I have been using a bare-bones solar system on an off-grid camper for a couple years but am upgrading to a (hopefully) better more reliable system with more capacity. I would like to share my thoughts and get feedback from the community. I recently purchased a Renogy 400W system with a 40A MPPT controller. It is installed with the (4) 100W panels in series. I want to be sure I am doing things in a way that I can go to 600W or 800W in a series-parallel arrangement in the future. I know this will start with a larger charge controller to handle the higher wattage. I am in a cold climate and depend on the system to keep the bare basics powered when I am away at times for weeks at a time. It is good if I never lose power on the camper, but it is not critical, especially if it is below freezing at the time. The system will see freezing temperatures. I am preparing to switch from lead acid to LiFePO4 batteries, and I want to be sure I properly protect my investment in the LiFePO4. I purchased an Eco-Worthy 280Ah LiFePO4.
From what I have read so far, I believe that I should maintain the charge between 12.5V (14%) and 13.3V (90%) to avoid shortening the battery life. I got that from reading various sources about “avoiding the shoulders,” and I verified the voltages that correspond to 14% and 90% in the battery manufacturer’s documentations. I also understand I should not charge below 32°F or discharge below 0°F.
The battery BMS has over- and under-voltage protection, but they are apparently at 14.8V and 8.0V. These seem too high and low and more for safety than protecting the battery life. Is this typical for the BMS, or is this because I bought a cheap battery?
I believe the charge controller can be programmed to avoid overcharging past 13.3V.
To avoid over-discharging below 12.5V, I think I can use a battery protection device like this https://www.victronenergy.com/battery_protect/battery-protect.
The BMS has high temp protection at 194°F, but again, it seems to be for safety, not for protecting the battery life. It does not have any low-temp protection on the charge or load side. Again, is this typical?
I am looking for a device that will disconnect the charging below 32°F and one that will disconnect the load below -4°F. Probably, that will be two of the same device, one on each side of the battery set at different temps, perhaps something like this, although I would need higher amperage https://www.ebay.com/itm/185814659317.
Any feedback would be appreciated, even if it is "let me better educate you" or “you shoulda bought a better battery.” Any advice on whether I have the right ideas to protect the battery or devices to do so would also be great.
Thank you for your time and expertise.
Bryan
From what I have read so far, I believe that I should maintain the charge between 12.5V (14%) and 13.3V (90%) to avoid shortening the battery life. I got that from reading various sources about “avoiding the shoulders,” and I verified the voltages that correspond to 14% and 90% in the battery manufacturer’s documentations. I also understand I should not charge below 32°F or discharge below 0°F.
The battery BMS has over- and under-voltage protection, but they are apparently at 14.8V and 8.0V. These seem too high and low and more for safety than protecting the battery life. Is this typical for the BMS, or is this because I bought a cheap battery?
I believe the charge controller can be programmed to avoid overcharging past 13.3V.
To avoid over-discharging below 12.5V, I think I can use a battery protection device like this https://www.victronenergy.com/battery_protect/battery-protect.
The BMS has high temp protection at 194°F, but again, it seems to be for safety, not for protecting the battery life. It does not have any low-temp protection on the charge or load side. Again, is this typical?
I am looking for a device that will disconnect the charging below 32°F and one that will disconnect the load below -4°F. Probably, that will be two of the same device, one on each side of the battery set at different temps, perhaps something like this, although I would need higher amperage https://www.ebay.com/itm/185814659317.
Any feedback would be appreciated, even if it is "let me better educate you" or “you shoulda bought a better battery.” Any advice on whether I have the right ideas to protect the battery or devices to do so would also be great.
Thank you for your time and expertise.
Bryan