Seeking Advice from the Pros

[Colton]

Hi guys,

My name is Colton and I just created this account. I'm a total noob when it comes to setting up my own solar/battery storage system but I'm eager to learn and have been reading/watching videos like crazy over the last little bit to try to get up to speed.

I have an enclosed cargo trailer that I want to pull solar on for charging batteries on the inside. From those batteries I want a couple of 120v outlets to run power tools and a 240v outlet to charge my car. (however slow it might be)

Overall it should be a pretty simple system, but since I'm new to this and don't want to blow myself up I figured I'd seek counsel from the pros. I started with Prowse's article and have read a lot of threads here which is why I decided to register. Overall this seems like a very friendly/helpful community.

I'm not looking for anyone to do all the work. I'll list what I have here and if by chance it looks okay, just let me know!

If I totally screwed something up please let me know that as well so that I can remedy it. Thanks in advance!

Solar Panels - I have 18 of these no-name panels. I'm very confident that they won't produce the advertised 250w each haha. Even if they only produce 50w a panel that gets me 900w during peak sunlight hours. My plan is to wire these panels in 3 series of 6, for around 96v 45a total to the charge controller.

Charge Controller

Batteries - My plan is to wire 2 of these in series for 48v

Battery Protect, Fuse and Battery Meter - These I got from William's article

Inverter - From what I can tell, this should be able to pull 48v at 60a from the modules and then I can use up to 3000w at a time either from the 120v or 240v outlets

I searched forever for the right BMS but it appears that the charge controller and inverter both have built in safeties for over discharge, over heat, etc. Combining them with the battery protect, is that enough?? Or do I need an official "BMS"?

Again, I'm very new to this so there's a chance I've bought all the wrong stuff and screwed this up. Trying my best lol

Really appreciate any input!

 

[MisterSandals]

Is there any reason in particular you chose those panels? Flexible panels are hard to mount and don't have the best longevity reputation.

• Optimum Operating Voltage (Vmp): 16V
• Open-Circuit voltage (Voc):19.2V-36V

?? I have never seen Voc expressed as a range. Have to use 36V for max voltage handling.

panels in 3 series of 6, for around 96v 45a total

6 in parallel? And 3 of those in series? For 6P3S? Very unusual - any reason for this?
108Voc
Where are you getting 45A number? 45A / 6 = 7.5A per panel Isc?
This is not adding up to 250W

45A exceeds most solar connector ratings and the 10AWG wires so you'd need to rewire all the panels. The themselves might not survive the 45A and would all need to be fused.

The array does not look workable as specified.

new to this and don't want to blow myself up

If this is a primary concern i wouldn't choose a value priced SCC for the heart and brains of the system. Not the place to save money.

 

[Colton]

Thank you for your reply!

I spent a lot of time agonizing over the right panels to buy. I know these ones are "cheap" but I figured I could get what I can out of them and be happy with it and if for some reason it performed WAY under expectations I could return them and buy a name brand.

I've read that flexible panels have some disadvantages but I'm near my weight capacity for my trailer so I don't really want to add another 150lbs in panels on top.

Again I don't believe the panels will produce 250w, probably not even half that. Based on the 16V vmp divided from the supposed 250w max that's 15.625amps, right? So 6 panels in series would be 96v @ 15amps correct? And if I had 3 of those series (18 panels) that would be 45amps to the charge controller @ 96v. Again, this would all be MAX but I expect it to produce a lot lower amperage. The charge controller can adapt to that though, correct?

I appreciate any input on how to rearrange my array. If these panels aren't even worth testing I guess I can return them and go back to square 1 trying to find some that fit this application.

Thanks for your help!!!

 

[HRTKD]

6s3p is what I think you're asking about. Six panels in series per string, three strings. Yes, that would give you 45 amps and 96 volts, in an optimal situation. You'll need fuses between each string.

They don't specify the actual Isc number, so I don't know that 15 amps is what you'll actually see.

 

[Hedges]

36Voc x 3 = 108Voc
We normally get spec for Voc at STC (Standard Test Conditions) and a temperature coefficient. Need to adjust for maximum voltage in coldest temperature, make sure that doesn't exceed what your hardware can handle.

240V to charge car - many EV accept either 120V and draw 15A or 240V and draw 25A. If your inverter can't handle the higher draw at 240V, then charging at 120V would be better.

