Can Renogy MPPT 40A controller ACCEPT 48V input from panels and still deliver 12V?

[motokrome]

My kit didn't come with those adapters to wire my panels in parallel, so I called them and the tech guy told me that I could wire all four panels in series (for 48V) and my controller would magically match that high voltage to my 12V battery bank.

Upon re-reading the manual, it says this controller can accept voltages from 12V - 24V nominal off-grid solar panel arrays. Should I ignore the manual and listen to the tech on the phone from Renogy? Does anyone have any experience with this controller stepping down 48V to 12V? Is it safe? (doesn't seem safe to me)

I just want to be sure I'm not going to fry anything before I wire this all up. I'd feel more comfortable wiring these panels in SERIES for 12V before trying to charge my 12V bank of four Trojan T-105's. Any advice much appreciated, thanks.

[lkruper]

My kit didn't come with those adapters to wire my panels in parallel, so I called them and the tech guy told me that I could wire all four panels in series (for 48V) and my controller would magically match that high voltage to my 12V battery bank.

Upon re-reading the manual, it says this controller can accept voltages from 12V - 24V nominal off-grid solar panel arrays. Should I ignore the manual and listen to the tech on the phone from Renogy? Does anyone have any experience with this controller stepping down 48V to 12V? Is it safe? (doesn't seem safe to me)

I just want to be sure I'm not going to fry anything before I wire this all up. I'd feel more comfortable wiring these panels in SERIES for 12V before trying to charge my 12V bank of four Trojan T-105's. Any advice much appreciated, thanks.

Maybe he meant make two series strings and then put them in parallel so that you end up with 24 volts?

[paulcheung]

Can you tell the exact model number of your Charge Controller? the 40A MPPT CC I know can accept up to 100 volts input and charge either 12 or 24 volts battery bank.

Is it this one?

http://www.amazon.com/Renogy-Amp-MPPT-Charge-Controller/dp/B00S9NW9HM/ref=sr_1_2?ie=UTF8&qid=1435851567&sr=8-2&keywords=Renogy+MPPT+40A+controller

If it is you have no problem to connect the panels in series.

[SunEagle]

Can you tell the exact model number of your Charge Controller? the 40A MPPT CC I know can accept up to 100 volts input and charge either 12 or 24 volts battery bank.

Is it this one?

http://www.amazon.com/Renogy-Amp-MPPT-Charge-Controller/dp/B00S9NW9HM/ref=sr_1_2?ie=UTF8&qid=1435851567&sr=8-2&keywords=Renogy+MPPT+40A+controller

If it is you have no problem to connect the panels in series.

I agree with you. I informed the OP in another thread that if those 100 watt panel had a Voc < 25v then that CC can accept 4 in series.

I believe the biggest confusion for some people is the verbiage of what a "battery" panel is rated. For some reason they get confused and think it is only rated 12volts which is what they will need to charge a 12volt battery. Total misconception on their part since you really need about 18volts input to charge a 12volt battery.

[motokrome]

Can you tell the exact model number of your Charge Controller? the 40A MPPT CC I know can accept up to 100 volts input and charge either 12 or 24 volts battery bank.

Is it this one?

http://www.amazon.com/Renogy-Amp-MPPT-Charge-Controller/dp/B00S9NW9HM/ref=sr_1_2?ie=UTF8&qid=1435851567&sr=8-2&keywords=Renogy+MPPT+40A+controller

If it is you have no problem to connect the panels in series.

Yeah, that's the one, but I'm not sure if it's the same as the one that's currently available: http://www.amazon.com/Renogy%C2%AE-T...Y0DJJDEJV4KZDT - either way, SunEagle (and Renogy) have confirmed it's good for up to 100V input and "magically" charges 12V or 24V battery-banks by "auto-sensing" their voltage.

SunEagle, I did not realize I'd need 18V to charge my "12V" bank, as I'm used to 14.6V maximum, during the "sulfation" phases of charging, but I'm thinking your 18V spec accounts for voltage drops across all these different devices that are at different degrees of efficiency and what not.

Do you guys put circuit-breakers/fuses between the panels and the controller? What about between the controller and the batteries for charging? I'm thinking I should just put fuses/circuit-breakers EVERYWHERE, just for the heck of it, but I've never fused chargers putting voltage INTO batteries before (between the charger and the batteries), but I want to be safe.

