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Forum Index : Solar : Low Voltage Charge Controller use
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solarwind Regular Member  Joined: 03/02/2008 Location: South AfricaPosts: 51 |
[Hi there! I once was told by a solar (PV) distributor that I could use a 24V charge controller on my 48V PV array by simply just by-passing two of the four PV modules.(Using a shunt regulator with a dump load). Has anyone so far make use of this principle and with what results? FONT=Arial] You don't have success until you've tried it! |
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| Privatteer Newbie  Joined: 09/06/2012 Location: AustraliaPosts: 39 |
Why the heck would you waste potential power like that? If you need 24v rewire the array to be 2 sets of 24v and put them in parallel. |
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| solarwind Regular Member Joined: 03/02/2008 Location: South AfricaPosts: 51 |
Nope! I think I'll waste less power in the dump load due to the lower voltage handled by the dump load. If you sense voltage at the battery and use this to control the dump load (across half the PV panels) the total charging voltage (++48V) will also drop. My question is if anyone on this forum has used this method before and what results were obtained? See the simplified illustration attached. thanks 
You don't have success until you've tried it! |
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fillm Guru  Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Why not just use a solar control like this HERE ,or another option, get a DC to DC charger HERE PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| solarwind Regular Member Joined: 03/02/2008 Location: South AfricaPosts: 51 |
I have 4 x 310 W panels, Voc of each is 45.2V. They are connected 2 in parallel. Each is 8.5 Amp, therefore I am looking at 17A at (2 x 36.5V) = 73V loaded or 90.4V unloaded. (1.24Kwp). This is the reason I rather look at using a dump load controller to handle the power. MPPT at this power is quite expensive out here. Thanks anyway for the info on the commercial controllers etc. You don't have success until you've tried it! |
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| solarwind Regular Member Joined: 03/02/2008 Location: South AfricaPosts: 51 |
"They are connected 2 in parallel". Correction!: I mean two in parallel connected in series with two more in parallel. You don't have success until you've tried it! |
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Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
That is not what your schematic shows Sometimes it just works |
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| fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
So are they now 24v panels, I think you will need to explain about the whole system PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| solarwind Regular Member Joined: 03/02/2008 Location: South AfricaPosts: 51 |
Yip! "24V" panels. I shall get MPPT later, but for now I shall start with a home-made shunt regulator which in principle works as illustrated. I have already used it on another series bank of 4 x 130Wp x 12V panels and it regulates perfectly. Only "problem" is the heat generated when batteries are full. (Not really a problem, because here, like in Oz, we now have winter, so dumping should be rare and can be put to other useful use!) Now I got 4 more (24V) panels of 310Wp each, but know that a lot more power might have to be "dumped" and therefore decided to only connect the dump load part of the regulator across half of the panels. The panels will be connected 2 x parallel then in series with the other two also in parallel. Sorry for the confusion with my original schematic which shows 4 panels in series. This was just an example to show that by regulating part of the series bank, you actually regulate the whole bank. I am just curious to know if anyone on this forum has tried this method before and what the results were. You don't have success until you've tried it! |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
What part of solar power dont people understand? Solar is not required a dumpload like a windmill to control the power, you can simply disconnect solar from the system at will without the need to shunt the power to a dumpload, as one would with a windmill. So why the need to disapate energy as heat just to control charging to a battery. A MPPT takes the input voltage and converts it to amps at the selected output voltage. But you can simply charge the battery till it reaches a upper limit and then switch off the solar input, it aint going to cause a solar panel runnaway like a windmill would. Im just unsure what you intend to want to do. Pete. Sometimes it just works |
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| solarwind Regular Member Joined: 03/02/2008 Location: South AfricaPosts: 51 |
Thanks Pete, Point taken. I shall then just use the controller(without the dump load) in series with my charging source ( the solar panels). I then only have to change the logic at the op-amp inputs too in order to turn the series transistor off, unlike turning it on in the shunt regulator when correct battery voltage is reached. You don't have success until you've tried it! |
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| brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548 |
I have 4x220 watt series/parallel for 48v nom. My regulator just turns the solid state relay,(in line with the solar input), off, when the required battery voltage is reached, and on when the voltage drops a volt or so . Been doing this for a year ,no adverse effect has been noticed. Bruce. Bushboy |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
A two part system is where I am headed. Group 1 Bulk charge with panels switched with solid state relays purely from voltage at the battery. on at 12.? volts and off at 14.? volts Group2 A smaller group of panels sized to finish the charge cycle hooked to a GOOD controller. By good I mean something that will keep the batteries in top condition for a lot of years. For me that is something that has tweakable settings. I wouldn't care how group 1 is controlled, a simple adjustable voltage switch with hysteresis or from an output wire on the group 2 controller. I will grudgingly accept that a MPPT controller will let you use cheaper grid connect panels in an offgrid system (by dealing with the large voltage mismatch). The downside is that multiple controllers on a network is it's never cheap or easy to maintain. I would rather spend a few extra dollars matching the panel voltage to the batteries for group 1 and stick with one controller, you don't need a lot of grunt to do the absorb, equalize, float parts of the cycle. I know it's not answering your specific question, but it's the best I can manage ATM. need some sleep  I'm confused, no wait... maybe I'm not... |
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