Watts needed

For 2*285W you need at least 40A MPPT.

Renogy Rover 40 should be able to do the job, though I would use slightly smaller panels with this one, 2*260W. This controller will try to equalize the battery every 2 months and I "think" this feature can't be disabled. Some people wouldn't want this to be done automatically in their absence. An economic alternative is Renogy MPPT Rover 30 with Bluetooth, it allows to disable equalization feature, but you would have to use panels no bigger than 400W total, i.e. 2*200W.

Victron MPPT 150/45 will handle 2*285W and will allow you to change the charging profile, including equalization.

Maybe people will suggest something cheaper than Victron 150/45 and not much worse, but 45A MPPT is a lot of a controller, this is gonna cost ya.

Two 285s in series will add their voltages so the controller does need about 80v for the total Voc so yes, 100Voc input would be right.

A 20 amper will just run what one of those 285s can do, so at least a 40 amper would be needed. I would choose a 40 instead of going to a 60 because the panels will get hot in the sun and be about 10% down in watts from that heating, so that keeps you under what a 40 can do. Also if mounted flat they will not get full sun, so that keeps the watts down too.

Tracer makes a decent 40 amp MPPT that would do at a good price. Lots of other choices with various features and prices.

MPPT uses output watts / battery voltage for amps out (which go to loads first and any left over go to the battery)

2 x 285 = 570w less 10% for heat = 513w minus say 2% wiring loss panels to controller, so now 503w input to the controller. controller efficiency maybe 96% so output watts = 483w so picking three battery voltages:

483/12 = 40.25 amps
483/13 = 37 amps
483/14= 34.5 amps

As you see, you get more amps to the battery when the battery is low. However you get more watts into the controller at mid-day high sun. but by then the battery is higher in voltage, so you likely never see the set--up doing all it could do. for that you would need to aim the panels at the sun at high noon and have the battery voltage down low.

Solar gets the job done though, so expect to be pleased you got it.

All right, I need some more help from the experts. I am looking at purchasing 2 residential panels with the following spec.;
Watts (STC) 285 W
Max Power Voltage (VMPP) 32.2 V
Max Power Current (IMPP) 8.84 A
Open Circuit Voltage (VOC) 39.2 V
Short Circuit Current (ISC) 9.61 A
Max System Voltage 1000 VDC

Am I correct in assuming that a mppt charge controller that will accepts 100 volts and 20 amps would work with these panels.

I am currently trying to get a better understanding of charge controllers so your help is greatly appreciated.

cliffy49 wrote:

I know that most people will reccomend the Victron line but I really do not want to spend that much on a controller. Does anyone have a less expensive option? Probably looking at the MPPT(?) type.

Renogy Rover 30 with Bluetooth: https://www.renogy.com/rover-li-30-amp-mppt-solar-charge-controller/.

Going MPPT makes future expansion easier, you can add panels in series onto the same #10 cable, just connect the pigtails between the panels. MPPT allows using 24V panels, those are cheaper per watt than 12V panels. Rover 30 can handle 400-450W array, so you can install a single 200-220W panel now and add another panel later if you want. The only drawback of 24 panel is 40 lbs weight, somebody should give you a hand to lift it on the roof.

When adding 24V panel later, it should better be same wattage so I suggest you install 400W from the beginning. Chances are that with 400W you won't need a generator, other than for running A/C.

Rover 40 could handle 2 pretty big panels, total 550-560W, same price as Rover 30 but no Bluetooth option. It probably has pre-programmed charging profiles for flooded, AGM and gel battery, so it will work.

I had a bad experience with MPPT Tracer aka Epever. Horrible proprietary software, help files are in impossible Chinglish - I am not new to controllers or software but this one was a big pain. Flimsy terminals. Sent it back and bought Renogy - not perfect but better. Though my case was unusual - I needed to adjust the charging parameters and on Epever this can only be done through the added software and laptop, inconvenient and the software is poor.

Forget "kits", they rarely have the panel you want with the controller you want with the length of MC4 #10 cable that you want.

cliffy49 wrote:

Boon Docker wrote:
200 watts is a good place to start. Be sure to get a charge controller with enough amperage if you want to upgrade the panels later.

Happy Camping

I know that most people will reccomend the Victron line but I really do not want to spend that much on a controller. Does anyone have a less expensive option? Probably looking at the MPPT(?) type.

"Tracer" charge controller has good reviews and won't break the bank. My "Tracer" has been charging my pair of GC2 batteries for almost 9 years now.

cliffy49 wrote:
Want to thank every one for all of the information. I am thinking that I will probably go with a kit in the 200/400 range. It will probably be closer to 200 watts since we have not yet tried boondocking.

At some point in the future we may but in the mean time we can always use the genny if absolutely needed.

a good starting point would be to fall in the middle. get say one 315 watt 24 Volt panel and get a controler than can handle 2 of them. then later if you decide you need just a bit more its cheep to add a second panel.

Steve

cliffy49,

Just make sure what ever you get will handle 400 watts. The charge controllers are often the most expensive part of the system.

Look at MorningStar, Outback, as well as Victron.

Boon Docker wrote:
200 watts is a good place to start. Be sure to get a charge controller with enough amperage if you want to upgrade the panels later.

Happy Camping

I know that most people will reccomend the Victron line but I really do not want to spend that much on a controller. Does anyone have a less expensive option? Probably looking at the MPPT(?) type.

200 watts is a good place to start. Be sure to get a charge controller with enough amperage if you want to upgrade the panels later.

Happy Camping

Want to thank every one for all of the information. I am thinking that I will probably go with a kit in the 200/400 range. It will probably be closer to 200 watts since we have not yet tried boondocking.

At some point in the future we may but in the mean time we can always use the genny if absolutely needed.