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34.5 Volt Panels PWM Charge Controller & 12V Batteries - I Don't Get It?!

nifty-stuff.com

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Hey guys, sorry this is probably a dumb set of questions, but here goes...

I have a handful of 34.5V panels I got cheap (see attached) from a friend. I thought this was going to be a simple way for me to "play with solar", but turns out to be a rabbit-hole of confusion and questions :(

It seems like almost all of the panels that go on roofs are high voltages like this, no?

I'd ideally like to use these without batteries (see my other thread here), but since it doesn't seem like that's an option, I figured I'd go with a cheap PWM Charge Controller (like this one) and a lead-acid battery, but I'm realizing the CC won't really work since the max V for a 12v setup is like 30v.

The only option would be to move to a 24v battery setup... maybe using two batteries in series, but that complicates everything else with my 12v inverter, etc., and I don't think there is a way to wire two 12v batteries in series for the CC and parallel for the inverter, right?

So, what do most people do in similar situations where they have panels with 30+volts and a 12v use-case (batteries, inverters, etc?).

Do they just pony-up for MPPT systems? From what I can tell, these play nicer with high input V way more than PWM, no?

Any other ideas / suggestions on how to utilize these panels without too much complexity and cost?

I'm starting to wonder if I'm over my head with this stuff. :(


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You can use a suitably rated PWM controller but you'd be throwing away a significant proportion of the potential output of the panel by pulling it way off Vmp.

A reasonable quality MPPT controller doesn't need to be expensive. While people here will recommend Victron and the like, I use Victron myself, you may not need a quality product like that. Take a look at the Renogy (OEM is SRNE) Rover line of MPPT controllers.

With the right one you could arrange your panels as 2 in series (Voc 87v) and then parallel those sets. The exact configuration would depend on the number of panels you have. Just remember you have to live within the output current of the controller. A 40 amp controller connected to a nominal 12v system is approx 500 watts. A 40 amp Rover will not make use of more power than that into a 12v battery (roughly speaking).

There are other reasonable quality MPPT controllers out there too, and there are heaps that are complete junk. So before buying anything, bounce it off the forum and see what people say about it.

Roof top panels tend to be that voltage range but there's nothing stopping people from putting '12v' panels on the roof, it just means they need to use heavier cabling to cope with the resulting increased current for a given array wattage.
 
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