Noob PVA Selection/Wiring Questions

Re: Noob PVA Selection/Wiring Questions

faraday wrote: »

Hi! I just registered for this forum. Seems like there are some people here who know what they're talking about in regards to installing solar systems.

My partner and I are doing a bus conversion. We're in the planning stages and we're thinking of using the following components, but are unsure of (several things including) which solar panels would work best with the controller, and how best to wire them for optimal use with the other pieces. (was eyeing these pups, but don't know...)

Any advice would be very much appreciated. Thanks!

1. Magnum Energy MS2812
2800 Watt Sine Wave, 12 Volt DC Input With 125 Amp Charger
http://www.solar-electric.com/maenms2020wa1.html

2. Morningstar TriStar 60 Amp MPPT Solar Charge Controller
http://www.solar-electric.com/motr60ampmps.html

3. (4) of these guys, wired in series/parallel for 12volts/~800 rated AH
Concorde AGM PVX-4050HT Sealed Deep Cycle Battery, 405 Amp Hour, 6 Volt
http://www.solar-electric.com/pvx-4050.html

Don't spend your $$ yet.

With what you are talking about, why not go to a 24V system. Batteries in series always works better than trying to get parallel ballanced. And the inverter will be happier with 2x the voltage droop capacity, and half the amps. (that a 12V inverter would need)

If getting the Tristar MPPT , also get the remote battery temp sensor, and the digital meter panel (replaces the blank front panel) Yes, extra $$, but you wont have to log into a web page to see what the batteries are doing. And at 24V, you get twice the watts (1440w) , as at 12V (720w) charging capacity

What is your charge source ?? With the batteries you listed, you should have about 700 - 900W of PV to keep them happy, and maybe a small genset (auto-throttle inverter type) to manage on cloudy days.

But even first, you need to know what your loads are, to size the batteries properly.

Re: Noob PVA Selection/Wiring Questions

A 2800 watt inverter is really a no go on a 12 vdc system, requiring wire sizes for ~ 250 amps with the requisite line loss. Doubling the voltage to 24 would reduce that to ~125 amps.

Besides, what are you planning on running on the inverter on a Bus any way. We live just fine with a 300 watt inverter. A 1000 watt inverter would be more in line with what one might expect. Also, please understand that running a A/C system, or coffee pots or electric stoves and even micro waves on a smallish battery based system are also no no's especially if you are primarily charging with PV.

Please also note the 50%X4 rule. Take the name plate rating of the PV, divide that number by 2 to account for all system and wiring loses then multiply that by 4 to account for the average number of hours of good sun one might reasonably expect per day on average over the course of the year.

So a 300 Watt RV installation might look like this,, 300/2=150*4= 600 watt/hours/day. (or 2.4 kwh/day) In a typical RV installation the numbers get even worse, primarily because the panel orientation is almost never ideal. Additionally, the biggest loads on most RVs is A/C loads so parking in the shade is often more palatable than parking in the sun.

The mistake most people make when delving into PV is over estimating the amount of solar energy they can actually harvest, whilst at the same time underestimating their load.

Good luck and keep in touch,

Tony

Ps edit after your previous post. 100 ah/day at 12 volts is ~ 1.2 kws,, about double what said same 300 watt system might produce. Also, I don't think that 2 Honda Eu 1000s will run a roof top A/C unit. If memory serves they require well over 2 kw to run. 2 Eu1000s will only put out a combined ~1800 watts with a few extra for surge, but not enough to start a roof A/C system. You might think about an unconventional installation of a Mini-split A/C system.