Wrong inverter purchased ?

Nuff · December 2013

I’m currently using the following off grid system to provide power for 300w of lighting , laptop charging , lpg fridge

1)Stand alone charge controller set for 24v http://www.ebay.co.uk/itm/140602461807?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
2) Two 190w Risen panels wired in series for 24v
SYP190S-M 190W 0~+3% 36.60 5.30 45.10 5.60 >14.88%
3) 4 x 6v 180A/H batteries coupled in series for 24v
4) 1 UPS 1500 tower inverter- without battery
http://www.ebay.co.uk/itm/APC-1500-tower-UPS-SUA1500i-refurbished-new-cells-/390337662650?pt=UK_Computing_Uninterruptible_Power_Supplies&hash=item5ae1f00eba

Problem
The batteries were not holding charge long enough to power lights for more than 2 or3 hours.
SG is ok although not great, amps from PV are between 1 and 5 max subject to sun.

Considered solution was to upgrade the whole system so I have some more 190w panels lined up and a bank of fork lift truck batteries ie
A 12 PACK OF 24V BATTERRIES CELLS
chloride 7cd420 all in a metal batterie tank 420 AMP PER HOUR H:780mm L:790mm W:215mm
I haven't bought the panels or the batteries yet

In a moment of stupidity however I did buy a new SMA 1700 grid tie inverter , because it was cheap, which I now know needs 180v to start it so it seems unsuitable for my battery bank.

Question. Can I use the new SMA 1700 with more panels, say 8 x 190w in total, to power my site and if so assuming this will this charge the batteries better should I retain the old UPS inverter to run the lights or just start all over again and sell the SMA 1700 ?

Blackcherry04 · December 2013

Re: Wrong inverter purchased ?

Nuff wrote: »

I’m currently using the following off grid system to provide power for 300w of lighting , laptop charging , lpg fridge

1)Stand alone charge controller set for 24v http://www.ebay.co.uk/itm/140602461807?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
2) Two 190w Risen panels wired in series for 24v
SYP190S-M 190W 0~+3% 36.60 5.30 45.10 5.60 >14.88%
3) 4 x 6v 180A/H batteries coupled in series for 24v
4) 1 UPS 1500 tower inverter- without battery
http://www.ebay.co.uk/itm/APC-1500-tower-UPS-SUA1500i-refurbished-new-cells-/390337662650?pt=UK_Computing_Uninterruptible_Power_Supplies&hash=item5ae1f00eba

Problem
The batteries were not holding charge long enough to power lights for more than 2 or3 hours.
SG is ok although not great, amps from PV are between 1 and 5 max subject to sun.

Considered solution was to upgrade the whole system so I have some more 190w panels lined up and a bank of fork lift truck batteries ie
A 12 PACK OF 24V BATTERRIES CELLS
chloride 7cd420 all in a metal batterie tank 420 AMP PER HOUR H:780mm L:790mm W:215mm
I haven't bought the panels or the batteries yet

In a moment of stupidity however I did buy a new SMA 1700 grid tie inverter , because it was cheap, which I now know needs 180v to start it so it seems unsuitable for my battery bank.

Question. Can I use the new SMA 1700 with more panels, say 8 x 190w in total, to power my site and if so assuming this will this charge the batteries better should I retain the old UPS inverter to run the lights or just start all over again and sell the SMA 1700 ?

Yep, wrong Inverter, even if you had enough panels ( DC input ) the Inverter will not work without a Grid reference voltage or being AC coupled.

verdigo · December 2013

Re: Wrong inverter purchased ?

Nuff wrote: »

In a moment of stupidity however I did buy a new SMA 1700 grid tie inverter , because it was cheap, which I now know needs 180v to start it so it seems unsuitable for my battery bank.

Question. Can I use the new SMA 1700 with more panels, say 8 x 190w in total, to power my site and if so assuming this will this charge the batteries better should I retain the old UPS inverter to run the lights or just start all over again and sell the SMA 1700 ?

If the SMA 1700 is a grid tie inverter its not going to charge batteries or use batteries to invert DC to A/C

mike95490 · December 2013

Re: Wrong inverter purchased ?

Wrong inverter. No charge controllers for 190VDC, the PV would cook the batteries.

