Thanks for the comments... Here's something I made a couple weeks back. Portable power source also charged by a small folding 40W PV array. I mainly use it to power a 12V electric fan in my bedroom just so it gets used daily. I do take it out though when I need a portable power supply.
http://quan-diy.com/projects/apower/powerbank.htm
I spoke with Bob Gudgel 3 months ago at a hamfest in Tacoma.
He is interested in finding a true 6 or 8 channel scope, not some combination of 2 good channels, 2 not so high bandwidth channels and 4 logic channels...
we talked a bit about cheap digital scopes, I tried to explain to him the biggest thing I miss is the Tek 475 split triggering as shown here:
btw, i have a blown up 475 if anyone needs parts.
and there is a whole lot more data on that screen than 8 bits...
Hi guys, I just bought another 235watt 37v panel. After I bought I was wondering how much wattage the solar kid can handle.
The ebay listing don't say. Would two x 175watt panels and a 235watt be to much?
Hi guys, I just bought another 235watt 37v panel. After I bought I was wondering how much wattage the solar kid can handle.
The ebay listing don't say. Would two x 175watt panels and a 235watt be to much?
The voltage will not be an issue. See specs
HEREIt can take up to 150V input.
The problem will be the output amps. You have a 12V battery bank, correct? With 585 watts of PV you could easily produce over 40A output on a sunny day if in Bulk charge mode - but the Kid will only put out 30A max. Best to go to at least a 24V battery bank with that much PV - or go to a bigger controller like the Midnite Classic (but more expensive!).
BTW - how do you plan to combine those panels? If all three will be in series the Imp's need to be close (within 10% or so). If in parallel, the Vmp's need to be close.
Thanks
I think I'll use the new panel on my old pwm controller and just use the 2 x 175's on the midnite kid.
Still not sure witch is best series or parallel.
Would I need blocking diodes if I use 2 controllers n one bank?
Thanks
I think I'll use the new panel on my old pwm controller and just use the 2 x 175's on the midnite kid.
Still not sure witch is best series or parallel.
Would I need blocking diodes if I use 2 controllers n one bank?
Putting your panels in series would reduce voltage drop and allow smaller wire size. On the other hand controller may be slightly less efficient due to need to buck voltage down further. The decision depends partly on how far panels are from the controller - i.e. how much voltage drop comes into play. Wire from panels to controller should be sized to keep voltage drop less than 2-3%.
No need for blocking diodes.
Thanks mtdoc.
I'll parallel them then as it very short distance.
One other advantage I see when reducing the voltage difference between PV Vmp and battery voltage is that the MPPT charge controllers spend less time "scanning" the entire PV voltage range to find the Vmp of the array.
A smaller voltage difference means the controller needs to sweep only a small voltage range to find it. It depends on the charge controller though. Outback controllers sweep only a percentage of the VOC of the PV array (50-90% IIRC) but my Epsolar controller always sweeps the entire range from battery voltage to the PV VOC.
Scanning does waste some energy, but it doesn't work like that. The losses would be very minimal. Monitoring panel temperature is a very effective way to track solar. IR losses can be dialed in. Conventional MPPT controllers are like your engines controller. When everything is OK it is very effective. When a fuel injector malfunctions it throws all the rest of them off. Fifteen years from now the single conventional MPPT controller used in large systems will be known as Panel Killers!
I wasn't talking about the method on how it is scanned... It was about how long it would take to sweep the entire range of the panel voltage.
If it was taking more time to sweep the entire range, then that is less time for the PV to run at its maximum power point which is energy not harvested and used by the loads.
FWIW, not all MPPT scanning algorithms are the same. In fact the Midnite controllers let you choose between a few different algorithms - some optimized for solar, hydro, wind, etc. They have regular firmware updates that sometimes includes changes to these.
It's not easy to do a carefully controlled comparison but Midnite claims that their controllers outperform others based on testing done by APRS world:
http://www.midnitesolar.com/pdfs/performanceComparison.pdf
I had been doing a test for a month with a 100W 12V panel boosting it up 35V to heat water with one of those cheap ebay 150W boost converters. I was taking it apart this morning and noticed the 35V output cap had blown apart. I was running it at the max voltage, but had several external capacitors in parallel so it wasn't a ripple current problem. Evidently the posted voltage is a real maximum. Much like the surge voltage that used to be listed on capacitors. Really blew up, still haven't found the case for it.
My midnite kid has been delayed as I have been stung with a £60 Import duty (Ouch)
Any why I have put my new 235 watt solar panel on my shed roof but as I'm waiting for the charge controller to come
id thought id connect it strait to the battery bank. My PWM controller is busy charging the bank but when I connect the new panel to the batteries the pwm turns off the charge, I think its seeing more voltage on the batteries and disconnecting the Charge.
I was wondering if there was a way around this.
Can you configure you battery bank for 24V?. What's the Vmp of your 235 W panel?
VMP is 30.3v
I cant set it up as 24v system cos my inverter is 12v.
30 volts will boil your 12V battery bank.
So best wait till the new charge controller comes then lol.