Choosing a Charge Controller for 2800W

GothamTransAuthority · 03-03-2021, 12:21 AM

Hey Everyone, I'm pretty new here but I have my 2004 Gillig Phantom pretty much gutted at this point and I'm in the planning stages. Looking at designing my solar system at this point and wanted to bounce my foundation off you guys for suggestions and advice. Although not 100% solidified yet, I'm looking to mount seven 400W Trina TSM-400-DE15H(II) panels on my roof wired in parallel to charge a 24V LiFePo4 battery bank. The panel specs are as follows:

Voc = 50.4
Isc = 10.18
Vmpp = 41.1
Impp = 9.74
V temp coeff = -0.29
I temp coeff = 0.05

I was looking to possibly run one of the Victron 150/100 MPPT controllers for this array but I know it's pushing it. Of course I'd like to keep things as simple as possible and one charge controller seems to be more simple/less expensive than two (less wasted power as well?). Would this fit the bill? What are my downsides/issues? Alternatives?

In addition, any recommendations for an inverter/charger for the 24V LiFePo4 battery bank? I'm looking for 240Vac output and around 6000W continuous capability.

john61ct · 03-03-2021, 12:33 AM

Going in series will lose some MPPT efficiency, and more importantly make output **very** vulnerable to partial shading.

Nice thing about Victron is, going to one SC per panel is usually not much more expensive.

75/15 is a tad too small if you usually will be in ideal insolation conditions.

I believe 100/20 is the next step up?

john61ct · 03-03-2021, 12:36 AM

Whoops missed that 24V.

75/15 will handle 400W with room to spare

GothamTransAuthority · 03-03-2021, 12:49 AM

Quote:

Originally Posted by john61ct

Whoops missed that 24V.

75/15 will handle 400W with room to spare

I didn't really think of that. You're suggesting running seven 75/15 charge controllers rather than wiring the panels in parallel to one 150/100? You're right, it does look to be about the same cost. What is the advantage to running one per panel aside from not pushing the controller to it's design limits? Disadvantages (self consumption)? One advantage I see is a failure would only account for about 15% of the production.

I'm also not stuck on Victron. Honestly, the only reason I brought them up was they seemed to be the only manufacturer of a single charge controller that "might" handle the size of my array on it's own.

john61ct · 03-03-2021, 01:00 AM

Sure excellent redundacy!

Each panel getting its own MPPT calculation is ideal.

But most of all is least possible impact of partial shading, which in most use cases is very frequent.

Design your rack to never cast shade, and keep the panels free of dust and leaves anyway!

Forget self-consumption, those Dutch engineers are clever fellas.

There are big controllers out there, but old school sticker shock, and not as efficient.

john61ct · 03-03-2021, 01:03 AM

Use your savings to tie them together with Victron's add-ons, checking your daily stats from your phone is addictive

quickly see (decently accurate!) SoC of the bank

as well as any production issues

can even store your data long-term in the cloud

GothamTransAuthority · 03-03-2021, 01:08 AM

Quote:

Originally Posted by john61ct

Sure excellent redundacy!

Each panel getting its own MPPT calculation is ideal.

But most of all is least possible impact of partial shading, which in most use cases is very frequent.

Design your rack to never cast shade, and keep the panels free of dust and leaves anyway!

Forget self-consumption, those Dutch engineers are clever fellas.

There are big controllers out there, but old school sticker shock, and not as efficient.

Great info, thank you! I have quite an array on my house so I'm a bit familiar, but I had no part in designing/installing the system. I do notice the difference after I clean the panels, like you mentioned.

Do you have any inverter/charger recommendations? I was looking at this --> https://www.amazon.com/PICOGLF60W24V...4751018&sr=8-4

rossvtaylor · 03-03-2021, 07:45 AM

John's suggestions are sound...so I'll comment on your bus. Nice! Welcome to the Phantom club. There are a few of us here. With their great build quality, high ceiling, and relatively flat roof they make a great platform for a conversion...with lots of solar panel real estate.

joeblack5 · 03-03-2021, 12:38 PM

Hi Gotham,
I use 4 MPPT charge controllers for redundacy.

