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Old 09-16-2021, 05:12 PM   #21
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Originally Posted by IC08 View Post
I am just lost then, from what I hear you take total wattage of panels divided by battery bank voltage to find amperage and therefore mppt size. I hate to be so helpless as I know everyone will just say do more research but the more I look the more it seems to be different for everybody. Can anyone recommend a good place to find the math and all that for sizing? The best I've found is
https://www.mobile-solarpower.com but he focuses more on "buy this and then that" and isn't very specific on the actual science of it all (unless you buy his book I guess)

And thanks for that about the charge controller, another question answered!

Youíre right about the amperage size. The charge controllers are weirdly specíd out. In victron the 150/70 is 150v max input voltage and 70a max charge output.

If youíre running parallel panels the big question you have to ask is the max wire size that the mppt will accept and if thatís kinda small then you should keep that wire length really short or consider running two panels in series and have 4 parallel circuits of 2 panels in series instead of 8 in order to make it all work. Itíll double your input voltage and half your wire size essentially.

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Old 09-16-2021, 05:20 PM   #22
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Originally Posted by IC08 View Post
I am just lost then, from what I hear you take total wattage of panels divided by battery bank voltage to find amperage and therefore mppt size. I hate to be so helpless as I know everyone will just say do more research but the more I look the more it seems to be different for everybody. Can anyone recommend a good place to find the math and all that for sizing? The best I've found is
https://www.mobile-solarpower.com but he focuses more on "buy this and then that" and isn't very specific on the actual science of it all (unless you buy his book I guess)

And thanks for that about the charge controller, another question answered!
Let me clarify. The charge controller has two sides with power. The incoming side is the side with the solar panels. The outgoing (system) side has the batteries. My point was that the battery size has nothing to do with the voltage&current (Wattage) of the solar panel side of the controller. You can have 2000W of solar connected, through a charge controller, to a 12V battery bank or a 56V battery bank. I hope that makes sense.

Now, the charge controller will be built to charge at a particular voltage (based on your battery bank/system voltage) and to carry a certain amount of current. The Watts on both sides are the same, minus some loss. True, on the battery side if you increase the voltage you decrease the current. That will help with specifying a charge controller, built to handle the right specs. But that side of the system doesn't impact the solar panel side of the system. Perhaps I misunderstood your statement? I probably did, so I wanted to clarify my thoughts on that here. Apologies if I muddied the waters!
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Old 09-16-2021, 09:18 PM   #23
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Remember that we're usually only talking about the system from the PV panels to the battery bank with 12VDC the generally used voltage for DC lines.
Sorry to be so dense, your post is very helpful and I do know a little of the basics of ohm's law and stuff -the things I learned in shop class at least.

My question is more about the inverter/charger: Does it factor in to the size of the solar array at all? I thought they were separate as in on opposite sides of the battery bank, but the one I posted above seems to say different.
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Old 09-16-2021, 11:07 PM   #24
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I'm not an expert in solar systems by any means but I do have a good background for sorting them out.
You can have a system where the PV goes into the solar charge controller and then to the batteries with the inverter fed from the batteries.
You can also have a system where the charge controller(s) go into the inverter/charger/transfer switch (or any combination of those) and that device sorts out what goes where.
I'm sure there are other configurations as well.
We have decided on a Victron Inverter/charger/transfer switch as it can supplement an insufficient shore (or other) power input by pulling from the batteries to make up the shortfall. It's expensive but it has features we like.
As far as sizing, the inverter/charger the inverter needs to be able to supply the wattage that you expect in normal operations as well as provide for surge needs (such as A/C startup). The charger side needs to be capable of putting all of the PV output into the batteries (the capacity of the charger in amps) without over charging them.
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Old 09-17-2021, 01:23 AM   #25
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Originally Posted by IC08 View Post
Sorry to be so dense, your post is very helpful and I do know a little of the basics of ohm's law and stuff -the things I learned in shop class at least.

My question is more about the inverter/charger: Does it factor in to the size of the solar array at all? I thought they were separate as in on opposite sides of the battery bank, but the one I posted above seems to say different.

