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RE: Solar Help
Interesting panel mounts.
Sticky Feet
I didn't see the 90A panel advertised at windturbine.ca. Got a link?
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Salvo
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05/23/13 12:02pm |
Tech Issues
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RE: Solar Help
A fuse between panel and controller will not provide fusing safety. However, many add a fuse, just to be able to disconnect panel from controller. Whenever you disconnect the 12V battery, for example to work on 12V cabling, you will also need to disconnect panel from controller.
A 20A fuse must be installed between battery and controller. It's best to install that fuse by the battery. That locattion not only protects the controller but also the 12V cable.
Sal
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Salvo
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05/22/13 05:28pm |
Tech Issues
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RE: Solar Help
Carrying a panel inside a B gets too complicated.
Here's what OP needs:
One 150w or two 80W panels. Watch out for shade on the roof!
http://www.windturbine.ca/sun_panels.html
A $20, 20A pwm controller.
http://www.ebay.com/itm/5-30A-Solar-Charge-Controller-Regulator-12V-24V-Battery-Charging-PWM-Solar-Panel-/221142180373?pt=LH_DefaultDomain_0&var=&hash=item337d19e215
As mentioned before, two 6V batteries will make camping much easier.
Sal
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Salvo
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05/22/13 11:19am |
Tech Issues
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RE: Solar Help
That 190W panel requires a mppt controller! If you are concerned about cost, stay with 12V panels and pwm controllers.
Sal
Yes I did make a big mistake on my last post...too many adult beverages I guess.
The 190 watt single:
Vmp. 26
Imp. 7.63
Voc. 33
Isc. 7.89
$ 207.10
Do these appear to be good prices? The single 190w panel weighs 37lb the two 90w weigh 35.28lb
Mick
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Salvo
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05/22/13 09:59am |
Tech Issues
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RE: Solar Help
If you're looking for max amps in a mppt controller, then nothing is simpler than:
Imax = Panel power / 12V
If you have 150W panel, then max controller current should be greater than:
I = 150W/12V = 13A
On top of that, derate by 20% to 16A.
In other words, a mppt controller connected to a 150W panel should be rated to 20A.
Sal
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Salvo
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05/22/13 09:54am |
Tech Issues
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RE: Solar Help
That's over simplified. MPPT current is highly dependent on panel temperature and battery voltage.
The temperature coefficient of PV cells is about -0.45%/C. A 25C rise in panel temperature is not uncommon. That means a 150W panel at 50C has dropped 11% of its rated power to 133W.
PWM is more or less unaffected by heat. The panel will output the same Isc.
Sal
Nobody tells you your expected max amps for any given wattage of panels--except me! :) here it is:-
use the same for either PWM or MPPT, they are nearly the same for this purpose:
expected amps = chosen wattage/130w x 8.2
EG, 230w/130w x 8.2 = 14.5a (jimindenver gets 15a from his with MPPT)
EG 80w/130w x 8.2= 5a (the Isc of an 80w panel and what I got with my 80w.) It works and its free! You are welcome.
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Salvo
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05/22/13 08:51am |
Tech Issues
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RE: Solar Help
The 12V, 150W panel looks good. I would use a $20 pwm controller. In addition you need a larger battery bank. If they fit, get 2 6V GC.
Sal
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Salvo
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05/21/13 02:14pm |
Tech Issues
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RE: Charge controller recommendations
Nothing wrong with terminating boost 10 min after battery reaches 14.6V. That's very similar to Iota's charging. Likewise, nothing wrong with terminating absorption 10 min after reaching 14.4V. It's not like it gets there in an instant. I'm sure someone conducted extensive studies to incorporate this regiment. I see nothing wrong with this program.
All the "experts" want program-ability. I question if they really have the knowledge to make wise decisions compared to professionals who are in the trade.
Sal
I want to choose my voltage and absorption time.
10 minutes seems short while in use, 2 hours seems long in storage.
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Salvo
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05/21/13 08:56am |
Tech Issues
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RE: Charge controller recommendations
I have a similar pwm charge controller. It's actually state of the art, containing an Atmel microcomputer. I don't use it for my rig but to charge a 17AH AGM battery used to power a pump that inflates kites. I'm impressed with this $20 controller.
Sal
Aside from Salvo's link below, nobody has really suggested a PWM controller. Especially one that would be considered reputable, yet cheap enough to be a viable alternative to MPPT.
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Salvo
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05/20/13 01:56pm |
Tech Issues
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RE: Charge controller recommendations
LOL, got them all already. But there's always room for another sail, board, kite or bike. Do you have a $5k mountainbike? Or do you ride a k-mart bike?
The point is, the price to extra performance ratio of a mppt controller is at a nose bleed level. I got more intelligent ways to spend my money.
http://i429.photobucket.com/albums/qq12/Calbiker/Boondocking/IMG_0068.jpg
On the other hand - I would purchase the mountain bike, wind surfer and the high end controller - but again all of us are different
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Salvo
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05/20/13 12:07pm |
Tech Issues
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RE: Charge controller recommendations
Of course it's not a doomsday scenario. My first post on the subject was to state ideally you want all charging sources on separate cables.
Sal
Not a doomsday scenario.
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Salvo
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05/20/13 10:11am |
Tech Issues
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RE: Charge controller recommendations
It may still have an impact on a charge controller (CC) that has fixed time limit. If generator/converter is run at sunrise (before solar production initiates) then once solar starts, CC may go directly into absorption, skipping bulk.