Lately I noticed that ElectroDacus uses a pretty smart set up with out MPPT controllers by matching the solar panels to the battery voltage.
So for 24 Volt battery you would use panels that have VMP of about 30 Volt.
You can read his arguments and see if it is interesting to you.
If you go Lithium you would want a BMS and having no charge controllers makes it easier and less expensive.
I had one MPPT failure in the last 3 years, I fixed it happy that I had the redundancy but having no CC is cleaner.

I can rewire my panels so I might do it myself as well.

Good luck
Johan

GothamTransAuthority · 03-03-2021, 03:47 PM

Quote:

Originally Posted by john61ct

Use your savings to tie them together with Victron's add-ons, checking your daily stats from your phone is addictive

quickly see (decently accurate!) SoC of the bank

as well as any production issues

can even store your data long-term in the cloud

I do really like that capability, especially since it'll help you manage power better! I'm a nerd with stuff like that but have some concerns with battery bank usage. I'm sure bluetooth communication is a minimal draw but a draw nonetheless...especially if it's constantly "looking."

GothamTransAuthority · 03-03-2021, 03:50 PM

Quote:

Originally Posted by rossvtaylor

John's suggestions are sound...so I'll comment on your bus. Nice! Welcome to the Phantom club. There are a few of us here. With their great build quality, high ceiling, and relatively flat roof they make a great platform for a conversion...with lots of solar panel real estate.

Thank you!

I've definitely noticed the build quality in the demo work. None of that stuff wanted to come out easy! I'm trying to maintain a rear rooftop deck area, which is definitely cutting my solar real estate, but it's not something I wanted to give up in my design.

GothamTransAuthority · 03-03-2021, 04:03 PM

Quote:

Originally Posted by joeblack5

Hi Gotham,
I use 4 MPPT charge controllers for redundacy.

Lately I noticed that ElectroDacus uses a pretty smart set up with out MPPT controllers by matching the solar panels to the battery voltage.
So for 24 Volt battery you would use panels that have VMP of about 30 Volt.
You can read his arguments and see if it is interesting to you.
If you go Lithium you would want a BMS and having no charge controllers makes it easier and less expensive.
I had one MPPT failure in the last 3 years, I fixed it happy that I had the redundancy but having no CC is cleaner.

I can rewire my panels so I might do it myself as well.

Good luck
Johan

Hey Joe,

I agree that it would be ideal if it's possible to pair panel voltage with your battery bank. I wasn't able to locate panels in a size that work for my project that could nail down a low enough voltage. To get my panel voltage down, I seem to end up with about 400w less of output for my available real estate.

I guess 1 failure in 3 years isn't bad. With 7 of them, I'd only be down about 15% and it'd only cost $110 to get back up and running.

john61ct · 03-04-2021, 02:32 AM

There is absolutely no reason to "pair voltage" that way

unless you are counting pennies and wanting to keep using WM SCs.

With MPPT SCs like Victron, so long as you avoid getting up to the max voltage sec'd

you actually get better improved output efficiency by going to modern 40+ Voc panels

whether your DC system is 12V or 24V

john61ct · 03-04-2021, 02:34 AM

Quote:

Originally Posted by GothamTransAuthority

I'm sure bluetooth communication is a minimal draw but a draw nonetheless...especially if it's constantly "looking."

Really not an issue.

Avoiding using inverters would be 2500x better energy savngs

joeblack5 · 03-04-2021, 07:04 AM

Absolutely Gotham , it was not clear if you bought your panels already, or that you were thinking about it. With such a mismatch the losses would be large.

