200 watt system recommendations for camper

hi everyone,
New to the site and looking for recommendations for my travel trailer. just got the trailer and drained batteries after 2.5 days of camping.
trailer has 2 relatively new 90amp batteries. im looking to get a 200w system that i can expand to 400w if i choose to at a later date. i was going to get a renogy 200w system but they seem really backed up and i like to get system asap. HQST , Rich and eco power are also possible considerations. Im interested in what you guys got and would do differently. MPPT controller or PVM , is Bluetooth remote monitoring really helpful? thx in advance for the help

Get a Victron Mppt 100/30

I'll vouch for Victron. Love my 150/100 bluetooth unit. Love being able to monitor the charge controller on my phone. They are a bit spendy though.

Go with MPPT.

Bluetooth, is more of a 'nice to have' than a necessity in my eyes. But the Victron BT app sure makes configuration and monitoring easy. You can download the victron connect app it has a demo mode where you can see what it looks like and what you can monitor and configure.

Victron 100/30 would possibly probably be a good fit, or get a Victron 75 /15 or 100/20 now and add a second when you buy the additional panels. Epever is another option and would be somewhat cheaper.

Does it make a difference if i get Controller with negative or postive ground?

wut?

brkylnkid said:

Does it make a difference if i get Controller with negative or postive ground?

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Maybe one of our resident EE's can weigh in on the theoretical side of this. In the absence of that I would say (in my uninformed opinion) definitely use a negatively grounded controller. Virtually everything I'm familiar with is negative grounded (including your vehicles electrical system).

unless you want the bluetooth option go with
Victron Bt or Renogy PG i have both they both and i just ordered another Renogy only because of the interface i prefer over victron . If you are only doing 200 watt in pv id start out with a pwm controller the cost for a mppt is 150 or more they have good quality pwm controllers for 30 bucks or so . Will has the renogy pwm on his site .
also for solar panels no matter what brand get mono panels for sure

decent quality PWM's can be had for pretty cheap- especially at 100-200w. 20 bucks or less will get it done.

+1 for the Victron SmartSolar 100|30. You could go for the cheaper SmartSolar 100|20 which would actually be a better fit for your 200W array, but you would be limited to 290W charging with your planned 400W array - it would still work fine, though (Victron actually recommend over-panelling their SCCs by 30%).

If you have no need for the Bluetooth monitoring you could buy their lower spec BlueSolar product but I'll bet there won't be much between them.

tictag said:

+1 for the Victron SmartSolar 100|30. You could go for the cheaper SmartSolar 100|20 which would actually be a better fit for your 200W array, but you would be limited to 290W charging with your planned 400W array - it would still work fine, though (Victron actually recommend over-panelling their SCCs by 30%).

If you have no need for the Bluetooth monitoring you could buy their lower spec BlueSolar product but I'll bet there won't be much between them.

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he probably should over panel anyways- RV's and travel trailers usually never have optimum angles.

madmax said:

he probably should over panel anyways- RV's and travel trailers usually never have optimum angles.

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Curious how one would over panel in this instance. Lets assume they're starting with 2 100 watt panels in parallel. Later upgrade to 2 additional 100 watt panels so the array is then wired 2S2P. Adding one more 100 watt panel would get you to 25% over panelled, but how would you add 1 more panel to a 2S2P configuration, if that is even possible? Sorry for my ignorance.

PatBlack said:

Adding one more 100 watt panel would get you to 25% over panelled, but how would you add 1 more panel to a 2S2P configuration, if that is even possible?

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That's not really what over-panelling means.

If you take any SCC, it will have a maximum charge current rating, in the case of the Victron SmartSolar 100|20 mentioned above, that's 20A (see table below). Delivered at 12V(nominal) that basically means a nominal output power of 292W (14.6V x 20A = 292W). In other words, you need at least a PV array of 292W in order to supply the SCC's nominal power output.

The thing is, it is very rare that you will actually get 292W out of a 292W PV array e.g. angle to sun, temperature, latitude from the equator etc so most people over-panel their arrays by some percentage, Victron recommend 30%. This means that you would install a 380W (292W x 30%) array in order to supply a 292W nominal output.

Does that make sense?

Most SCCs will support over-panelling so long as you do not exceed their Maximum PV Voltage or Maximum Isc Current specifications. Most SCC manufacturers will specify Maximum PV Power instead of Maximum Isc Current ... Victron specify their SCCs differently to most i.e. they use Nominal PV Power:



Using the example of the Victron SmartSolar 100|20, you can actually over-panel up to 2,000W (Max Voc = 100V, Max Isc = 20A) but it would only ever provide its 290W nominal charging power, the rest would be 'left on the table'. Over-panelling is a balancing act between optimising for cloudy days and leaving PV power 'on the table'. As a rule of thumb, 30% is a good number.

