Small inverter options?

[Brushless]

I am keen to build up a small, economical solar system for my PC/TV/LED lights in a detached office. I have a 150W panel and plan to get another one to have 150W @24V, I also have two 105Ah deep cycle batts in series and a 24V solar charger. Saw this inverter which seems a good buy, 2400VA/1440W for R1508: http://www.geewiz.co.za/mecer-invert...ontroller.html

Any other good buy's around? Or any other suggestions?

[Czauto]

Hi Graham,
The inverter you're referring to is actually an UPS. I used one for more than 2 years with my whole house's lights and some dedicated plugs for tv, explora, etc connected to it.
When plugged in to an AC supply it will be in 'linethrough" mode when AC supply is available. As soon as there is a power failure it switches over to the batteries to supply AC to it's outlets. I guess if you leave the supply side disconnected and charge the batteries via a seperate solar charge controller it will work. That was actually my plan as well nut i decided to rather purchase a 5kva MKS Axpert and run my whole house from it.
I gave my old system (mecer ups) to my father in law and it's still running 100% with the same 4 year old Shoto 102Ah batteries. It has been used as UPS system it's whole life though, not permanent solar application. Not sure how it's going to hold up when the inverter section is going to be used 24/7

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[___]

It's a modified sine wave inverter with a pretty terrible transfer time (20ms), but for the intended use case it's probably perfect :-)

[pilotfish]

I previously had a 5 kVA modified sine inverter backing up my tv/pc/lights during rolling blackouts, the TV buzzed and dimmers flickered unless set to full bright - otherwise all OK.

[___]

Anything with a switch mode power supply (such as modern televisions, not the old CRT types), computers, cell phones, they are not going to care. LED lamps... some will care and some not. The MR16s I have with the transformer and a built-in SMPS... they are not going to care. But some lamps (GU10s, of course not all of them) might use a capacitive dropper to do at least part of the work, those might care. And electrical motors.

So of the things he mentioned, only the lights might be a concern.

Also, don't connect it to the house wiring. Most MSW inverters can't have their neutral bonded to earth.

[Guest]

On 6/9/2017 at 6:30 PM, Graham said:

Saw this inverter which seems a good buy, 2400VA/1440W for R1508

Steer clear of those ones. Good for their designed purpose, but not for solar application as they are not designed to run 24/7/365.

Start here, as the guys here will say good value for money with lots of support here: http://www.geewiz.co.za/1473-rct-inverters

If you have lots of cash, like in a lot, and don't want to tinker, then look here: https://www.victronenergy.com/

[Brushless]

Thanks for all the replies. The system will run probably 8-10 hours a day mostly at fairly low wattage (300-500W) so based on what has been said that inverter will probably do the job just fine. And R1500 compared to R4850 for the RCT is a substantial price difference.

I wondered if there are any other inverters around that price better than the Mecer?

[Gnome]

The price difference is aligned with the quality of the product.

The RCT is pure sine wave inverter designed for 24/7 operation and can be wired into your installation.

The Mecer is a modified sine wave meant for backup purposes and cannot be wired into an installation. IMO you will end up abandoning it if you try to use it for solar. But if you are going ahead with it, then come back and post your experiences.

This isn't about being right or wrong, more about what the expected experience will be.

[SilverNodashi]

My father used to use a 1000W chinese "cheap-ass" inverter in the Africa for his TV, lights and latop while he was working there. Never had any issues with it. I think he paid R800 for it a few years ago. He left it with one of the locals last year when his contract ended. 

[Czauto]

To begin your solar experience with, i guess it's fine but remember, you WILL need to upgrade in future.



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[Guest]

15 hours ago, Graham said:

The system will run probably 8-10 hours a day mostly at fairly low wattage (300-500W) so based on what has been said that inverter will probably do the job just fine

Ok, 3 things about those Mercers.
Thing One: Out of 20 I solf, 4 came back broken after a few months.
Thing Two: The are quite noisy.
Thing Three: Running them for 10 hours per day for 7 days a week, not sure if they will last.

In my opinion, your are throwing away R1500 for as Czauto said, you are going to replace it. I would bet within 6 months if the solar bug bites you. Been there done that.

If you are after a solid small inverter, max 300w at peak, see my add under Classifieds for the Victron Phoenix little 375VA inverter, it has a warranty still, it is quiet, it is pure sine wave, also 24v and at the same price.

[Chris Hobson]

23 minutes ago, The Terrible Triplett said:

If you are after a solid small inverter, max 300w at peak, see my add under Classifieds for the Victron Phoenix little 375VA inverter, it has a warranty still, if is quiet, it is pure sine wave, also 24v and at the same price.

