small system design help request

[rcmedic]

I am building a small system to run my remote "Bee Barn" 8' x 16'. I am using 4 100 watt Renogy rigid panels with 4 Trojan 6 volt AGM 2S2P connected to a Renogy Adventurer 30A PWM and a 3000 watt Pure Sine Inverter. My question is: should I connect the panels like the batteries S2P2 or straight parallel. If I do S2P2 hookup of panels, is 30A CB or fuse appropriate? In any case, should I also install CB or fuse on my batteries?

 

[Q-Dog]

I would lean towards swapping that PWM charge controller for an MPPT charge controller.

 

[HarryN]

While I agree in general with Q-dog, what you are doing will work.

As far as the wiring, look at your battery pack - so in this case it is ~ 12 volt, so as it charges and discharges, the voltage will go from roughly 14 volts fully charged to 11.5 - 12 volts discharged.

The solar panel voltage ( Vmp ) needs to be slightly higher than this range, so at least ( 14 + 1 volt ). Let's call it 15 volts minimum to work.

Now look at your solar panel label and the Vmp number on the back. It is probably ~ 18 volts, so that meets the minimum to charge the system using your pwm controller.

If so, then wire the panels to maintain that ~ 18 volts, or in parallel.

As you mount the panels, keep in mind the time of day that you need the power, so sometimes that means having some facing the morning sun or late afternoon sun. ( or both )

 

[HarryN]

Trojan makes a nice AGM battery setup, most of them are designed for long, slow discharge vs high current discharge rates.

So pulling ~ 100 amps / 1000 watts from the pack is viable, but fully powering the 3000 watt inverter is unlikely. Not a problem, just mentioning it.

 

[mikefitz]

a Renogy Adventurer 30A PWM

It's a 12v system, the PWM only transfers panel current to the battery, thus the 100 watt panels will deliver 5 amps maximum each, if all are connected in parallel, 20 amps. In theory charging at 14.4 volts, that's a maximum of 290 watts. If you use a series/ parallel solar array you will lose half that unless you use a MPPT controller.
The Trojans are good batteries but running a 3000 watt inverter at full power is too demanding, ( approaching 300 amps). Try to limit the load to a maximum of 1500 watts.
Having a suitable fuse as close as possible to the battery positive to feed the inverter, 300 amps, and a second suitable fuse , 20 amps, to feed the controller, is a useful safety feature .
Since the panels are all in parallel, in theory you need a series fuse on each panel before the parallel conection, 7.5 amps.

 

[rcmedic]

Trojan makes a nice AGM battery setup, most of them are designed for long, slow discharge vs high current discharge rates.

So pulling ~ 100 amps / 1000 watts from the pack is viable, but fully powering the 3000 watt inverter is unlikely. Not a problem, just mentioning it.

In the majority of cases, the inverter will only be running LED lighting with an occasional use to drive honey processing equipment that I suspect will be less than 1000 watts, intermittently.

 

[rcmedic]

I would lean towards swapping that PWM charge controller for an MPPT charge controller.

I will opt for the MPPT. I used what I had on hand and figured I might get away with it.

 

[HarryN]

In the majority of cases, the inverter will only be running LED lighting with an occasional use to drive honey processing equipment that I suspect will be less than 1000 watts, intermittently.

In that case, it might be worth considering to use DC led lighting instead of AC powered LED lighting if you don't already have the lights.

Most inverters will burn 30 - 60 watts just being turned on, which can be a significant amount of the total load power.

Obviously if you already have the lights, it does not make sense to change them.

But just as an example, these are some example suppliers of led strips and misc that can run on DC.

LEDSupply - For All Your LED Project Needs!

LED Lighting For Everything | Super Bright LEDs

Super Bright LEDs is one of the largest online retailers of LED lighting for commercial and residential uses. Enjoy free/same-day shipping on qualifying orders!

www.superbrightleds.com

 

[rcmedic]

In that case, it might be worth considering to use DC led lighting instead of AC powered LED lighting if you don't already have the lights.

Most inverters will burn 30 - 60 watts just being turned on, which can be a significant amount of the total load power.

Obviously if you already have the lights, it does not make sense to change them.

But just as an example, these are some example suppliers of led strips and misc that can run on DC.

LEDSupply - For All Your LED Project Needs!

LED Lighting For Everything | Super Bright LEDs

Super Bright LEDs is one of the largest online retailers of LED lighting for commercial and residential uses. Enjoy free/same-day shipping on qualifying orders!

www.superbrightleds.com

Thank you for the info. I will check it out.

 

[rcmedic]

I will opt for the MPPT. I used what I had on hand and figured I might get away with it.

I ordered an Epever MPPT controller 12/24v regulator 150v 40A & MT50

 

[HarryN]

I ordered an Epever MPPT controller 12/24v regulator 150v 40A & MT50

In that case, then :
- you will want to look at the max input voltage of that controller
- run at least 2 panels in series
- but keep the Voc of the panel array down to ~ 60 - 70% of the controller input voltage number.