This unit is strange, I think they call it an Ďall in oneí but it contains the mppt charge controller in the inverter charger unit. Most do not, so the mppt controller rating has nothing to do with the inverter most of the time. With this if you exceed the charge controller rating youíre kinda done i think where in typical systems you can just add more charge controllers if you needed them. May be able to add an external charge controller to this too but Iím not really sure.
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Old 09-17-2021, 01:49 AM   #26
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May be able to add an external charge controller to this too but Iím not really sure.
If I could answer this I would be one and done right now. If I could just throw another mppt on top of this then I'd save thousands. I just can't afford the victron stuff and everything else has terrible reviews about faulty equipment getting shipped out and no return

At least I can say that after a few days straight reading and talking with all of you lovely people I almost understand what I'm doing!
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Old 09-17-2021, 01:58 AM   #27
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I have eight 60-cell 255W panels in two separate tiltable arrays; each array of four panels is wired in parallel to produce (theoretically) about 34A at about 30V. I run each array's power through its 50A circuit breaker to its Morningstar TS-MPPT-60 charge controller that converts the PV power to about twice the current and half the voltage, then sends it through a 80A CB to that array's battery bank of four GC2 batteries in series and parallel. In effect I have two entirely separate systems running in parallel (redundancy is always good!), and each battery bank feeds though its 250A Schottky diode to the common DC load center that in turn powers all DC house loads and the Magnum MS2000 inverter/charger and the two eventual smaller PSW inverters for the freezer and fridge. Contrary to what some nay-sayers here have opined about two separate PV systems in parallel, my setup is working just fine!

MPPT charge controllers work most efficiently when their voltage step-down is as small as possible. My Morningstar CCs are running in the high-90s percent efficiency, meaning less heat and a longer service life. Another consideration is cooling: fan-cooled CCs can introduce dust and dirt into the inside of the CC when they operate in typical western-USA boondocking environments, so a fanless CC can be preferable in a bus conversion or RV. Besides, what's the first thing likely to fail in a fan-cooled CC?

Good luck, John
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Old 09-17-2021, 11:49 AM   #28
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I cannot fathom how anyone would think Victron SmartSolar "expensive".

Save up a while then.

Cheap crap is not good value.

Buy once cry once.
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Old 09-17-2021, 11:52 AM   #29
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Do not buy combined units

Inverter separate, maybe a collection of different quality & sizes for specific load devices. Best to avoid AMAP buy DC powered ones.

MPPT SC separate from DCDC and ACDC chargers if needed.

No need to use one SC for all your panels either.
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Old 09-17-2021, 12:44 PM   #30
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I cannot fathom how anyone would think Victron SmartSolar "expensive".

Save up a while then.

Cheap crap is not good value.

Buy once cry once.
Its not the smart solar I'm worried about, even though there is the MPPT recommended by Wil Prowse thats $200 less (for two) and looks pretty good

my main issue is the multiplus inverter, its like the cadillac and I'm more of a toyota guy -comes out to about double of the other ones but 24v inverters are pretty limited and come with bad customer service stories on amazon

While the "all in one" deal seems a little sketchy, I think I've found one that looks high grade and is perfectly sized to my system. If I get at least a year out of it then "saving up" will be much easier and I can go full on victron later. But I acknowledge fully I have no idea what I'm talking about and won't know until after taking the plunge


https://www.amazon.com/gp/product/B0...9ORKNPBO&psc=1
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Old 09-17-2021, 02:11 PM   #31
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Do not buy combined units

Inverter separate, maybe a collection of different quality & sizes for specific load devices. Best to avoid AMAP buy DC powered ones.

MPPT SC separate from DCDC and ACDC chargers if needed.

No need to use one SC for all your panels either.
Exactly this ^^^^^

Every system I design, or assist with, avoids combination units. When they work, they're great. But consider the long-term reliability and what would happen if one function failed. And having separate inverters also minimizes idle energy consumption...have a small one that you can run often or all the time, to power AC things you need all the time, and have a larger one that you can turn on/off as needed for your induction cooktop and microwave and such.
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Old 09-17-2021, 02:16 PM   #32
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Yep, and for even better off grid efficiency, try to avoid appliances that are designed for AC shore power.
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Old 09-17-2021, 04:36 PM   #33
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Actually the Victron **charger** inverter units are fantastic

combine grid power and energy from your bank as needed.

