First solar setup . . . questions

[catdog]

Hi all, I'm pretty new here. I've been reading for a while as I've been researching, and now I'd like to get some personalized feedback on my intended setup.

I am building a camper in a currently gutted cargo van. I want to charge the house batteries with solar, and from the alternator and/or shore power to supplement when need be. I already have two 6v 415ah AGMs, and two 300 watt 60-cell pv panels. It will be a 12v system. I estimate that we (husband and I) will use only up to about 125ah on a daily basis, powering a few small led lights, 12v dc fridge, 12v ceiling fans (two of those), and charging phones, tablets, laptops, and other batteries for power tools, a battery-powered blender, cameras, etc.. No aircon, microwaves, coffeemakers, heaters, or anything like that. We will use propane for cooking and heating. We will be living in it full time.

I plan to purchase Victron Energy everything:
Phoenix Inverter 12v / 800w
MPPT cc 100v / 50a
BMV-712 battery monitor with temp sensor
Smart Blue charger 12v / 15a
Argo FET battery isolator

My questions at this point are:

1) Will the 100/50 MPPT cc be enough for the 600w of panels? They are well within the cc rating for volts, but I have read in many places that you should allow for an additional 25% on the amp rating, meaning that my 600watt panels on a 12v battery bank would need a cc with a rating higher than 62.5a. Why do some people size their cc this way and others don't?

2) How do I size the battery isolator? Victron offers a 100 or 200 amp model, and I am not sure how to determine what I need.

3) Here's the tricky one: We only have room for one of the panels on the roof, as I don't like the idea of huge panels overhanging the sides of the van and catching everyone's eye all the time. One will fit nicely between the vent fans on top, and the other can be slid underneath the bed/table area inside the van, and taken out when needed. Because our daily draw is only around 30% DOD on our bank, and we are in TN for the time being (good amount of sun usually), and we will be able to charge via the alternator or plugging in (we have family here), I'm not worried about using only the one panel full time. When we are parked for a few days at a time and don't have anything to charge with but solar, we can pull out the second panel and plug it in. That is my ideal setup at this point. In reality I have no idea if this is possible. I haven't been able to find much about other people doing this, let alone how they did it.

I've still got quite a lot to learn about how exactly to set this all up, but this forum has been absolutely invaluable thus far. Thanks to anyone reading, let me know if you have any advice or other resources for me.

-cat

[Mike90250]

One panel will not do much for charging the battery, 2 panels will be only a tiny bit better 300w @ 15v = about 10 amps since the panel has poor aim at the sun, being flat on the roof

10ah x 5 hours 50ah harvest to offset your 125ah of daily load. You will need to run your engine a bit to keep the batteries charged, even if you wire up the 2nd panel.

[catdog]

Hi Mike, thanks for your input.

I have been trying to think of some clever way to be able to tilt the roof panel a bit when parked. I've seen it done before I just need to decide if it is something I want to mess with. The second panel, if/when I set it up, will be on the ground and I will be able to position it as I need. Does that require a separate charge controller? Is there a way I can set that up to be a quick disconnect type of deal? I haven't found much in my searches, I keep ending up at links about those portable suitcase panels, or nothing at all. I am hoping to set that up in such a way as to be able to plug the panel into a cable near the side or back door, without having to connect anything at the actual battery bank every time I plug in the second panel.

And to give a little bit more information, while we will be living in the van full time, my husband works and is gone for about 10 hours each weekday. I will also be gone at times working, and at times will work from home/the van. My estimate of up to 125ah per day was based on us needing to use everything every day, which will likely never be the case. We will have the fridge as our largest draw (it's a Dometic crx 65), and beyond that it will look like daily phone charging, a few hours of running the lights and ceiling vent/fans, my laptop charging daily, and every few days the blender battery, husband's laptop, and a camera battery or two will need charging. So hopefully in practice our draw is less than 125ah per day.

We will be driving at least around 30 minutes most days, and I do have 4 different family members with houses nearby who can let me plug in if need be.

I chose the 415ah AGM because I wanted to aim for less than 30% daily DOD to give myself some wiggle room as I learn how to manage my setup, to be able to grow into the bank a bit if our usage goes up in the future, and hopefully to make the batteries last longer from lighter use/fewer cycles. AGM because it's a van and the batteries will be under our bed. I plan to keep them in a sealed box and vent them outside. I have seen that a lot of people don't vent their AGM batteries at all but that makes me nervous.

[littleharbor]

While there are virtually hundreds of ways to mount up panels on a vehicle roof, basically every installation is unique to itself. I can see the use of some quick release pins being quite valuable in a part time tilting panel setup. When flat they could be the attachment point on one end of the panel, You could have a pivoting arm connected to the mounting structure that just swivels up to set the elevated angle. Pull two pins, tilt, swing up arms and insert pins, done.

These are stainless steel, $17.99 for a set of four on everybody's favorite auction site.Quik release pins.jpg

[Mike90250]

If you are driving 30 min a day, the alternator is going to do more recharge than any panels you could fit.

Anderson Connectors are rugged, with vehicle mount options, that would be great for the remote panel. Tow trucks and police cars use anderson connectors at the front grill to connect jumper cables.

Adding identical panels in parallel is fine up to two panels. More than that, and you need fuses on each panel for protection.

[john95]

catdog,

Even though the solar panels are rated 300 watts a panel; now in real life I found out that you may get like 1/2 or even much less of what they are rated.
When I was getting my 4x 320 watts 24 V panels I thought that I was getting 1,280 watts per hour. I'm getting in real life like 864 watts for the 4 panels in the best conditions; and just for a few moments, then they go down to like 500 ~ 600 watts and when it is cloudy they go down to about 150 ~ 200 watts.

So, in your case, I think that you may get like 1/3 of your 600 watts, about 200 watts in your best conditions and go down from there to like 100 watts and in cloudy days about 25 ~ 50 watts.

I made my calculations and I need like 32x 320 watts 24 v panels (8 times what the 4 panels produce now) and about 32x 6 volt batteries for 43 kWh battery bank or 2 Tesla PowerWall2 14 kWh (28 kWh) batteries, more chargers and a bigger Inverter to keep up with my 20 kWh electricity daily usage.

Average house is like 25 ~ 30 kWh per day here in California. Solar is still a big joke for the people. I'm getting 4 ~ 5 kWh per day now with these cloudy days.
This system is for testing purposes only. I'm spending about 2.8 kWh a day max out of my 10.8 kWh battery bank.