Have I bought the wrong setup?

davo

Hello all,today I went to a local solar panel supplier and purchased 3x 290w 44v 8.4amp hosun panels,and an 80a pwm,I have a 240amp 12v bank to charge,will this be ok and if I choose to swop to mppt at a later date will I be able to use a 60a mppt or do i need and 80a?thank you in advance I am not electrically minded and just thought more the merrier but i am now realsiing maybe this is npt the case!

vtmaps

Re: Have I bought the wrong setup?

davo wrote: »

Hello all,today I went to a local solar panel supplier and purchased 3x 290w 44v 8.4amp hosun panels,and an 80a pwm,I have a 240amp 12v bank to charge,will this be ok and if I choose to swop to mppt at a later date will I be able to use a 60a mppt or do i need and 80a?thank you in advance I am not electrically minded and just thought more the merrier but i am now realsiing maybe this is npt the case!

If you put the three panels in parallel you will get maximum 25.2 amps with a PWM controller. If you use a MPPT controller you will get a maximum current of 72 amps.

Maximum current assumes full mid-day sun and cold temperatures. In more typical conditions you should derate those currents by about 25%.

--vtMaps

H2SO4_guy

Re: Have I bought the wrong setup?

The controller will be wasting quite a bit of power if it will even work with the 44 volt (Is that VOC?). You will get at best about 25 amps at 12 volts where as with a MPPT controller you will get about 47 amps. That is without losses, so you would get a bit less in both cases, but you get the idea that you are leaving a lot of power on the table by using a PWM controller for a 12 volt setup. Now if you change to a 24 volt setup, then you're doing better, but you would need an additional panel to mate up with the system.

Good luck and let us know,

Skip

Cariboocoot

Re: Have I bought the wrong setup?

In a word, yes.
Those panes have a Vmp around 35. Running them through a PWM type controller to a 12 Volt system means about half their power potential will be wasted because it cannot down-convert the higher Voltage to greater current.

On the up side, you will get about 25 Amps from the panels as-is which actually sufficient for charging a 240 Amp hour 12 Volt battery bank. It's just not very efficient.

When you go with an MPPT controller the panels should be able to produce about 55 Amps on a 12 Volt system. A 60 Amp controller should suffice, providing you're not planning any further expansion.

davo

Re: Have I bought the wrong setup?

Thank you all,so I will return the pwm and order the mppt,I had initially planned for 60a,mppt but they had none in stock and 25day wait-I have lovely new trojan bank and dont want to run them down for 25days waiting for the mppt,I might use the pwm until the mppt arrives and then sell it on ebay,thank you all for the info.much appreciated!

Cariboocoot

Re: Have I bought the wrong setup?

Word of caution: 240 Amp hours will not like having 50+ Amps put to it (over 20% charge rate). As such you should get a controller which allows you to program a current limit more suited to the batteries. About 36 Amps max. The 'extra' panel would be better able to supply current in less-than-sunny conditions. Alternately, leave out one 290 Watt panel.

davo

Re: Have I bought the wrong setup?

Ok thanks,I was intending to put a couple of 8x4 sheets of ply over the top of then in the summer,really apreciate the help,we have been running a big 300ah bank on a gennie and 200w of panels,fine in summer but now we are losing the battle,battery bank is deado and flattens in a few hours,really looking forward to getting the new batterys and panels setup and hopefully chucking the gennie! All the best

westbranch

Re: Have I bought the wrong setup?

Tell us a bit about the old battery system and how it became deado ? Were you able to EQ them?

icarus

Re: Have I bought the wrong setup?

Perhaps more importantly, tell us about your loads. All design considerations stem from the loads. Loads dictate battery bank size, battery bank size dictates PV size. Any other way is "ready, fire, aim".


If you have killed one set of batteries, finding out why is important, so as to not kill the next set. More batteries are not always the solution, (nor is more PV always!) Over drawing them, coupled with under charging is often the culprit, but it could well be overcharging as well.

I suggest you read and understand the following links:


http://www.batteryfaq.org/

http://www.solar-electric.com/deep-cycle-battery-faq.html



Tony

davo

Re: Have I bought the wrong setup?

my loads are 1w leds x5, 11w x1strip light and tv /radio 35w aplus water pump 7a shuflo occasional,all are approx 6 hrs per day apart from pump, on average day,more on weekends I think my problem was undercharging a mishmash of batterys 1 110ah leisure and 3x various sized second hand cranking car batteries,I didnt have enough solar to keep them charged and I have a very non electric load aware partner who will happily watch tv on the weekend until the batteries are very low,and then they sit low all night until sun up,and also using a rubbish 2stroke gennie,that puts out uneven charge didnt help,but hey we were on a tight budget and it did the job,I think my loads are small now in comparison,my battery bank is a more reasonable size and much better quality and I have roughly 5x the solar power I had before,just ordered the 60A mppt by the way!

icarus

Re: Have I bought the wrong setup?

more detail please. For example a Tv. How many watts does it draw, for how long. Assume for the moment a very efficient Tv, drawing 75 watts, for 6 hours, thAt would be ~450 Wh/day.

Your 870 watts of PV in a best case scenario put out about 1.5 Kw/ day on averqge, so the Tv alone uses nervous. 1/3 of your PV capacity, not your battery capacity.

Tony

davo

Re: Have I bought the wrong setup?

Hello,Tv is 12v 35w seems to draw approx 2.5 amps radio approx half that also 12v.thanks

couchsachraga

Re: Have I bought the wrong setup?

Your surflo will pull more than 7a if you are pressurizing a tank as it gets up to the max pressure. I have one, works great, but I also have a trimetric meter setup and can watch the amp draw climb….

davo

Re: Have I bought the wrong setup?

hello all, Would like some more advice on bank size I have currently 240a trojan 6v x 2 as 12v in series so 12v 240ah I have pv 870w at 43v with an mppt charger,also 200w at 18v with pwm charger (ok to have two pv arrays on seperate charge controllers doing one bank yes?) I currently have loads of 35w 12v tv 5x 1w led lights and 1x 11w striplight these are on fir 6hours daily I also have occasional shurflo pump approx 5min per day @ 7a and I am about to fit a D2 eberspacher heater on 7 day timer,it will be run 1 hour per day-my main heat is woodburner but this just to take the edge off in the morning and in the bathroom,.Do I need more batteries to run eberspacher?I have 200a of bosch silver starting bbattery bank on small seperate pv array,I could combine the two to make 440ah 12v or buy two more trojans if necessary.Your thoughts and advice much appreciated,or will my 240ah be sufficient? seems great as is without the eberspacher,even on cloudy days I am getting a good charge.nearly 3amp today in the rain!..thanks!

davo

Re: Have I bought the wrong setup?

also forgot to mention shurflo doesnt pressurize tank only approx 8metre of 15mm piping,500litre tank is before the pump in system, fully pressurised in seconds

SolInvictus

Re: Have I bought the wrong setup?

If you will use an Eberspacher Airtronic D2, then its electrical power consumption ranges from 8 W on the lower power setting to 34 W on the highest setting. Up to a 3 ampere draw for 1 hour from a 12 V, 240 Ah battery array is small, about 1% of the battery capacity. If these assumptions are correct, then you do not need more batteries.