WAIT on the forklift battery, you don't have near enough PV wattage to keep it charged.
If the battery is 500AH, you need at least 50AH (10%) of charge current to keep it happy and de-stratified.

SolInvictus · December 2013

Re: Wrong inverter purchased ?

Two 190 W PV panels, 300 W of lamps and batteries about 75% efficient.

PV panels output 1.7 kWh/day, 1.3 kWh/day comes out of batteries and lamps use it all after 4 hours and 20 minutes. During winter, you may be getting less than 1.7 kWh/day from the PV panels.

You do not have enough PV panels.

Nuff · December 2013

Re: Wrong inverter purchased ?

Thanks for your answers everyone. A few more questions though.

1) What do you folks think of the Hosun 290w panels.

2) Can I add two to my current 2 x 190w panels or should I stick with 190w.

3) Will I have enough power to charge the fork truck batteries or would 4 Crown 6V 220Ah batteries be more suitable.

westbranch · December 2013

Re: Wrong inverter purchased ?

from your first post those panels are putting out 5.6A @ 36.6V, 2 in series = 5.6A @ 73.2V, for 24V output you should get ~ 7.3A @ 28V... that is enough to charge a 73 - 145Ahr battery. (5%-10% charge rate)
Adding a 3 rd panel in series is not all that good fro a variety of reasons, need higher rated Circuit breakers etc. 2 panels in series would have close to 90V open circuit...! Not to be trifled with.

Nuff · December 2013

Re: Wrong inverter purchased ?

westbranch wrote: »

from your first post those panels are putting out 5.6A @ 36.6V, 2 in series = 5.6A @ 73.2V, for 24V output you should get ~ 7.3A @ 28V... that is enough to charge a 73 - 145Ahr battery. (5%-10% charge rate)
Adding a 3 rd panel in series is not all that good fro a variety of reasons, need higher rated Circuit breakers etc. 2 panels in series would have close to 90V open circuit...! Not to be trifled with.

Thanks for your help westbranch and excuse my ignorance here but how do I increase my pv array as recommended earlier.

westbranch · December 2013

Re: Wrong inverter purchased ?

For a battery based system, you can add panels to it by paralleling more panels, if you go for 3 they will all have to be in parallel, so they are all at the same voltage.
4 (or ? in multiples of 2) is your next option.
You can add to the CC's max output or to the battery banks needs, which ever comes first...
Depending where you are there may be the option to over panel, with caution.
hth

Nuff · December 2013

Re: Wrong inverter purchased ?

Thanks again.
So if I purchase two 290w (36.7v max /7.9A) panels should I couple them in parallel with the two 190w (36.6v max/ 5.6A) panels I already have ?
If so will they be sufficiently powerful to charge a set of 24 volt 465amp fork truck batteries ?

bmet · December 2013

Re: Wrong inverter purchased ?

Nuff wrote: »

Thanks again.
So if I purchase two 290w (36.7v max /7.9A) panels should I couple them in parallel with the two 190w (36.6v max/ 5.6A) panels I already have ?
If so will they be sufficiently powerful to charge a set of 24 volt 465amp fork truck batteries ?

You seem bent on forklift batteries. Let me repeat the words of SolInvictus;

You do not have enough PV panels

You need a Current charge of at least 10% to keep forklift batteries maintained (45 Amps before system losses). Depending on manufacturer, that percentage may be spec'd higher. The two additional panels won't be enough. The number posted are STC, meaning those measurements were made at a controlled amount of light that are rarely seen in real world. mulitply by 85% to get more down to earth numbers, or 6.5 Amps under real sunlight, pointed directly at the sun.

Nuff · December 2013

Re: Wrong inverter purchased ?

Solinivictus was saying as I understood it that two panels weren't enough for my current system/usage.
I asked politely about using two more.
It is wrong to be impetuous and reckless which I'm not, hence I asked for advice.
Thanks for the capitals BMet but they weren't necessary, we all have to start somewhere.
Knowledge is power isn't it ?

SolInvictus · December 2013

Re: Wrong inverter purchased ?

How many hours per day do the 300 W of lights run?

Nuff · December 2013

Re: Wrong inverter purchased ?

Approx 5 hours.

