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Old 01-02-2011, 00:29   #1
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Solar Power

What are some of the average amount of amps you can expect from a solar panel setup? I am thinking 780watt solar systems.....the ones from talco electronics, they have 390watt kits X 2 equals 780 watts they say they can generate 96-120amp/hrs per day....is this realistic? on the low side? on the high side? for cruising in the tropics. i want to try to get as much electricity from solar as possible.
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Old 01-02-2011, 00:37   #2
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my guess would be that their estimates are going to be on the high side, as they are mounting them perfectly and angles just right and all that...

on your boat the angle will most definitely be wrong right off the bat.. then you will only get some light some of the time as you are moving, bouncing and all that...

but, again, just a guess.. hope to hear other comments..
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Old 01-02-2011, 01:29   #3
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depends on location and season.

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Originally Posted by cat49 View Post
What are some of the average amount of amps you can expect from a solar panel setup? I am thinking 780watt solar systems.....the ones from talco electronics, they have 390watt kits X 2 equals 780 watts they say they can generate 96-120amp/hrs per day....is this realistic? on the low side? on the high side? for cruising in the tropics. i want to try to get as much electricity from solar as possible.
We have 400 watts of solar and get around 100 amp/hrs per day on the north coast of Australia in winter.

Presently in the south of Tasmania in summer and are averaging 20 per day.
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Old 01-02-2011, 01:45   #4
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What are some of the average amount of amps you can expect from a solar panel setup? I am thinking 780watt solar systems.....the ones from talco electronics, they have 390watt kits X 2 equals 780 watts they say they can generate 96-120amp/hrs per day....is this realistic? on the low side? on the high side? for cruising in the tropics. i want to try to get as much electricity from solar as possible.
it sounds like to me there is a missprint in either the solar panel watts or the amps generated.... my experience with solar, on a motorhome in australian sun (so not sure of the shade on boat versus motorhome) is..... if you divide the solar panel watts by 4.5 it will give you the average daily total in amps. i.e. 125 watt solar panel divided by 4.5 will give an average daily total of 27.7 amps.......if you divide the watts by 3 it will give you the daily total of amps on the very best day.... if you divide watts by 13 it will give you the total of amps on the very worst day. but an average year round figure would be to divide by 4.5 if this was the case with 780 watts of panel it would give you 780 divided by 4.5 = 173 amps for the average day... if your quoted figures are correct then they are underestimated. 780 watts is a lot of solar power to fit on a boat,especially a sailboat. 780 watts would also need approx 780 amphours of deep cycle batteries to store the power.....lot of weight!!
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Old 01-02-2011, 02:01   #5
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it sounds like to me there is a missprint in either the solar panel watts or the amps generated.... my experience with solar, on a motorhome in australian sun (so not sure of the shade on boat versus motorhome) is..... if you divide the solar panel watts by 4.5 it will give you the average daily total in amps. i.e. 125 watt solar panel divided by 4.5 will give an average daily total of 27.7 amps.......if you divide the watts by 3 it will give you the daily total of amps on the very best day.... if you divide watts by 13 it will give you the total of amps on the very worst day. but an average year round figure would be to divide by 4.5 if this was the case with 780 watts of panel it would give you 780 divided by 4.5 = 173 amps for the average day... if your quoted figures are correct then they are underestimated. 780 watts is a lot of solar power to fit on a boat,especially a sailboat. 780 watts would also need approx 780 amphours of deep cycle batteries to store the power.....lot of weight!!
Are you talking 12v or 24v?? ..... as this calculation matches exactly with the results I get from my 24v battery bank
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Old 01-02-2011, 02:07   #6
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these are the specs for the solar kit. they also have a 260 watt system. will this work with a regualr 12 volt setup. i have 4 Deep cycle batteries (765 amp hours) on the boat.
390 Watt Marine Solar Power Kit



390 WattsModel NumberSE-24000Wattage390 WattsPeak Output24 A@16.5 voltsApprox. Watt-Hrs / Day***1560-1950Approx. Amp Hrs / Day***96-120Dimensions (in/cm)3x(60.24 x 28 x 1.4) /
3x(153.2 x 71.1 x 3.6)Weight (lb/kg)90 / 40.8Temperature Range-40ºF to 176ºF / -40ºC to 80ºCWarranty20 Years
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Old 01-02-2011, 02:09   #7
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390 Watt Marine Solar Power Kit

