Series/Parallel adapter clarification needed for 4x100w

[iamblakeh]

On a 400w (4x100w panel system) in this video

why are so many branch adapters required?

Can't I simply plug + and - MC4 connector directly without any additional adapter(s) from each series pair and then use a Branch Y Connector in (MMF+FFM) so that I up with one + lead and one - lead?

In my simple drawing I'm circling the only place where I was planning to use the branch connector. In the video from Renogy, there's a branch connector at every connection. What am I misunderstanding?



Thanks in advance!

 

[snoobler]

He's wiring 4P

You're wiring 2S2P. If that's your goal, then you're correct.

 

[SolarQueen]

The video has 4 parallel panels. Your drawing shows 2 parallel strings of 2 in series. Theirs stays at 12V, yours is 24V.

 

[iamblakeh]

Thank you both for the help. I can see now what he's doing in the video. oops.

I'm still confused about what I'm doing since I'm aiming for a 12V system (12V battery, 12V appliances, etc.) but would like to wire in series/parallel.

 

[snoobler]

As long as you use an MPPT charge controller, 2S2P or possibly even 4S would be fine for charging 12V. If you're using PWM, you MUST use parallel 12V panels.

 

[iamblakeh]

OK. So it sounds like I'm confusing voltage of panels with system voltage, yes? I'm planning to use: https://www.renogy.com/dcc50s-12v-50a-dc-dc-on-board-battery-charger-with-mppt/

Thank again!

 

[SolarQueen]

OK. So it sounds like I'm confusing voltage of panels with system voltage, yes? I'm planning to use: https://www.renogy.com/dcc50s-12v-50a-dc-dc-on-board-battery-charger-with-mppt/

Thank again!

Why did you pick that product? That's not really a solar charge controller. It is primarily used to charge from an alternator or another battery. While it can be used for solar, it's not the ideal solution. You would have to have the panels in parallel, as the max PV input is 25V. Don't confuse that with nominal voltage, that is Voc, which is around 22V for a 12V panel. You would be much better off with a true MPPT solar charge controller. If you don't have any shading, you can even wire them all in series, making for an easier install, lower current, smaller wire.

 

[snoobler]

Unfortunately, that's one of the exceptions. It may be MPPT, but it has a 25V PV input limit, so you have to go 4P.

 

[snoobler]

Better and possibly cheaper to have a separate MPPT solar charge controller and a DC-DC charger for alternator.

 

[SolarQueen]

Better and possibly cheaper to have a separate MPPT solar charge controller and a DC-DC charger for alternator.

Ah, I see now it can be used for both alternator and solar at once. I get the charm of an all in one. But I'd rather be able to go in series with a solar charge controller.

 

[iamblakeh]

Wow, Thank you both for all the hand-holding!

I actually already own this: https://www.renogy.com/rover-li-40-amp-mppt-solar-charge-controller/

but because I want to add alternator charging it was recommended that I swap for the DCC50S 12V 50A DC-DC battery charger with MPPT.

I think you helped me with this before @SolarQueen so would you still recommend this to add to the 40-amp-mppt I have linked from Renogy along with this: https://www.victronenergy.com/dc-dc-converters/orion-dc-dc-converters-12v-24v-48v-110v

If not, what product(s) would you recommend?

Distilling: Am I able to Series/Parallel panels and use the 40amp mppt along with the dc-dc linked above?

...and in the spirit of teaching a person to fish rather than just feeding me fish, @snoobler, you mentioned "It may be MPPT, but it has a 25V PV input limit, so you have to go 4P." Are you looking at the "Max. Solar Input Voltage : 25V" spec on the MPPT"all-in-one?" I assume so...and how then do I calculate the output from the panels - seems like you just knew that off the top of your head regarding a setup like I'm describing and I'd like to be able to know/calculate the output so I can help someone else.

 

[SolarQueen]

What do you have for solar panels and batteries? A lot of your questions depend on that info.

 

[iamblakeh]

...as soon as I replied I thought I should have added more info. Also, just found your YouTube channel WOW!

My aim is to have a 200ah LiFePo4 - However, currently, not ideally, what I could get my hands on is this: https://www.renogy.com/deep-cycle-hybrid-gel-battery-12-volt-200ah/

(each new comment opens a new conversation, doesn't it?)

