in the dark South africa

System · April 2011

Hi guys

Glad to finally find a forum where i could speak to people who actually have experience of solar powered systems and not to a shark that just want to sell you a bunch of stuff and not giving any information on how to connect it!

This is my information

Solar panels = 6 X 200 watt PV panels 55volt max open circuit
Controller = MPPT controller max input 55volt /output 12 volt
Battery bank = 17 X 12v 105 aHr batteries
Inverter = 3000 watt 12 volt pure sine wave
Back up generator = Ryobi 5.5 kva generator

We are completely off the grid and absolutely relying on the solar power system but it's just not working!
The generator is working over time and obviously were sitting with a pretty big gas bill...

The PV system at this stage cant manage to power two fridges of +/- 300 watt and two tv's of 200watts

what am I doing wrong? Or are we consuming to much power?

mike95490 · April 2011

Re: in the dark South africa

Too much usage is my guess.

2 fridges would use 3Kwh daily, and 2 TVs @ 200W ea, for 3 hr ea, =1,200Kwh for a total guesstimate of 4200Kwh daily. if your fridges are less than super efficient, this will be even more !

1200w of pv for 4 hours = 4800 which on paper is "break even", but factoring in all the system losses, you have only half the PV that you actually need.

You should, if you can switch to a 48V battery system, that eliminates a lot of "parallel battery bank" issues, but you only have half the needed solar

BB. · April 2011

Re: in the dark South africa

Also, depends on your local weather--I think one poster from your region talked about >7 hours of full noon time equivalent sun per day!:D

So, where you saw Mike use 4 hours of sun per day--that is what we use around the USA as a generic average for OK weather and winter/summer sun averages... Substitute ~7 hours of sun per day and your numbers may work out much better.

Full sun, no clouds, no shade from trees/poles/etc. are critical for solar PV arrays. Put a simple pole or bush in front, and you may loose 1/2 your power per day.

-Bill

Cariboocoot · April 2011

Re: in the dark South africa

You know what I'd be suspicious of?

1). Seventeen 12 Volt batteries all hooked in parallel. 1785 Amp hours = a need for 89 Amps charging current minimum and some very good wiring practices (i.e. bus bars).
2). Enough panel to put out 65 Amps - only an FM80 will handle that. Not enough to charge that much battery all at once.
3). A consumption that appears to work out to approximately 8 kW hours per day (possibly) with panels only capable of harvesting about 3 kW hours per day.

This is what is known as an unbalanced system.

Where do you want to start fixing?
Get an accurate daily usage number. A Kill-A-Watt meter will help you there.
Get some numbers on your solar production either from the charge controller (if it logs data) or a reasonable estimate from PV Watts if possible.
Get a hydrometer if those are flooded cell batteries and check each cell. Charge them all separately as soon as possible. See how many can be saved.

westbranch · April 2011

Re: in the dark South africa

I agree you are out of balance and in addition to what the others have said, I picked up on some facts below

Nigrini wrote: »

Solar panels = 6 X 200 watt PV panels 55volt max open circuit
Controller = MPPT controller max input 55volt /output 12 volt
Battery bank = 17 X 12v 105 aHr batteries

what am I doing wrong? .....?

we need to know what brand Charge Controller, batteries and PV's you are using. Helps in diagnosing the whole system

If what you have stated about the max V into the CC and your PVs are 55Voc this may also be a problem. You could easily go over the CC's limits.

My first inclination is you need a higher capacity MPPT CC, so you can go to a 24 or 48 Volt system and put the solar panels in series (110V) ( 24 V would allow you to reuse most of you existing wiring)

HTH
Eric

niel · April 2011

Re: in the dark South africa

"not to a shark that just want to sell you a bunch of stuff and not giving any information on how to connect it!"

ouch. it sounds like that is what happened to you. too bad you didn't find us sooner to make a bit of a rough overview of what you may actually need or want. in the meantime it may be advisable to run the frigs and other loads on the genny while your batteries are then allowed to come back up to full charge. while that is going on do as the guys have asked and give more details. as to your loads you should have a better idea of what your loads actually are over time and a power meter such as a killawatt meter does that, but for 120vac 50/60hz. if you are 220vac then a different meter may be needed.

preliminarily, i'd say you don't have enough pv for the batteries and loads you have, but more details may give a better handle on what the real scoop is. remember that it isn't just watts as it is those watts over time or watthours. batteries have amphour ratings and as such if you multiply that x the voltage it will give you the total watthours of the batteries. keep in mind that you don't want to use all of the power of the batteries as that kills the battery life and no more than half of the capacity should be used.

example: 105ah x 12v = 1260wh / 2 = 630wh usable.

in that example the pv power to provide enough power into the battery must provide not only the power used, but it must overcome all other losses in charging. this may be seen as around 1.23x as much power and this can vary somewhat with installation particulars. also note that stc ratings on pvs are not typical ratings of consistent power delivered.

btw, africa isn't so dark as you most likely get more sun than i probably do.;)

System2 · April 2011

Re: in the dark South africa

thanx guys for the feed back I'll get the requested information

in the dark South africa

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