Should I just go with 40A circuit-breaker between the MPPT controller and the batteries (since it's rated as a 40A unit)? And would you advise something like a 10A circuit-breaker between the panels and the MPPT controller? Thanks.

[paulcheung]

I use 15 Amps DC breaker between each series panels and the CC, 60 and 80 amps between each CC and the battery bank, 250 amps breaker between the battery banks and the inverter.

[lkruper]

Yeah, that's the one, but I'm not sure if it's the same as the one that's currently available: http://www.amazon.com/Renogy%C2%AE-T...Y0DJJDEJV4KZDT - either way, SunEagle (and Renogy) have confirmed it's good for up to 100V input and "magically" charges 12V or 24V battery-banks by "auto-sensing" their voltage.

SunEagle, I did not realize I'd need 18V to charge my "12V" bank, as I'm used to 14.6V maximum, during the "sulfation" phases of charging, but I'm thinking your 18V spec accounts for voltage drops across all these different devices that are at different degrees of efficiency and what not.

Do you guys put circuit-breakers/fuses between the panels and the controller? What about between the controller and the batteries for charging? I'm thinking I should just put fuses/circuit-breakers EVERYWHERE, just for the heck of it, but I've never fused chargers putting voltage INTO batteries before (between the charger and the batteries), but I want to be safe.

Should I just go with 40A circuit-breaker between the MPPT controller and the batteries (since it's rated as a 40A unit)? And would you advise something like a HUGE 500A circuit-breaker between the panels and the MPPT controller? Thanks.

If I understand correctly, the panel needs to output a minimum of 18v at the best of conditions to ensure the CC has enough power to charge the battery for the full 4-6 hours or so it requires. The battery does see 14.6.

[motokrome]

Sweetness. What 250A circuit breaker do you use? I have a 150A Blue Sea Systems right now, but it's not really enough, the manual recommends a 250A, but all I could find in that spec were cheaper "Car Audio" brands, like Stinger and didn't know if that'd be good enough.

So, to figure the rating for between the panels and the CC, did you just divide the total wattage by their VOC? So for my 400W (4 x 100W panels), I should divide 400 by 22.5? 400 ÷ 22.5 = 17.777A, so I should use 18A fuse? If they're only available in 15A or 20A, should I go with 15A? (wait, no . . . 4 panels VOC would be like 90V, 400 ÷ 90 = 4.444A, so I'd only need a 5A fuse?) I'm confusing myself now.

Thanks for all the help for I'm a total newbie!

[motokrome]

If I understand correctly, the panel needs to output a minimum of 18v at the best of conditions to ensure the CC has enough power to charge the battery for the full 4-6 hours or so it requires. The battery does see 14.6.

Gotcha, thanks for the help! I've been stalling hooking everything up and been sitting on this rig for like six months now - just kind of slowly piecing it all together (and losing money on all that sun I'm not harnessing!). I just need to get the fuses/circuit-breakers and some more cable to finish! I'm getting excited!

[motokrome]

Do I need to fuse BETWEEN each panel?

How should I determine the fuse ratings for everything? Do I multiply by 1.25? So would a 50A fuse be what's needed between the 40A CC and the batteries? Or do I just match the amp rating of the CC and go with a 40A fuse? Thanks, and sorry for all the questions!

[Naptown]

The only time you need fuses on the output of the panels is when there are three or more PARALLEL strings.
With 4 panels the only way to do that would be to put all 4 in parallel
2 strings of 2 no fuses required
1 string of 4 no fuse required.
Now two things that have not been addressed
Cold weather.
This will increase the open circuit voltage of the panels. So find the record low temperature of where these will be used and do calculate the coefficient per the panel specs. ( data sheet will tell you )
Or just multiply VOC by a percentage as found in the NEC.
SECONDLY
The wires from the panels to the charge controller will need to be sized to take 156% of the short circuit current. So a string with a 10 amp ISC
Would need a wire suitable for 15.6 amps.

[paulcheung]

Sweetness. What 250A circuit breaker do you use? I have a 150A Blue Sea Systems right now, but it's not really enough, the manual recommends a 250A, but all I could find in that spec were cheaper "Car Audio" brands, like Stinger and didn't know if that'd be good enough. .

http://midnitesolar.com/productPhoto...ctCatName=Mini DC Disconnect&productCat_ID=8&sortOrder=5&act=pc