Recommended pure sine wave inverter for non-solar off-grid installation?

[Mitker]

Hello!

I've been searching for the last 5 hours among the posts on TV and couldn't get a clear picture so I prefer to ask for advice/opinion of fellow members.

I'm thus looking for a reliable inverter able to supply stabilized 220V-240V current from regular 12V batteries. A power of 2 KW should do the trick.

The context is as follow:

Our workplace is totally off-grid. By day, we run a 10KW diesel generator to power our activities. By night, we rely on batteries for light housing appliances (no AC or other heavy consumption - mostly lighting, security system, led TV, computers..)

There are 2 issues we are trying to solve:

1) by day, our current is fluctuating significantly due to equipments turning on/off (welding equipment, air compressors...); a couple of devices containing electronics suffered the consequences (a motor controller, cordless tools battery chargers and a laundry machine so far)

2) off working hours, we need a stable electrical source for the electronic devices

The idea is to create two parallel lines: one for heavy but simple machinery (welding, motors..) fed directly by the generator (by day) and a second one for low consumption but sensitive equipments (mostly containing electronics), fed 24/24 by the sought inverter relying itself on 12V batteries charged by day by the main power unit (alternator mounted on the main diesel engine)

Most of the info I've found in my searches concerns solars projects where the inverters are especially designed multipurpose devices (chargers/inverters/switches) or are not available here.

Amorn is often mentioned however I have a mixed feeling about them since half my visits there concern exchanges/repairs.

I developed the same feeling toward local "specialists"

So my question is: does anyone has experience or info about a simple yet robust inverter, 12V->220V, pure sine wave, around 2KW that can be purchased in Thailand?

Single phase should be ok; working on a multiple of 12V would be feasible too, but less hassle if 12V.

A non nonsensical price tag would be a plus.

Thanks in advance for any reply

[Crossy]

+1 for Leonics, mid price, reasonable quality.

But I will ask, do you really need pure-sine? We have simple modified sine UPS's driving all sorts of kit (even fans) with no issues whatever, motors are a bit noisy but I've never had one fail even during the floods when we ran our fans all night on inverters for 6 months.

One issue is that many inverters are not rated for 100% duty which your idea will demand from them. Also will your genset alternator have the oomph to keep the batteries charged and run the kit (it's intended to keep the starter battery charged).

Have you considered feeding your 'clean' supply from the genset via an AVR (automatic voltage regulator) and some transient suppressors?

[Mitker]

I just bought one from Leonics. 24V, 2Kw. 2Kw at 12V is quite big, but they have 1Kw. Search for "Apollo S-211A"

Leonicsdotcom

They are expansive, but two years warrantly, and pure sine.

If you can not find I have a PDF file with specs. PM me.

Arjen.

Thanks for this Arjen.

I will check this model. Always good to have first hand experience. I had briefly visited their website. Since you both recommend the brand; will make a deeper search.

If it's the way to go, I may opt for higher source voltage by putting a couple of batteries in series

Mitker

[Mitker]

+1 for Leonics, mid price, reasonable quality.

But I will ask, do you really need pure-sine? We have simple modified sine UPS's driving all sorts of kit (even fans) with no issues whatever, motors are a bit noisy but I've never had one fail even during the floods when we ran our fans all night on inverters for 6 months.

One issue is that many inverters are not rated for 100% duty which your idea will demand from them. Also will your genset alternator have the oomph to keep the batteries charged and run the kit (it's intended to keep the starter battery charged).

Have you considered feeding your 'clean' supply from the genset via an AVR (automatic voltage regulator) and some transient suppressors?

Thanks to you too Crossy

For the pure sine wave, I just have the feeling that opting for the best design would allow us to plug safely virtually any device now and in the future.

I mostly worry for the electronics. The motor speed controller we burned was a rather pricey equipment imported from Europe (as was the Bosch laundry machine)

I would thus stay on the safe side, but I admit it's mostly because of my limited knowledge in the matter

In terms of duty, it would indeed have to supply power permanently but the average power demand would rather be below 200 W. The reason I'm looking for 2 KW is just equipments like the laundry machine (cold water cycle) that I believe is somewhere in the range of 1.2 KW max. But such demand would be limited to short periods.