That's a good offer

[Czauto]

Maybe off topic but same difference. I wanted to get some mud terrain tyres for my 4x4 colt. Seeing that these pittbull/bulldog remoulded tyres were so cheap I was very close to buying a set of 4 for R4400. That's excluding shipping, fitment and balancing. Seeing that they don't like speed, or heat, or gravel roads, or anything else for that matter, i would use them only for offroading. I would keep my existing dunlops on a extra set of rims for long distances. Then it got me thinking? What if i want to go and do the Louvain 4x4 route for example? I cannot drive there with the remoulds so i would need to carry an extra set of wheels the whole trip. Nah! So i went shopping, shopping hard. I've ordered 4 x 33" yokohama mud terrains today for R9k (everything included) and i can even pay the guy in 4 installments. This is almost double the price of the cheapies but I now have tyres that can do what it's supposed to do.
Same thing with inverters. Rather save a bit longer and get something that can do the job properly before you get the cheap "remoulds" and be sorry afterwards.

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[___]

23 hours ago, Graham said:

I wondered if there are any other inverters around that price better than the Mecer?

I assume you mean the cheap Mecer linked in the first post? Cheap inverters (modified sine wave, no soft-start, little protection, often can't even deliver the advertised power) price around the same level as a generator per unit of power. If you look on Adendorff's site right now, you're talking about R1.10 per watt (they have a 8.75kva for 9.5k). It's been around this price for a decade, roughly R1/watt (capacity). Good inverters start at twice the price of a generator. That's a good rule of thumb.

At the power levels you speak of, I'd get this one instead. Full sine, surge power capable of around 200% nominal, and you can chuck it in the car boot when you go camping.

[Brushless]

OK, I got the Mecer 1440W Inverter/UPS having read up on it more here: https://mybroadband.co.za/vb/showthread.php/698166-Opinions-on-Mecer-Inverter , and generally the opinions on it were quite favourable.

It works great, just a little noisy as noted in that thread, it has what seems to be a standard PC fan so has just about the same noise footprint as a standard desktop PC, not too intrusive at all.

I'm only drawing 210W max with everything running so it's not stressed at all. My two 150W panels in series are currently producing 8A at 26V so ~208W in full winter JHB midday sun.

So I think I'll probably be getting another two 150W panels for a bit extra charging capacity.

[PaulF007]

Having had a quick look at the marketing info you got a PWM SCC. As this is the heart of any solar system I would recommend you wait on getting more panels and get a MPPT SCC. Be Aware that sometimes you end up spending twice the amount intended  because of cheap "plans" .  
As a rule panels will last you quite a long time but SCC's are a different story especially in the PWM market. .. 

[Brushless]

My SCC is MPPT not PWM.

[PaulF007]

Ok cool , what SCC did you get?

[Brushless]

Actually correction there, it's MPPC not MPPT. It's a HCDP 360W controller which I've adapted.

[___]

2 hours ago, Graham said:

MPPC not MPPT

I had to look up MPPC :-)

Indeed, just controlling the flow and not automatically tracking it is probably a good compromise for places with lots of sun or when camping. You essentially set it at the voltage it should operate (Vmp for your panels, or just under it) and leave it there. Should do better than a PWM but worse than an MPPT. Would be interesting to know how much worse, since there is only a 33% difference between PWM and MPPT. Will it be closer to MPPT than PWM? I think it will...

[Brushless]

Yes, not as good as MPPT but better than PWM. I have an old 10A PWM Phocos SCC that I must try and see the difference.
That reminds me about another question regarding PWM vs MPPT. In good sun and warm temperatures it seems a MPPT SCC might not have the benefit that it would in cold climates and weak/obscured sun. What would the realistic % improvement be in our climate? 10-20%?

[Chris Hobson]

50 minutes ago, Graham said:

 What would the realistic % improvement be in our climate? 10-20%?

What is more important is how well matched are the panels and battery bank are. If the PV voltage is very high in relation to the battery voltage you lose a whole lot. If panel voltage is just above battery voltage you lose just a little. The PWM "shaves off"  the excess voltage.

[Brushless]

That makes sense. So my panels' open circuit voltage is 45.2V (22.6V x 2) and max power voltage is 36V with a max battery voltage of 28.8V (14.4V x 2).

So would a MPPT SCC give me extra 30% current here?
 

[Gnome]

On 6/9/2017 at 11:43 PM, plonkster said:

<snip>

Also, don't connect it to the house wiring. Most MSW inverters can't have their neutral bonded to earth.

That and your earth leakages don't work anymore. Neutral is at 120v relative to earth, so even if a plug is off you can get electrocuted. Unlike a safe installation, you will get shocked and the circuit breaker will not bat an eyelid. It'll happily keep electrocuting you all day long without tripping.

Of all the things that make an installation unsafe, this one is particularly hazardous.

[___]

3 minutes ago, Gnome said:

Neutral is at 120v relative to earth

Yeah, that ironically makes it safer to leave ground unbonded, ie a IT earthing system (supply ungrounded, appliances grounded to a local ground). And as you said, no ELB protection.