because:
1) they require a good battery to be connected or you get no power out, not even pass-through house power. if the unit thinks there's an issue with the battery it will shut down completely and will require manual intervention to restart it, even if house power is on. I argued with the tech guys at Tripplite about this and they insisted it was a deliberate design decision -- I called it a design flaw.
2) There's multiple "safety shut down" features that will cause the unit to completely shut down even if a good battery is connected and house AC power is on --- and again it requires manual intervention to restart it. I would randomly find it shut down for no reason at all -- battery 100%, house AC on - no power out. Tripplite said "you probably had a power surge on your AC mains".... so you shut the whole dang thing off??
3) the built in battery charger was mediocre (not applicable to the HF unit).

After several years of unpredictable service I switched to regular inverters and built my own auto transfer switches with 40A DPDT relays (load across the common, house AC across the coil and NO, inverter across the NC) and those have been bullet proof for 8yrs in continuous duty service. Not matter what's going on with the inverter or batteries there's always AC power to the load so long as house power is live.

 

[meep]

I have several "all in one" inverter/charger/auto transfer switch units --- Tripplite APS2012, the "utility" version of it, and a cheap offshore model. I no longer use them because:
1) they require a good battery to be connected or you get no power out, not even pass-through house power. if the unit thinks there's an issue with the battery it will shut down completely and will require manual intervention to restart it, even if house power is on. I argued with the tech guys at Tripplite about this and they insisted it was a deliberate design decision -- I called it a design flaw.
2) There's multiple "safety shut down" features that will cause the unit to completely shut down even if a good battery is connected and house AC power is on --- and again it requires manual intervention to restart it. I would randomly find it shut down for no reason at all -- battery 100%, house AC on - no power out. Tripplite said "you probably had a power surge on your AC mains".... so you shut the whole dang thing off??
3) the built in battery charger was mediocre (not applicable to the HF unit).

After several years of unpredictable service I switched to regular inverters and built my own auto transfer switches with 40A DPDT relays (load across the common, house AC across the coil and NO, inverter across the NC) and those have been bullet proof for 8yrs in continuous duty service. Not matter what's going on with the inverter or batteries there's always AC power to the load so long as house power is live.

Beautiful. What are you powering with this home brew UPS? I assume theres a modest float charger propping the batteries and idling inverters up? What inverter brand have you settled on?

 

[sky jumper]

Beautiful. What are you powering with this home brew UPS? I assume theres a modest float charger propping the batteries and idling inverters up? What inverter brand have you settled on?

the battery charger is a bit tricky. it has to float 13.6v while providing enough charge current to power the inverters. I've only found 2 that will do it --- a Stanley BC25BS and a cheap 8A "7 stage" charger on aliexpress-- 8A charger . It's noteworthy that I have 3 of the Stanley chargers and only 1 will hold the 13.6V. I have 6 of those 8A Foxsur chargers from aliexpress and they all work very well, keep them on all my vehicles/lawn tractors/etc.
I like the EDECOA pure sine inverters on Amazon. they are dirt cheap and work well.

 

[Quantico]

In my opinion I would buy a blue optima large battery. Or similar deep discharge type. Put it in a large boat battery box and get 12 volt cables from inverter clamped w large clamps like they use for mid size jumper cables. The inverter just needs the clamps bolted on its leads. You get a noka 1.5 amp battery maintainer and leave that battery on the tender...
You need power just unplug the battery tender and plug your ox generator into the inverter.

I have had good luck with the 500 or 750 watt harbor freight inverters. And bet the power out will be just fine.
I used this setup with my pontoon boat.. with a 1.5 amp charger.. the boat had ac power 750 watts.. and that 12 volt battery ran a stereo and lights. Ran for days with a huge optima battery. Very reliable..

Optima bat. 250.00
Inverter about 70.00
Boat bat box. 20.00
Clamps. 20.00
If you need an extention cord use a 12 guage.. short as you can get away with.