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Old 09-22-2014, 08:59 AM   #1
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Solar Charge Controller Question

I'm about to order one of the Renogy Solar kits off Ebay, with 2x100 watt panels, charge controller, connectors, etc. The kit comes with a basic charge controller, but for an extra $100 I can upgrade to their 20-amp MPPT controller. I know MPPT controllers are better, but for basic use do they really matter that much? I'm mainly interested in keeping my batteries charged while parked, as it's not easy to keep the van plugged in where I park it. Or should I take that extra $100 and put it toward a brand-name MPPT controller like the Blue Sky, for ~$250?

I have three Group 27 batteries for about 314 amp-hours total.

Here's the "stock" controller that comes with the kit: https://www.renogy-store.com/30-amp-cha ... -pwm30.htm
And Renogy's MPPT: https://www.renogy-store.com/MPPT-Charg ... mppt20.htm
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Old 09-22-2014, 09:23 AM   #2
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Re: Solar Charge Controller Question

I just bought the 100 kit with basic controller. I'll be watching with interest.
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Old 09-22-2014, 09:26 AM   #3
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Re: Solar Charge Controller Question

Without knowing your usage requirements, other than you want to keep your batteries topped off, I think you have plenty of margin between your available solar power and your usage requirements, not to have to worry about squeezing out as much efficiency as possible, and I think you'll be fine with the PWM controller.

Myself, I did go with an MPPT controller, but I went with a cheapy import version. I never used a PWM controller with my 120W portalbe panel though, so I can't provide a direct comparison as to what I gained, if anything, with the MPPT controller. I believe that an MPPT controller has advantages if the panels are partially shaded, so that may be more important with a fixed panel rather than a portable panel.

The controller I bought:
http://www.ebay.com/itm/15A-MPPT-Solar- ... 20d4e9d467


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Old 09-22-2014, 09:36 AM   #4
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Re: Solar Charge Controller Question

Quote:
Originally Posted by 86Scotty
I just bought the 100 kit with basic controller. I'll be watching with interest.
Hey Scotty, what do you think of the kit? (I assume you have it in your hands?) I've read good reviews of it.

My driveway is full sun for a lot of the day, so it's perfect for keeping the batteries charged. I figure $300 or so for solar panels is cheaper in the long run that dead batteries because I forgot to plug the van in!

We are an all-electric van, with a 1500 watt inverter and the three batteries. But apart from the frig, LED interior lights, use of a 12v Endless Breeze fan at night, and charging electronics with USB, we're not heavy power users. We do have a microwave, but rarely use it when not plugged in, or run the van engine when using it if not on shore power. Our travels rarely have us camping for more than 2-3 nights without driving the van, so we've never had a problem drawing down the batteries while traveling.
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Old 09-22-2014, 12:03 PM   #5
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Re: Solar Charge Controller Question

I've got a Renogy 100W panel and a Sunforce controller that I got a good deal on.

With my fridge running on warm days I never get into "float" charge, other than that, the batteries stay topped off.

I thought about going with 200W, but so far 100W has been sufficient and leaves me plenty of room on the roof for "stuff."
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Old 09-22-2014, 08:42 PM   #6
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Re: Solar Charge Controller Question

I've had both. Basically I've read that the MPPT controller is more useful during overcast skies, fog, and lower light conditions and found that to be true. The type panel also makes a difference but to grab all the sun power you can get go with the MPPT. Higher grade more tech worthy controllers usually have better charging characteristics and the more solar you have the more important it is that the system doesn't overcharge your batteries. Smaller systems usually don't generate enough amperage to boil or overcharge batteries especially the bigger type like 4-D or larger. Some controllers have the option to install a temp probe that hooks to the battery to cut the charge down if the battery gets too hot.
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Old 09-23-2014, 12:42 AM   #7
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Re: Solar Charge Controller Question

for 1 low wattage panel mppt wont give you any advantages. I had a 120 watt kycora panel and I actually got more amps with pwm than mppt (7 amps to 6 amps). If you have multiple low wattage panels and you connect them in series mppt becomes useful.
On the otherhand if you have one large panel, say 240 watts then mppt definitely will work. I get 12 amps with mppt and only 7 amps using pwm.
I recommend you research what mppt controller you going to get, some of the cheaper models arent mppt, even though they say mppt. I like to see pictures of the interior of the charger to see if its a real mppt or get a good review. Real mppt will have a donut type looking circuit inside, thats what converts excess voltage to more amps.
I use the ecoworthy 20 amp mppt, its made in china but I been using nonstop 24/7 for almost 1.5 years. For the 102 dollars I paid it does its job.

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Old 09-23-2014, 08:11 AM   #8
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Re: Solar Charge Controller Question

Quote:
Originally Posted by BrianW
Quote:
Originally Posted by 86Scotty
I just bought the 100 kit with basic controller. I'll be watching with interest.
Hey Scotty, what do you think of the kit? (I assume you have it in your hands?) I've read good reviews of it.

My driveway is full sun for a lot of the day, so it's perfect for keeping the batteries charged. I figure $300 or so for solar panels is cheaper in the long run that dead batteries because I forgot to plug the van in!

We are an all-electric van, with a 1500 watt inverter and the three batteries. But apart from the frig, LED interior lights, use of a 12v Endless Breeze fan at night, and charging electronics with USB, we're not heavy power users. We do have a microwave, but rarely use it when not plugged in, or run the van engine when using it if not on shore power. Our travels rarely have us camping for more than 2-3 nights without driving the van, so we've never had a problem drawing down the batteries while traveling.
Brian, it looks well made but I haven't installed it yet. It sounds like our setups and habits are very similar though. I'll be really happy if it keeps us charged for 2-3 nights off grid at a time and so I don't always have to remember to plug in at home. I have about 1/2 sun at home due to trees. I hope to have it installed before Expo East but we'll see. I'll update soon.

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