BillWNC
New Member
I'm building a 200 watt system. Will's video shows the two panels in series. This will feed 24 volts into the charge controller, right? Will the controller then automatically feed 12 volts into the battery?
minimalist system
- Thread starter BillWNC
- Start date
MisterSandals
Participation Medalist
Depends on the exact voltage of the panels. Your panels might be anywhere from 22V to 35V each. Look at the specs. And when selecting an SCC, use the panel Voc numbers when determining if it will handle your array volts.
This is what charge controllers do; take array volts and convert to battery specific charging voltage.
But charging volts will be more like 14V to your 12.8V nominal battery.
MichaelK
Solar Wizard
How big is the battery you are intending to use? With 200W of panels and assuming you never get more than 85% real-world output, what you are likely to see is (200W/13Vcharging) X 85% = 13A. That's about right for a 100Ah battery at 12V. Assuming you are using larger golf-cart batteries, about 400W is more appropriate.
With Li batteries a low charging rate is more acceptable than for lead-acid. Traditional lead-acid batteries die a premature death from chronic undercharging.
What's the goal of this system? What is it that you intend to power? Have you done any kind of power audit to see the maximal number of watthours (Wh) you need? My gut feeling is that this might be too small for your actual needs?
With Li batteries a low charging rate is more acceptable than for lead-acid. Traditional lead-acid batteries die a premature death from chronic undercharging.
What's the goal of this system? What is it that you intend to power? Have you done any kind of power audit to see the maximal number of watthours (Wh) you need? My gut feeling is that this might be too small for your actual needs?
BillWNC
New Member
I'm using a single 95AH AGM battery. Limited output, but that's what I have. The charge controller is a 20 amp older Renogy, new in box that's only for lead/acid. I also have a 40 amp Renogy, also NIB.
I'm just charging cellphone and running a few strings of COB LED lights. The panels are 100w X 2. They are 12 volt.
BillWNC
New Member
Looking forward to expanding to 400w. In time I'll get a newer charge controller and lithium battery. For now I have to use what I have.
sunshine_eggo
Happy Breffast!
Didn't see it mentioned, but if you are installing these panels in series, the controller must be a MPPT.
If PWM, they simply short the panel to the battery during the bulk phase and 2X 100W panels in series will perform no better than just one.
If PWM, they simply short the panel to the battery during the bulk phase and 2X 100W panels in series will perform no better than just one.
BillWNC
New Member
They both are MPPT, just older and not suitable for lithium, or so I'm told.
sunshine_eggo
Happy Breffast!
"not suitable for lithium" typically means they do not have a specific lithium setting. It does not mean that they are not suitable.
Expensive Outback FM80 MPPT have no lithium settings, but they are regularly used.
Criteria for LFP:
Bulk/boost/absorption (three names for same voltage): 13.8-14.6V
Duration of above cycle ("boost duration", etc.): 30 minutes at 14.6V to 120 minutes at 13.8V
Float: 13.5 preferred, 13.6-13.8V tolerable
Equalization set to same as bulk/boost/absorption OR disabled.
Temperature compensation disabled - sometimes this is just disconnecting the sensor.
In most cases, a user setting or SLA, GEL or AGM settings are workable provided you can disable temp comp. Those three types either disable or have equalization set to the same as boost.
BillWNC
New Member
Both CCs (20&40 amp) I have are MPPT, but older and don't have an option for lithium. I bought the system some years back and its just sat in the boxes, cool and dry.
sunshine_eggo
Happy Breffast!
Have seen some of the older Renogy stuff, and you can usually find a setting that works. I'm a cheap bastid - big fan of use what you have on hand if it works.