But those are thou$and$ intended for yachts, not something RVs need.

And nothing to do with the solar controllers.

Again, buy good value standalone MPPT SCs.

If you insist on that Amazon crap, great you are being a pioneer, collect the arrows in your back

and report back how you go as a service to the community.
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Old 09-17-2021, 05:07 PM   #34
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Actually the Victron **charger** inverter units are fantastic

combine grid power and energy from your bank as needed.

But those are thou$and$ intended for yachts, not something RVs need.

And nothing to do with the solar controllers.

Again, buy good value standalone MPPT SCs.

If you insist on that Amazon crap, great you are being a pioneer, collect the arrows in your back

and report back how you go as a service to the community.
Any inverter/chargers you would recommend besides the multiplus?
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Old 09-18-2021, 12:54 AM   #35
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Magnum and Mastervolt.

Neither are any cheaper.
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Old 09-18-2021, 07:40 AM   #36
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We're happy with our Xantrex Freedom XC 2000W inverter/charger. Looks like it's a couple hundred bucks cheaper now that when we bought it 18 months ago. We had an AIMS that the social media influencers were pushing at the start of our build, but that crapped out less than 2 years in and we got absolutely no tech support from AIMS. Xantrex has held up so far, knock wood, but I suppose that's subject to change.
I'm a little more careful about the influencer recommendations after the AIMS debacle and for some reason I steer well clear of Will Prowse.
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Old 09-18-2021, 09:52 AM   #37
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We're happy with our Xantrex Freedom XC 2000W inverter/charger. Looks like it's a couple hundred bucks cheaper now that when we bought it 18 months ago. We had an AIMS that the social media influencers were pushing at the start of our build, but that crapped out less than 2 years in and we got absolutely no tech support from AIMS. Xantrex has held up so far, knock wood, but I suppose that's subject to change.
I'm a little more careful about the influencer recommendations after the AIMS debacle and for some reason I steer well clear of Will Prowse.

Iím pretty sure will prowse tore apart an aims and said it was junk, couldíve been someone else on YouTube.

I had three Amazon inverters and sent them all back because they were junk.

The bottom line to me: some of the Chinese inverters do weird things like make 55v on the hot and 55v on the neutral which is a little scary and unorthodox and not for me at all and should be tossed in the trash. Others are just overrated literally. A 3000w inverter is probably able to put out 3000w once but if you do that often itís gonna crap out on you. Itís probably Ďequivalentí to a 1500w name brand inverter, but they run them really hard and theyíll fail eventually.

I ended up starting with a xantrex 3000w modified sine inverter that sat in a garage for 10 years and still works just fine until I got my Victron. Iíd look at name brand inverters used before Iíd look at the Chinese clones, and if I had no choice Iíd look at the 5000-8000w model chinese thing and treat it like a 2000-3000w model in hopes of longevity.
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Old 09-18-2021, 10:04 AM   #38
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I think I've read some complaints here about Xantrex support, but I've personally had good experiences with them and their products. I've installed Xantrex inverters in remote villages and have removed (and then reused) Xantrex inverters from ambulances, both cases where reliable power is important. Given the option to buy a used Xantrex or a new no-name, I'd go for the used Xantrex and still expect it to last longer.
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Old 09-18-2021, 10:42 AM   #39
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I think I've read some complaints here about Xantrex support, but I've personally had good experiences with them and their products. I've installed Xantrex inverters in remote villages and have removed (and then reused) Xantrex inverters from ambulances, both cases where reliable power is important. Given the option to buy a used Xantrex or a new no-name, I'd go for the used Xantrex and still expect it to last longer.

Xantrex was bought by Schneider I think, not sure if that made it better or worse, but customer service aside Iíve heard nothing bad about their old products at least. Less about the new stuff under the new ownership.
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Old 09-18-2021, 01:06 PM   #40
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I steer well clear of Will Prowse.
+1000

He's OK for noob orientation like Battery University,

but def no expert and yes a sponsored shill as with nearly all youtubers and SM influencers

not a good primary source for detailed info.
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