Just wanted to bring the concept under your attention. I used to be a firm believer in MPPT as well but Electrodacus brings up a very good argument with good calculations as well.

Even with my current 4 pieces 24V 20 Amp Mppt that I have right now at $70 / each that still adds up to $280 , I blew one up , that resulted in a week loss of of 1/4 of the power and another $70 ,, that is no pennies ,,
Lower voltage panels are smaller and so more in parallel are needed and that gives less shading issues.

Either way having a simpler system is more robust , potential more efficient then MPPT or as least as efficient and at a lower cost. As long as yo
Just shows there are more routes to Rome.

John61CT , maybe you can check them out and give your expert opinion and counter calculation of what this guy from electrodacus proposes / makes.

I would be curious about where you think he goes wrong.

Good luck
Johan

GothamTransAuthority · 03-04-2021, 02:12 PM

Quote:

Originally Posted by john61ct

Really not an issue.

Avoiding using inverters would be 2500x better energy savngs

Good to know, thank you!

I'd love to not use an inverter but I'm trying to retain a few "features" in which there aren't viable DC options I'd be happy with.

GothamTransAuthority · 03-04-2021, 02:52 PM

Quote:

Originally Posted by joeblack5

Absolutely Gotham , it was not clear if you bought your panels already, or that you were thinking about it. With such a mismatch the losses would be large.

Just wanted to bring the concept under your attention. I used to be a firm believer in MPPT as well but Electrodacus brings up a very good argument with good calculations as well.

Even with my current 4 pieces 24V 20 Amp Mppt that I have right now at $70 / each that still adds up to $280 , I blew one up , that resulted in a week loss of of 1/4 of the power and another $70 ,, that is no pennies ,,
Lower voltage panels are smaller and so more in parallel are needed and that gives less shading issues.

Either way having a simpler system is more robust , potential more efficient then MPPT or as least as efficient and at a lower cost. As long as yo
Just shows there are more routes to Rome.

John61CT , maybe you can check them out and give your expert opinion and counter calculation of what this guy from electrodacus proposes / makes.

I would be curious about where you think he goes wrong.

Good luck
Johan

Very interesting. I did some reading, although some of it seems "above my pay grade" at this time

I don't think the decrease in wattage of my array to go with a system not requiring MMPT controllers would outweigh the decrease in system loss, but I'm definitely no expert!

I like the idea of heat recovery I read about!

john61ct · 03-04-2021, 05:15 PM

Quote:

Originally Posted by GothamTransAuthority

Good to know, thank you!

I'd love to not use an inverter but I'm trying to retain a few "features" in which there aren't viable DC options I'd be happy with.

Rather than one huge wasteful inverter

Buy small ones, per circuit or even per device

at the right size (watts) and quality (MSW vs PSW) needed

both much cheaper and much more efficient

turn off each except when needed.

Doktari · 03-05-2021, 03:56 PM

Yes,what about Electrodacus? Seven of the control relays at $37 each is only $259. And no need to buy a battery monitor. Is there something I’m missing? Twelve volt panels need to be used with a 12 volt system and 24 volt panels with a 24 volt system. Does anyone know if two 12 volt panels can be used in series with a 24 volt system using a Electrodacus? (I ask because I have four 12 volt panels and a 24 volt inverter).
Otherwise, I’ve owned a Victron inverter and have no complaints. The Samlex inverters have good specs too. Idle power is a concern. A lot of off grid solar energy stems have a large inverter and a small inverter.

GothamTransAuthority · 03-05-2021, 03:57 PM

Quote:

Originally Posted by john61ct

Rather than one huge wasteful inverter

Buy small ones, per circuit or even per device

at the right size (watts) and quality (MSW vs PSW) needed

both much cheaper and much more efficient

turn off each except when needed.

Thank you John! You're clearly demonstrating I should be looking at this differently than a stationary, stick built home. I was going to run one inverter to a traditional load center, but you have opened my eyes and it makes more sense!

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