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Discussion Starter #1
Question about DC/DC Mppt . I have 2 138ah 12v Lithium Valence Batteries for my storage. I have the opportunity to purchase some 60cell 305 watt Monocrystalline Solar panels new for very cheap ($110) . With that being said I would not be matching 12v panel with a 12v battery. My question is, could I run this efficiently and safely thru a proper DC/DC Mppt controller, and would it work? I am trying to avoid running 3 smaller panels in lieu of a larger panel on top of my Van.
2 options for me in this configuation a 305w and 310w panel.

So this is not a true 24v panel ( 72 Cell ) and would be more like an 18V panel ( 60 cell ). Would the MPPT controller adjust to the difference?
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As long as you size the solar controller to be big enough, you will be fine. 2 panels in series would be about 80V (subject to thermal changes), so the victron 75/15 would be too small. Their 100/30 would be fine.
 

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Many ways to skin that cat . . .

To be clear you are talking about one panel, either a 310w or a 305w, correct?

According to the specs on the sticker you posted, something like this should work:


Battery input voltage range: 8-32V
Max. PV open circuit voltage: 92V
Max. PV input power:390W(12V Battery)

Basically, it will take anything from the solar panel at up to 92 volts, and stuff that into your 12v battery. This SKU also includes a little remote meter.

I'm using four of the smaller EpEver MPPT controllers (one per each of my 4 panels) and they seem to work fine.
 

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Discussion Starter #5
Thanks Guys
Baxsie - To clarify, I would probably just be running one of the 310 watt panels. I will also be be wiring the system to my Alternator to charge while I drive. Will that product above still work if I do this?
 

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These devices take care of alternator and solar charging and can be programmed to a custom charging profile for your lithium batteries. People who have them seem to like them. You could use a separate mppt controller and dc/dc charger, the only potential issue would be if you exceed the maximum recommended charge rate for your batteries, which would be difficult to achieve with two 138ah batteries.

 

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I have heard those called "B2B" for Battery to Battery charger.

The Kisae is new to me -- price looks good.

I have a Sterling BB1260 which is more expensive but has a completely archaic and backward user interface.

There are also Renogy B2B units in 20, 40, and 60 amp versions.

Renogy also has an MPPT solar controller plus B2B charger in a combined unit, but the input voltage range is not large enough for your panel.

Some folks use a relay of some sort to short the vehicle battery to the coach battery. I can't get on board with that approach -- others can and do.
 

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Discussion Starter #8
Thanks guys. I decided to only run one 305W solar panel as I dont think Ill need the second one.
I bought the Kisae DMT-1250 DC to DC Solar/charge controller.
Now looking for a 2000 watt Inverter/Charger ( want to be able to hook up to Shore Power)
 

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Something like this Renogy 2000 sine inverter / charger ($615) might work. Kinda spendy :-(

I've seen quite a few of these "Green" Aims inverter / chargers ($536) in people's builds -- frankly I'm not sure the difference between them and the much more expensive "Blue" Aims inverter / chargers ($795). Reddit says: "The green inverter charger doesn't include some of the bells and whistles such as; dip switches for priority mode, optional battery temperature sensor and auto gen start."

For my build, I used an AmpInv 3000w ($598). It had some issues--polarity on outlets was wrong -- easy enough to fix but . . . .

This "no name" SOYOND 3000w inverter / charger ($359) might be a candidate. Price is better.

I guess it depends on your risk tolerance?

Be aware that these 2000 ~ 3000 watt inverters need a massive cable from the batteries to the inverter. I used a 4/0 (four ought) kit which is not overkill for 3000 watts.

Also, you will need a crimper. I got this hydraulic monster cable crimper ($57) because I am a tool sl*t. You could probably get by with a much cheaper hammer crimper ($18).
 

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Good choice on the Kisae, I have been eying this for a while and will buy it soon as well.

I wonder why Power Distribution Centers with a converter charger plus a separate simple inverter are not more popular, instead of the very pricey inverter chargers, oftentimes $1,200.

I have already a 1000W Renogy inverter ($190) for my modest AC needs and am about to order this Progressive Dynamics Lithium compatible shore power charger/distribution center for under $200. PD4045LIK-PD4045LIK 45 Amp Lithium Ion Inteli-Power Mighty M

Am I missing something in why not more people go this route?
 
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As folks write up their more expensive and often unnecessary control systems a trend develops and others feel they need to follow. If someone has a system they like then others take that endorsement as necessary equipment not as an expensive alternative. My $500 solar and $700 complete electrical system listed in my signature shows what a good basic system can look like. It uses a converter and inverter and can be upgraded if you need more power. Internet influencers are always bragging up expensive stuff to make their click money too.
 
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This "no name" SOYOND 3000w inverter / charger ($359) might be a candidate. Price is better.
The cheaper your inverter is the more likely it's going to catch on fire or something. If that thing could actually output 3000w that's drawing ~285 amps! Not where you want to cut corners.

Please don't buy something like this unless you are going to test it rigorously before installing it, it's $200 cheaper than the cheap options, for pete's sake.

The main way to control costs on your electrical system is by adjusting the capacity of it. Not that you need to buy the most expensive things, just be real.
 

