Anybody know if you can run inverters in parallel?

SB118

SB118

SB118

Soldato
Joined
18 Oct 2002
Posts
7,700
Location
"Sunny" Plymouth
Been pricing up an inverter for a project, and it seems that "economy of scale" doesn't seem to apply here.

600w units go for just over £30, but 1000w units are £70.

If i could get the 600w units to run in parallel, i could save a few quid.

So..... any clever begger out there want to enlighten me?

cheers
 
Correct, 10 points, have a badge.

I'd also have an additional 200w capacity to play with.

And if i CAN run in parallel, i could run 3 600w units and have nearly the same capacity as a pair of 1000w units. 3 x 30 quid vs 2 x 70 quid, now does the query make sense?

edit, and i might learn to type faster too! :D
 
Tomsk said:
Probably won't work as the phases won't be synchronised.
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He's right you know, and OP, just clarify, are we talking about true sinewave inverters, modified sine, square, or what?
 
Tomsk is correct. It would take an enormous amount of creative wiring between the two to get the phases to synchronise.

Otherwise plugging two seperate inverters together to parallel them is going to amount to a terrific amount of smoke and two dead inverters.

Sorry, SB. Not gonna work.

The only thing you can do is divide up your loads so that you can put some on one inverter and the rest on the other. Then the two inverters CAN be hooked up to the same power source.

Just remember that 1000W @ 12V = 831/3 amps. That'll draw a standard car battery down in a little over 21/2 hours (455CCA batery dropping below minimum voltage, not completely dead). And even if your car is running at the time, most cars only run a 35 - 55 Amp alternator. So all you've done is delayed the inevitable.

As I found out the hard way. I was running my 1600W inverter off my truck, which was idling. Now, it has a GM 105A alternator, but with the truck idling the alternator couldn't put out full power. So after running my saw for a couple hours, my truck sputtered to a stop. I thought I'd run out of petrol. Come to find out the battery had gone so flat it didn't have enough power to fire the ignition coil. I had to take the battery out of the truck and carry it back to the garage to put it on the charger (for 24 hours it was so dead).

So please be careful as to what you hook a 1000W inverter up to.
 
Can you not get one off an old junked generator? Probably be able to get a 3KW jobbie for not much
 
Mickey_D said:
That would work, but what are you going to spin it with? ;)
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This do ya? :) (just the green bit!)

listerd.jpg
 
Mickey_D said:
The only thing you can do is divide up your loads so that you can put some on one inverter and the rest on the other. Then the two inverters CAN be hooked up to the same power source.

Just remember that 1000W @ 12V = 831/3 amps. That'll draw a standard car battery down in a little over 21/2 hours (455CCA batery dropping below minimum voltage, not completely dead). And even if your car is running at the time, most cars only run a 35 - 55 Amp alternator. So all you've done is delayed the inevitable.

As I found out the hard way. I was running my 1600W inverter off my truck, which was idling. Now, it has a GM 105A alternator, but with the truck idling the alternator couldn't put out full power. So after running my saw for a couple hours, my truck sputtered to a stop. I thought I'd run out of petrol. Come to find out the battery had gone so flat it didn't have enough power to fire the ignition coil. I had to take the battery out of the truck and carry it back to the garage to put it on the charger (for 24 hours it was so dead).

So please be careful as to what you hook a 1000W inverter up to.
Click to expand...

Looks like i'll have to make do with a single 1000w unit then, going to have a half dozen or so batteries, so hopefully they shouldn't run flat overnight. :eek: Going to need a bigass charger to get juice into them during the day though, or i could even push a couple of car alternators into the loop, if i could find a way to stop them overcharging the batteries.
 
PeterNem said:
I don't have any advise for you SB118, but am genuinely intrigued as to what it is you are trying to rig up!
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I second that! What global domination scheme are you working on?
 
I'm looking at going "off grid", 6hp Lister engine (got!), 5kw alternator (need), pile-o-batteries & a nice big inverter.
 
Yup, and the Lister engines love the veggie too = free leccy :D and depending on the heat output i can use the coolant circuit to heat a couple of rooms in the flat, doing away with our portable calor fire = more savings :)
 
I hope you understand the implications of connecting stuff to something like this, if you are using more than just say a single appliance, you should tie the supply down to physical earth, then you have to make sure its adiquately protected against indirect contact, over current devices are unlikely to be sufficent as the fault current will be limited from such a set up, and you'll likely to need to protect against indirect contact via way of RCD.

Anyway, what you thinking of doing, fitting a changeover switch before your CU, and having it switch between the supply from the grid and a ceeform inlet socket?
 
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