this is the link to the solar kit on the website that i want it gives all the specs
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Old 01-02-2011, 02:16   #8
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hi fuss, did`nt think of that..... must be my old age!!! my calculations are for a 12 volt system & have proved over many years to be fairly accurate....... maybe the 780watt panels quoted were for a 24volt system ? i have no experience with 24 volt systems so i cant comment
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Old 01-02-2011, 02:25   #9
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hi fuss, did`nt think of that..... must be my old age!!! my calculations are for a 12 volt system & have proved over many years to be fairly accurate....... maybe the 780watt panels quoted were for a 24volt system ? i have no experience with 24 volt systems so i cant comment
I have not checked too often but generally in the med. I seem to get around 60a a day from my 2 x 135w panels into my 24v battery bank.... but this is in the middle of summer. I never got 270w/3 = 90amps even on the best day as on my boat a portion of the day (early morning and late evening) has the panels shaded by the backstays.
But its strange that your calculation seems to fit my 24v system...could it be due to the mppt controller ???
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Old 01-02-2011, 02:41   #10
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the kit comes with three solar panels.....for a total watt of 390. so 3 130w panels. the specs are for the whole system....all three panels.
it says
peak output: 24A @ 16.5v
approx: watthours/day 1560-1950
approx: amphours/day 96-120
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Old 01-02-2011, 02:43   #11
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I am totally confused with the above. My humble physical knowledge says

P(in watt) = U (in volt) * A (Amp)

If the solar panel is 789 W (seems to me very very high) and the boat is 12 V, it should generate 789/12= 65 A. This is what my alternator is generating out of 40 HP engine..
From what I see, the new panels are rated 75-125 W each. If you put 3 or max 4 (on a large cat) makes about 400 W / 12 = 33 A max. On a average day this should give roughly 180-200 Ah.
In a long passage daily consumption could be;
chart ploter 2 A * 24= 48 Ah,
frigo 5 A for 12 hours =60 Ah
autopilote 2 A *24 = 48 Ah
Stereo 2 A * 4 hours = 8 Ah
Lights (assuming LED) 0,2*10 hours= 2 Ah
Safety factor = 20 Ah

Total= 186 Ah.

That means you 4X 100 w solar panel will keep you off from starting yr engine or genset to keep charged yr batteries. With 50% charging ratio, you would need 400 Ah batteries.

I would suggest you add one wind generator to cover the cloudy days to make 100% sure..

Am I missing anything ??

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Old 01-02-2011, 02:44   #12
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We have 400 watts of solar and get around 100 amp/hrs per day on the north coast of Australia in winter.

Presently in the south of Tasmania in summer and are averaging 20 per day.
How many panels and where mounted on what sort of boat? Into what sort of battery with what sort of controller? There are so many variables that it is good to get as much info as possible.
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Old 01-02-2011, 02:47   #13
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From what I see, the new panels are rated 75-125 W each.
Am I missing anything ??
Only that panels now are circa 180- watt, in many cases,
they are standard fit on our boats now.

I have 2 x 120 panels mounted on targa
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Old 01-02-2011, 02:54   #14
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my system was 2x125watt panels & 1x80 watt panel..330 watts all up. my regulator was a plasmatronics PL 20 (beaut regulator) and 400 amps of battery bank (12volt) on one very rare occassion i saw 26 amps coming in, but only for about 10 minutes..... in the best part of the day i`d normally bring in 19 amps which would heat up my regulator a little. the cheap regulators on the market would bring in only half to two thirds of my figures as they cut out totally and dont come on again until the voltage drops considerably... a 3 phase (boost, absorbsion,float) regulator is the way to go. but again, i know nothing about 24 volt systems... maybe 24 volt panels are twice the size of 12 volt panels which would account for you getting similar figures to my calculations... i believe a 12 volt panel produces approx 19 volts.... a 24 volt panel may have to produce 38 volts and thus be twice the size... i`m really not sure & out of my depth with 24 volt systems
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Old 01-02-2011, 03:51   #15
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cat49, best to try and keep this simple and not to get too technical. if your 765 amps of battery bank is a 12 volt system, then that is a large battery bank. i`ve checked your link and the solar panels are for a 12 volt system and i totally stand by my original calculations for a 12 volt system. 3x 130watt panels will give on a yearly average, in the tropics, with a good regulator/controller...86.6 amps per DAY. they will on a great day bring in UP TO 130amps per day. on a very bad day 30 amps per day. with your size battery bank, if you had the room, you could put 6 x 130 watt panels on without increasing your battery bank. i feel that 3 x 130 watt panels is not really enough watts to keep your size battery bank in a reasonably fully charged state. with 6x 130 watt panels you would need a regulator/controller that would handle about 50 to 60 amps. you will get a little more amps out of brand new panels but only for the first few months... they will soon settle down to my simple calculations.
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