| Author |
Message |
Tony & Kim Rian (Rianrts)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, May 23, 2005 - 12:49 pm: | |
Time to buy solar panels for the bus. The goal is to have less run time on the gen set which is a 7.5 kw also 6 golf cart batts. Its so hard to look and figure out which set-up is truly the best. I found this seller who is only 1hr from the house and the way he acts the best from his web page take a look and give me feed back.
http://www.amsolar.com/sunrunner100-22.html
I forgot to say our style of useage. We dragboat race all summer at the lake 4-5days every other weekend. We can run the gen set anytime we want but it would be nice to have the batts charging when we are away from the bus I don't like leaving the gen running when away. thanks everyone |
James Maxwell (Jmaxwell)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, May 23, 2005 - 8:28 pm: | |
Compute the wattage you will need from the panels; now buy twice that much for starters. |
Geoff (Geoff)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, May 23, 2005 - 10:16 pm: | |
Save your money by not buying the panels and run your generator an extra 20 minutes a day. |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 24, 2005 - 5:47 am: | |
The only way to get the batts back to 100% charged is with a LOOOng charge, otherwise short cycling the charge leads to perminant loss of capacity.
If you run the noisemaker while your there, the 5 or 6 hours of direct sun (yes you gotta park unshaded) should get the bank from 85 or 90% full the noisemaker will do..
If you can monitor the bat set just be sure the noisemaker gets the Bulk charge done , and the solar will take care of the rest.
A good Equalizing charge is usefull after the deep cycle weekend , and a good solar controller will do this at the push of a button.
We chose the Trace C-12 which handles 12A of charging , but we only use a single pannel (so far).
Our use is to have fully charged batts at all times while the coach is stored for a couple of months at a time , unpowered , while we go sailing.
Solar is THE way to go if you seldom have a power cord avilable,
OR the way to bring batts to 100% so they can "live long & prosper" with the least amount of noisemaker time..
FAST FRED |
James Maxwell (Jmaxwell)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 24, 2005 - 3:00 pm: | |
Be aware, if u use AGM batteries, DO NOT equalize charge them, a very dangerous proposition at worst, and very expensive at least. |
CoryDaneRTS
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 24, 2005 - 7:35 pm: | |
I have 4 64watt panels on the bus that keeps all the battery up when it is sitting. Never had a battery go bad yet since the installation.
Now if you plan to use Solar when on the go, camping and such, you will have to crunch some numbers for the amount you will need.
for instance, one 64watt panel should put out about 5 amps at 12v. on a sunny day, you might hope for 10 hours of sun which will charge batts or can be used for lighting/tv, whatever up to the amount your solar panel can supply, thus saving the battery from expending power until the sun goes down.
if you supply a 24v battery, the total watts will be divided by 2. That is 2 panels at 64 watt connected in series for 24vdc will provide 64 watts of power. (half of the 64+64=128)
If you supply a 12v battery, the watts will double, that is 2 panels at 64 watt connected in parallel will provide 128 watts of power. (total of both panels 64+64=128)
Do your homework and have at least an idea of how much the panels will provide for you and you won't be disapointed. In some cases, you won't be able to live on solar alone unless you have quite a few panels. But just being able to keep the batts charged when the bus is parked is well worth the trouble.
cd |
Jeff Pritchard (Jeffpritchard)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 24, 2005 - 9:20 pm: | |
"if you supply a 24v battery, the total watts will be divided by 2. That is 2 panels at 64 watt connected in series for 24vdc will provide 64 watts of power. (half of the 64+64=128)
If you supply a 12v battery, the watts will double, that is 2 panels at 64 watt connected in parallel will provide 128 watts of power. (total of both panels 64+64=128) "
Sorry my friend, this is not correct. Two panels produce twice the wattage regardless of how they are connected. The current and voltage change depending on how they are connected, but the power from each panel stays the same. Two panels in parallel to give you "12V" gives twice the current, so twice the wattage. Two connected in series gives the same current at twice the volts, so twice the wattage.
Watts equals volts times current, even with solar panels.
best,
jp |
R.C.Bishop
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 24, 2005 - 11:00 pm: | |
An 11 watt solar panel with controller has kept my 2 8D's up to snuff for three years now.