Inverter
"【High Efficiency and Plenty of Power 】Up to 91.6% efficiency ,with maximum 12.5A current output in the 240V circuit, perfectly adapted to high-power 240VAC appliances.Supports a maximum 12.5A hardwire terminal and dual 120V 12.5Amp output circuits : AC1 and AC2，can support the 1500W output at the same time"

Note that says 12.5A at 240V or 12.5A at 120V. Only 1500W at 120V, not 3000W. Not 15A, so need to know what your EV charger will draw.

If you can get by with 120V only, you can select a 3000W 120V inverter.

If you can return those panels, you can get others that actually deliver the wattage. Expect about 200 watts per square meter from newer model panels. Check new and used at SanTan solar to get an idea, typically as low as $0.12/W for deteriorated old panels up to $1/W. If you did pay 9 x $170 for those kits, you can afford freight shipping of a pallet. Also other sources locally (check eBay and Craigslist). Smaller panels can be shipped UPS, sometimes worth the higher price per watt.

 

[Colton]

Yeah HRTKD that's what I was trying to say haha 6s3p
Good advice on the fuses between panels I didn't know about that


Hedges thanks for your input. I'd like to be able to level 2 charge my car but maybe this isn't the right inverter? I know when I plug my car into a 120v outlet it charges WAY too slow. I'm pretty sure the Model X can charge at the amperage I select, even less than 12A. Also for an overnight charge if it were charging at 3000w that would drain my total 10kw of storage in just a few hours right?

You're saying only 1500w for my 120v side though huh? That might be too little...Unless that's for both "sides" of my 120v plugs?? Excuse my ignorance.

I looked at SanTan and almost bought some used Tesla panels from them but I'm kind of in a hurry and didn't know how long the freight would take. Also, as stated before, I don't really want to add the extra weight.

More than happy to return these panels though if that's best. Amazon has plenty of name brand flex panels that I could try.

I noticed my fuse isn't rated for 48v so I need to return that anyway.

Is my charge controller okay? It seemed really inexpensive but I thought the specs were sufficient. Also, in terms of "BMS" should I be doing something other than that Victron battery protect?

Thanks guys! ?

 

[HRTKD]

with maximum 12.5A current output in the 240V circuit,

My level 2 charging of my Nissan Leaf SV+ pulls around 32 amps on the 220 amp circuit. If you use a programmable EVSE then it may be possible.

You're not going to get level 2 charging out of that inverter. I do level 1 charging of my EV on my Victron Multiplus 12/3000 and it's pulling a lot of juice out my 560 Ah battery bank and the 640 watt PV.

 

[Hedges]

6s3p, now you have twice as high PV voltage. Charge controller must accept that.

Many brands to choose from. Midnight has good chargers (various PV voltages to choose from) and their new "Rosie" inverter. Others too. Decide what loads you're going to power. If you have "Tesla" money to play with, you can afford tier one equipment and big enough for level 2 charge plus power other things.

Most people consider powering their house from their EV not charging EV from house battery. Well, they may start out thinking that way, but takes a big battery. Preferable approach is to charge EV while sun is on PV panels, but that means being home during the day. Or charging from the grid. Or buying two Teslas, alternate which one you drive.

"BMS" isn't battery overall voltage protect. It is per cell of lithium battery. You either do a DIY build or buy an assembled battery with BMS.

Oh, Tesla battery. Sure, two of those could charge from PV and then charge your car level 2 whenever you want. This is DIY, and you do need BMS. Either from Tesla or aftermarket. 25.2V max per unit may be a bit non-standard. You need the right BMS and configuration. You won't have the cooling system that Tesla uses as part of thermal runaway protection. Probably best to locate outside any buildings you're attached to, and be careful about charge and discharge protection. I think some companies offer after-market BMS, don't know how good.

 

[Colton]

The batteries have the OEM BMS board on them but I have no idea what I need to do to make it work. Ideally I could find something plug and play with a digital interface haha

As far as charging the car level 2, I really just want to filter extra power in the batteries at the end of the day into the car. At max it would equate to 10kwh so if this inverter can charge at 3000W that's more than good enough.

One of the things that has overwhelmed me about all this is that there are 1000s of options for each piece of the system and everybody has an opinion as to what works and what is crap. Took me forever to finally just place an order for parts and I guess I'm just hoping that my general parameters are being met and that the system can work.