Panels are 4 x RNG-100D-SS https://www.renogy.com/100-watt-12-volt-monocrystalline-solar-panel-compact-design/

 

[snoobler]

Wow, Thank you both for all the hand-holding!

I actually already own this: https://www.renogy.com/rover-li-40-amp-mppt-solar-charge-controller/

but because I want to add alternator charging it was recommended that I swap for the DCC50S 12V 50A DC-DC battery charger with MPPT.

I think you helped me with this before @SolarQueen so would you still recommend this to add to the 40-amp-mppt I have linked from Renogy along with this: https://www.victronenergy.com/dc-dc-converters/orion-dc-dc-converters-12v-24v-48v-110v

If not, what product(s) would you recommend?

Distilling: Am I able to Series/Parallel panels and use the 40amp mppt along with the dc-dc linked above?

...and in the spirit of teaching a person to fish rather than just feeding me fish, @snoobler, you mentioned "It may be MPPT, but it has a 25V PV input limit, so you have to go 4P." Are you looking at the "Max. Solar Input Voltage : 25V" spec on the MPPT"all-in-one?" I assume so...and how then do I calculate the output from the panels - seems like you just knew that off the top of your head regarding a setup like I'm describing and I'd like to be able to know/calculate the output so I can help someone else.

12V 100W panels are around 20-22V (open circuit), and they work optimally around 17-18V. Their open circuit voltage must not exceed the 25V of the MPPT. SQ mentioned this concept in post #7.

The Rover you linked has a 100V input limit. 4 of your 100W panels in series would likely be about 88V, which is probably okay provided it doesn't get too cold (cold panels produce higher voltages). 2S2P would be fine for sure.

...as soon as I replied I thought I should have added more info. Also, just found your YouTube channel WOW!

My aim is to have a 200ah LiFePo4 - However, currently, not ideally, what I could get my hands on is this: https://www.renogy.com/deep-cycle-hybrid-gel-battery-12-volt-200ah/

(each new comment opens a new conversation, doesn't it?)

Panels are 4 x RNG-100D-SS https://www.renogy.com/100-watt-12-volt-monocrystalline-solar-panel-compact-design/

When sizing your lead-acid batteries/solar panels, max solar current needs to be about 10-15% of capacity, e.g., 400W/12V = 33.3A

33.3A/.15 = 222Ah
33.3A/.10 = 333Ah

So anything in that range is fine. I tend to prefer .15 as most solar charging starts at much lower current in the morning and doesn't ramp up until mid-day where you may already be fully charged.

Good news is that LFP batteries don't care. Just don't go over their charge limit, typically 0.5C or the battery's BMS charge current limit.

Your panels are 21.6Voc, so 2S2P would be 43.2V. Fine with the MPPT Rover

 

[SolarQueen]

...as soon as I replied I thought I should have added more info. Also, just found your YouTube channel WOW!

My aim is to have a 200ah LiFePo4 - However, currently, not ideally, what I could get my hands on is this: https://www.renogy.com/deep-cycle-hybrid-gel-battery-12-volt-200ah/

(each new comment opens a new conversation, doesn't it?)

Panels are 4 x RNG-100D-SS https://www.renogy.com/100-watt-12-volt-monocrystalline-solar-panel-compact-design/

There are several ways to design a system, and most of the time, many are right. There is rarely only one way to do it correctly. If you already have a nice MPPT solar charge controller that has a 100V input, I would personally use that for the solar. You can wire the panels the way you drew it, with 2 parallel strings of 2 in series or maybe 4 in series (more on this later). Then get just a DC/DC converter for the alternator. Saves you some money so you can put that towards the lithium batteries.

Solar panels have multiple voltages associated to them. I do explain it in my latest videos, but to summarize, Voc is the highest voltage you will see out of the panel, so that is the voltage used when sizing the charge controller. Your panels have a Voc of 21.6V, 4 in series is 86.4V. You also have to take cold into consideration, as the voltage goes up as it gets colder. Multiply the 86.4V by the correction factor for the coldest daylight temp to see if it will stay under the 100V limit.

 

[SolarQueen]

Once again, snoobler and I were typing at the same time (happens a lot). I agree with what he says (also happens a lot).

 

[iamblakeh]

Love and knowledge! Doesn't get much better. Thank you team!

 

[snoobler]

Just a moment to remind any readers that if SQ and I disagree, she is way more righter than me.