5 House batteries require another 11 watts...no problem...not sure why one would need so much power for batteries.
FWIW
RCB
'64 Crown Supercoach (HWC) |
James Maxwell (Jmaxwell)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 25, 2005 - 1:20 am: | |
I have to agree w/ Jeff; the wattage is constant, only the voltage and amperage vary with configuration. And, without a sun-tracker and very clear skies, optimum wattage for a 64w 12v panel is probably in the neighborhood of 50-55 watts, and not over 7 hrs/day. Every "authority" I have spoken with or read, considers 80% of max for flat mounted panels, w/max wattage being based on the open voltage capacity and the max amperage output. It is impossible to exceed those amounts, consequently, no one will ever get max rated and listed wattage from a solar panel unless it is un-regulated and "aimed" on a bright, clear, sunny day. |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 25, 2005 - 5:45 am: | |
" It is impossible to exceed those amounts, consequently, no one will ever get max rated and listed wattage from a solar panel unless it is un-regulated and "aimed" on a bright, clear, sunny day."
True enough but most battsets only loose 1% per day internally , so keeping up a coach with solar isnt so hard that max everything is needed.
Size does count ,
FAST FRED. |
cd
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 25, 2005 - 7:28 am: | |
(((" the wattage is constant, only the voltage and amperage vary with configuration "}}}
Sorry but the AMPERAGE and WATTAGE are directly related in the formula.
It is similar to battery connections where two batteries in series will supply 24v but the amperage remains at the lower level, as I indicated above.
This was indicated in the panel instruction I received and proven when I connected the panels and tested the outputs.
What technology are you using? I can use some of that EXTRA power.
cd |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 25, 2005 - 8:50 am: | |
A 12 volt panel capable of producing 64 watts will have an output of 5.333 amps at 12 volts.
Two 12 volt panels connected in PARALLEL will produce 10.666 amps at 12 volts for a total of 128 watts.
Two 12 volt panels panels connected in SERIES will produce 5.333 amps at 24 volts for a total of 128 watts.
Richard |
James Maxwell (Jmaxwell)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 25, 2005 - 11:46 am: | |
Thank u DML. CD, wattage is a derivative of both Amperage and Voltage in whatever combination the configuration yields. That is why I prefer to utilize wattage when discussing solar, rather than amps or volts. Several reasons for it. The voltage rating of a panel is based on the open voltage capacity, usually 17.5-18v for 12v applications. Readily apparent is the fact that a significant portion of the voltage rating is unused in a practical sense.
Next, the amperage rating is based on open voltage max. It is physically impossible to exceed that rating; therefore, if a panel is rated at say 5.5 amps, that figure does not increase when the voltage is regulated down, which degrades the wattage output capacity. That is one of the reasons that I "question" MPPT technology. I have to admit, I have never seen or gotten a clear, definitive answer as to whether amperage output is directly related to the regulated voltage level. In other words, if I reduce the voltage by regulation am I also reducing the amperage a proportional amount?
As a practical matter of application, it is impossible to achieve the maximum wattage output of a panel(s) in a regulated system. Given that the wattage rating of a panel is based on open voltage output and max. amperage at that voltage, the wattage is downrated by a minimum of 14%; figuring a 17.5v panel regulated down to max. of 15v. OK, I'm off of my solar soap box. |
Jerry W Campbell
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 25, 2005 - 2:50 pm: | |
Hi James,
This is also a foggy area for me as is MPPT Technology. It looks to me like you have enough knowledge and experience to be able to ask the right questions. Here are some folks I believe have the answers.
Jerry
'75 Crown
http://www.outbackpower.com/forum/viewforum.php?f=9&sid=7ac2861e93da40995b0c195ef1bbddef |
Jim (Jim_in_california)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 25, 2005 - 2:50 pm: | |
James: if the solar panels "want to" put out at, say, 17v but the batteries can recieve a max of about 14v (varies some by battery type, we need not get that detailed) then it seems to me that an MPPT controller "decoupling" the solar panel voltage from the battery voltage would be a good idea. |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 25, 2005 - 6:06 pm: | |
I believe the 17 volts discussed is an open circuit voltage that will drop significantly when a load is placed on it. This is very typical of of this type of equipment. I would suspect that if a 3-4 ohm load is placed on the panel the voltage would drop to the 13-14 volt level. The resistance would of course have to rated to dissapate the 60 watts of power being dropped across it.