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@MaggieMarty

IMO you are going in the right direction with a power center. In my case, I self researched & purchased a Victron 12/3000/120 multi charger/inverter & then after a few conversations with a very experienced electrician buddy of mine he convinced me to leave it out & go with a “Power Center”. I constantly think about decisions I make & I have pondered this choice many times & come to the same conclusion - It was the right choice to go with a power center for me. The Victron sits in my house, never been installed, & I will probably incorporate it into my “off grid cabin”.


@RDinNHandAZ

Well written & what I believe also.

RV building was new to me (even though building & science has been my life & career). I am so far removed, from novice DIYers that have never built anything or have no construction or building science, that I question my ability to place myself in their shoes. Even so, the learning curve of RV building was very steep for me (or so it felt).

It is my perspective, ever since I was a kid, it has been a societal trend for people to equate money spent to quality and also to place brand names above less known. Sometimes that is the case & sometimes not.

If novice DIYers have not seen your $700 basic electrical design I would (& have) urge them to at least review it.
 

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The cheaper your inverter is the more likely it's going to catch on fire or something. If that thing could actually output 3000w that's drawing ~285 amps! Not where you want to cut corners.

Please don't buy something like this unless you are going to test it rigorously before installing it, it's $200 cheaper than the cheap options, for pete's sake.

The main way to control costs on your electrical system is by adjusting the capacity of it. Not that you need to buy the most expensive things, just be real.
Thanks for this @ferall 👍

I recently looked into inverters & came to the same conclusion regarding higher power rated inverters. Then I considered the draw from my 250Ahr AGM house bank. I then axed the idea of inverting my van power at this time

A I have a new Victron 12/3000/120 (6000 W peak) inverted collecting dust in my house.

It is not just the inverter, it is also the support to it “included the wires & connectors for the system. Peak 6000W / 12volt = 500amps 😳. Put that in your van & smoke it.
 

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The DC current drawn from a 2KW ~ 3KW inverter is no joke. In my load testing the 4/0 (four ought, as big around as my thumb) cables still got warm to the touch. You could put a screwdriver next to them and feel the magnetic field vibrating.

I definitely agree that RDinNHandAZ's low-cost solar post is a good starting point from an experienced van person with real-life experience. Do you really need the 2KW power?

As far as the cheap inverter vs the Renogy or Aims . . . well they are likely made in a similar factory with similar components. However, with the Aims or Renogy inverters, the Aims or Renogy engineers have supposedly tested, worked with the factory, fixed any problems, and approved the quality and performance of the units before stamping their names on them. Also, you have a local contact in case anything goes wrong. That service is not free and could easily account for the $200 difference in price.

For the AMPINV that I purchased or the even cheaper SOYOND, you are buying directly from the far-east supplier and the risk is yours. As an electrical engineer, I had the tools and took the time to vet the AMPINV but I am not sure I would recommend it to a novice-it did have some trouble. The SOYOND? Could be a smokin' great deal, could be a smokin' hazard. You need to consider your risk tolerance and skill level.

At the end of the day, I like my setup, including 3KW inverter, 2x 200AH LifePo4 batteries, 4x MPPT controllers, and 60-amp B2B. I do not stress to plug in the 1500w heat gun when the 2x 500w halogen lights are on (not a camping situation, but something that I did when working on the van). But my budget was blown about a week into shopping before I ever picked up a tool and I do have the electrical chops to be confident in my system (including the no-name inverter) being safe.
 

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As far as the cheap inverter vs the Renogy or Aims . . . well they are likely made in a similar factory with similar components. However, with the Aims or Renogy inverters, the Aims or Renogy engineers have supposedly tested, worked with the factory, fixed any problems, and approved the quality and performance of the units before stamping their names on them. Also, you have a local contact in case anything goes wrong. That service is not free and could easily account for the $200 difference in price.
Yup 2KW 12v draw is no joke & hopefully no magic smoke.

In Canada products that “make the grade” have been independently tested and get a CSA label. CSA is internationally recognized.

I believe in the USA, you have a similar program “UL” ?

Regardless; For me Products that are tested by “their” own engineers are not in the same classification as CSA tested & approved products. If I ever question a product for safety I look to see if it is CSA Approved.

Victron is for at least the Victron stuff I purchased;
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Yes, I would not be surprised if some of the no-name devices were stickered as UL / CE / CSA while either not being tested at all or being "pencil whipped" through "approval".

The brand names (Victron, Renogy, and Aims for instance), having a legal footing in the UK, US, or Canada would have more incentive to make sure that their certificates were legitimate.
 

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I wonder why Power Distribution Centers with a converter charger plus a separate simple inverter are not more popular, instead of the very pricey inverter chargers, oftentimes $1,200 . . .


Am I missing something in why not more people go this route?
Not sure if you're missing something, or not, as we're not familiar with the Power Distribution Centers product. But for us, we chose one of the combo charger/inverter units (a Magnum 2812), in part, due to its built-in automatic transfer from "Shore Power" to "Inverter Power" (and back again). This automatic switching function also handles the required 120 volt 'ground switching' function - - namely, grounding the 120 volt 'ground pin' to the van chassis when operating from the inverter and lifting that ground connection when operating from Shore Power.

Our system is completely transparent. All of our 120vac duplex outlets are treated the same and all always have 120 volts available. This means we can have our computers plugged-in running on shore power, then 'yank' the shore power connection without any interruption of 120 volts at the outlets. The computers don't reboot or even hiccup. It's like an Uninterruptable Power Supply. The same transparent switching occurs when shore power is restored.

If the PDC unit doesn't do this, then, we think you're missing something.
 
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