One of the joys of DIY ?‍

As always, I really appreciate you guys helping me learn so that I can get this right

 

[Colton]

You guys have indicated that it's best to return my panels and get something else.

Maybe these ones?? Seems like a reputable brand and I could get 6 of them on my trailer for a 1200W system. Looking at Ecoworthy and Renogy flex panels as well..

 

[MisterSandals]

Maybe these ones?? Seems like a reputable brand and I could get 6 of them on my trailer for a 1200W system. Looking at Ecoworthy and Renogy flex panels as well..

Where are you located? Panels can often be found locally for less than $.50 per watt.
What are your size limitations? Will you have to Tetris them on the roof around fixtures?

This is the first in the search near me:

Solar Panel 327 Watt Sunpower Mono Solar Panels - electronics - by...

Solar power with power optimizers!! $149 Solar Panel by itself $125 I have 20 left serious inquires make offer. Pickup union city. 972-774-865nine

sfbay.craigslist.org

 

[HRTKD]

At this point in the technology cycle, I wouldn't put flex panels on anything that I could put rigid panels on.

I would consider flex panels for a ground deployed system. One that I lay out at my destination and pull back up before I leave. I currently use 320 watt rigid panels for my ground deployed system and it sucks moving those panels in/out of the RV.

Look around on Craig's List for someone selling used panels. I have a local source that I bought four 250 watt panels from and they work well. Shipping panels is risky. There are many posts here on the forum of panels that arrived broken.

There are also local sources for new panels, you have to look a little harder. Check out https://www.greentechrenewables.com. They have branches throughout the U.S. but you have to CALL the local office, not the national number. They usually deal with commercial installers, so you have to know what you want and not take up too much of their time. My four panels came from them in 2020 and my local office did a great job.

 

[Ampster]

Or do I need an official "BMS"?

It is always highly recommended that you use a BMS. Since you are using batteries that are the more volatile NCR chemistry you should definitely use a BMS. Also when picking an inverter be sure you check the voltage settings because the Tesla Modules have a different voltage range than most 24 or 48 volt batteries. Some inverters may not have a low voltage discharge limit which is low enough for those Modules.

The batteries have the OEM BMS board on them but I have no idea what I need to do to make it work

I think it is just the connector and that vendor may sell an interface connector that would simplify connecting to the BMS which you select. Be sure and select one that can handle twelve cells in series since each of those Modules contain a number of parallel cells in groups of six in series.

 

[HRTKD]

Batteries - My plan is to wire 2 of these in series for 48v

If you need a 48 volt battery, then build a 48 volt battery. Putting LiFePO4 batteries in series has issues that you can avoid by making one battery. Or, you could put those two 24 volt batteries in parallel.

 

[Colton]

MisterSandals I’m currently in the Reno area to assemble the trailer. Will be deploying in in the Tracy CA area. 6x12 roof area with a little wiggle room on either end..no fixtures.

HRTKD I’ll look locally for rigid but I need to find some lightweight ones..

Ampster I want a BMS and any sort of safety system possible to not burn my trailer down lol. Just a matter of finding a solution I’m smart enough to deploy which really narrows it down..

 

[Colton]

HRTKD I already own the two Tesla modules, no return on those…I read that running them in parallel is a lot more complex than in series, hence my call for 48v…

 

[HRTKD]

HRTKD I already own the two Tesla modules, no return on those…I read that running them in parallel is a lot more complex than in series, hence my call for 48v…

I'm not familiar with Tesla modules. I would be interested in reading why parallel is an issue. Can you post a link to that source?

 

[400bird]

You guys have indicated that it's best to return my panels and get something else.

Maybe these ones?? Seems like a reputable brand and I could get 6 of them on my trailer for a 1200W system. Looking at Ecoworthy and Renogy flex panels as well..

That link takes me to panels that are $1/watt
There are much better deals on better brands. Where are you located? You could pick up panels from AltE, CED greentec, many other places. Or buy used and save even more!

HRTKD I already own the two Tesla modules, no return on those…I read that running them in parallel is a lot more complex than in series, hence my call for 48v…

Run them in series is fine, but you NEED to run a BMS.

 

[Colton]

I’m in the Reno, NV area. Any recommendations on an easy-to-implement BMS for these modules??

Thank you all!!

 

[400bird]

I’m currently in the Reno area to assemble the trailer. Will be deploying in in the Tracy CA area.

Are you looking to purchase in Reno or California?