Another reason why not to put CC and converter on same cable is because the mppt CC will have charge reduction. The OP's 6 awg cable may have 20 mohm resistance. If the converter charge is 45A, then there's a 45A * 20 mohm = 0.9V cable drop. The CC is now seeing battery voltage plus cable drop = 12.5V + 0.9V = 13.4V. While a pwm CC will not be affected, the mppt CC will lose much, if not all of its advantage.
Sal
No effect on my Morningstar as it will hold absorption for the programmed time.
Not sure in all practical use this would be a big deal anyway.
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Salvo
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05/20/13 09:21am |
Tech Issues
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RE: Charge controller recommendations
Ideally you want each charging source (alternator, converter, charge controller) to have separate cables. If you connect charge controller to converter then both the converter and charge controller will be fooled as to the correct battery voltage. The converter may not go into boost or the charge controller may go unnecessarily into absorption or float mode. It depends on the magnitude of the cable line drop.
Sal
My current charge controller is in the same compartment as the converter, and therefore connected to the battery cables at the same location (Essentially the output of both devices are wired together). I plan on installing the new one in the same location. Does anybody see a problem with this?
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Salvo
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05/19/13 06:29pm |
Tech Issues
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RE: Charge controller recommendations
I would rather throw that money at say windsurfing, kite surfing or mountainbiking equipment than buy a $500 controller that's at best 8% better than a $20 pwm controller. I predict those high prices will be cut in half in 3 - 4 years. At that time the OP may want to upgrade.
Sal
It's a one time expense for a GOOD to VERY good quality MPPT controller. Expect it to cost $400 to $500 something that will give you ample headroom for future expansion, be fully programmable and will last longer than the RV. One time expense and you would be done with the issue forever.
Just my two cents worth
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Salvo
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05/19/13 06:17pm |
Tech Issues
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RE: Eco-worthy 20a MPPT controller
The specified standby current is 15 mA. That's probably the night load when buck regulator is off. Specified converter efficiency is > 96%. A 300W module will dissipate 12W within the converter. So we're talking about max 1A loss in charging current when using a 300W panel. Now you're using a 45W panel. Current loss won't scale directly. Perhaps 200mA of the total 1A could be considered regulator quiescent current. The rest of the current (800mA) probably scales. That means current loss within the controller is:
I_loss = 200 mA + 800 mA * (45W/300W) = 320 mA
That's my best guess.
BTW, I'm up the coast from you in Goleta. Today is a great sunny day to run solar tests. Will be looking forward for further results.
Sal
I have not measured quiescent current draw of the unit 'officially' but the clamp on meter which has 10mA resolution is showing 20mA draw during standby/snooze.
Yeah, probably not so great due to me operating it really low in its power handling capability. I do have 2 qty 45W panels though I'm only using one right now, but one of the tests I want to do is compare the charging amps with the panels in parallel vs in series going through the MPPT controller, and also vs in parallel going through a PWM controller or direct to the battery.
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Salvo
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05/19/13 05:58pm |
Tech Issues
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RE: Eco-worthy 20a MPPT controller
Thanks for the testing. The 0.1A gain compared to direct charge does seem quite low; especially when battery is at 12.5V. Is the controller's operating current high that it impacts your measurements? Perhaps using a panel that's greater than 100W will provide better results.
Sounds like there's a relay in your controller. It may be measuring open circuit voltage of the panel. Time to pull out the scope.
Sal
I'm a bit disappointed to not have a much greater charging amps (only ~ 0.1A greater) given the delta between the battery and the panel is about 4V. Thinking that I may just be so low in power that I'm not in a high efficiency zone for this MPPT controller.
Putting my ear to the MPPT controller, I hear a regular 'ticking' noise. Will at some point drag out my digital scope and take some measurements to see what is going on.
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Salvo
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05/19/13 12:00pm |
Tech Issues
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RE: Initial test manual home brew $8 MPPT controller
You're operating up to 2V below the specified maximum power point of the panel. Therefore you're not operating at the max power point. It's extremely hard to believe that you're still getting 10% more current from this configuration. There might be something wrong with your pwm controller. Where's the data (panel I & V and battery I & V)?
Sal
So I count the original as a fail, but the buck converter as a success. It is indeed a manual tracking MPPT device. I found my real Vmpp to be between Vmppspec and Vmppspec -2v.
Jim
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Salvo
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05/18/13 07:12pm |
Tech Issues
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RE: Charge controller recommendations
Those are very nice panels! Being able to configure them to 6V makes them very versatile.
Your options are:
1. Go with a low cost pwm controller. Wire 12V panels in parallel. It's easy to add third panel.
2. Go with medium cost mppt controller (<40V Voc). Wire 6V panels in series. You can add a third 6V panel.
3. Go with medium cost mppt controller (<30V Voc). Wire 12V panels in parallel. You can add a third 12V panel.
4. Go with higher cost mppt controller (greater than 70V Voc). Wire 12V panels in series. You can add a third 12V panel.
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Salvo
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05/18/13 06:32pm |
Tech Issues
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RE: Built-in Onan Generator - inverter compatibility
The Onan has noise spikes that upsets this inverter functionality. Perhaps a few de-spiking capacitors at the inverter can fix the problem. Otherwise, it may be easier to replace the inverter.
Sal
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Salvo
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05/18/13 02:37pm |
Tech Issues
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RE: Built-in Onan Generator - inverter compatibility
IIRC Wayne's Microlite does not provide clean power to his PD converter. That gen does not provide pure sine waves. The PD does not function well in that environment.
The Marquis Gold manual states it has digital voltage regulation. Sounds that it may not be pure sine wave. I would connect an oscilloscope to the loaded ac to verify waveform.
Sal
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Salvo
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05/18/13 01:52pm |
Tech Issues
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