Solar Charge Controller Confusion

[Brianna]

Here is the combiner box I built (based on Brian's idea from "RVing With Tito").

All cables feed down a 1"conduit.

10ga from pv panels to the box, then 6ga to the controller. Then 6ga to the batteries. Hopefully a straight shot through the bedroom cabinets.

Room for more solar, or a wifi booster or whatever, in the future.

[Old Scout]

….so all 5 panels will go in parallel or individually to combiner box.....tell me again the pros/cons of going in parallel Vs in-series or partial in-series to the MPPT controller....eg. more volts and less amps, so smaller/less wire runs??????

[paul65k]

Originally Posted by Old Scout

….so all 5 panels will go in parallel or individually to combiner box.....tell me again the pros/cons of going in parallel Vs in-series or partial in-series to the MPPT controller....eg. more volts and less amps, so smaller/less wire runs??????

Panels wired in Parallel are less susceptible to the effects of partial shading vs being wired in series. Parallel panels operate at a lover voltage and as such have more line loss (resistance) and as a result dictate a larger gauge wire based on length.

I think Brianna has the gauges right........I only wonder why you are using such small 100W panels in today's environment.....why not 200W or larger.

I understand that the larger 300 - 400W panels are large but most of the new 200W panels are not much different in size to the 100W.

I was able to mount (8) 200W panels and still have room for 4 more if the need is there in the future (Mini-split A/C?) but it seems like if you're gonna do the work to mount, wire, buy mounts, etc.... why not just go with 200W to start???

[Brianna]

Paul65k, you are probably right.

I can still return the 100 panels.

The renogy tilt mounts I have are rated for 100 panels but as you say, the size is not that different.

I looked back at your install thread. It's a really cool system.

[paul65k]

Originally Posted by Brianna

Paul65k, you are probably right.

I can still return the 100 panels.

The renogy tilt mounts I have are rated for 100 panels but as you say, the size is not that different.

I looked back at your install thread. It's a really cool system.

Thanks!
PM me anytime if I can help

[Our05Winneba]

They typically quote the max output current. This is because all solar controllers are designed to do just that - control the solar electricity going into your batteries. As your batteries reach full charge then the controller's job is to shut down the electricity flowing to the batteries - regardless of how much solar input they are receiving.

[neonwizard]

Please go to You tube and look up DIY Solar Power with Will Prowes. He is very knowledgeable. You should find what you need there. I sure did 🤠

[fratermus]

Originally Posted by Brianna

I have read books.
When one thinks about a 40 Amp MPPT Controller, should one be thinking of 40A being the most that can come in or the most that can come out?

IIRC the most common meaning of the spec is the amount of current that can be supplied to the combined BATT and LOAD outputs. Ie, 40A to the batt, or 35A to the batt whil 5A load is being drawn from the LOAD output.

Originally Posted by Brianna

I have read books.
So, in other words, can a 60A controller slam more amps into the batteries, or at a faster rate, than a 40A controller using the same battery bank and the same solar panels?

Maybe. If 1. the banks only will accept 40A then 60A of charging capacity won't get you through Bulk (for example) any faster, all other things being equal and 2. the panels can supply > 40A (ie the 40A controller was overpaneled).

[orangeminnie]

Originally Posted by rarebear.nm

You are correct, in series you add voltage, in parallel you add wattage.

In parallel you add current (amperage). Total wattage = E x I (volts x amps), so the wattage adds up regardless whether the panels are in series or parallel.


Also, the MPPT rating is for the output current. By definition, the input current will (almost always) be lower, and the voltage (from the PV panels) will be be higher.

[Magic Bus II]

A friend has a PWM controller (GoPower) for his two 100w panels that incorporates a 'boost' button. He takes delight in pointing out that his controller will usually indicate a full battery charge by mid-morning (although it is not a battery monitor).

Then, if his batteries are still not fully charged by late afternoon he simply presses the 'boost' button which pushes in 'extra' power to aid in charging the batteries.

My question is ... if his system can somehow 'boost' the charge at the end of the day with the push of a button why doesn't it just manage the power over the entire day to charge his batteries? How would pushing a button allow it to 'find' more charging power? Is this something normal with PWM systems or as I suspect, some kind of marketing hype?

[RVPioneer]

Does your friend own Magic Bus 1?

[Brianna]

There is a 34 page instruction book online

"GP-PWM-30-UL also features Maximum Power Boost Technology™ for manual bulk and absorption charge at any stage of the charge cycle."

That can't be great for the batteries, can it?

[Mark_K5LXP]

Originally Posted by Brianna

There is a 34 page instruction book online

"GP-PWM-30-UL also features Maximum Power Boost Technology™ for manual bulk and absorption charge at any stage of the charge cycle."

That can't be great for the batteries, can it?

Sez the boost applies absorb voltage for 30 minutes. Not sure what you can practically get from this. With banks in the hundreds of Ah (even just a couple GC-2's) you sit at absorb for several hours anyway, another 30 minutes isn't going to do a lot. So if the controller had gone through a complete charge phase and was sitting at float when you hit the boost, about all you'd accomplish is to dissolve a little more water in the batteries. If the batteries weren't fully charged, then the net effect is zero since they're already in bulk or absorb phase anyway. So I'm not sure what this function is supposed to accomplish other than the "upon initial installation" comment in the manual. It's not going to put any more Ah into them than what the panels had already delivered, or the batteries were able to accept.

I wonder if the battery parameters are adjustable for this controller. As stated in the user manual they're not what I would want for flooded batteries. Maybe there's a parameter setup menu that's not shown in the user manual, don't know.

Mark B.
Albuquerque, NM

[fratermus]

Originally Posted by Magic Bus II

A friend has a PWM controller (GoPower) for his two 100w panels that incorporates a 'boost' button. He takes delight in pointing out that his controller will usually indicate a full battery charge by mid-morning (although it is not a battery monitor).

ie, has entered Float. This may or may not coincide with the bank being fully charged.

Originally Posted by Magic Bus II

Then, if his batteries are still not fully charged by late afternoon he simply presses the 'boost' button which pushes in 'extra' power to aid in charging the batteries.

Sounds like it's a button that restarts Absorption. Additional evidence: Chinese mfgrs often call Absorption "boost" . If the batteries were fully charged in the AM and not run down in the interim, pushing the button would not charge the batteries any better.

It could, however, slightly increase the amount of power available for loads because of the way PWM ties panel voltage (Vpanel) to battery voltage (Vbatt). That would be the most generous explanation for the "boost" nomenclature in a PWM context.

Originally Posted by Magic Bus II

My question is ... if his system can somehow 'boost' the charge at the end of the day with the push of a button why doesn't it just manage the power over the entire day to charge his batteries?

It does manage the power, albeit possibly poorly.

Possibilities:

* the designer making a rational decision to kill batteries of inattentive users later (sulfation) rather than earlier (outgassing).
* the company wanted to get that "Charged!" light on ASAP to make people like your friend happy
* at the controller's price point there is not sufficient logic to restart Absorption in daytime after significant voltage depression (heavy inverter load, for example) . Having a button override might be a cheap workaround.