New to the game... have several questions

[ericfx1984]

Hello and thank you for all your help in advance

I recently acquired an RV... 2009, 34 foot, 5th wheel, bunk house, master bedroom in the front, kids double bunk in the rear

It is already setup with solar and I have been living in it off grid on our property in rural Kansas for nearly a month now... RV is parked MOSTLY South with the panels pitched a hair to the West... might move it at some point to fix this

Currently getting between 1Kwh and 2Kwh a day... batteries are staying charged

I have several questions and have noticed several little issues

setup is as follows:

3x Hitech 200 watt solar panels, in parallel

Victron 100/50 MPPT

4x Duracell GC2 golf cart lead acid batteries, setup @ 12v

1/0 wire on the batteries to the inverter (2 foot run)

cheap china 300 amp breaker

AIMS Power 3000 watt inverter charger, etl rated with the remote control panel

additionally I have a battery display also mounted inside

Adding 2x Silfab Sil-330hl in series and a EP Ever Tracer 40 amp MPPT in the next few days

Additionally i will be building a large off grid 7500 watt, 16s 30khw, 10000 watt system, but this will be SEPERATE from the RV system, it will RUN the RV and the entire property (shop and eventually a 700 square foot cabin)


On to my questions:

1.) does the inverter NEED bigger wiring (currently 1/0, 2 foot run)? I have noticed that IF I run the microwave OR the electric tea pot, it will sometimes pop the breaker... To experiment, I had my wife fire up the tea kettle which pulls around 1200 watts on the DC side of the inverter (so maybe 1000-1100 on the AC) What I noticed was that the voltage measured at the battery was around 12.6 vs the voltage measured at the inverter being nearly 11.7 ALMOST a volt different... and within about 20-45 seconds the 300 amp china breaker would POP

When you count all the other things running on the inverter (work laptop and monitors, phone charging, personal laptop) the total wattage coming off the battery is between 1600-1900 watts! But even at 11.7 volts and 1900 watts, that should only be around 165 amps at the breaker... just over 50% of the breaker's rating... Considering just going 400 amp ANL fuse and 1 foot run 4/0 (or 2x 1/0 and double 200 amp ANL?)


2.) Considering upgrading my battery, mostly looking for more capacity... the batteries I currently have are in fantastic condition... I COULD just add 2 or 4 more of them, I have the room in the bay

OR

I could build a LIFEPO4 4s out of china 280 ah cells... my biggest concern is the cost of BMS... I would like to be able to full power the 3000 watt 12v inverter which in COULD require up to 313 amps at 12v(after accounting for the unit being less that 100% efficient)


3.) is it worth it to convert the RV to 24v? I mean BOTH of my MPPT SCC can handle a 24v battery system... I would need to run a few 24-12 DCtoDC convertors...


4.) Is it worth it to run my current 3x 200 watt panels in series? My guess that they would build a max of around 66v and would reach a usable charge voltage much sooner in the morning and continue to charge a little later in the day

5.) I see that my inverter charge has multiple smaller lines that connect to each battery I assuming this is used a balancing function?

 

[MisterSandals]

IF I run the microwave OR the electric tea pot, it will sometimes pop the breaker...

cheap china 300 amp breaker

You know the answer right here.

1.) does the inverter NEED bigger wiring (currently 1/0, 2 foot run)?

If the wire is too small, it will get warm in use. If you want to run the numbers check the voltage drop calculator.

4.) Is it worth it to run my current 3x 200 watt panels in series?

It depends on the Voc of your panels whether you can run them in series. It is probably not going to help however. Do you suspect a problem with your array?

5.) I see that my inverter charge has multiple smaller lines that connect to each battery I assuming this is used a balancing function?

Happen to have a pic? Could be temp probes?

 

[rmaddy]

1. 1/0 is much too small to safely carry 2000W, let alone the full 3000W supported by your inverter on a 12V system. 2/0 would be ok for 2000W. But for 3000W at 12V you need 4/0 (or equivalent). Cheap Chinese breakers are known to be problematic. Get a high quality well known named brand breaker that won't trip until the proper rated current.

3. Going from 12V to 24V would lower the current and it would make the 1/0 cable sufficient. But buying a new inverter is probably a lot more expensive than replacing a few feet of wire, not to mention the need for the DC-DC converters. And some loads may be too high (such as slide outs) for a DC-DC converter.

4. Series would be good for the reason you stated but you need to worry about shade and you need to verify the Voc of the panels to see if the 100/50 will still work.

 

[ericfx1984]

4. Series would be good for the reason you stated but you need to worry about shade and you need to verify the Voc of the panels to see if the 100/50 will still work.

just checked VOC = 24.335v

 

[ericfx1984]

You know the answer right here.


If the wire is too small, it will get warm in use. If you want to run the numbers check the voltage drop calculator.

It depends on the Voc of your panels whether you can run them in series. It is probably not going to help however. Do you suspect a problem with your array?



Happen to have a pic? Could be temp probes?

OK ANL fuse time then

Ok I may just run 1/0 x2 (same cross section as 4/0, and $0)

VOC is 24.335

no pics, sorry

 

[rmaddy]

just checked VOC = 24.335v

So in 3S you're close to 75V. Add 15% or so for cold weather. You're still safely below 100V so you can put the 3 panels in series with the 100/50.

 

[ericfx1984]

An additional question I ran into ... Seems like the only time that I have shading on one of my panels is about the last hour of usable sunlight before the sun goes behind the trees in the Southwest.. at that point one of the panels which is situated ahead into the West a few feet shades the other panel causing it to have about a 25% reduction in output

One way that I can solve this is by going to a less steep angle on the panel that is in front

For another option might be to change the orientation of one or both of the panels going from a landscape to a portrait

Or moving the panel that is causing shading back a little ways or even further to the West

But then there's the other option just not giving a damn because it's producing pretty good throughout the day and doesn't have any shading every time that I've checked it except for that last hour

I mean I know that the effects of not having the right angle is pretty bad.. but I think the shading would be an even worse effect overall correct me if I'm wrong?

 

[rmaddy]

Panels in series should always be in the same plane so you can't angle one differently than the others. In parallel you can angle each one as needed.

What do you mean by "usable sunlight" here? Are you talking about just before sunset or the end of the main midday window of max sun?

 

[ericfx1984]

It's just before sunset.. and it's steering late fall early winter so I don't anticipate it being a problem during the spring and summer months as the sun will be higher in the sky

 

[rmaddy]

You won't be getting much that late in the day so losing a little that late shouldn't be much of a problem unless you need to get every photon to finish charging really low batteries. But your extra panels and SCC you are adding soon should make up for it.

 

[ericfx1984]

You won't be getting much that late in the day so losing a little that late shouldn't be much of a problem unless you need to get every photon to finish charging really low batteries. But your extra panels and SCC you are adding soon should make up for it.

I have attached a picture so you can see the shading, I think a super easy way to correct this would be to buy a couple pieces of aluminum stock, maybe l-shaped and raise the rear panel up a foot or so...

I realize it's not completely necessary.. but I do feel like it will be helpful

As far as needing every stray proton I'm fairly new to this and it seems pretty important to me to really optimize this system since I am going to be off grid with this RV for the next 2 years at least

Another thing that I might be able to do as it seems I have the roof space to do so is place these in line with each other perhaps fairly close to the start of the roofline I'm not really sure why they didn't do that before

I do know there's a crank up antenna that is kind of in the way but it doesn't seem to work so I've been considering removing it anyway we don't usually watch local television so I could easily remove it and seal that back up making room to put all three of them in line