Recommendations for solar charge/controller

[jodeb720]

It appears a buddy of mind is going to donate two used 300 watt panels.

They are rated at 30 volts with about 8 amps open voltage (he got them for a song - used I should say)

We’ve been out in the desert in socal and after wiring in a progressive dynamics charger, a 2000 watt psw inverter and a midnight 150 charge controller we are pretty happy with the results.

Since he bought 6 and needs only 4, they are going to be donated to me.

Questions:

1. How many amps should I size tge controller at?
2. PWM or MPPT?
3 Any brand you’d recommend.

Im running 420 amps (2-battery banks GC4 so two 210 banks)
I generally charge the separately (my house batteries are from July 2014 and they are still going strong!) , the other bank feeds my 1000 psw inverter for coffee.

Thanks in advance….

[Bobbo]

Voltage drop is related to wire size and amps flowing. Putting the panels in series keeps the amps low. That gives you less voltage drop. However, since the VOC is 45.29v, be sure that the MPPT controller is good to at least 100v.

If you opt for parallel, then be sure the wire is heavy enough to be capable of carrying 20 amps.

ON EDIT: corrected some numbers. I had misremembered and put numbers for 3 panels.

[jodeb720]

since I have two battery banks (each bank is two 6v gc batts of 210 ah)
I isolate them from each other (one is my house battery bank, one feeds my inverter).

As noted above, one set of batteries is from 2014 - still going strong and the other is from last summer.

The 2014's are in good shape - but they aren't a matched set to the 2022 set.

Can I Switch between each battery bank once bank 1 is recharged to 80%?

What would I have to do in order to make that kind of switch? disconnect the PV panel feed, then switch from bank 1 to bank 2 - removing the load?

In a perfect world, I'd get 4 brand new 6v gc's and do a full charge with my 120volt 3 stage charger until full - and then put them into the trailer - but that seems like a huge waste of capital on the new set of batteries.

thoughts?

[SJ-Chris]

You will love the "free" (after cost of installation) AHs your batteries get anytime the sun is shining. Plus, when in storage your batteries will keep/remain charged.

If you don't think you will add more wattage in the future, getting a 30amp controller will be fine. If you think you might want to add more panels in the future, then you should look to buy a 40-60amp controller.

As mentioned, you 100% need to get an MPPT controller, otherwise you will only get ~40% of the watts that you are expecting/hoping out of your panels.

Since you have two separate battery banks, it would be kinda cool if you incorporate a switch of some sort such that you can charge either (or both at the same time) bank that you want.

Parallel vs series probably won't make much difference overall. In either case, you should install them away from any tall items (ie. AC unit) on your roof.

Good luck!
Chris

[jodeb720]

I got the info - regarding the panels, because I've always been told design is based on reality, not vaporware (software design I should say)....

Brand: AstronEnergy
Model: CHSM6612p-305
Open Circuit Voltage (VOC): 45.29v
Short Circuit Current (ISC) 8.95A
Voltage at PMax (Vmp): 35.77v
Current at PMax (Imp): 8.95A
It's a poly cell

Since I'm going to mount them on the roof (obviously) and there is some shading possible depending on orientation due to vents and AC, do I want wire them in series upping the voltage or parallel?

Also, I remember reading a very lengthy discussion regarding some important stuff about wiring in parallel vs series - and whether the panels have diodes in them so the shaded panel doesn't detract from the panel in full sun?

I'm not planning on mounting the panels at an angle. I'm just hoping my friend Bernoulli doesn't decide to make a wing out of the panels (maybe the solution would be to put something in front of the panel to create vortices to disturb the airflow over the panels and prevent laminar flow - disrupting the lift from the natural cord shape.

[ktmrfs]

looks like what you have are 24V panels, so that heads you to MPPT controller.

I have the midnite solar kid controller (actually two, one for the roof panels,one for portable)

[StirCrazy]

unless you are planning to install a whole eco system and spend lots of money stay away from Victron. If all you want to do is install your free panels and keep the price down, look at Renogy. You do want an MPPT set up. If you wire your panels in series, you will up the voltage going into the controller but keep the amps where they are at so you can get away with say a 40-amp MPPT controller from renogy as it will take a 100v input. This is what I use in my camper

[dalej]

Might check out Morningstar controllers. Mine has been reliable.

[Vintage465]

I think you need to get the spec's on the panel output to size the controller correctly. In my case, my panels provide just a bit more than 8 amps(best case), time three panels equals around 24v +/- a bit so I have a thirty amp controller. I think Victron is the top of the line and if you can afford it that's the way to go. Also, if you plan to increase, get a controller to match the possibilities.

[Second_Chance]

As stated, you'll need to go MPPT - Victron makes quality, well-regarded units.

Rob

[pianotuna]

Hi,

You will need to go to MPPT for the controller due to the 30 volts output.