Richard |
CoryDaneRTS
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 25, 2005 - 7:27 pm: | |
THANK YOU Richard Bowyer (Drivingmisslazy)
That was exactly what I said. It seems there are those who don't read what is typed before them and it takes an outsider to explain to them better.
If you still want to argue, HOLD THAT THOUGHT...
I came home sick, dunno what it is yet, but tonight its EARLY TO BED.
When I feel better, I will be ready to continue this thread, like Superman, spreading the truth.
Right now, I just have to go lay down.
But be ready when I come back.
cd |
ChuckMC9 (Chucks)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 25, 2005 - 9:18 pm: | |
Richard ain't no outsider! |
Jeff Pritchard (Jeffpritchard)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 25, 2005 - 9:58 pm: | |
Those of you discussing MPPT are thinking about only one side of the issue. While you will get a wee little bit of advantage from MPPT by scaling down higher voltages to maximize charging current during a small part of the charging cycle, the interesting story is on the other end of the voltage range.
When it's early in the morning or late in the afternoon and your panels are putting out less than 14 volts (even open circuit), ahhh, that's when you get some real use of MPPT. You see, the voltage is too low to charge the batteries, so no charging current flows. Here you would get zero current and zero power from your solar-panels/charger until the sun gets higher without the benefit of MPPT. With MPPT, whatever voltage and current you can get out of your solar panels is "converted" into useful energy at a voltage that can charge the batteries. True, it isn't peak power, but it's better than zero.
jp |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 09, 2005 - 1:47 am: | |
I have studied some of those ratings on panels, too. I have typically seen three ratings: maximum power in watts, maximum open circuit voltage and maximum short circuit current in amps.
It is obvious that as either voltage or current approaches its maximum, the other must fall off. Because of this, maximum power is always going be generated at something less than the maximum for either voltage or current.
Hence the smoke and mirrors.
When I have attempted to figure out what the current curve looks like as voltage falls to battery charging voltage from a direct connection to batteries, the current has been most of the short circuit value.
I get the impression that what James is talking about is that the panel output is NOT the maximum current times the maximum voltage. This means that any charge configuration will be at less than the maximum value of voltage AND current.
I think that problem is just a matter of whether the manufacturer and sales people are going to furnish useful specifications. I'm sure that many don't.
The MPPT unit is just a continuously variable, self adjusting DC to DC converter, so that whatever power is available from the panels is translated to the most beneficial voltage and current for recharging, after it takes its cut.
That's assuming that the unit does everything that the manufacturer claims that it will, which is sometimes assuming an awful lot.
I usually look for net wattage available at battery charging voltage and consider whether the claims for the product make sense. Usually, when someone is chiseling on claims, a careful reading of the claims will make it apparent.
I have yet to see any believable specs for more than 15% efficiency in making electric power. That means that the other 85% is hanging around, warming things up.
For what it's worth.
Tom Caffrey PD4106-2576
Suncatcher |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 09, 2005 - 5:36 am: | |
Back issues of Home Power will discuss their
"Democracy Rack" where a dozen solar panels were mounted side by side , and the actual output recorded for one year.
Better than speculation,
ON line ,+ FREE
FAST FRED |
Tom Caffrey (Pvcces)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 09, 2005 - 8:49 pm: | |
Thanks, Fast Fred. I did go to their site, but everything that was in the back issues has a charge, $5 per download of one back issue.
However, I poked around some and found some specs for the Kyocera panels. In the case of the KC 120, they gave open and short circuit specs plus the maximum power voltage and current.
The way it worked out, at 79% of maximum voltage, they claimed they could get 95% of maximum current. They also gave the power of the sunlight as a kilowatt per square meter, IIRC.
These are probably the most useful specs that I have seen, so far.
Tom Caffrey PD4106-2576
Suncatcher |
|