The charging shouldn't be too much of a problem.

Our generating unit is an open architecture. We purchased a second hand tractor and made a belt transmission unit mounted between the rear PTO and the generator. That way, according to the machinery to be used, we can select - via the PTO gearbox - the optimal engine RPM (and thus necessary torque) while maintaining the same generator RPM. We designed the belt transmission unit so that extra pulleys can be placed on its shaft to run extra alternators or even the pistons of an air compressor. The tractor keeps on running its own original set of alternator and battery.

Still on my do-list is to install the automatic start you explained in a former post (but I would have to add an hydraulic feature activating the clutch to have the generator disengaged during engine start/stop phases... hmm)

As for the AVR, our generator proudly displays an AVR switch but it didn't prevent the damages. Here once again, my knowledge doesn't allow me to perform the necessary tests to check if it is working properly or not. But to be honest, I think that our activities put a serious strain on the current flow with repetitive and serious drop/peak cycles in voltage (and frequency?). The welding is the main culprit here. That's why I see the batteries "transit" as a definitive protection against these cycles.

Thanks again,

Mitker

[Crossy]

You won't run the washer from a 2kVA inverter, the motor start current will kill it dead

The AVR I'm talking about isn't the same as the unit in your genset, it's a separate mains conditioner.

How about a separate generator for the sensitive stuff, hook it to the same prime-mover if the speed regulation is good?

[Mitker]

You won't run the washer from a 2kVA inverter, the motor start current will kill it dead

The AVR I'm talking about isn't the same as the unit in your genset, it's a separate mains conditioner.

How about a separate generator for the sensitive stuff, hook it to the same prime-mover if the speed regulation is good?

Thanks for the warning. I will check the offer of independent AVR (I'm not familiar with these)

The original idea was to mount a 2nd, smaller generator on the transmission (mostly for backup purpose) and we have it already. Currently the shelter accommodating the main unit doesn't allow room enough for this extra equipment. When we'll move the whole unit to its final location, we'll add it. Meanwhile I should check how much RPM we lose when large equipments are turned on.

Anyway, I will need the inverter for the night supply. I have purchased 4 cheap inverters in the last 12 months. 3 have been trashed already. Irreparable.

I'll need a serious one before the last one follows the same path.

[Crossy]

After "using up" several cheap Chinese inverters over the years we're using modified computer UPS's to keep the lights, TV and fans alive over night when PEA have decided that we don't really need power and we don't want to run the genset.

You can pick up an 800VA 'refurb' unit for 1000-1500 Baht, hook up to an external battery and charger (remove the beeper too) and be good to go.

I've decided that, for our situation at least, a number of smaller units is the way to go, no single point of failure and they tend to be more reliable if you keep below about 50% of their rating. Run several off a single large battery.

Have you investigated a proper welding generator which directly feeds the torches? How about a pukka genset rather than the home brew system?

Obviously budget is a controlling factor but considering the stuff that's been killed already it may be worth it in the long run.

[Mitker]

Where do you get the "refurb"? Sounds a good option. Do they supply a correct wave? At least it seems your electronics didn't suffer.

We use MIG welding equipments (wire+gas) and from my experience, the welding generators sold here are only suitable for the common TIG (sticks) machines. On the other side, the supply must also feed a series of electric motors from 1/4 HP single to 6 HP 3-phase (not simultaneously). A few larger machines are also waiting for years that I dedicate some spare time to wake them up..

The home-made design results from several requirements: the fun/curiosity + the search for a design where the different components can be repaired/interchanged/upgraded independently (-> flexibility, reliability and own control) + possibility to add specific functions (like the air compression kit) etc.. Some remote projects, a little long to detail, also imply such an open architecture

(I had the opportunity to test a pricey, nice looking integrated diesel generator: it had to be sent back to BKK for repairs after only 3 months - meanwhile, we didn't have more than 2 days interruption during the 18 months we have been running our own Frankenstein stuff).

Apart from the sensitive equipments, the current power fits the bill. Therefor my idea to add to the existing line of raw power a secondary, light, clean supply.