Edit: Added maximum PV power additional note.

Dzl said:

Maybe one of our resident EE's can weigh in on the theoretical side of this. In the absence of that I would say (in my uninformed opinion) definitely use a negatively grounded controller. Virtually everything I'm familiar with is negative grounded (including your vehicles electrical system).

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@Dzl, as the forum's chief research officer, this is a topic maybe you can sink your teeth into. I've been wondering about all this myself for a while. Why are so-called "positive ground" controllers cheaper? Why does everyone say to avoid them? It seems the terminology the industry has chosen has made things more confusing. The clue to what's really going on comes from this post from a couple months ago. See the quote below.

bdl said:

The term "positive ground" or "negative ground" doesn't actually refer to the case of the device, rather which side is switched. It's a rather bad choice of labelling if you ask me. They should have used "high side switching" and "low side switching", which is both the more conventional electronics term, is accurate and specific, and not liable to be confused with other separate concepts.

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This article helps make sense of some of it. After reading it and some other info, I'm of the mind that if you design your system correctly a PG controller should be fine in a lot of applications. Still not sure about in a vehicle though.

I picked up the 200W system that HQST has on sale that includes a 20A MPPT controller. It seems to be a nice kit, that comes with everything needed except the wires to connect the SCC to the battery. It supports 3 different LA battery types, has a basic profile for Lithium and has a User mode that can be further configured to dial in your preferred charging profile. Even though they didn't show it in the kit photo, it also came with the remote pad for configuring and monitoring the system
From looking at the specs, I should be able to safely add a 3rd 100W panel to the setup in either a 3S or 3P scenario without risk to the controller, but adding a 4th panel might exceed the max current rating and risk damage to the controller in ideal solar conditions.

Dzl said:

or get a Victron 75 /15 or 100/20 now and add a second when you buy the additional panels.

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@brkylnkid, if near-term budget is a concern, I like this idea. It gets you a top tier SCC now and spreads the cost out over time. And depending on your use cases, maybe you find that it works well enough and you don't actually need to get more panels. If you've got the extra bucks, the 100/30 that was originally recommended won't let you down.

(I've got a Victron 100/20 and two 100/50s. They work great.)

Bob142 said:

@Dzl, as the forum's chief research officer, this is a topic maybe you can sink your teeth into. I've been wondering about all this myself for a while. Why are so-called "positive ground" controllers cheaper? Why does everyone say to avoid them? It seems the terminology the industry has chosen has made things more confusing. The clue to what's really going on comes from this post from a couple months ago. See the quote below.




This article helps make sense of some of it. After reading it and some other info, I'm of the mind that if you design your system correctly a PG controller should be fine in a lot of applications. Still not sure about in a vehicle though.

Low side vs. High side transistor switch - Bald Engineer

When using a transistor as a switch, there are two configurations to consider. Do you use a low-side or a high-side transistor switch? And why?

www.baldengineer.com

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Thanks, I'll read up on it!

So after your research, are you any closer to understanding why they exist? are they advantageous in some way? cheaper to produce?

Dzl said:

Thanks, I'll read up on it!

So after your research, are you any closer to understanding why they exist? are they advantageous in some way? cheaper to produce?

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My recollection is that low side switching circuitry is cheaper because it's less complex. We probably need someone like @BiduleOhm to bring the smarts. I'm all out of them at the moment...

We usually prefer low side switching because NPN transistors and N mosfets have better specs than PNPs and P mosfets cost being equal. It's also because in a multi rails system (for example 12 V for the high power things and 5 V for the control logic) the common point between them is a negative ground and you can't control a high side transistor with the 5 V logic (you need at the very least one more transistor and some resistors).

So in short: it's cheaper and simpler to use low side switching rather than high side switching.

BiduleOhm said:

We usually prefer low side switching because NPN transistors and N mosfets have better specs than PNPs and P mosfets cost being equal. It's also because in a multi rails system (for example 12 V for the high power things and 5 V for the control logic) the common point between them is a negative ground and you can't control a high side transistor with the 5 V logic (you need at the very least one more transistor and some resistors).

So in short: it's cheaper and simpler to use low side switching rather than high side switching.

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If this is the case, do you have any insight why 'high side switching' seems to be the default for charge controllers? Are there advantages that justify the cost?