SolInvictus · December 2013

Re: Wrong inverter purchased ?

In my opinion you need at least 3 more 190 W PV panels, but because the two you currently have are in series, you need 4 more for a total of 6 PV panels in 3 series strings.

Your current battery array might have some difficulty running the lights for 5 hours when they are old and cold, but I would get more PV panels before replacing the battery array.

bmet · December 2013

Re: Wrong inverter purchased ?

Nuff wrote: »

Solinivictus was saying as I understood it that two panels weren't enough for my current system/usage.
I asked politely about using two more.
Hell bent is to be impetuous and reckless which I'm not, hence I asked for advice.
Thanks for the capitals BMet but they weren't necessary, we all have to start somewhere.
Knowledge is power isn't it ?

1.) I never wrote "Hell". Your words, sir.

2.) The words are not capitalized. They are emphasized.

If you want to draw the wrong conclusion, that is your decision. You've already made two mistakes about my response.

You should read up on the battery FAQ of our host. It contains sections about charging and charge controllers. Then, after you have better information from which to design your system, we can focus on the types of products to make that system possible.

Cariboocoot · December 2013

Re: Wrong inverter purchased ?

No more increased size typeface, guys; it's like yelling and we do not need that.

And let's keep the language civil and family-friendly.

300 Watts for 5 hours is 1500 Watt hours. Without conversion efficiency, inverter use, and other losses that's about 125 Amp hours on 12 Volts, or a minimum 250 Amp hour battery. At 25% DOD it would be a 500 Amp hour 12 Volt battery.

To recharge that with a peak 10% current you'd have (50 Amps * 12 Volts / 0.77 efficiency) or 779 Watts on an MPPT controller. The nearest approximate multiple of 190 Watt panels would be 4.

In Watts returned from panels without being stored in battery (unlikely because who uses lights during the day?) over 4 hours you'd need approximately 487 Watts of panel to harvest that much energy (1500 Watt hours / 4 hours equivalent good sun / 0.77 average efficiency).

Showing the math is good.

SolInvictus · December 2013

Re: Wrong inverter purchased ?

Assumptions:
300 W of lighting for 5 hours/day
laptop charging: 80 Wh/day
lpg fridge: 0 Wh/day although it might use electric lights
2 to 3 hours of running lights in winter when the expected time is 5 hours suggests 50% to 60% sunlight (whether from insolation or shading) in the winter. I assume 50%.

Since the lighting dominates the power consumption and is probably operated at night, I assume approximately all loads discharge the batteries which is never true because the inverter and charge controller consume half of their power directly from the PV panels.

(300 W * 5 h/day + 80 Wh/day)/ .75 (efficiency of inverter, charge controller & wiring) / .75 (efficiency of battery) / 6 h (of sun in optimal illumination)) / .5 (suboptimal sunlight in winter) = 936 W

Which is 4.93, 190 W PV panels rounding up to five.

Because the battery array is 24 V and the charge controller is MPPT, he connects 2 PV panels in series requiring an even number of PV panels. Thus he needs six 190 W PV panels.

Nuff · December 2013

Re: Wrong inverter purchased ?

Thank you gentlemen your advice is much appreciated and I am following the maths and learning.
One last thing though.
I'm in the UK now and returning to my cabin in the Greek woods in February.
Batteries in Greece are three times the price here and that's a possibility I can't afford.
I'm looking for the optimum size battery bank plus room to expand by maybe 25%.
What would you recommend ?

Cariboocoot · December 2013

Re: Wrong inverter purchased ?

Other than saying "batteries with 25% more capacity than you need now" it's hard to say because I'm in Canada, not the UK, and have no idea what is available to you.

Just remember you have to be able to recharge the whole battery, regardless of size; you can't base recharging on the 'amount you use'.

Six 190 Watt panels (1140 Watts) should produce about 73 Amps on a 12 Volt system using an MPPT controller (must be an 80 Amp controller like Outback's FM80 or MidNite's Classic 150). As such that would do for up to 730 Amp hours @ 12 Volts. If you're in that power range you should probably be running a 24 Volt system (37 Amps into 370 Amp hours @ 24 Volts). Just to give you some idea of the amount of battery that array could support.

Wrong inverter purchased ?

Comments

Categories